U.S. patent application number 10/373217 was filed with the patent office on 2003-09-11 for vapor-compression type refrigerating machine and heat exchanger therefor.
Invention is credited to Honda, Tomoo, Takeuchi, Hirotsugu.
Application Number | 20030167793 10/373217 |
Document ID | / |
Family ID | 27784925 |
Filed Date | 2003-09-11 |
United States Patent
Application |
20030167793 |
Kind Code |
A1 |
Honda, Tomoo ; et
al. |
September 11, 2003 |
Vapor-compression type refrigerating machine and heat exchanger
therefor
Abstract
An oil repellent film 31a is formed on an inner wall of the tube
31. By the formation of the oil repellent film 31a, it becomes
possible to prevent refrigerating machine oil remaining in the
evaporator 30. Therefore, a sufficiently large quantity of
refrigerating machine oil can be returned to the compressor, and
the occurrence of seizing of the compressor can be prevented. As it
is possible to prevent refrigerating machine oil remaining in the
evaporator 30, while a reduction in the coefficient of heat
transfer between refrigerant and the tube is being prevented, it is
possible to prevent a substantial sectional area of the refrigerant
path of the tube 31 from decreasing. Therefore, an increase in the
pressure loss in the evaporator 30 can be prevented. Accordingly,
the heat absorbing property of the evaporator 30 can be
enhanced.
Inventors: |
Honda, Tomoo; (Obu-City,
JP) ; Takeuchi, Hirotsugu; (Nagoya-City, JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
27784925 |
Appl. No.: |
10/373217 |
Filed: |
February 24, 2003 |
Current U.S.
Class: |
62/500 ;
62/84 |
Current CPC
Class: |
F28F 13/187 20130101;
F28F 2245/04 20130101; F25B 43/02 20130101; F25B 2341/0012
20130101; F25B 39/02 20130101; F25B 41/00 20130101; F28F 13/18
20130101; F25B 2500/18 20130101 |
Class at
Publication: |
62/500 ;
62/84 |
International
Class: |
F25B 043/02; F25B
001/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 8, 2002 |
JP |
2002-063425 |
Claims
1. A heat exchanger applied to a vapor-compression type
refrigerating machine, an oil repellent film having an oil
repelling property being formed on an inner wall face of a tube
composing a refrigerant path.
2. A heat exchanger applied to an evaporator, which is one of the
heat exchangers provided in a vapor-compression type refrigerating
machine and exhibits a refrigerating capacity by evaporating
refrigerant, an oil repellent film having an oil repelling property
being formed on an inner wall face of a tube composing a
refrigerant path.
3. A heat exchanger according to claim 1, wherein surface tension
of material composing the oil repellent film is lower than that of
refrigerating machine oil mixed with refrigerant.
4. A heat exchanger according to claim 1, wherein material
composing the oil repellent film is silicon resin or
fluororesin.
5. A vapor-compression type refrigerating machine using an ejector,
comprising; a compressor for sucking and compressing refrigerant; a
radiator for cooling refrigerant discharged from the compressor; an
evaporator for evaporating refrigerant so as to absorb heat,
composed of a heat exchanger described in claim 1; a nozzle for
converting pressure energy of refrigerant of high pressure, which
has flowed out from the radiator, into velocity energy by expanding
refrigerant in a reduced pressure; an ejector including a boosting
section for boosting the pressure of refrigerant by converting
velocity energy into pressure energy when refrigerant of gas phase
evaporated in the evaporator is sucked by a flow of refrigerant of
high velocity injected from the nozzle and then refrigerant
injected by the nozzle and refrigerant sucked from the evaporator
are mixed with each other so as to convert velocity energy into
pressure energy; and a gas-liquid separator for separating
refrigerant into gas-phase refrigerant and liquid-phase refrigerant
and supplying the liquid-phase refrigerant to the evaporator and
also supplying gas-phase refrigerant to the compressor.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an evaporator used for a
vapor-compression type refrigerating machine in which heat is moved
from the low temperature side to the high temperature side. The
present invention is effectively applied to a vapor-compression
type refrigerating machine having an ejector by which suction
pressure of a compressor is increased when expansion energy of
refrigerant is converted into pressure energy while the refrigerant
is expanded while being decompressed.
