U.S. patent application number 12/909581 was filed with the patent office on 2011-06-02 for refrigerating apparatus.
This patent application is currently assigned to SANYO ELECTRIC CO., LTD.. Invention is credited to Susumu Kobayashi, Hiroyuki Sato, Fukuji Yoshida, Jiro Yuzawa.
Application Number | 20110126575 12/909581 |
Document ID | / |
Family ID | 43805637 |
Filed Date | 2011-06-02 |
United States Patent
Application |
20110126575 |
Kind Code |
A1 |
Kobayashi; Susumu ; et
al. |
June 2, 2011 |
REFRIGERATING APPARATUS
Abstract
There is disclosed a refrigerating apparatus which can more
efficiently cool the inside of a chamber to an ultralow
temperature. In a refrigerating apparatus R1 which condenses a
refrigerant discharged from a compressor 14, reduces a pressure of
the refrigerant by a capillary tube 18 and evaporates the
refrigerant by an evaporator 13 to exert a cooling function, the
capillary tube 18 is passed through a suction piping line 32
through which the refrigerant returning from the evaporator 13 to
the compressor 14 flows, to constitute a double tube structure.
Furthermore, the suction piping line 32 (a piping line 32A) formed
in the double tube structure by passing the capillary tube 18
therethrough is surrounded with an insulating material 35.
Inventors: |
Kobayashi; Susumu; (Osaka,
JP) ; Yoshida; Fukuji; (Osaka, JP) ; Yuzawa;
Jiro; (Osaka, JP) ; Sato; Hiroyuki; (Osaka,
JP) |
Assignee: |
SANYO ELECTRIC CO., LTD.
Osaka
JP
|
Family ID: |
43805637 |
Appl. No.: |
12/909581 |
Filed: |
October 21, 2010 |
Current U.S.
Class: |
62/333 ;
165/104.26; 62/498 |
Current CPC
Class: |
F25B 40/00 20130101;
F25B 41/37 20210101; F25B 7/00 20130101; F25B 2400/052 20130101;
F25B 2400/054 20130101; F25B 9/006 20130101 |
Class at
Publication: |
62/333 ;
165/104.26; 62/498 |
International
Class: |
F25D 17/00 20060101
F25D017/00; F28D 15/04 20060101 F28D015/04; F25B 1/00 20060101
F25B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2009 |
JP |
2009-272410 |
Claims
1. A refrigerating apparatus which condenses a refrigerant
discharged from a compressor, reduces a pressure of the refrigerant
by a capillary tube, and evaporates the refrigerant by an
evaporator to exert a cooling function, wherein the capillary tube
is passed through a suction piping line through which the
refrigerant returning from the evaporator to the compressor flows,
to constitute a double tube structure.
2. A refrigerating apparatus comprising: a high temperature side
refrigerant circuit and a low temperature side refrigerant circuit
to constitute independent closed refrigerant circuits, each of
which condenses a refrigerant discharged from a compressor, reduces
a pressure of the refrigerant by a capillary tube and evaporates
the refrigerant by an evaporator to exert a cooling function, the
evaporator of the high temperature side refrigerant circuit and a
condenser of the low temperature side refrigerant circuit
constituting a cascade heat exchanger, the evaporator of the low
temperature side refrigerant circuit being configured to exert a
final cooling function, wherein the capillary tube of the low
temperature side refrigerant circuit is passed through a suction
piping line through which the refrigerant returning from the
evaporator to the compressor of the low temperature side
refrigerant circuit flows, to constitute a double tube
structure.
3. A refrigerating apparatus which comprises a compressor, a
condenser, an evaporator, a single or a plurality of intermediate
heat exchangers connected so that a refrigerant returning from the
evaporator circulates therethrough and a plurality of capillary
tubes and into which a plurality of types of non-azeotropic mixed
refrigerants are introduced and which allows a condensed
refrigerant of the refrigerants flowing through the condenser to
join the refrigerants in the intermediate heat exchangers through
the capillary tubes, cools a non-condensed refrigerant of the
refrigerants in the intermediate heat exchangers to condense the
refrigerant having a lower boiling point, and evaporates the
refrigerant having the lowest boiling point by the evaporator
through the capillary tube of the final stage to exert a cooling
function, wherein the capillary tube of the final stage is passed
through a suction piping line through which the refrigerant
returning from the evaporator to the compressor flows, to
constitute a double tube structure.
4. A refrigerating apparatus comprising: a high temperature side
refrigerant circuit and a low temperature side refrigerant circuit
to constitute independent closed refrigerant circuits, each of
which condenses a refrigerant discharged from a compressor, reduces
a pressure of the refrigerant by a capillary tube and evaporates
the refrigerant by an evaporator to exert a cooling function, the
low temperature side refrigerant circuit comprising the compressor,
a condenser, the evaporator, a single or a plurality of
intermediate heat exchangers connected so that the refrigerant
returning from the evaporator circulates therethrough and a
plurality of capillary tubes, a plurality of types of
non-azeotropic mixed refrigerants being introduced, the
refrigerating apparatus having a constitution which allows a
condensed refrigerant of the refrigerants flowing through the
evaporator to join the refrigerants in the intermediate heat
exchangers through the capillary tubes, cools a non-condensed
refrigerant of the refrigerants in the intermediate heat exchangers
to condense the refrigerant having a lower boiling point, and
evaporates the refrigerant having the lowest boiling point by the
evaporator through the capillary tube of the final stage to exert
the cooling function, the evaporator of the high temperature side
refrigerant circuit and the condenser of the low temperature side
refrigerant circuit constituting a cascade heat exchanger, the
evaporator of the low temperature side refrigerant circuit being
configured to exert a final cooling function, wherein the capillary
tube of the final stage of the low temperature side refrigerant
circuit is passed through a suction piping line through which the
refrigerant returning from the evaporator to the compressor of the
low temperature side refrigerant circuit flows, to constitute a
double tube structure.
5. The refrigerating apparatus according to claim 2, wherein the
capillary tube of the high temperature side refrigerant circuit is
passed through the suction piping line through which the
refrigerant returning from the evaporator to the compressor of the
high temperature side refrigerant circuit flows, to constitute the
double tube structure.
6. The refrigerating apparatus according to claim 1, wherein the
suction piping line formed in the double tube structure by passing
the capillary tube therethrough is surrounded with an insulating
material.
7. The refrigerating apparatus according to claim 1, wherein a flow
of the refrigerant through the capillary tube and a flow of the
refrigerant through the suction piping line outside the capillary
tube form a counter flow.
8. The refrigerating apparatus according to claim 2, wherein the
suction piping line formed in the double tube structure by passing
the capillary tube therethrough is surrounded with an insulating
material.
9. The refrigerating apparatus according to claim 2, wherein a flow
of the refrigerant through the capillary tube and a flow of the
refrigerant through the suction piping line outside the capillary
tube form a counter flow.
10. The refrigerating apparatus according to claim 3, wherein the
suction piping line formed in the double tube structure by passing
the capillary tube therethrough is surrounded with an insulating
material.
11. The refrigerating apparatus according to claim 3, wherein a
flow of the refrigerant through the capillary tube and a flow of
the refrigerant through the suction piping line outside the
capillary tube form a counter flow.
12. The refrigerating apparatus according to claim 4, wherein the
suction piping line formed in the double tube structure by passing
the capillary tube therethrough is surrounded with an insulating
material.
13. The refrigerating apparatus according to claim 4, wherein a
flow of the refrigerant through the capillary tube and a flow of
the refrigerant through the suction piping line outside the
capillary tube form a counter flow.
14. The refrigerating apparatus according to claim 5, wherein the
suction piping line formed in the double tube structure by passing
the capillary tube therethrough is surrounded with an insulating
material.
15. The refrigerating apparatus according to claim 5, wherein a
flow of the refrigerant through the capillary tube and a flow of
the refrigerant through the suction piping line outside the
capillary tube form a counter flow.
16. The refrigerating apparatus according to claim 6, wherein a
flow of the refrigerant through the capillary tube and a flow of
the refrigerant through the suction piping line outside the
capillary tube form a counter flow.
17. The refrigerating apparatus according to claim 4, wherein the
capillary tube of the high temperature side refrigerant circuit is
passed through the suction piping line through which the
refrigerant returning from the evaporator to the compressor of the
high temperature side refrigerant circuit flows, to constitute the
double tube structure.
18. The refrigerating apparatus according to claim 17, wherein the
suction piping line formed in the double tube structure by passing
the capillary tube therethrough is surrounded with an insulating
material.
19. The refrigerating apparatus according to claim 17, wherein a
flow of the refrigerant through the capillary tube and a flow of
the refrigerant through the suction piping line outside the
capillary tube form a counter flow.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a refrigerating apparatus
which condenses a refrigerant discharged from a compressor and then
evaporates the refrigerant by an evaporator to exert a cooling
function.
[0002] Heretofore, in a refrigerating apparatus for an ultralow
temperature refrigerator used for storage of frozen food to be
stored at a low temperature for a long period of time or storage of
an anatomy, a specimen or the like at an ultralow temperature, a
non-azeotropic mixed refrigerant including butane, ethylene and R14
(carbon tetrafluoride: CF.sub.4) or a non-azeotropic mixed
refrigerant including butane, ethane and R14 is introduced in a
refrigerant circuit, to secure handleability of the refrigerant in
the refrigerating apparatus owing to operability of butane having a
high boiling point in such non-azeotropic mixed refrigerant gases,
at ordinary temperature. Moreover, ethane or ethylene having a
remarkably low boiling point is evaporated by the evaporator,
thereby setting a temperature of the inside of a storage chamber to
an ultralow temperature below -60.degree. C.
PRIOR ART DOCUMENT
Patent Document
[0003] [Patent Document 1] Japanese Patent Application Laid-Open
No. 2007-107858
SUMMARY OF THE INVENTION
[0004] However, to realize a desirable ultralow temperature, a
compressor having a larger capability has to be selected. In such a
case, a problem occurs to involve enlargement of an apparatus and
steep rise of a cost. Moreover, with the increase of the capability
of the used compressor, the increase of power consumption is
incurred. Therefore, there has been desired the development of a
refrigerating apparatus which can more efficiently cool the inside
of a storage chamber to the ultralow temperature.
[0005] The present invention has been developed to solve a
conventional technical problem, and an object thereof is to provide
a refrigerating apparatus which can more efficiently cool the
inside of a storage chamber to an ultralow temperature.
[0006] A refrigerating apparatus of the present invention of a
first aspect condenses a refrigerant discharged from a compressor,
reduces a pressure of the refrigerant by a capillary tube, and
evaporates the refrigerant by an evaporator to exert a cooling
function, characterized in that the capillary tube is passed
through a suction piping line through which the refrigerant
returning from the evaporator to the compressor flows, to
constitute a double tube structure.
[0007] A refrigerating apparatus of the present invention of a
second aspect comprises a high temperature side refrigerant circuit
and a low temperature side refrigerant circuit to constitute
independent closed refrigerant circuits, each of which condenses a
refrigerant discharged from a compressor, reduces a pressure of the
refrigerant by a capillary tube and evaporates the refrigerant by
an evaporator to exert a cooling function, the evaporator of the
high temperature side refrigerant circuit and a condenser of the
low temperature side refrigerant circuit constituting a cascade
heat exchanger, the evaporator of the low temperature side
refrigerant circuit being configured to exert a final cooling
function, characterized in that the capillary tube of the low
temperature side refrigerant circuit is passed through a suction
piping line through which the refrigerant returning from the
evaporator to the compressor of the low temperature side
refrigerant circuit flows, to constitute a double tube
structure.
[0008] A refrigerating apparatus of the present invention of a
third aspect is a refrigerating apparatus which comprises a
compressor, a condenser, an evaporator, a single or a plurality of
intermediate heat exchangers connected so that a refrigerant
returning from the evaporator circulates therethrough and a
plurality of capillary tubes and into which a plurality of types of
non-azeotropic mixed refrigerants are introduced and which allows a
condensed refrigerant of the refrigerants flowing through the
condenser to join the refrigerants in the intermediate heat
exchangers through the capillary tubes, cools a non-condensed
refrigerant of the refrigerants in the intermediate heat exchangers
to condense the refrigerant having a lower boiling point, and
evaporates the refrigerant having the lowest boiling point by the
evaporator through the capillary tube of the final stage to exert a
cooling function, characterized in that the capillary tube of the
final stage is passed through a suction piping line through which
the refrigerant returning from the evaporator to the compressor
flows, to constitute a double tube structure.
[0009] A refrigerating apparatus of the present invention of a
fourth aspect comprises a high temperature side refrigerant circuit
and a low temperature side refrigerant circuit to constitute
independent closed refrigerant circuits, each of which condenses a
refrigerant discharged from a compressor, reduces a pressure of the
refrigerant by a capillary tube and evaporates the refrigerant by
an evaporator to exert a cooling function, the low temperature side
refrigerant circuit comprising the compressor, a condenser, the
evaporator, a single or a plurality of intermediate heat exchangers
connected so that the refrigerant returning from the evaporator
circulates therethrough and a plurality of capillary tubes, a
plurality of types of non-azeotropic mixed refrigerants being
introduced, the refrigerating apparatus having a constitution which
allows a condensed refrigerant of the refrigerant flowing through
the evaporator to join the refrigerants in the intermediate heat
exchangers through the capillary tubes, cools a non-condensed
refrigerant of the refrigerants in the intermediate heat exchangers
to condense the refrigerant having a lower boiling point, and
evaporates the refrigerant having the lowest boiling point by the
evaporator through the capillary tube of the final stage to exert
the cooling function, the evaporator of the high temperature side
refrigerant circuit and the condenser of the low temperature side
refrigerant circuit constituting a cascade heat exchanger, the
evaporator of the low temperature side refrigerant circuit being
configured to exert a final cooling function, characterized in that
the capillary tube of the final stage of the low temperature side
refrigerant circuit is passed through a suction piping line through
which the refrigerant returning from the evaporator to the
compressor of the low temperature side refrigerant circuit flows,
to constitute a double tube structure.
[0010] A refrigerating apparatus of the present invention of a
fifth aspect is characterized in that in the invention of the
second or fourth aspect, the capillary tube of the high temperature
side refrigerant circuit is passed through the suction piping line
through which the refrigerant returning from the evaporator to the
compressor of the high temperature side refrigerant circuit flows,
to constitute the double tube structure.
[0011] A refrigerating apparatus of the present invention of a
sixth aspect is characterized in that in the inventions of the
above aspects, the suction piping line formed in the double tube
structure by passing the capillary tube therethrough is surrounded
with an insulating material.