[0003] 2. Description of the Related Art
[0004] Usually, in the vapor-compression type refrigerating
machine, sliding sections provided in the compressor are lubricated
when refrigerant mixed with refrigerating machine oil is circulated
in the refrigerating machine.
[0005] Therefore, refrigerating machine oil flows into a heat
exchanger, such as an evaporator, together with the refrigerant.
When refrigerating machine oil flowing into the heat exchanger
stays in the heat exchanger, the following problems may be
encountered.
[0006] (1) As a quantity of refrigerating machine oil returning to
the compressor is reduced, lubrication of the compressor becomes
incomplete, which causes seizing of the compressor.
[0007] (2) Refrigerating machine oil staying in the heat exchanger
adheres to the inner walls of the tubes of the heat exchanger, and
a substantial sectional area of the refrigerant path is reduced, so
that a pressure loss (refrigerant circulating resistance) is
increased in the heat exchanger, and the coefficient of heat
transfer between the refrigerant and the tubes is decreased. As a
result, the heat exchanging capacity of the heat exchanger is
lowered.
SUMMARY OF THE INVENTION
[0008] In view of the above problems, the present invention has
been accomplished. It is an object of the present invention to
solve the above problems described in the above items (1) and
(2).
[0009] In order to accomplish the above object, according to an
aspect of the present invention, there is provided a heat exchanger
applied to a vapor-compression type refrigerating machine, an oil
repellent film (31a) having an oil repelling property being formed
on an inner wall face of a tube (31) composing a refrigerant
path.
[0010] Due to the foregoing, it is possible to prevent
refrigerating machine oil from staying in the heat exchanger (30).
Therefore, a sufficiently large quantity of refrigerant machine oil
can be returned to the compressor. Accordingly, the occurrence of
trouble such as seizing of the compressor can be prevented.
[0011] As it is possible to prevent refrigerating machine oil from
staying in the heat exchanger (30), while the coefficient of heat
transfer between refrigerant and the tube (31) is prevented from
deteriorating, a substantial reduction of the sectional area of the
refrigerant path of the tube (31) can be prevented. Therefore, an
increase in the pressure loss in the heat exchanger (30) can be
prevented, and the heat exchanging capacity of the heat exchanger
(30) can be enhanced.
[0012] According to another aspect of the present invention, there
is provided a heat exchanger applied to an evaporator, which is one
of the heat exchangers provided in a vapor-compression type
refrigerating machine and which exhibits a refrigerating capacity
by evaporating refrigerant, an oil repellent film (31a) having an
oil repelling property being formed on an inner wall face of a tube
(31) composing a refrigerant path.
[0013] Due to the foregoing, it is possible to prevent
refrigerating machine oil from staying in the heat exchanger (30).
Therefore, a sufficiently large quantity of refrigerant machine oil
can be returned to the compressor. Accordingly, the occurrence of
trouble such as seizing of the compressor can be previously
prevented.
[0014] As it is possible to prevent refrigerating machine oil from
staying in the heat exchanger (30), while the coefficient of heat
transfer between refrigerant and the tube (31) is prevented from
deteriorating, a substantial reduction of the sectional area of the
refrigerant path of the tube (31) can be prevented. Therefore, an
increase in the pressure loss in the heat exchanger (30) can be
prevented, and the heat exchanging capacity of the heat exchanger
(30) can be enhanced.
[0015] In this connection, it is preferable that surface tension of
material composing the oil repellent film (31a) is lower than that
of refrigerating machine oil mixed with refrigerant.
[0016] It is preferable that material composing the repellent oil
film (31a) is silicon resin or fluororesin.