[0012] A refrigerating apparatus of the present invention of a
seventh aspect is characterized in that in the invention of the
above aspects, a flow of the refrigerant through the capillary tube
and a flow of the refrigerant through the suction piping line
outside the capillary tube form a counter flow.
[0013] According to the present invention of the first aspect, in
the refrigerating apparatus which condenses the refrigerant
discharged from the compressor, reduces the pressure of the
refrigerant by the capillary tube, and evaporates the refrigerant
by the evaporator to exert the cooling function, the capillary tube
is passed through the suction piping line through which the
refrigerant returning from the evaporator to the compressor flows,
to constitute the double tube structure. Therefore, efficiency of
the heat exchange between the refrigerant in the suction piping
line and the refrigerant in the capillary tube can be enhanced to
improve a performance of the refrigerating apparatus.
[0014] In particular, the capillary tube is passed through the
suction piping line just exiting from the evaporator to constitute
the double tube structure, thereby enabling the heat exchange by
conduction of heat transmitted along the wall surface of the whole
periphery of the capillary tube. According to this constitution,
the refrigerant having the lowest boiling point is efficiently
cooled by the refrigerant returning from the evaporator, whereby
the performance can remarkably be improved.
[0015] According to the invention of the second aspect, the
refrigerating apparatus comprises the high temperature side
refrigerant circuit and the low temperature side refrigerant
circuit to constitute the independent closed refrigerant circuits,
each of which condenses the refrigerant discharged from the
compressor, reduces the pressure of the refrigerant by the
capillary tube and evaporates the refrigerant by the evaporator to
exert the cooling function. The evaporator of the high temperature
side refrigerant circuit and the condenser of the low temperature
side refrigerant circuit constitute the cascade heat exchanger. The
evaporator of the low temperature side refrigerant circuit exerts
the final cooling function. In this refrigerating apparatus, the
capillary tube of the low temperature side refrigerant circuit is
passed through the suction piping line through which the
refrigerant returning from the evaporator to the compressor of the
low temperature side refrigerant circuit flows, to constitute the
double tube structure. Therefore, the efficiency of the heat
exchange between the refrigerant in the suction piping line and the
refrigerant in the capillary tube can be enhanced to improve the
performance.
[0016] In particular, the capillary tube of the low temperature
side refrigerant circuit is passed through the suction piping line
just exiting from the evaporator to constitute the double tube
structure, thereby enabling the heat exchange by the conduction of
the heat transmitted along the wall surface of the whole periphery
of the capillary tube. According to this constitution, the
refrigerant having the lowest boiling point is efficiently cooled
by the refrigerant returning from the evaporator of the low
temperature side refrigerant circuit, whereby the performance can
remarkably be improved.
[0017] According to the invention of the third aspect, the
refrigerating apparatus comprises the compressor, the condenser,
the evaporator, the single or the plurality of intermediate heat
exchangers connected so that the refrigerant returning from this
evaporator circulates therethrough, and the plurality of capillary
tubes. Into the refrigerating apparatus, the plurality of types of
non-azeotropic mixed refrigerants are introduced. The refrigerating
apparatus allows the condensed refrigerant of the refrigerants
flowing through the condenser to join the refrigerants in the
intermediate heat exchangers through the capillary tubes, cools the
non-condensed refrigerant of the refrigerants in the intermediate
heat exchangers to condense the refrigerant having the lower
boiling point, and evaporates the refrigerant having the lowest
boiling point by the evaporator through the capillary tube of the
final stage to exert the cooling function. In the refrigerating
apparatus, the capillary tube of the final stage is passed through
the suction piping line through which the refrigerant returning
from the evaporator to the compressor flows, to constitute the
double tube structure. Therefore, the efficiency of the heat
exchange between the refrigerant in the suction piping line and the
refrigerant in the capillary tube can be enhanced to improve the
performance.
[0018] In particular, the capillary tube is passed through the
suction piping line just exiting from the evaporator to constitute
the double tube structure, thereby enabling the heat exchange by
the conduction of the heat transmitted along the wall surface of
the whole periphery of the capillary tube. According to this
constitution, the refrigerant having the lowest boiling point is
efficiently cooled by the refrigerant returning from the
evaporator, whereby the performance can remarkably be improved.
[0019] According to the present invention of the fourth aspect, the
refrigerating apparatus comprises the high temperature side
refrigerant circuit and the low temperature side refrigerant
circuit to constitute the independent closed refrigerant circuits,
each of which condenses the refrigerant discharged from the
compressor, reduces the pressure of the refrigerant by the
capillary tube and evaporates the refrigerant by the evaporator to
exert the cooling function. This low temperature side refrigerant
circuit comprises the compressor, the condenser, the evaporator,
the single or the plurality of intermediate heat exchangers
connected so that the refrigerant returning from this evaporator
circulates therethrough and the plurality of capillary tubes. The
plurality of types of non-azeotropic mixed refrigerants are
introduced. The refrigerating apparatus has the constitution which
allows the condensed refrigerant of the refrigerants flowing
through the evaporator to join the refrigerants in the intermediate
heat exchangers through the capillary tubes, cools the
non-condensed refrigerant of the refrigerants in the intermediate
heat exchangers to condense the refrigerant having the lower
boiling point, and evaporates the refrigerant having the lowest
boiling point by the evaporator through the capillary tube of the
final stage to exert the cooling function. The evaporator of the
high temperature side refrigerant circuit and the condenser of the
low temperature side refrigerant circuit constitute the cascade
heat exchanger, and the evaporator of the low temperature side
refrigerant circuit is configured to exert the final cooling
function. In the refrigerating apparatus, the capillary tube of the
final stage of the low temperature side refrigerant circuit is
passed through the suction piping line through which the
refrigerant returning from the evaporator to the compressor of the
low temperature side refrigerant circuit flows, to constitute the
double tube structure. Therefore, the efficiency of the heat
exchange between the refrigerant in the suction piping line and the
refrigerant in the capillary tube can be enhanced to improve the
performance.
[0020] In particular, the capillary tube of the low temperature
side refrigerant circuit is passed through the suction piping line
just exiting from the evaporator to constitute the double tube
structure, thereby enabling the heat exchange by the conduction of
the heat transmitted along the wall surface of the whole periphery
of the capillary tube. According to this constitution, the
refrigerant having the lowest boiling point is efficiently cooled
by the refrigerant returning from the evaporator of the low
temperature side refrigerant circuit, whereby the performance can
remarkably be improved.
[0021] According to the invention of the fifth aspect, in the
invention of the second or fourth aspect, the capillary tube of the
high temperature side refrigerant circuit is passed through the
suction piping line through which the refrigerant returning from
the evaporator to the compressor of the high temperature side
refrigerant circuit flows, to constitute the double tube structure.
Therefore, also in the high temperature side refrigerant circuit,
the efficiency of the heat exchange between the refrigerant in the
suction piping line and the refrigerant in the capillary tube can
further be enhanced to further improve the performance of the
refrigerating apparatus.
[0022] Moreover, in the inventions of the respective aspects, as in
the invention of the sixth aspect, the suction piping line formed
in the double tube structure by passing the capillary tube
therethrough is surrounded with the insulating material, which can
further enhance the efficiency of the heat exchange.
[0023] Furthermore, in the inventions of the above aspects, as in
the invention of the seventh aspect, the flow of the refrigerant
through the capillary tube and the flow of the refrigerant through
the suction piping line outside the capillary tube form the counter
flow, which can further improve a heat exchange ability.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a side view of an ultralow temperature
refrigerator to which a refrigerating apparatus is applied;
[0025] FIG. 2 is a refrigerant circuit diagram in an embodiment of
the ultralow temperature refrigerator of FIG. 1;
[0026] FIG. 3 is a diagram for explaining a double tube structure
of a heat exchanger obtained by passing a capillary tube through a
suction piping line of the present invention shown in FIG. 2;
[0027] FIG. 4 is a graph concerning each data in a case where the
weight of a mixed refrigerant of R245fa and R600 and the weight of
R14 are set to be constant, while the weight of R23 is varied;
[0028] FIG. 5 is a graph concerning each data in a case where the
weight of the mixed refrigerant of R245fa and R600 and the weight
of R23 are set to be constant, while the weight of R14 is
varied;
[0029] FIG. 6 is a refrigerant circuit diagram in a second
embodiment (Embodiment 2);
[0030] FIG. 7 is a refrigerant circuit diagram in a third
embodiment (Embodiment 3); and
[0031] FIG. 8 is a refrigerant circuit diagram in a fourth
embodiment (Embodiment 4).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0032] Hereinafter, embodiments of the present invention will be
described in detail with reference to the drawings.
Embodiment 1
[0033] FIG. 1 is a side view of an ultralow temperature
refrigerator 1 to which a refrigerating apparatus of the present
invention is applied. The ultralow temperature refrigerator 1 is
used, for example, to store refrigerated food to be stored at a low
temperature for a long period of time or to store an anatomy, a
specimen or the like at an ultralow temperature. A main body of the
refrigerator is constituted of an insulating box member 2 having an
open upper surface, and a mechanical chamber (not shown) which is
positioned in the lower part of the insulating box member 2 and in
which a compressor 14 and the like are installed to constitute a
refrigerant circuit of a refrigerating apparatus R1 of the present
embodiment therein.
[0034] The insulating box member 2 is constituted of an outer box 3
and an inner box 4 both made of steel plates and having open upper
surfaces; a breaker 5 made of a synthetic resin and connecting the
upper ends of both the boxes 3 and 4 to each other; and a
polyurethane resin insulating material 7 charged in a space
surrounded by the outer box 3, the inner box 4 and the breaker 5 by
an in-situ foaming system. The inside of the inner box 4 is a
storage chamber 8 having an open upper surface.
[0035] In the present embodiment, to set a temperature in the
storage chamber 8 (hereinafter referred to as the in-chamber
temperature) to a target temperature below, for example,
-80.degree. C., the insulating box member 2, which insulates the
inside of the storage chamber 8 from outside air, requires a larger
insulating ability as compared with a low temperature refrigerator
where the in-chamber temperature is set around 0.degree. C.
Therefore, when the insulating ability is acquired only by the
polyurethane resin insulating material 7 described above, the
material has to be formed with a considerable thickness, which
causes a problem that the storage amount of the storage chamber 8
cannot sufficiently be acquired with a limited main body dimension.
Consequently, in the insulating box member 2 of the present
embodiment, a vacuum insulating material such as glass wool is
disposed on the inner wall surface of the outer box 3, and the
thickness of the polyurethane resin insulating material 7 is set to
a small dimension in accordance with the insulating ability of the
vacuum insulating material.
[0036] Moreover, the upper surface of the breaker 5 is formed in a
staircase pattern, and an insulating door 9 is provided rotatably
around one end thereof, i.e., the rear end in the present
embodiment via a packing 11. In consequence, the upper surface
opening of the storage chamber 8 is openably closed with the
insulating door 9. Moreover, the other end of the insulating door
9, i.e., the front end thereof in the present embodiment is
provided with a grip portion 10, and the grip portion 10 is
operated to open and close the insulating door 9. Furthermore, an
evaporator (a refrigerant piping line) 13 constituting the
refrigerant circuit of the refrigerating apparatus R1 is attached
to the peripheral surface of the inner box 4 on an insulating
material 7 side so as to perform heat exchange (in the heat
exchange manner).
[0037] Next, the refrigerant circuit of the refrigerating apparatus
R1 of the present embodiment will be described with reference to
FIG. 2. The refrigerant circuit of the refrigerating apparatus R1
of the present embodiment has a constitution of a single unit/stage
of a refrigerant circuit 12. The compressor 14 constituting the
refrigerant circuit 12 is an electromotive compressor using a
single phase or three phase alternator. The compressor 14 is
connected to a disperse heater 20 in a constitution which once
discharges a refrigerant compressed by the compressor 14 to the
outside to radiate heat, returns the refrigerant into a shell of a
sealed container and again discharges the refrigerant to a
refrigerant discharge tube 31. The refrigerant discharge tube 31
connected to the compressor 14 on a discharge side thereof is
connected to a preliminary condenser 21. The preliminary condenser
21 is connected to a frame pipe 22 for heating the opening edge of
the storage chamber 8 to prevent dew condensation, and then
connected to a condenser 15.
[0038] Moreover, the refrigerant piping line exiting from the
condenser 15 is connected to a dry core 17 and a condensing pipe
23. The dry core 17 is water removal means for removing water from
the refrigerant circuit 12. The condensing pipe 23 constitutes a
heat exchanger 16 together with a part of a suction piping line 32
exiting from the evaporator 13 and returning to the compressor
14.
[0039] The refrigerant piping line exiting from the condensing pipe
23 is connected to the evaporator 13 via a capillary tube 18 as a
pressure reducing unit. The capillary tube 18 is passed through a
part (a piping line 32A) of the suction piping line 32 exiting from
the evaporator 13 and returning to the compressor 14. Specifically,
the capillary tube 18 is passed through the piping line 32A as a
part of the suction piping line 32 positioned on a discharge side
(the outlet side) of a header 26 provided on the discharge side of
the evaporator 13 and on a suction side of the heat exchanger 16,
to constitute a double tube structure as shown in FIG. 3. In such a
double tube structure, it is possible to perform heat exchange
between the refrigerant flowing through the capillary tube 18
inside a double tube 25 (hereinafter referred to as the double tube
structure) and the refrigerant flowing from the evaporator 13
through the piping line 32A outside the capillary tube.
[0040] Here, a manufacturing method of the double tube structure 25
will be described. First, the linearly tubular capillary tube 18 is
passed through the linearly tubular piping line 32A having a
comparatively large diameter. Next, such a double tube is spirally
wound as much as a plurality of stages. At this time, the tube is
wound so that the axial center of the piping line 32A coincides
with the axial center of the capillary tube 18 as much as possible,
to form the spiral double tube. In consequence, a gap is formed
between the inner wall surface of the piping line 32A and the outer
wall surface of the capillary tube 18 as consistently as possible.
In this way, the double tube is spirally wound as much as the
plurality of stages to form the spiral double tube structure,
thereby enabling miniaturization while sufficiently acquiring the
length of the capillary tube 18 and sufficiently acquiring such a
heat exchange portion of the double tube structure.
[0041] Next, cap-like connection piping lines (not shown) having
both end holes and side holes are attached to both ends of the
piping line 32A, the ends of the capillary tube 18 are drawn from
the side holes, respectively, and then the side holes are welded
and sealed. Furthermore, one end of the connection piping line
attached to the one end of the piping line 32A and a connecting
portion of the piping line 32A are welded, the other end of the
connection piping line is connected to the suction piping line 32
connected to the evaporator 13 on the discharge side thereof, and
this connecting portion is welded. Similarly, one end of the
connection piping line attached to the other end of the piping line
32A and a connecting portion of the piping line 32A are welded, the
other end of the connection piping line is connected to the suction
piping line 32 leading to the heat exchanger 16, and this
connecting portion is welded. Moreover, the piping line 32A formed
in such a double tube structure is surrounded with an insulating
material 35, whereby the double tube structure 25 of the present
embodiment can be obtained.
[0042] Additionally, in a conventional refrigerating apparatus
formed so that heat exchange between the capillary tube and the
suction piping line exiting from the evaporator can be performed,
the capillary tube has been disposed along the outer peripheral
surface of the suction piping line so that the outer wall of the
capillary tube can come in contact with the outer wall of the
suction piping line in the heat exchange manner. In this case, the
suction piping line only linearly comes in contact with the
capillary tube. Therefore, a heat exchange performance is so poor
that the heat exchange cannot sufficiently be performed.
[0043] On the other hand, the capillary tube 18 is passed through
the suction piping line 32 (the piping line 32A) to constitute the
double tube structure as in the present invention, thereby
performing the heat exchange between the refrigerant flowing
through the capillary tube 18 and the refrigerant flowing through
the suction piping line 32 by conduction of heat transmitted along
the wall surface of the whole periphery of the capillary tube 18.
In consequence, a heat exchange performance can remarkably be
improved as compared with a conventional structure. In particular,
the whole outer periphery of the piping line 32A having the double
tube structure is surrounded with the insulating material 35 as
described above, whereby the structure is not easily influenced by
the heat from the outside. Moreover, it is possible to further
improve the ability of the heat exchange between the refrigerant in
the piping line 32A and the refrigerant in the capillary tube
18.
[0044] Furthermore, the refrigerant is allowed to flow through the
capillary tube 18 inside the double tube structure and through the
suction piping line 32 (the piping line 32A) outside the capillary
tube 18 so as to form the counter flow of the refrigerant, whereby
the heat exchange ability in the double tube structure 25 can
further be improved.
[0045] The double tube structure 25 is disposed in the insulating
material 7. Specifically, as shown in FIG. 1, the double tube
structure is removably received in the insulating material 7 under
the heat exchanger 16 on the back surface side of the inner box
4.
[0046] On the other hand, the suction piping line 32 exiting from
the double tube structure 25 is connected to the compressor 14 on
the suction side thereof successively through the heat exchanger
16, a check valve 27 and an accumulator 28. It is to be noted that
in the present embodiment, the preliminary condenser 21 and the
condenser 15 have a constitution of an integral condenser, and are
cooled by a condensing fan 29 as a blower for the condenser.
[0047] In the present embodiment, a mixed refrigerant of R245fa and
R600 and a non-azeotropic mixed refrigerant of R23 and R14 are
charged in the refrigerant circuit 12. R245fa is
1,1,1,-3,3-pentafluoropropane (CF.sub.3CH.sub.2CHF.sub.2) and has a
boiling point of +15.3.degree. C. R600 is butane (C.sub.4H.sub.10)
and has a boiling point of -0.5.degree. C. R600 has a function of
returning, to the compressor 14, a lubricant of the compressor 14
or mixed water which cannot be absorbed by the drier 17 in a state
where the water is dissolved in R600. R600 is a combustible
substance. However, when R600 is mixed with incombustible R245fa at
a predetermined ratio of R245fa/R600=70/30 in the present
embodiment, whereby the substance can be treated as an
incombustible substance. R23 is trifluoromethane (CHF.sub.3) and
has a boiling point of -82.1.degree. C. R14 is tetrafluoromenthane
(CF.sub.4) and has a boiling point of -127.9.degree. C.
[0048] Moreover, a composition of these mixed refrigerants in the
present embodiment includes 64% by weight of the mixed refrigerant
of R245fa and R600, 24% by weight of R23 and 12% by weight of R14
in total.
[0049] It is to be noted that in FIG. 2, arrows show the flow of
the refrigerant circulating through the refrigerant circuit 12.
Specifically, a high temperature gaseous refrigerant discharged
from the compressor 14 is once discharged from the sealed container
to the disperse heater 20 through a refrigerant discharge tube on a
disperse heater 20 side, radiates heat and again returns into the
shell of the sealed container. In consequence, the inside of the
sealed container can be cooled by the refrigerant which has
radiated the heat in the disperse heater 20 to lower the
temperature thereof. Moreover, such a high temperature gaseous
refrigerant is discharged from the sealed container through the
refrigerant discharge tube 31, condensed by the preliminary
condenser 21, the frame pipe 22 and the condenser 15 to radiate the
heat, and is liquefied, followed by removing the water contained in
the refrigerant by the dry core 17. Afterward, the refrigerant
flows into the heat exchanger 16. In the heat exchanger 16, the
heat exchange between the refrigerant from the condenser 15 and the
low temperature refrigerant in the suction piping line 32 disposed
in the heat exchange manner is performed, whereby the non-condensed
refrigerant is cooled, condensed and liquefied. Afterward, the
refrigerant flows into the capillary tube 18.
[0050] Here, the heat exchange between the refrigerant in the
capillary tube 18 and the refrigerant flowing through the suction
piping line 32 disposed around the whole periphery of the capillary
tube 18 is performed by the conduction of the heat transmitted
along the wall surface of the whole periphery of the capillary tube
18. Afterward, the refrigerant having a pressure thereof reduced
while lowering the temperature flows into the evaporator 13.
Subsequently, in the evaporator 13, the refrigerants R14 and R23
take the heat from the ambient atmosphere to evaporate. At this
time, the refrigerants R14 and R23 evaporate in the evaporator 13
to exert a cooling function, thereby cooling the ambient atmosphere
of the evaporator 13 to an ultralow temperature of -85.degree. C.
In this case, the evaporator (the refrigerant piping line) 13 is
wound along the inner box 4 on the insulating material 7 side in
the heat exchange manner as described above, whereby the inside of
the storage chamber 8 of the ultralow temperature refrigerator 1
can be set to an in-chamber temperature below -80.degree. C. by
such cooling of the evaporator 13.
[0051] Afterward, the refrigerant evaporated by the evaporator 13
exits from the evaporator 13 via the suction piping line 32 to
return to the compressor 14 through the header 26, the double tube
structure 25, the heat exchanger 16, the check valve 27 and the
accumulator 28.
[0052] At this time, the finally reaching temperature of the
evaporator 13 of the compressor 14 which is being operated is from
-100.degree. C. to -60.degree. C. At such a low temperature, R245fa
in the refrigerant has a boiling point of +15.3.degree. C., and
R600 has a boiling point of -0.5.degree. C. Therefore, the
refrigerant does not evaporate but still has a liquid state in the
evaporator 13, and hence the refrigerant hardly contributes to
cooling. However, R600 has a function of returning, to the
compressor 14, the lubricant of the compressor 14 or the mixed
water which cannot be absorbed by the dry core 17 in the state
where the water is dissolved in R600, and the liquid refrigerant
also has a function of evaporating in the compressor 14 to lower
the temperature of the compressor 14.
[0053] The evaporation temperature in the evaporator 13 varies in
accordance with the composition ratio of the non-azeotropic mixed
refrigerant introduced in the refrigerant circuit 12. Hereinafter,
the evaporator temperature, in-chamber temperature, high pressure
side pressure and low pressure side pressure with respect to the
composition ratio of each refrigerant will be described based on
each experiment result in detail. FIG. 4 is a graph showing the
evaporator inlet temperature, the in-chamber temperature, the high
pressure side pressure and the low pressure side pressure in a case
where the weight of the mixed refrigerant of R245fa and R600 and
the weight of R14 are set to be constant, while the weight of R23
is varied. FIG. 5 is a graph showing the evaporator inlet
temperature, the in-chamber temperature, the high pressure side
pressure and the low pressure side pressure in a case where the
weight of the mixed refrigerant of R245fa and R600 and the weight
of R23 are set to be constant, while the weight of R14 is
varied.
[0054] In the experiment result of FIG. 4, the weight ratio of R23
with respect to the total weight of the introduced refrigerants is
increased from 20.0% by weight to 42.0% by weight. According to
this result, with the 20.0% by weight regarded as the minimum
amount in such an experiment, the inlet temperature of the
evaporator 13 is -88.0.degree. C., whereas the in-chamber
temperature is -71.0.degree. C. On the other hand, when the weight
ratio of R23 is 21.3% by weight, the inlet temperature of the
evaporator 13 rapidly lowers to -95.9.degree. C., whereas the
in-chamber temperature also lowers to -87.5.degree. C. Afterward,
with the increase of the weight ratio of R23 to 42.0% by weight,
the temperature only slightly rises, and in either case, the
in-chamber temperature can be set below about -85.degree. C.
[0055] Moreover, in the experiment result of FIG. 5, the weight
ratio of R14 with respect to the total weight of the introduced
refrigerants is increased from 0.0% by weight to 14.1% by weight.
According to this result, in the case of 0.0% by weight regarded as
the minimum amount in such an experiment, i.e., in a case where R14
is not included, the inlet temperature of the evaporator 13 is
-66.1.degree. C., whereas the in-chamber temperature is
-66.9.degree. C. On the other hand, when the weight ratio of R14 is
1.8% by weight, the inlet temperature of the evaporator 13 rapidly
lowers to -80.2.degree. C., whereas the in-chamber temperature also
lowers to -74.1.degree. C. The weight ratio of R14 is gradually
increased, and in the present experiment, at 14.1% by weight, the
inlet temperature of the evaporator 13 lowers to -98.9.degree. C.,
whereas the in-chamber temperature lowers to -90.0.degree. C. R14
has a boiling point of -129.7.degree. C. Therefore, it is then
expected that when the weight ratio of R14 is increased, the
temperature of the evaporator 13 and the in-chamber temperature
further lower.
[0056] However, as seen from the graph of FIG. 5, the high pressure
side pressure rises, as the weight ratio of R14 increases. In
consequence, there occurs a problem that when the weight ratio of
R14 is increased to 20% by weight or more, the high pressure side
pressure excessively increases to, for example, 3 MPa or more. The
rise of the high pressure side pressure causes a problem that an
apparatus such as the compressor 14 is damaged or a problem that
the start properties of the compressor 14 deteriorate. Therefore,
when the in-chamber temperature is preferably set to a target
temperature below -75.degree. C., the weight ratio of the R14 is
preferably set to a range of 3% by weight to 20% by weight of the
total weight.
[0057] It is to be noted that R23 has a boiling point of
-82.1.degree. C. as described above. Therefore, only by R23, the
temperature of the evaporator 13 cannot be set to a temperature
which is not higher than the boiling point. However, as in the
present invention, a predetermined amount, for example, about 5% or
more by weight of R14 having a remarkably low boiling point is
added, whereby the cooling function of R14 can constantly realize
an ultralow temperature below -80.degree. C. as the evaporation
temperature in the evaporator 13.
[0058] It is seen from the above experiment results that as to the
non-azeotropic mixed refrigerant introduced in the refrigerant
circuit 12, the total weight ratio of the mixed refrigerant of
R245fa and R600 is from 40% by weight to 80% by weight with respect
to the total weight, the weight ratio of R23 is from 15% by weight
to 47% by weight, and the weight ratio of R14 is from 3% by weight
to 20% by weight, whereby the incombustible non-azeotropic mixed
refrigerant can realize the ultralow temperature so that the
in-chamber temperature is below -70.degree. C. In particular, as to
the non-azeotropic mixed refrigerant introduced in the refrigerant
circuit 12, the total weight ratio of the mixed refrigerant of
R245fa and R600 is from 49% by weight to 70% by weight with respect
to the total weight, the weight ratio of R23 is from 21% by weight
to 42% by weight, and the weight ratio of R14 is from 9% by weight
to 20% by weight, whereby the incombustible non-azeotropic mixed
refrigerant can realize the ultralow temperature so that the
in-chamber temperature is below -85.degree. C.
[0059] In consequence, the storage of food, anatomy, specimen or
the like for a long period of time can further be stabilized, and
reliability can be improved. Moreover, since the non-azeotropic
mixed refrigerant is incombustible, the refrigerant can safely be
used, handling properties are improved, and it is possible to avoid
a disadvantage that when the mixed refrigerant leaks owing to the
damage of the refrigerant piping line or the like, the refrigerant
is combusted.
[0060] In particular, when as to the composition ratio of each
component of the non-azeotropic mixed refrigerant, the ratio of the
mixed refrigerant of R245fa and R600 is 64% by weight, the ratio of
R23 is 24% by weight and the ratio of R14 is 12% by weight, the
ultralow temperature can be realized so that the in-chamber
temperature is below -80.degree. C. In consequence, the food,
anatomy, specimen or the like can further stably be stored for a
long period of time, and the reliability of the apparatus can be
improved.
[0061] It is to be noted that the refrigerant is not limited to
R23. For example, R116 (hexafluoroethane: CF.sub.3CF.sub.3), or
R508A (R23/R116=39/61, a boiling point: -85.7.degree. C.) or R508B
(R23/R116=46/54, a boiling point: -86.9.degree. C.) obtained by
mixing R23 and R116 at a predetermined ratio can produce a similar
effect.
[0062] Moreover, when the non-azeotropic mixed refrigerant is used
as in the present embodiment, the conventional refrigerant circuit
hardly has to be changed in accordance with the change of the
refrigerant composition, but the performance of the circuit can be
maintained. Moreover, it is possible to cope with an environment
problem such as depletion of ozone layer.
[0063] Furthermore, as in the present invention described above,
the capillary tube 18 is passed through the suction piping line 32
(the piping line 32A) through which the refrigerant returning from
the evaporator 13 to the compressor 14 flows, constitute the double
tube structure, whereby the efficiency of the heat exchange between
the refrigerant in the piping line 32A and the refrigerant in the
capillary tube 18 can be enhanced to improve the performance. In
particular, as in the present invention, the capillary tube 18 is
passed through the piping line 32A of the suction piping line 32
just exiting from the evaporator 13, to constitute the double tube
structure which enables the heat exchange by the conduction of the
heat transmitted along the wall surface of the whole periphery of
the capillary tube 18. In consequence, the refrigerant returning
from the evaporator 13 can efficiently cool the refrigerant having
the lowest boiling point, and hence the performance can remarkably
be improved.