[0017] According to still another aspect of the present invention,
there is provided a vapor-compression type refrigerating machine
comprising; a compressor (10) for sucking and compressing
refrigerant; a radiator (20) for cooling refrigerant discharged
from the compressor (10); an evaporator (30) for evaporating
refrigerant so as to absorb heat, composed of a heat exchanger as
described before; a nozzle (41) for converting the pressure energy
of a refrigerant at high pressure, which has flowed out from the
radiator (20), into velocity energy by expanding refrigerant in a
reduced pressure; an ejector (40) including a boosting section (42,
43) for boosting the pressure of refrigerant by converting velocity
energy into pressure energy when refrigerant of a gas phase,
evaporated in the evaporator (30), is sucked by a flow of
refrigerant of high velocity injected from the nozzle (41) and then
the refrigerant injected by the nozzle (41) and the refrigerant
sucked from the evaporator (30) are mixed with each other so as to
convert velocity energy into pressure energy; and a gas-liquid
separator (50) for separating refrigerant into gas-phase
refrigerant and liquid-phase refrigerant and supplying the
liquid-phase refrigerant to the evaporator (30) and also supplying
gas-phase refrigerant to the compressor (10).
[0018] Due to the foregoing, it is possible to enhance the
operating efficiency of the vapor-compression type refrigerating
machine.
[0019] In this connection, numbers written in the parentheses after
each means represent an example of a corresponding relation of the
specific means in the embodiment described later.
[0020] The present invention may be more fully understood from the
description of preferred embodiments of the invention, as set forth
below, together with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In the drawings:
[0022] FIG. 1 is a view showing a model of an ejector cycle
relating to an embodiment of the present invention;
[0023] FIG. 2A is a perspective view of an evaporator applied to
the ejector cycle relating to the embodiment of the present
invention;
[0024] FIG. 2B is a sectional view of a tube;
[0025] FIG. 3 is a view showing a model of the ejector relating to
the embodiment of the present invention; and
[0026] FIG. 4 is a p-h diagram.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] In this embodiment, an ejector cycle of the present
invention is applied to an air-conditioner for vehicle use. FIG. 1
is a view showing a model of the ejector cycle.
[0028] In FIG. 1, the compressor 10 is a well known variable
displacement type compressor in which refrigerant is sucked and
compressed when power is supplied to the compressor from an engine.
The radiator 20 is a heat exchanger on the high pressure side for
exchanging heat between refrigerant, which has been discharged from
the compressor 10, and outside air so as to cool refrigerant.
[0029] In this connection, as chlorofluorocarbon is used as
refrigerant in this embodiment, the pressure of the refrigerant in
the radiator 20 is not higher than the critical pressure of the
refrigerant. Therefore, the refrigerant is condensed in the
radiator 20.
[0030] The evaporator 30 is a heat exchanger on the low pressure
side in which heat is exchanged between the air blowing out into a
room and the liquid phase refrigerant so that the liquid phase
refrigerant can be evaporated and the air blowing out into the room
can be cooled.
[0031] In this connection, as shown in FIG. 2A, the evaporator 30
is composed in such a manner that a plurality of tubes 31 composing
the refrigerant paths are serpentined and the thin sheet-shaped
fins 32, to increase the heat transfer area with respect to air,
are joined to the outer faces of the tubes 31.
[0032] As shown in FIG. 2B, on the inner wall face of each tube 31,
the oil repellent film 31a having an oil repelling property is
formed. This oil repellent films 31a is made of a material, the
surface tension of which is lower than that of refrigerating
machine oil. In this embodiment, the oil repellent film 31a is made
of silicon resin or fluororesin.
[0033] In this connection, refrigerating machine oil lubricates
sliding sections and other sections provided in the compressor 10.
Silicon resin has groups of CH.sub.3, and fluororesin has groups of
CF.sub.3 or CF.sub.2.
[0034] In this embodiment, the tube 31 is made of phosphorus
deoxidized copper alloy, and the oil repellent film 31a is made of
silicon resin, and the thickness of the film is kept at 0.1 to 3
.mu.m. The oil repellent film 31a is formed on the tube 31 when the
tube 31 is soaked in a solution in which material of the oil
repellent film 31a is dissolved.