[0064] Furthermore, the piping line 32A formed in the double tube
structure by passing the capillary tube 18 therethrough is
surrounded with the insulating material 35, whereby the heat
exchange efficiency can further be enhanced. In addition, the flow
of the refrigerant through the capillary tube 18 and the flow of
the refrigerant through the piping line 32A outside the capillary
tube 18 form the counter flow, whereby the heat exchange ability
can further be improved.
[0065] In consequence, energy saving of about 15% to 20% can be
achieved as compared with a similarly used conventional
refrigerating apparatus. Moreover, a lower temperature can be
realized as the ambient temperature of the evaporator 13 as
compared with the conventional apparatus. In consequence, even when
the compressor is changed to a compressor having a smaller
capability than a heretofore used compressor, a sufficient
performance can be acquired. In consequence, further decrease of
power consumption and miniaturization of the apparatus can be
achieved.
[0066] Generally according to the present invention, a so-called
multistage refrigerating system is not used, but the ultralow
temperature can be realized by a single stage refrigerating system
as in the present embodiment, whereby the apparatus can be
simplified and costs can be decreased.
[0067] It is to be noted that the refrigerating apparatus of the
present invention is not limited to the refrigerating apparatus R1
of the embodiment, and the present invention is effective as long
as the refrigerant discharged from the compressor is condensed, has
the pressure thereof reduced by the capillary tube, and is
evaporated by the evaporator to exert the cooling function.
Moreover, when the heat exchanger 16 is not used in the present
embodiment, the temperature of the compressed gas may be lowered to
the above temperature range by use of another known cooling means,
to proceed with a targeted condensing process.
[0068] Furthermore, in the present embodiment, it has been
described that there is introduced, in the refrigerant circuit 12,
the non-azeotropic mixed refrigerant including R245fa, R600, R23
and R14, the non-azeotropic mixed refrigerant including R245fa,
R600, R116 and R14, the non-azeotropic mixed refrigerant including
R245fa, R600, R508A and R14 or the non-azeotropic mixed refrigerant
including R245fa, R600, R508B and R14. However, the present
invention is not limited to this embodiment, and the present
invention is also effective, when a single refrigerant is used.
Embodiment 2
[0069] Next, a refrigerating apparatus of another embodiment of the
present invention will be described with reference to FIG. 6. FIG.
6 is a refrigerant circuit diagram of the embodiment having a
constitution of the refrigerating apparatus for the ultralow
temperature refrigerator 1 of FIG. 1. In this case, compressors 54
and 84 and the like constituting the refrigerant circuit of a
refrigerating apparatus R2 are installed in a mechanical chamber
(not shown) positioned in the lower part of an insulating box
member 2 of the ultralow temperature refrigerator 1, and an
evaporator (a refrigerant piping line) 83 is attached to the
peripheral surface of an inner box 4 on an insulating material 7
side in a heat exchange manner, similarly to the evaporator 13 of
Embodiment 1 described above.
[0070] The refrigerant circuit of the refrigerating apparatus R2 of
the present embodiment is a multiunit (two units) single stage
refrigerant circuit constituted of a high temperature side
refrigerant circuit 52 and a low temperature side refrigerant
circuit 82 constituting independent closed refrigerant circuits,
respectively. The compressor 54 constituting the high temperature
side refrigerant circuit 52 is an electromotive compressor using a
single phase or three phase alternator. The compressor 54 is
connected to a disperse heater 60, and has a constitution which
once discharges a refrigerant compressed by the compressor 54 to
the outside to radiate heat, returns the refrigerant into a shell
of a sealed container and again discharges the refrigerant to a
refrigerant discharge tube 71. The refrigerant discharge tube 71
connected to the compressor 54 on a discharge side thereof is
connected to a preliminary condenser 61. The preliminary condenser
61 is connected to a frame pipe 62 for heating the opening edge of
a storage chamber 8 to prevent dew condensation. The refrigerant
piping line exiting from the frame pipe 62 is connected to an oil
cooler 84C of the compressor 84 constituting the low temperature
side refrigerant circuit 82, and is then connected to a condenser
55.
[0071] Moreover, the refrigerant piping line exiting from the
condenser 55 is connected to a high temperature side dehydrator (a
dry core) 57 and a capillary tube 58. The dehydrator 57 is water
removal means for removing water from the high temperature side
refrigerant circuit 52. Moreover, the capillary tube 58 is passed
through a part (72A) of a suction piping line 72 exiting from a
high temperature side evaporator 59 of a cascade heat exchanger 56
and returning to the compressor 54.
[0072] Specifically, the capillary tube 58 is passed through the
piping line 72A as a part of the suction piping line 72 positioned
on the discharge side of the evaporator 59 and on the suction side
of an accumulator 68, to constitute a double tube structure as
shown in FIG. 3. According to such a double tube structure, it is
possible to perform heat exchange between the refrigerant flowing
through the capillary tube 58 inside a double tube 67 (hereinafter
referred to as the double tube structure) and the refrigerant
flowing from the evaporator 83 through the piping line 72A outside
the capillary tube.
[0073] The double tube structure 67 is manufactured by a method
similar to that of the double tube structure 25 described above in
Embodiment 1. That is, first, the linearly tubular capillary tube
58 is passed through the linearly tubular piping line 72A having a
comparatively large diameter. Next, such a double tube is spirally
wound as much as a plurality of stages. At this time, the tube is
wound so that the axial center of the piping line 72A coincides
with the axial center of the capillary tube 58 as much as possible,
to form the spiral double tube. In consequence, a gap is formed
between the inner wall surface of the piping line 72A and the outer
wall surface of the capillary tube 58 as consistently as possible.
In this way, the double tube is spirally wound as much as the
plurality of stages to form the spiral double tube structure,
thereby enabling miniaturization while sufficiently acquiring the
length of the capillary tube 58 and sufficiently acquiring such a
heat exchange portion of the double tube structure.
[0074] Next, cap-like connection piping lines (not shown) having
both end holes and side holes are attached to both ends of the
piping line 72A, the ends of the capillary tube 58 are drawn from
the side holes, respectively, and then the side holes are welded
and sealed. Furthermore, one end of the connection piping line
attached to the one end of the piping line 72A and a connecting
portion of the piping line 72A are welded, the other end of the
connection piping line is connected to the suction piping line 72
connected to the evaporator 59 on the discharge side thereof, and
this connecting portion is welded. Similarly, one end of the
connection piping line attached to the other end of the piping line
72A and a connecting portion of the piping line 72A are welded, the
other end of the connection piping line is connected to the suction
piping line 72 leading to the accumulator 68, and this connecting
portion is welded. Moreover, the outer periphery of the piping line
72A formed in such a double tube structure is surrounded with an
insulating material (not shown), whereby the double tube structure
67 of the present embodiment can be obtained.
[0075] In this way, the capillary tube 58 is passed through the
suction piping line 72 (the piping line 72A) to constitute the
double tube structure, thereby performing heat exchange between the
refrigerant flowing through the capillary tube 58 and the
refrigerant flowing through the suction piping line 72 (the piping
line 72A) by conduction of heat transmitted along the wall surface
of the whole periphery of the capillary tube 58. In consequence, a
heat exchange performance can remarkably be improved as compared
with a conventional structure in which a capillary tube is attached
to the outer peripheral surface of a suction piping line.
[0076] Furthermore, the whole outer periphery of the piping line
72A having the double tube structure is surrounded with the
insulating material as described above, whereby the structure is
not easily influenced by the heat from the outside. Moreover, it is
possible to further improve the ability of the heat exchange
between the refrigerant in the piping line 72A and the refrigerant
in the capillary tube 58. Furthermore, the refrigerant is allowed
to flow through the capillary tube 58 inside the double tube
structure and through the suction piping line 72 (the piping line
72A) outside the capillary tube 58 so as to form the counter flow
of the refrigerant, whereby the heat exchange ability in the double
tube structure 67 can further be improved.
[0077] Moreover, the refrigerant piping line exiting from the
capillary tube 58 is connected to the high temperature side
evaporator 59 disposed in a heat exchange manner with respect to an
evaporator 85 of the low temperature side refrigerant circuit 82.
The high temperature side evaporator 59 constitutes the cascade
heat exchanger 56 together with the evaporator 85 of the low
temperature side refrigerant circuit 82.
[0078] The suction piping line 72 exiting from the high temperature
side evaporator 59 is connected to the compressor 54 on the suction
side successively through a high temperature side header 66, the
double tube structure 67, the accumulator 68 and a check valve
69.
[0079] In the high temperature side refrigerant circuit 52, R404A
is introduced as the refrigerant. R404A comprises R125
(pentafluoroethane: CHF.sub.2CF.sub.3), R143a
(1,1,1-trifluoroethane: CH.sub.3CF.sub.3) and R134a
(1,1,1,2-tetrafluoroethane: CH.sub.2FCF.sub.3), and a composition
thereof includes 44% by weight of R125, 52% by weight of R143a and
4% by weight of R134a. This mixed refrigerant has a boiling point
of -46.5.degree. C.
[0080] It is to be noted that the refrigerant introduced in the
high temperature side refrigerant circuit 52 is not limited to
R404A described above. For example, also when R407C as a mixed
refrigerant of three types R134a, R32 (difluoromethane:
CH.sub.2F.sub.2) and R125 is introduced as the refrigerant, the
present invention is effective.
[0081] In FIG. 6, broken-line arrows show the flow of the
refrigerant circulating through the high temperature side
refrigerant circuit 52. That is, a high temperature gaseous
refrigerant discharged from the compressor 54 is once discharged
from the sealed container to the disperse heater 60 through a
refrigerant discharge tube on a disperse heater 60 side, radiates
heat and again returns into the shell of the sealed container. In
consequence, the inside of the sealed container can be cooled by
the refrigerant which has radiated the heat in the disperse heater
60 to lower the temperature thereof. Moreover, such a high
temperature gaseous refrigerant is discharged from the sealed
container through the refrigerant discharge tube 71, condensed by
the preliminary condenser 61, the frame pipe 62, the oil cooler 84C
of the compressor 84 of the low temperature side refrigerant
circuit 82 and the condenser 55 to radiate the heat, and is
liquefied, followed by removing the water contained in the
refrigerant by the dehydrator 57. Afterward, the refrigerant flows
into the capillary tube 58 of the double tube structure 67.
[0082] Here, the heat exchange between the refrigerant in the
capillary tube 58 and the refrigerant flowing through the suction
piping line 72 (the piping line 72A) disposed along the whole
periphery of the capillary tube 58 is performed by conduction of
heat transmitted along the wall surface of the whole periphery of
the capillary tube 58. Furthermore, the refrigerant has a pressure
thereof reduced while lowering the temperature, and flows into the
evaporator 59. Subsequently, in the evaporator 59, the refrigerant
R404A absorbs the heat from the refrigerant flowing through the
evaporator 85 of the cascade heat exchanger 56 to evaporate. At
this time, the refrigerant R404A evaporates to cool the refrigerant
flowing through the evaporator 85.
[0083] Afterward, the refrigerant which has evaporated in the
evaporator 59 exits from the high temperature side evaporator 59
through the suction piping line 72, flows into the double tube
structure 67 through the high temperature side header 66, and
performs heat exchange between the refrigerant and the refrigerant
flowing through the capillary tube 58. Then, the refrigerant
returns to the compressor 54 through the accumulator 68 and the
check valve 69.
[0084] On the other hand, the compressor 84 constituting the low
temperature side refrigerant circuit 82 is an electromotive
compressor using a single phase or three phase alternator in the
same manner as in the compressor 54 of the high temperature side
refrigerant circuit 52. The compressor 84 is connected to a
disperse heater 90, and has a constitution which once discharges
the refrigerant compressed by the compressor 84 to the outside to
radiate the heat, then returns the refrigerant into the shell of
the sealed container and again discharges the refrigerant to a
refrigerant discharge tube 101. The refrigerant discharge tube 101
connected to the compressor 84 on the discharge side is connected
to a preliminary condenser 91. The refrigerant piping line exiting
from the preliminary condenser 91 is connected to an oil separator
92. The oil separator 92 is connected to an oil return tube 103
returning to the compressor 84.
[0085] The refrigerant piping line exiting from the oil separator
92 leads to an inner heat exchanger 93. The inner heat exchanger 93
is a heat exchanger for performing heat exchange between the high
pressure side refrigerant compressed by the compressor 84 and
flowing toward a capillary tube 88 and the low pressure side
refrigerant evaporated in the evaporator 83 and returning to the
compressor 84.
[0086] The high pressure side refrigerant piping line passing
through the inner heat exchanger 93 is connected to the evaporator
85. The evaporator 85 constitutes the cascade heat exchanger 56
together with the high pressure side evaporator 59 of the high
temperature side refrigerant circuit 52 as described above. The
refrigerant piping line exiting from the evaporator 85 is connected
to a low temperature side dehydrator (a dry core) 87 and the
capillary tube 88. The dehydrator 87 is water removal means for
removing water from the low temperature side refrigerant circuit
82. Moreover, the capillary tube 88 is passed through a part (a
piping line 102A) of a suction piping line 102 exiting from the
evaporator 83 and returning to the compressor 84.
[0087] Specifically, the capillary tube 88 is passed through the
piping line 102A as a part of the suction piping line 102
positioned on the discharge side of the evaporator 83 and on the
suction side of the inner heat exchanger 93, to constitute the
double tube structure as shown in FIG. 3. In such a double tube
structure, it is possible to perform heat exchange between the
refrigerant flowing through the capillary tube 88 inside a double
tube (hereinafter referred to as the double tube structure) and the
refrigerant flowing from the evaporator 83 through the piping line
102A outside the capillary tube.
[0088] The double tube structure 95 is manufactured by a method
similar to that of the double tube structure 25 described above in
Embodiment 1. That is, first, the linearly tubular capillary tube
88 is passed through the linearly tubular piping line 102A having a
comparatively large diameter. Next, such a double tube is spirally
wound as much as a plurality of stages. At this time, the tube is
wound so that the axial center of the piping line 102A coincides
with the axial center of the capillary tube 88 as much as possible,
to form the spiral double tube. In consequence, a gap is formed
between the inner wall surface of the piping line 102A and the
outer wall surface of the capillary tube 88 as consistently as
possible. In this way, the double tube is spirally wound as much as
the plurality of stages to form the spiral double tube structure,
thereby enabling miniaturization while sufficiently acquiring the
length of the capillary tube 88 and sufficiently acquiring such a
heat exchange portion of the double tube structure.
[0089] Next, cap-like connection piping lines (not shown) having
both end holes and side holes are attached to both ends of the
piping line 102A, the ends of the capillary tube 88 are drawn from
the side holes, respectively, and then the side holes are welded
and sealed. Furthermore, one end of the connection piping line
attached to the one end of the piping line 102A and a connecting
portion of the piping line 102A are welded, the other end of the
connection piping line is connected to the suction piping line 102
connected to the evaporator 83 on the discharge side thereof, and
this connecting portion is welded. Similarly, one end of the
connection piping line attached to the other end of the piping line
102A and a connecting portion of the piping line 102A are welded,
the other end of the connection piping line is connected to the
suction piping line 102 leading to the inner heat exchanger 93, and
this connecting portion is welded. Moreover, the outer periphery of
the piping line 102A formed in such a double tube structure is
surrounded with an insulating material 105, whereby the double tube
structure 95 of the present embodiment can be obtained.
[0090] In this way, the capillary tube 88 is passed through the
suction piping line 102 (the piping line 102A) to constitute the
double tube structure, thereby performing heat exchange between the
refrigerant flowing through the capillary tube 88 and the
refrigerant flowing through the suction piping line 102 (the piping
line 102A) by the conduction of the heat transmitted along the wall
surface of the whole periphery of the capillary tube 88. In
consequence, a heat exchange performance can remarkably be improved
as compared with a conventional structure in which the capillary
tube is attached to the outer peripheral surface of the suction
piping line.
[0091] Furthermore, the whole outer periphery of the piping line
102A having the double tube structure is surrounded with the
insulating material 105 as described above, whereby the structure
is not easily influenced by the heat from the outside. Moreover, it
is possible to further improve the ability of the heat exchange
between the refrigerant in the piping line 102A and the refrigerant
in the capillary tube 88. Furthermore, the refrigerant is allowed
to flow through the capillary tube 88 inside the double tube
structure and through the suction piping line 102 (the piping line
102A) outside the capillary tube 88 so as to form the counter flow
of the refrigerant, whereby the heat exchange ability in the double
tube structure 95 can further be improved.
[0092] The double tube structure 95 is removably received in the
insulating material 7 under the inner box 4 on the back surface
side thereof in the same manner as in the double tube structure 25
of Embodiment 1.
[0093] On the other hand, the refrigerant piping line 102 exiting
from the capillary tube 95 is connected to the compressor 84 on the
suction side through the inner heat exchanger 93. The compressor 84
is further connected to a refrigerant piping line 106, and the
refrigerant piping line 106 is connected to expansion tanks 107 in
which the refrigerant is stored at the stop of the compressor 84
through a capillary tube 108 as a pressure reducing unit.
[0094] On the other hand, in the low temperature side refrigerant
circuit 82, R508A is introduced as the refrigerant. R508A comprises
R23 (trifluoromethane: CHF.sub.3) and R116 (hexafluoroethane:
CF.sub.3CF.sub.3), and a composition thereof includes 39% by weight
of R23 and 61% by weight of R116. This mixed refrigerant has a
boiling point of -85.7.degree. C.
[0095] It is to be noted that the refrigerant introduced in the low
temperature side refrigerant circuit 82 is not limited to R508A
described in the present embodiment. For example, also when R508B
(R23/R116:46/54) having a different mixture ratio of R23 and R116
is used in place of R508A, the present invention is effective.
[0096] In FIG. 6, solid-line arrows show the flow of the
refrigerant circulating through the low temperature side
refrigerant circuit 82. The flow of the refrigerant in the low
temperature side refrigerant circuit 82 will specifically be
described. The high temperature gaseous refrigerant discharged from
the compressor 84 is once discharged from the sealed container to
the disperse heater 90 through a refrigerant discharge tube on a
disperse heater 90 side, radiates heat and again returns into the
shell of the sealed container. In consequence, the inside of the
sealed container can be cooled by the refrigerant which has
radiated the heat in the disperse heater 90 to lower the
temperature thereof. Moreover, such a high temperature gaseous
refrigerant is discharged from the sealed container through the
refrigerant discharge tube 101, radiates the heat in the
preliminary condenser 91, and flows into the oil separator 92.
[0097] A large part of the lubricant oil of the compressor 84 mixed
with the refrigerant in the oil separator 92 and a part of the
refrigerant condensed and liquefied in the preliminary condenser 91
are returned to the compressor 84 through the oil return tube 103.
On the other hand, the refrigerant discharged from the oil
separator 92 is condensed to radiate the heat and is liquefied by
the inner heat exchanger 93 and the evaporator 85. Afterward, the
water contained in the refrigerant is removed by the low
temperature side dehydrator 87, and the refrigerant flows into the
capillary tube 88.
[0098] Here, the heat exchange between the refrigerant in the
capillary tube 88 and the refrigerant flowing through the suction
piping line 102 (the piping line 102A) disposed along the whole
periphery of the capillary tube 88 is performed by the conduction
of the heat transmitted along the wall surface of the whole
periphery of the capillary tube 88. Furthermore, the refrigerant
has a pressure thereof reduced while lowering the temperature, and
flows into the evaporator 83. Subsequently, in the evaporator 83,
the refrigerant R508A absorbs the heat from the ambient atmosphere
to evaporate. At this time, the refrigerant R508A evaporates in the
evaporator 83 to exert a cooling function, thereby cool the
periphery of the evaporator 83 to an ultralow temperature in a
range of -86.degree. C. to -87.degree. C. In this case, the
evaporator (the refrigerant piping line) 83 is wound along the
inner box 4 on the insulating material 7 side in the heat exchange
manner as described above, whereby the inside of the storage
chamber 8 of the ultralow temperature refrigerator 1 is set to an
in-chamber temperature below -80.degree. C. by such cooling of the
evaporator 83.
[0099] Afterward, the refrigerant evaporated in the evaporator 83
is discharged from the evaporator 83 through the suction piping
line 102, and returns to the compressor 84 through the double tube
structure 95 and the inner heat exchanger 93 as described
above.
[0100] On the other hand, the ON-OFF control of the compressor 84
constituting the low temperature side refrigerant circuit 82 is
performed by a control apparatus (not shown) based on the
in-chamber temperature of the storage chamber 8. In this case, when
the operation of the compressor 84 is stopped by the control
apparatus, the mixed refrigerant in the low temperature side
refrigerant circuit 82 is collected in the expansion tanks 107
through the refrigerant piping line 106 and the capillary tube
108.
[0101] In consequence, the pressure in the refrigerant circuit 82
can be prevented from rising. Moreover, when the compressor 84 is
started by the control apparatus, the refrigerant is gradually
returned from the expansion tanks 107 into the compressor 84, which
can alleviate a start load on the compressor 84.
[0102] As described above in detail, the capillary tube 88 is
passed through the suction piping line 102 (the piping line 102A)
through which the refrigerant returning from the evaporator 83 to
the compressor 84 flows, to constitute the double tube structure,
whereby the efficiency of the heat exchange between the refrigerant
in the piping line 102A and the refrigerant in the capillary tube
88 can be enhanced to improve the performance.
[0103] In particular, as in the present invention, the capillary
tube 88 is passed through the piping line 102A of the suction
piping line 102 just exiting from the evaporator 83, to constitute
the double tube structure which enables the heat exchange by the
conduction of the heat transmitted along the wall surface of the
whole periphery of the capillary tube 88. In consequence, the
refrigerant returning from the evaporator 83 can efficiently cool
the refrigerant having the lowest boiling point, and hence the
performance can remarkably be improved. Therefore, the present
invention is especially effective in the ultralow temperature
refrigerator 1 of the present embodiment.
[0104] Furthermore, the piping line 102A formed in the double tube
structure by passing the capillary tube 88 therethrough is
surrounded with the insulating material 105, whereby the heat
exchange efficiency can further be enhanced. In addition, the flow
of the refrigerant through the capillary tube 88 and the flow of
the refrigerant through the piping line 102A outside the capillary
tube 88 form the counter flow, whereby the heat exchange ability
can further be improved.
[0105] Additionally, in the present embodiment, the capillary tube
58 as pressure reducing means of the high temperature side
refrigerant circuit 52 is also formed in the double tube structure
in the same manner as in capillary tube 88 of the low temperature
side refrigerant circuit 82, and the piping line 72A having such a
double tube structure is surrounded with the insulating material.
Furthermore, the flow of the refrigerant becomes the counter flow
in the capillary tube 58 inside the double tube structure and the
suction piping line 72 (the piping line 72A) outside the capillary
tube 58. In consequence, the refrigerant returning from the
evaporator 59 can efficiently cool the refrigerant in the capillary
tube 58. Consequently, the heat exchange efficiency can further be
enhanced to further improve the performance.
[0106] Generally according to the present invention, it is possible
to realize the ultralow temperature refrigerator 1 in which the
inside of the storage chamber 8 can more efficiently be cooled to a
desirable ultralow temperature. In particular, according to the
present invention, energy saving of about 15% to 20% can be
achieved as compared with a similarly used conventional
refrigerating apparatus. Moreover, the ambient temperature of the
evaporator 13 has heretofore been about -83.degree. C., but
according to the above structure of the present invention, a lower
temperature in a range of -86.degree. C. to -87.degree. C. can be
realized. In consequence, even when a compressor having a 200 V
specification and heretofore used as the compressor of the low
temperature side refrigerant circuit 82 is changed to a compressor
having a smaller capability and having 115 V specification, a
sufficient performance can be acquired. In consequence, further
decrease of power consumption and miniaturization of the apparatus
can be achieved.
Embodiment 3
[0107] Next, a refrigerating apparatus of a further embodiment of
the present invention will be described with reference to FIG. 7.
FIG. 7 is a refrigerant circuit diagram of the embodiment having a
constitution of the refrigerating apparatus for the ultralow
temperature refrigerator 1 of FIG. 1. In this case, a compressor
114 and the like constituting the refrigerant circuit of
refrigerating apparatus R3 are installed in a mechanical chamber
(not shown) positioned in the lower part of an insulating box
member 2 of the ultralow temperature refrigerator 1, and an
evaporator (a refrigerant piping line) 113 is attached to the
peripheral surface of an inner box 4 on an insulating material 7
side in a heat exchange manner.
[0108] The refrigerant circuit of the refrigerating apparatus R3 of
the present embodiment is constituted of a single unit multistage
(two stages) refrigerant circuit 112 comprising the compressor 114,
a condenser 115, an evaporator 113, a single intermediate heat
exchanger 116 connected so that a refrigerant returning from the
evaporator 113 circulates therethrough and a plurality of capillary
tubes 118 and 135. The compressor 114 constituting the refrigerant
circuit 112 is an electromotive compressor using a single phase or
three phase alternator in the same manner as in the above
embodiments. A refrigerant discharge tube 131 connected to the
compressor 114 on a discharge side thereof is connected to a
preliminary condenser 121. The preliminary condenser 121 is
connected to a frame pipe 122 for heating the opening edge of the
storage chamber 8 to prevent dew condensation, an oil cooler 114C
of the compressor 114, and then the condenser 115. It is to be
noted that in the present embodiment, the preliminary condenser 121
and the condenser 115 have an constitution of an integral
condenser, and are cooled by a condensing fan 129 as a blower for
the condenser.
[0109] Moreover, the refrigerant piping line exiting from the
condenser 115 is connected to a flow diverter 130 via a dehydrator
(a dry core) 117. The dehydrator 117 is water removal means for
removing water from the refrigerant circuit 112. The flow diverter
130 is a gas-liquid separator for separating a refrigerant
condensed and liquefied while flowing through the preliminary
condenser 121, the frame pipe 122 and the condenser 115 from a
refrigerant which is not condensed yet and still has a liquid
state. A gas phase piping line 133 connected to the flow diverter
130 on a suction side (an outlet side) thereof to take a gas phase
refrigerant (the non-condensed refrigerant) separated by the flow
diverter 130 is connected to a condensing pipe 123.
[0110] The condensing pipe 123 constitutes the intermediate heat
exchanger 116 together with a preliminary evaporator 136. The
intermediate heat exchanger 116 reduces, by the capillary tube 135,
a pressure of the liquid phase refrigerant (the condensed
refrigerant) separated by the flow diverter 130, and allows the
refrigerant to flow through the preliminary evaporator 136 of the
intermediate heat exchanger 116 to evaporate the refrigerant
therein, thereby cooling the gas phase refrigerant (the
non-condensed refrigerant) flowing through the condensing pipe 123
to condense the refrigerant. The refrigerant piping line exiting
from the condensing pipe 123 is connected to the evaporator 113 via
the capillary tube (the capillary tube of the final stage) 118.
[0111] The capillary tube 118 is passed through a part (a piping
line 132A) of a suction piping line 132 exiting from the evaporator
113 to return to the compressor 114. Specifically, the capillary
tube 118 is passed through the piping line 132A as a part of the
suction piping line 132 positioned on the discharge side of the
evaporator 113 and on the suction side of the intermediate heat
exchanger 116, to constitute the double tube structure as shown in
FIG. 3. Such a double tube structure has a constitution which can
perform heat exchange between the refrigerant flowing through the
capillary tube 118 inside a double tube 125 (hereinafter referred
to as the double tube structure) and the refrigerant flowing from
the evaporator 113 through the piping line 132A outside the
capillary tube.
[0112] The double tube structure 125 is manufactured by a method
similar to that of the double tube structure 25 described above in
Embodiment 1. That is, first, the linearly tubular capillary tube
118 is passed through the linearly tubular piping line 132A having
a comparatively large diameter. Next, such a double tube is
spirally wound as much as a plurality of stages. At this time, the
tube is wound so that the axial center of the piping line 132A
coincides with the axial center of the capillary tube 118 as much
as possible, to form the spiral double tube. In consequence, a gap
is formed between the inner wall surface of the piping line 132A
and the outer wall surface of the capillary tube 118 as
consistently as possible. In this way, the double tube is spirally
wound as much as the plurality of stages to form the spiral double
tube structure, thereby enabling miniaturization while sufficiently
acquiring the length of the capillary tube 118 and sufficiently
acquiring such a heat exchange portion of the double tube
structure.
[0113] Next, cap-like connection piping lines (not shown) having
both end holes and side holes are attached to both ends of the
piping line 132A, the ends of the capillary tube 118 are drawn from
the side holes, respectively, and then the side holes are welded
and sealed. Furthermore, one end of the connection piping line
attached to the one end of the piping line 132A and a connecting
portion of the piping line 132A are welded, the other end of the
connection piping line is connected to the suction piping line 102
connected to the evaporator 113 on the discharge side thereof, and
this connecting portion is welded. Similarly, one end of the
connection piping line attached to the other end of the piping line
132A and a connecting portion of the piping line 132A are welded,
the other end of the connection piping line is connected to the
suction piping line 102 leading to the intermediate heat exchanger
116, and this connecting portion is welded. Moreover, the outer
periphery of the piping line 132A formed in such a double tube
structure is surrounded with an insulating material 140, whereby
the double tube structure 125 of the present embodiment can be
obtained.
[0114] In this way, the capillary tube 118 is passed through the
suction piping line 132 to constitute the double tube structure,
thereby performing heat exchange between the refrigerant flowing
through the capillary tube 118 and the refrigerant flowing through
the suction piping line 132 by conduction of heat transmitted along
the wall surface of the whole periphery of the capillary tube 118.
In consequence, a heat exchange performance can remarkably be
improved as compared with a conventional structure in which the
capillary tube is attached to the outer peripheral surface of the
suction piping line.
[0115] Furthermore, the whole outer periphery of the piping line
132A having the double tube structure is surrounded with the
insulating material 140 as described above, whereby the structure
is not easily influenced by the heat from the outside. Moreover, it
is possible to further improve the ability of the heat exchange
between the refrigerant in the piping line 132A and the refrigerant
in the capillary tube 118. In addition, the refrigerant is allowed
to flow through the capillary tube 118 inside the double tube
structure and through the suction piping line 132 (the piping line
132A) outside the capillary tube 118 so as to form the counter flow
of the refrigerant, whereby the heat exchange ability in the double
tube structure 125 can further be improved.
[0116] The double tube structure 125 is removably received in the
insulating material 7 under the inner box 4 on the back surface
side thereof in the same manner as in the double tube structures 25
and 95 of the above embodiments.
[0117] On the other hand, the suction piping line 132 exiting from
the evaporator 113 is connected to the preliminary evaporator 136
through the piping line 132A of the double tube structure 125.
Moreover, the suction piping line 132 exiting from the preliminary
evaporator 136 is connected to the compressor 114 on the suction
side thereof. Furthermore, an expansion tank 137 for storing the
refrigerant at the stop of the compressor 114 is interposed between
the compressor 114 and the preliminary evaporator 136 along the
suction piping line 132, via a capillary tube 138 as a pressure
reducing unit.
[0118] Moreover, a non-azeotropic mixed refrigerant constituted of
a plurality of types of mixed refrigerants having different boiling
points is introduced as a refrigerant in the refrigerant circuit
112. In the present embodiment, a non-azeotropic mixed refrigerant
comprising R245fa (1,1,1,-3,3-pentafluoropropane:
CF.sub.3CH.sub.2CHF.sub.2), R600 (butane:
CH.sub.3CH.sub.2CH.sub.2CH.sub.3), R23 (trifluoromethane:
CHF.sub.3) and R14 (tetrafluoromethane: CF.sub.4) is introduced in
the same manner as in Embodiment 1.
[0119] It is to be noted that the refrigerant introduced in the
refrigerant circuit 112 is not limited to the above non-azeotropic
mixed refrigerant including R245fa, R600, R23 and R14. For example,
a non-azeotropic mixed refrigerant including R245fa, R600, R116 and
R14, a non-azeotropic mixed refrigerant including R245fa, R600,
R508A and R14 or a non-azeotropic mixed refrigerant including
R245fa, R600, R508B and R14 may be introduced. Also when another
refrigerant is used, the present invention is effective.
[0120] In FIG. 7, arrows show the flow of the refrigerant
circulating through the refrigerant circuit 112. This will
specifically be described. A high temperature gaseous refrigerant
discharged from the compressor 114 is discharged from the sealed
container through the refrigerant discharge tube 131, and
successively flows through the preliminary condenser 121, the frame
pipe 122, the oil cooler 114C of the compressor 114 and the
condenser 115. The high temperature gaseous refrigerant discharged
from the compressor 114 radiates heat while flowing through the
preliminary condenser 121, the frame pipe 122, the oil cooler 114C
and the condenser 115, and the refrigerants (R245fa and R600)
having a high boiling point in the mixed refrigerant is condensed
and liquefied.
[0121] Subsequently, the water contained in the mixed refrigerant
discharged from the condenser 115 is removed by the dehydrator 117,
and the refrigerant flows into the flow diverter 130. At this time,
R23 and R14 in the mixed refrigerant, having a remarkably low
boiling point, are not condensed yet and have a gas state, and
R245fa and R600 having a high boiling point are condensed and
liquefied. Therefore, R23 and R14 are allowed to flow through the
gas phase piping line 133, and R245fa and R600 are separately
allowed to flow through a liquid phase piping line 134. The
refrigerant mixture which has flowed into the gas phase piping line
133 flows into the condensing pipe 123 constituting the
intermediate heat exchanger 116.
[0122] Moreover, the mixed refrigerant which has flowed into the
liquid phase piping line 134 has a pressure thereof reduced by the
capillary tube 135, and flows into the preliminary evaporator 136
constituting the intermediate heat exchanger 116 together with the
condensing pipe 123, to cool R23 and R14 flowing through the
condensing pipe 123 together with the low temperature refrigerant
returning from the evaporator 113. In consequence, R23 and R14
flowing through the condensing pipe 123 are condensed and
liquefied. Subsequently, in the intermediate heat exchanger 116,
condensed R23 and R14 then exit from the condensing pipe 123 to
flow into the capillary tube 118.
[0123] Here, heat exchange between the refrigerant in the capillary
tube 118 and the refrigerant flowing through the suction piping
line 132 (the piping line 132A) disposed along the whole periphery
of the capillary tube 118 is performed by conduction of heat
transmitted along the wall surface of the whole periphery of the
capillary tube 118. Furthermore, the refrigerant has a pressure
thereof reduced while further lowering the temperature, and flows
into the evaporator 113. Subsequently, in the evaporator 113, the
refrigerants R14 and R23 take the heat from the ambient atmosphere
to evaporate. At this time, the refrigerants R14 and R23 evaporate
in the evaporator 113 to exert a cooling function, thereby cooling
the periphery of the evaporator 113 to an ultralow temperature of
-85.degree. C. In this case, the evaporator (the refrigerant piping
line) 113 is wound along the inner box 4 on the insulating material
7 side in the heat exchange manner, whereby the inside of the
storage chamber 8 of the ultralow temperature refrigerator 1 can be
set to an in-chamber temperature below -80.degree. C. by such
cooling of the evaporator 113.
[0124] Subsequently, the refrigerant evaporated in the evaporator
113 exits from the evaporator 113 through the suction piping line
132, flows into the preliminary evaporator 136 of the intermediate
heat exchanger 116 through the double tube structure 125 described
above, and then joins the refrigerants (R245fa and R600) evaporated
in the preliminary evaporator 136 and having a high boiling point.
Afterward, the refrigerant exits from the preliminary evaporator
136 to return to the compressor 114.
[0125] On the other hand, ON-OFF control of the compressor 114
constituting the refrigerant circuit 112 is performed by a control
apparatus (not shown) based on the in-chamber temperature of the
storage chamber 8. In this case, when the operation of the
compressor 114 is stopped by the control apparatus, the mixed
refrigerant in the low temperature side refrigerant circuit 112 is
collected in the expansion tank 137 through the capillary tube
138.
[0126] In consequence, the pressure in the refrigerant circuit 112
can be prevented from rising. Moreover, when the compressor 114 is
started by the control apparatus, the refrigerant is gradually
returned from the expansion tank 137 into the refrigerant circuit
112 through the capillary tube 138, which can alleviate a start
load on the compressor 114.
[0127] As in the present embodiment described above in detail, the
capillary tube 118 is passed through the suction piping line 132
(the piping line 132A) through which the refrigerant returning from
the evaporator 113 to the compressor 114 flows, to constitute the
double tube structure, whereby the efficiency of the heat exchange
between the refrigerant in the piping line 132A and the refrigerant
in the capillary tube 118 can be enhanced to improve the
performance. In particular, as in the present invention, the
capillary tube 118 is passed through the piping line 132A of the
suction piping line 132 just exiting from the evaporator 113, to
constitute the double tube structure which enables the heat
exchange by the conduction of the heat transmitted along the wall
surface of the whole periphery of the capillary tube 118. In
consequence, the refrigerant returning from the evaporator 113 can
efficiently cool the refrigerant having the lowest boiling point,
and hence the performance can remarkably be improved. Therefore,
the present invention is especially effective in the ultralow
temperature refrigerator 1 of the present embodiment.
[0128] Furthermore, the piping line 132A formed in the double tube
structure by passing the capillary tube 118 therethrough is
surrounded with the insulating material 140, whereby the heat
exchange efficiency can further be enhanced. In addition, the flow
of the refrigerant through the capillary tube 118 and the flow of
the refrigerant through the suction piping line 132A outside the
capillary tube 118 form the counter flow, whereby the heat exchange
ability can further be improved.
[0129] Generally according to the present invention, it is possible
to realize the ultralow temperature refrigerator 1 in which the
inside of the storage chamber 8 can more efficiently be cooled to a
desirable ultralow temperature. In particular, according to the
present invention, energy saving of about 15% to 20% can be
achieved as compared with a similarly used conventional
refrigerating apparatus. Moreover, the ambient temperature of the
evaporator 113 can be set to a low temperature as compared with the
conventional apparatus. In consequence, even when the compressor is
changed to a compressor having a smaller capability than the
conventional compressor, a sufficient performance can be acquired.
In consequence, further decrease of power consumption and
miniaturization of the apparatus can be achieved.
[0130] It is to be noted that in the present embodiment, the only
refrigerant circuit 112 described above may constitute the
refrigerating apparatus R3 of the ultralow temperature refrigerator
1, but as shown in FIG. 7, in addition to the refrigerant circuit
112, a refrigerant circuit 152 having a circuit constitution
similar to the refrigerant circuit 112 may be disposed in parallel,
and the two refrigerant circuits 112 and 152 may constitute the
refrigerating apparatus R3 of the ultralow temperature refrigerator
1. The circuit constitution and refrigerant flow of the refrigerant
circuit 152 are similar to those of the refrigerant circuit 112
described above, and hence the constitution is denoted with the
same reference numerals as those of the members constituting the
refrigerant circuit 112. That is, the members denoted with the same
reference numerals as those of the refrigerant circuit 112 produce
the same or similar effect or function, and hence description
thereof is omitted here.
[0131] A compressor 114 and the like constituting the refrigerant
circuit 152 are installed in a mechanical chamber (not shown)
positioned in the lower part of the insulating box member 2 of the
ultralow temperature refrigerator 1 in the same manner as in the
compressor 114 of the refrigerant circuit 112, and an evaporator
113 of the refrigerant circuit 152 is also attached to the
peripheral surface of the inner box 4 on the insulating material 7
side in the heat exchange manner, similarly to the evaporator 113
of the refrigerant circuit 112. Furthermore, refrigerants
introduced in the refrigerant circuit 152 and circulation of the
refrigerants are similar to those of the refrigerant circuit 112
described above, and hence description thereof is omitted here.
[0132] In this way, in a case where the refrigerating apparatus R3
of the ultralow temperature refrigerator 1 has a constitution in
which two independent refrigerant circuits 112 and 152 having
substantially the same performance are arranged side by side, when
one of the refrigerant circuits breaks down, the other refrigerant
circuit can be used as a backup. That is, for example, even when
the refrigerant circuit 112 breaks down, the refrigerant circuit
152 is operated without any trouble, and the evaporator 113 of the
refrigerant circuit 152 can keep the inside of the storage chamber
8 at the ultralow temperature. In consequence, reliability of the
ultralow temperature refrigerator 1 can be enhanced.
[0133] It is to be noted that in the present embodiment, each
refrigerant circuit constituting the refrigerating apparatus is
described as the refrigerant circuit for the single unit two stage
system refrigerating apparatus R3, comprising the compressor 114,
the condenser 115, the evaporator 113, the single intermediate heat
exchanger 116 connected so that the refrigerant returning from the
evaporator 113 circulates therethrough and the plurality of
specifically, two capillary tubes 135 and 118. The plurality of
types of non-azeotropic mixed refrigerants are introduced, the
condensed refrigerant of the refrigerants passed through the
condenser 115 is allowed to join the intermediate heat exchanger
116 through the capillary tube 135, and the non-condensed
refrigerant of the refrigerants is cooled in the intermediate heat
exchanger 116, whereby the refrigerant having a lower boiling point
is condensed, and the refrigerant having the lowest boiling point
is evaporated by the evaporator 113 through the capillary tube 118
of the final stage to exert the cooling function. However, the
present invention is not limited to this embodiment, and, for
example, a plurality of intermediate heat exchangers may be
connected in series to constitute the circuit.
Embodiment 4
[0134] Next, a refrigerating apparatus of a still further
embodiment of the present invention will be described with
reference to FIG. 8. FIG. 8 is a refrigerant circuit diagram of the
embodiment having a constitution of the refrigerating apparatus for
the ultralow temperature refrigerator 1 of FIG. 1. In this case,
compressors 214 and 254 and the like constituting the refrigerant
circuit of a refrigerating apparatus R4 are installed in a
mechanical chamber (not shown) positioned in the lower part of an
insulating box member 2 of the ultralow temperature refrigerator 1,
and an evaporator (a refrigerant piping line) 253 is attached to
the peripheral surface of an inner box 4 on an insulating material
7 side in a heat exchange manner, similarly to the evaporators 13,
83 and 113 of the above embodiments.
[0135] The refrigerant circuit of the refrigerating apparatus R4 of
the present embodiment is a multiunit multistage refrigerant
circuit, i.e., a two-unit two-stage refrigerant circuit comprising
a high temperature side refrigerant circuit 212 and a low
temperature side refrigerant circuit 252 constituting independent
refrigerant closed circuits, respectively. The compressor 214
constituting the high temperature side refrigerant circuit 212 is
an electromotive compressor using a single phase or three phase
alternator. A refrigerant discharge tube 231 connected to the
compressor 214 on a discharge side thereof is connected to a
preliminary condenser 221. The preliminary condenser 221 is
connected to a frame pipe 222 for heating the opening edge of a
storage chamber 8 to prevent dew condensation.
[0136] The frame pipe 222 is connected to an oil cooler 214C of the
compressor 214, and is then connected to a condenser 215. Moreover,
the refrigerant piping line exiting from the condenser 215 is
connected to an oil cooler 254C constituting the low temperature
side refrigerant circuit 252, and is then connected to a condenser
223. The refrigerant piping line exiting from the condenser 223 is
connected to a high temperature side evaporator 213 as an
evaporator portion constituting the evaporator of the high
temperature side refrigerant circuit 212 successively via a drier
(a dry core) 217 and a capillary tube 218 as a pressure reducing
unit.
[0137] The high temperature side evaporator 213 constitutes a
cascade heat exchanger 216 together with a condensing pipe 255 as a
condenser of the low temperature side refrigerant circuit 252. A
suction piping line 232 exiting from the preliminary evaporator 213
is connected to an accumulator 228 as a refrigerant liquid storage,
and the suction piping line 232 exiting from the accumulator 228 is
connected to the oil cooler 214C on the suction side. It is to be
noted that in the present embodiment, the preliminary condenser 221
and the condensers 215 and 223 have a constitution of an integral
condenser, and are cooled by a condensing fan 229 as a blower for
the condensers.
[0138] A refrigerant comprising R407D and n-pentane is charged as a
non-azeotropic refrigerant in the high temperature side refrigerant
circuit 212. R407D comprises R32 (difluoromethane:
CH.sub.2F.sub.2), R125 (pentafluoroethane: CHF.sub.2CF.sub.3) and
R134a (1,1,1,2-tetrafluoroethane: CH.sub.2FCF.sub.3), and a
composition of the refrigerant includes 15% by weight of R32, 15%
by weight of R125 and 70% by weight of R134a. As to boiling points
of the refrigerants, R32 has -51.8.degree. C., R125 has
-48.57.degree. C. and R134a has -26.16.degree. C. Moreover,
n-pentane has a boiling point of +36.1.degree. C.
[0139] In such a constitution, a high temperature gaseous
refrigerant discharged from the compressor 214 is condensed,
radiates heat and is liquefied by the preliminary condenser 221,
the frame pipe 222, the oil cooler 214C, the condenser 215, the oil
cooler 254C of the compressor 254 of the low temperature side
refrigerant circuit 252 and the condenser 223, water contained in
the refrigerant is removed by the drier 217, and then the
refrigerant flows into the capillary tube 218. Subsequently, the
refrigerant having the pressure thereof reduced by the capillary
tube 218 flows into the high temperature side evaporator 213
constituting the cascade heat exchanger 216. In the high
temperature side evaporator 213, the refrigerants R32, R125 and
R134a absorb the heat from the refrigerant flowing through the
condensing pipe 255 to evaporate. At this time, in the cascade heat
exchanger 216, the refrigerant of the high temperature side
evaporator 213 of the high temperature side refrigerant circuit 212
evaporates, thereby cooling the refrigerant flowing through the
condensing pipe 255 in the low temperature side refrigerant circuit
252.
[0140] Subsequently, the refrigerant evaporated by the high
temperature side evaporator 213 exits from the evaporator 213
through the suction piping line 232, and then returns to the
compressor 214 through the accumulator 228.
[0141] At this time, the compressor 214 has a capability of, for
example, 1.5 HP, and the finally reaching temperature of the high
temperature side evaporator 213 which is being operated is in a
range of -27.degree. C. to -35.degree. C. At such a low
temperature, the boiling point of n-pentane in the refrigerant is
+36.1.degree. C., and hence the refrigerant does not evaporate and
still has a liquid state in the high temperature side evaporator
213. Therefore, the refrigerant hardly contributes to the cooling.
However, the refrigerant has a function of returning, to the
compressor 214, a lubricant of the compressor 214 or mixed water
which cannot be absorbed by the drier 217 in a state where the
water is dissolved in the refrigerant, and the liquid refrigerant
has a function of evaporating in the compressor 214 to lower the
temperature of the compressor 214.
[0142] On the other hand, the low temperature side refrigerant
circuit 252 comprises the compressor 254, the condensing pipe (the
condenser) 255, the evaporator 253, a plurality of intermediate
heat exchanges 262, 266, 270 and 272 connected so that the
refrigerant returning from the evaporator 253 circulates
therethrough, and a plurality of capillary tubes 264, 268 and 258.
Specifically, the compressor 254 constituting the low temperature
side refrigerant circuit 252 is an electromotive compressor using a
single phase or three phase alternator in the same manner as in the
compressor 214, and a refrigerant discharge tube 281 connected to
the compressor 254 on the discharge side is connected to an oil
separator 260 via a radiator 259 made of a wire condenser. The oil
separator 260 is connected to an oil return tube 287 returning to
the compressor 254. The refrigerant piping line connected to the
oil separator 260 on the discharge side is connected to the
condensing pipe 255 as a condenser constituting the cascade heat
exchanger 216 together with the high temperature side evaporator
213.
[0143] Moreover, the refrigerant piping line connected to the
condensing pipe 255 on the discharge side is connected to a first
gas-liquid separator 261 via a drier (a dry core) 257. The gas
phase refrigerant (the non-condensed refrigerant) separated by the
first gas-liquid separator 261 flows through the first intermediate
heat exchange 262 via a gas phase piping line 283, and flows into a
second gas-liquid separator 265. On the other hand, the liquid
phase refrigerant (the condensed refrigerant) separated by the
first gas-liquid separator 261 flows into the first intermediate
heat exchange 262 via a liquid phase piping line 284 through a
drier 263 and the capillary tube 268 as a pressure reducing unit.
The first intermediate heat exchange 262 allows the liquid phase
refrigerant (the condensed refrigerant) separated by the first
gas-liquid separator 261 to join the intermediate heat exchange 262
through the capillary tube 264. In the heat exchanger, the gas
phase refrigerant (the non-condensed refrigerant) flowing through
the gas phase piping line 283 is cooled, thereby condensing the
refrigerant having a lower boiling point.
[0144] The liquid phase refrigerant separated by the second
gas-liquid separator 265 flows through a drier 267 via a liquid
phase piping line 286, and then flows into the second intermediate
heat exchanger 266 through the capillary tube 268 as a pressure
reducing unit. Moreover, the gas phase refrigerant separated by the
second gas-liquid separator 265 flows through the second
intermediate heat exchanger 266 through a gas phase piping line
285. The second intermediate heat exchanger 266 allows the liquid
phase refrigerant (the condensed refrigerant) separated by the
second gas-liquid separator 265 to join the intermediate heat
exchanger 266 through the capillary tube 268. In the heat
exchanger, the gas phase refrigerant (the non-condensed
refrigerant) flowing through the gas phase piping line 285 is
cooled, thereby condensing the refrigerant having a lower boiling
point.
[0145] Next, the gas phase piping line 285 which has flowed through
the second intermediate heat exchanger 266 flows into the capillary
tube 258 as a pressure reducing unit through the third intermediate
heat exchanger 270, the fourth intermediate heat exchanger 272 and
a drier 274.
[0146] The capillary tube 258 is passed through a part (a piping
line 282A) of a suction piping line 282 exiting from the evaporator
253 and returning to the compressor 254. Specifically, the
capillary tube 258 is passed through the piping line 282A as a part
of the suction piping line 282 positioned on a discharge side of
the evaporator 253 and on a suction side of the fourth intermediate
heat exchanger 272, to constitute a double tube structure as shown
in FIG. 3. In such a double tube structure, it is possible to
perform heat exchange between the refrigerant flowing through the
capillary tube 258 inside a double tube 295 (hereinafter referred
to as the double tube structure) and the refrigerant flowing from
the evaporator 253 through the piping line 282A outside the
capillary tube.
[0147] The double tube structure 295 is manufactured by a method
similar to that of the double tube structure 25 described above in
Embodiment 1. That is, first, the linearly tubular capillary tube
258 is passed through the linearly tubular piping line 282A having
a comparatively large diameter. Next, such a double tube is
spirally wound as much as a plurality of stages. At this time, the
tube is wound so that the axial center of the piping line 282A
coincides with the axial center of the capillary tube 258 as much
as possible, to form the spiral double tube. In consequence, a gap
is formed between the inner wall surface of the piping line 282A
and the outer wall surface of the capillary tube 258 as
consistently as possible. In this way, the double tube is spirally
wound as much as the plurality of stages to form the spiral double
tube structure, thereby enabling miniaturization while sufficiently
acquiring the length of the capillary tube 258 and sufficiently
acquiring such a heat exchange portion of the double tube
structure.
[0148] Next, cap-like connection piping lines (not shown) having
both end holes and side holes are attached to both ends of the
piping line 282A, the ends of the capillary tube 258 are drawn from
the side holes, respectively, and then the side holes are welded
and sealed. Furthermore, one end of the connection piping line
attached to the one end of the piping line 282A and a connecting
portion of the piping line 282A are welded, the other end of the
connection piping line is connected to the suction piping line 282
connected to the evaporator 253 on the discharge side thereof, and
this connecting portion is welded. Similarly, one end of the
connection piping line attached to the other end of the piping line
282A and a connecting portion of the piping line 282A are welded,
the other end of the connection piping line is connected to the
suction piping line 282 leading to the fourth intermediate heat
exchanger 272, and this connecting portion is welded. Moreover, the
piping line 282A formed in such a double tube structure is
surrounded with an insulating material 297, whereby the double tube
structure 295 of the present embodiment can be obtained.
[0149] In this way, the capillary tube 258 is passed through the
suction piping line 282 to constitute the double tube structure,
thereby performing heat exchange between the refrigerant flowing
through the capillary tube 258 and the refrigerant flowing through
the suction piping line 282 by conduction of heat transmitted along
the wall surface of the whole periphery of the capillary tube 258.
In consequence, a heat exchange performance can remarkably be
improved as compared with a conventional structure in which a
capillary tube is attached to the outer peripheral surface of the
suction piping line.
[0150] Furthermore, the whole outer periphery of the piping line
282A having the double tube structure is surrounded with the
insulating material 297 as described above, whereby the structure
is not easily influenced by the heat from the outside. Moreover, it
is possible to further improve the ability of the heat exchange
between the refrigerant in the piping line 282A and the refrigerant
in the capillary tube 258. In addition, the refrigerant is allowed
to flow through the capillary tube 258 inside the double tube
structure and through the suction piping line 282 (the piping line
282A) outside the capillary tube 258 so as to form the counter flow
of the refrigerant, whereby the heat exchange ability in the double
tube structure 295 can further be improved.
[0151] The double tube structure 295 is removably received in the
insulating material 7 under the inner box 4 on the back surface
side thereof in the same manner as in the double tube structure 25
of Embodiment 1 described above.
[0152] On the other hand, the suction piping line 282 exiting from
the double tube structure 295 is successively connected to the
fourth intermediate heat exchanger 272, the third intermediate heat
exchanger 270, the second intermediate heat exchanger 266 and the
first intermediate heat exchange 262, and is then connected to the
compressor 254 on the suction side. Furthermore, expansion tanks
288 for storing the refrigerant at the stop of the compressor 254
are interposed between the compressor 254 and the first
intermediate heat exchange 262 along the suction piping line 282,
via a capillary tube 289 as a pressure reducing unit. Moreover, the
capillary tube 289 is connected to a check valve 290 so that the
direction of the expansion tanks 288 is a forward direction.
[0153] On the other hand, in the low temperature side refrigerant
circuit 252, a non-azeotropic mixed refrigerant including R245fa.
R600, R404A, R508, R14, R50 and R740 is introduced as a mixed
refrigerant of seven types of refrigerants having different boiling
points. R245fa is 1,1,1,-3,3-pentafluoropropane
(CF.sub.3CH.sub.2CHF.sub.2) and R600 is butane
(CH.sub.3CH.sub.2CH.sub.2CH.sub.3). R245fa has a boiling point of
+15.3.degree. C. and R600 has a boiling point of -0.5.degree. C.
Therefore, when these refrigerants are mixed at a predetermined
ratio, the refrigerant can be used in place of heretofore used R21
having a boiling point of +8.9.degree. C.
[0154] It is to be noted that R600 is a combustible substance.
Therefore, when the substance is mixed with incombustible R245fa at
a predetermined ratio, i.e., R245fa/R600=70/30 in the present
embodiment, the substance can be introduced as an incombustible
substance in the refrigerant circuit 252. It is to be noted that in
the present embodiment, the weight ratio of R245fa is 70% by weight
with respect to the total weight of R245fa and R600, but if the
weigh ratio is above this value, the refrigerant becomes
incombustible. Therefore, the weight ratio may be above the
value.
[0155] R404A comprises R125 (pentafluoroethane: CHF.sub.2CF.sub.3),
R143a (1,1,1-trifluoroethane: CH.sub.3CF.sub.3) and R134a
(1,1,1,2-tetrafluoroethane: CH.sub.2FCF.sub.3), and a composition
thereof includes 44% by weight of R125, 52% by weight of R143a and
4% by weight of R134a. The mixed refrigerant has a boiling point of
-46.48.degree. C. Therefore, the refrigerant can be used in place
of heretofore used R22 having a boiling point of -40.8.degree.
C.
[0156] R508 comprises R23 (trifluoromethane: CHF.sub.3) and R116
(hexafluoroethane: CF.sub.3CF.sub.3), and a composition thereof
includes 39% by weight of R23 and 61% by weight of R116. The mixed
refrigerant has a boiling point of -88.64.degree. C.
[0157] Moreover, R14 is tetrafluoromethane (carbon tetrafluoride:
CF.sub.4), R50 is methane (CH.sub.4) and R740 is argon (Ar). As to
boiling points of these refrigerants, R14 has -127.9.degree. C.,
R50 has -161.5.degree. C. and R740 has -185.86.degree. C. It is to
be noted that R50 might combine with oxygen to be in danger of
exploding. However, the refrigerant is mixed with R14, the danger
of the exploding is eliminated. Therefore, even if a leak accident
of the mixed refrigerant occurs, any explosion is not caused.
[0158] It is to be noted that as to these refrigerants, R245fa and
R600 and R14 and R50 are once mixed beforehand to obtain an
incombustible state. Afterward, the mixed refrigerant of R245fa and
R600, R404A, R508A, the mixed refrigerant of R14 and R50, and R740
are beforehand mixed, and then introduced in the refrigerant
circuit 252. Alternatively, R245fa and R600, next R404A, R508A, R14
and R50 and finally R740 are introduced in order from a higher
boiling point. The composition of the respective refrigerants
includes, for example, 10.3% by weight of the mixed refrigerant of
R245fa and R600, 28% by weight of R404A, 29.2% by weight of R508A,
26.4% by weight of the mixed refrigerant of R14 and R50 and 5.1% by
weight of R740.
[0159] It is to be noted that in the present embodiment, 4% by
weight of n-pentane may be added to R404A (in a range of 0.5 to 2%
by weight with respect to the total weight of the non-azeotropic
refrigerants).
[0160] Next, the circulation of the refrigerant through the low
temperature side refrigerant circuit 252 will be described. A high
temperature high pressure gaseous mixed refrigerant discharged from
the compressor 254 flows into the radiator 259 through the
refrigerant discharge tube 281, and radiates heat in the radiator,
whereby a part of n-pentane or R600 as an oil carrier refrigerant
having a high boiling point in the mixed refrigerant and having a
satisfactory solubility in oil is condensed and liquefied.
[0161] The mixed refrigerant discharged from the radiator 259 flows
into the oil separator 260, and a large part of lubricant oil of
the compressor 254 mixed with the refrigerant and a part of the
refrigerant condensed and liquefied in the radiator 259 (a part of
n-pentane or R600) are returned to the compressor 254 through the
oil return tube 287. In consequence, a low boiling point
refrigerant having a higher purity flows through the refrigerant
circuit 252 behind the cascade heat exchanger 216, whereby an
ultralow temperature can efficiently be obtained. Consequently,
even when the compressors 214 and 254 have the same capability, the
inside of the storage chamber 8 as a cooling target having a larger
capacity can be cooled to a predetermined ultralow temperature,
which enables the increase of a storage capacity without enlarging
the whole refrigerating apparatus R.
[0162] Here, in the present embodiment, the refrigerant which has
flowed into the oil separator 260 is once cooled in the radiator
259, and hence the temperature of the refrigerant flowing into the
cascade heat exchanger 216 can be lowered. Specifically,
heretofore, the temperature of the refrigerant flowing into the
cascade heat exchanger 216 has been about +65.degree. C., but in
the present embodiment, the temperature can be lowered to about
+45.degree. C.
[0163] Therefore, in the cascade heat exchanger 216, it is possible
to alleviate a load added to the compressor 214 of the high
temperature side refrigerant circuit 212 for cooling the
refrigerant in the low temperature side refrigerant circuit 252.
Moreover, the refrigerant in the low temperature side refrigerant
circuit 252 can effectively be cooled, and hence it is possible to
alleviate a load added to the compressor 254 constituting the low
temperature side refrigerant circuit 252. In consequence, the
operation efficiency of the whole refrigerating apparatus R4 can be
enhanced.
[0164] As to the other mixed refrigerants themselves, in the
cascade heat exchanger 216, a part of the refrigerant (a part of
R245fa, R600, R404A or R508) discharged from the high temperature
side evaporator 213, cooled to about -40.degree. C. to -30.degree.
C. and having a high boiling point in the mixed refrigerant is
condensed and liquefied. Subsequently, the mixed refrigerant
discharged from the condensing pipe 255 flows into the first
gas-liquid separator 261 through the drier 257. At this time, R14,
R50 and R740 in the mixed refrigerant have a remarkably low boiling
point, are not condensed yet and still have a gas state, and an
only part of R245fa, R600, R404A or R508 is condensed and
liquefied, whereby R14, R50 and R740 are diverted to the gas phase
piping line 283, and R245fa, R600, R404A and R508A are diverted to
the liquid phase piping line 284.
[0165] The refrigerant mixture which has flowed into the gas phase
piping line 283 is condensed by heat exchange between the mixture
and the first intermediate heat exchange 262, and then reaches the
second gas-liquid separator 265. In this separator, the low
temperature refrigerant returning from the evaporator (the
refrigerant piping line) 253 flows into the first intermediate heat
exchange 262, and the liquid refrigerant which has flowed into the
liquid phase piping line 284 has a pressure thereof reduced by the
capillary tube 264 through the drier 263. Afterward, the
refrigerant flows into the first intermediate heat exchange 262 to
evaporate therein, and hence contributes to the cooling. Therefore,
a part of non-condensed R14, R50, R740 or R508 is cooled, with the
result that an intermediate temperature of the first intermediate
heat exchange 262 becomes about -60.degree. C. Therefore, R508 in
the mixed refrigerant flowing through the gas phase piping line 283
is completely condensed and liquefied, and diverted to the second
gas-liquid separator 265. R14, R50 and R740 further have a low
boiling point and still have the gas state.
[0166] In the second intermediate heat exchanger 266, R508
separated by the second gas-liquid separator 265 has water therein
removed by the drier 267, has a pressure thereof reduced by the
capillary tube 268, flows into the second intermediate heat
exchanger 266, and then cools R14, R50 and R740 in the gas phase
piping line 285 together with the low temperature refrigerant
returning from the evaporator 253, to condense R14 having the
highest evaporation temperature in these refrigerants. In
consequence, the intermediate temperature of the second
intermediate heat exchanger 266 becomes about -90.degree. C.
[0167] The gas phase piping line 285 passing through the second
intermediate heat exchanger 266 subsequently passes through the
third intermediate heat exchanger 270 and the fourth intermediate
heat exchanger 272. Here, the refrigerant just discharged from the
evaporator 253 through the double tube structure 295 is returned to
the fourth intermediate heat exchanger 272. According to an
experiment, the intermediate temperature of the fourth intermediate
heat exchanger 272 reaches a considerably low temperature of about
-130.degree. C.
[0168] Here, heat exchange between the refrigerant in the capillary
tube 258 and the refrigerant flowing through the suction piping
line 282 (the piping line 282A) disposed along the whole periphery
of the capillary tube 258 is performed by the conduction of the
heat transmitted along the wall surface of the whole periphery of
the capillary tube 258, and the refrigerant further has a pressure
thereof reduced while lowering the temperature thereof, to flow
into the evaporator 253. Subsequently, in the evaporator 253, the
refrigerant takes the heat from the ambient atmosphere to
evaporate. According to the experiment, at this time, the ambient
temperature of the evaporator 253 is an ultralow temperature in a
range of -160.3.degree. C. to -157.3.degree. C.
[0169] In this way, the refrigerant still having a gas phase state
is successively condensed in the intermediate heat exchanges 262,
266, 270 and 272 by use of each refrigerant evaporation temperature
difference in the low temperature side refrigerant circuit 252,
whereby an ultralow temperature below -150.degree. C. can be
acquired in the evaporator 253 of the final stage. Consequently, in
a constitution in which the evaporator 253 is wound along the inner
box 4 on the insulating material 7 side in the heat exchange
manner, the inside of the storage chamber 8 can realize an
in-chamber temperature below -152.degree. C.
[0170] Afterward, the refrigerant evaporated in the evaporator 253
is discharged from the evaporator 253 through the suction piping
line 282, successively flows into the double tube structure 295,
the fourth intermediate heat exchanger 272, the third intermediate
heat exchanger 270, the second intermediate heat exchanger 266 and
the first intermediate heat exchange 262, joins the refrigerant
evaporated in each heat exchanger, and returns to the compressor
254.
[0171] The oil mixed in the refrigerant and discharged from the
compressor 254 has a large part thereof separated by the oil
separator 260 and is returned to the compressor 254, but mist-like
oil discharged from the oil separator 260 together with the
refrigerant is returned to the compressor 254 in a state where the
oil is dissolved in R600 having a high solubility in the oil. This
can prevent the compressor 254 from causing defective lubrication
or locking. Moreover, R600 still having the liquid state returns to
the compressor 254 to evaporate in the compressor 254, whereby the
discharge temperature of the compressor 254 can be lowered.
[0172] It is to be noted that ON-OFF control of the compressor 254
constituting the low temperature side refrigerant circuit 252 is
performed by a control apparatus (not shown) based on the
in-chamber temperature of the storage chamber 8. In this case, when
the operation of the compressor 254 is stopped by the control
apparatus, the mixed refrigerant in the low temperature side
refrigerant circuit 252 is collected in the expansion tanks 288
through the check valve 290 so that the direction of the expansion
tanks 288 is a forward direction.
[0173] Therefore, it is possible to remarkably rapidly collect the
refrigerant in the refrigerant circuit 252 into the expansion tanks
288 through the check valve 290 as compared with a case where the
refrigerant is collected in the expansion tanks 288 through the
capillary tube 289 at the stop of the compressor 254.
[0174] In consequence, the pressure in the refrigerant circuit 252
can be prevented from rising. When the compressor 254 is started by
the control apparatus, the refrigerant is gradually returned from
the expansion tanks 288 into the refrigerant circuit 252 through
the capillary tube 289, which can alleviate a start load on the
compressor 254.
[0175] Therefore, the refrigerant can rapidly be collected into the
expansion tanks 288 at the stop of the compressor 254, whereby the
pressure in the refrigerant circuit 252 can rapidly come to
equilibrium. When the compressor 254 is restarted, any load is not
applied to the compressor 254, but the compressor 254 can smoothly
be restarted. In consequence, a time required for obtaining an
equilibrium pressure in the refrigerant circuit 252 at the start of
the compressor can remarkably be shortened, whereby the operation
efficiency of the compressor 254 can be enhanced, and a time
required in, for example, a pull-down operation can be shortened to
enhance convenience.
[0176] As in the present invention described above in detail, the
capillary tube 258 is passed through the suction piping line 282
(the piping line 282A) through which the refrigerant returning from
the evaporator 253 to the compressor 254 flows, to constitute the
double tube structure, whereby the efficiency of the heat exchange
between the refrigerant in the piping line 282A and the refrigerant
in the capillary tube 258 can be enhanced to improve performance.
In particular, as in the present invention, the capillary tube 258
is passed through the piping line 282A of the suction piping line
282 just exiting from the evaporator 253 to constitute the double
tube structure, thereby enabling the heat exchange by the
conduction of the heat transmitted along the wall surface of the
whole periphery of the capillary tube 258, whereby the refrigerant
returning from the evaporator 253 efficiently can cool the
refrigerant having the lowest boiling point, to remarkably improve
the performance. Therefore, the present invention is especially
effective in the ultralow temperature refrigerator 1 of the present
embodiment.
[0177] Furthermore, the piping line 282A formed in the double tube
structure by passing the capillary tube 258 therethrough is
surrounded with the insulating material 297, whereby the heat
exchange efficiency can further be enhanced. In addition, the flow
of the refrigerant through the capillary tube 258 and the flow of
the refrigerant through the piping line 282A outside the capillary
tube 258 form the counter flow, whereby the heat exchange ability
can further be improved.
[0178] Generally, according to the present invention, the ultralow
temperature refrigerator 1 can be realized in which the inside of
the storage chamber 8 can efficiently be cooled to a desirable
ultralow temperature. In particular, according to the present
invention, energy saving of about 15% to 20% can be achieved as
compared with a similarly used conventional refrigerating
apparatus. Moreover, a lower temperature can be realized as the
ambient temperature of the evaporator 253 as compared with the
conventional apparatus. In consequence, even when the compressor is
changed to a compressor having a smaller capability than a
conventional compressor, a sufficient performance can be acquired.
In consequence, further decrease of power consumption and
miniaturization of the apparatus can be achieved.
[0179] It is to be noted that in the present embodiment, the only
capillary tube 258 of the final stage of the low temperature side
refrigerant circuit 252 is formed in the double tube structure of
the present invention, but the present invention is not limited to
this embodiment, and the present invention is effective even for a
double tube structure obtained by similarly passing the capillary
tube 218 of the high temperature side refrigerant circuit 212
through a part of the suction piping line 232 through which the
refrigerant returning from the evaporator 213 to the compressor 214
in the high temperature side refrigerant circuit 212 flows. In this
case, also in the high temperature side refrigerant circuit 212,
the ability of the heat exchange between the refrigerant in the
suction piping line 232 and the refrigerant in the capillary tube
218 can be improved. In consequence, the performance of the
refrigerating apparatus R4 can further be improved.
[0180] Moreover, in the present embodiment, the refrigerant circuit
constituting the refrigerating apparatus has been described as the
refrigerating apparatus R4 of the two unit multistage system
comprising the high temperature side refrigerant circuit 212 and
the low temperature side refrigerant circuit 252 to constitute
independent closed refrigerant circuits, each of which condenses a
refrigerant discharged from the compressor 214 or 254, reduces a
pressure of the refrigerant and evaporates the refrigerant by the
evaporator 213 or 253 to exert the cooling function. The low
temperature side refrigerant circuit 252 comprises the compressor
254, the condensing pipe 255, the evaporator 253, the plurality of,
i.e., four intermediate heat exchangers 262, 266, 270 and 272
connected in series so that the refrigerant returning from the
evaporator 253 circulates therethrough and the plurality of, i.e.,
three capillary tubes 264, 268 and 258. The plurality of types of
non-azeotropic mixed refrigerants are introduced. The refrigerating
apparatus allows the condensed refrigerant of the refrigerants
flowing through the condensing pipe 255 to join the refrigerants in
the intermediate heat exchangers through the capillary tubes, cools
a non-condensed refrigerant of the refrigerants in the intermediate
heat exchangers to successively condense the refrigerants having a
lower boiling point, and evaporates the refrigerant having the
lowest boiling point by the evaporator 253 through the capillary
tube 258 of the final stage to exert the cooling function.
Moreover, the evaporator 213 of the high temperature side
refrigerant circuit 212 and the condensing pipe 255 of the low
temperature side refrigerant circuit 252 constitute the cascade
heat exchanger 216, and the evaporator 253 of the low temperature
side refrigerant circuit 252 acquires the ultralow temperature.
However, the present invention is not limited to this embodiment,
and may be a refrigerating apparatus of a multiunit multistage
system. Moreover, the present invention is effective also for a
refrigerating apparatus of a two-unit single-stage system including
one gas-liquid separator and one intermediate heat exchanger.
DESCRIPTION OF REFERENCE NUMERALS
[0181] R refrigerating apparatus [0182] 1 ultralow temperature
refrigerator [0183] 2 insulating box member [0184] 7 insulating
material [0185] 8 storage chamber [0186] 9 insulating door [0187]
12 refrigerant circuit [0188] 13 evaporator [0189] 14 compressor
[0190] 15 condenser [0191] 16 heat exchanger (cascade condenser)
[0192] 18 capillary tube [0193] 21 preliminary condenser [0194] 22
frame pipe [0195] 23 condensing pipe [0196] 25 double tube
structure [0197] 31 refrigerant discharge tube [0198] 32 suction
piping line [0199] 32A piping line (constituting a part of the
suction piping line) [0200] 35 insulating material
* * * * *