[0035] In FIG. 1, the ejector 40 expands refrigerant under the
condition that the pressure is reduced, so that the ejector 40
sucks gas-phase refrigerant which has evaporated in the evaporator
30. Further, the ejector 40 converts expansion energy into pressure
energy so that the suction pressure of the compressor 10 can be
increased.
[0036] In this connection, as shown in FIG. 3, the ejector 40
includes: a nozzle 41 which converts pressure energy of high
pressure refrigerant, which flows into the ejector 40, into
velocity energy so that refrigerant can be isoentropically expanded
under the condition that pressure is reduced; a mixing section 42
for sucking gas-phase refrigerant, which has evaporated in the
evaporator 30, by a flow of refrigerant of high velocity injected
by the nozzle 41 and mixing it with a flow of refrigerant injected
from the nozzle 41; and a diffuser 43 for boosting the pressure of
refrigerant by converting velocity energy into pressure energy
while refrigerant injected from the nozzle 41 is mixed with
refrigerant sucked from the evaporator 30.
[0037] In this embodiment, in order to increase the velocity of
refrigerant jetting out from the nozzle 41 to a value not lower
than the sound velocity, a Laval nozzle is adopted which has a
throat section, the path area of which is the smallest, in the
middle of the path.
[0038] In the mixing section 42, mixing is conducted so that a sum
of the momentum of a flow of refrigerant injected from the nozzle
41 and the momentum of a flow of refrigerant sucked from the
evaporator 30 to the ejector 40 can be preserved. Therefore, static
pressure is increased even in the mixing section 42. On the other
hand, in the diffuser 43, when the sectional area of the path is
gradually increased, a dynamic pressure of refrigerant is converted
into a static pressure. Therefore, in the ejector 40, the pressure
of refrigerant is increased in both the mixing section 42 and the
diffuser 43. Therefore, the mixing section 42 and the diffuser 43
are generically called a boosting section.
[0039] In FIG. 1, the gas-liquid separator 50 is a gas-liquid
separating means into which refrigerant flows after it has flowed
out from the ejector 40, and the refrigerant, which has flowed into
the gas-liquid separator 50, is separated to gas-phase refrigerant
and liquid-phase refrigerant, and the thus separated liquid-phase
refrigerant is stored. An outlet for gas-phase refrigerant of the
gas-liquid separator 50 is connected with the suction side of the
compressor 10, and an outlet for liquid-phase refrigerant of the
gas-liquid separator 50 is connected with the entry side of the
evaporator 30.
[0040] In this connection, FIG. 4 is a diagram showing a relation
between p (absolute pressure of refrigerant) and h (specific
enthalpy). In this diagram, the overall macro operation of the
ejector cycle is shown. This macro operation of the ejector cycle
is the same as that of the well-known ejector cycle. Therefore, in
this embodiment, an explanation of the overall macro operation of
the ejector cycle are omitted. In this connection, mark
.circle-solid. shown in FIG. 4 represents a state of refrigerant at
a position indicated by mark .circle-solid. in FIG. 1.
[0041] Next, characteristics of this embodiment will be described
as follows.
[0042] In this embodiment, as the oil repellent film 31a is formed
on the inner wall of each tube 31, it is possible to prevent
refrigerating machine oil from staying in the evaporator 30.
Therefore, a sufficiently large quantity of refrigerant machine oil
can be returned to the compressor 10. Accordingly, the occurrence
of trouble such as seizing of the compressor 10 can be
prevented.
[0043] As it is possible to prevent refrigerating machine oil from
staying in the evaporator 30, while the coefficient of heat
transfer between refrigerant and the tube (31) is prevented from
deteriorating, a reduction of the substantial sectional area of the
refrigerant path can be prevented. Therefore, an increase in the
pressure loss in the evaporator 30 can be prevented, and the heat
absorbing capacity of the evaporator 30 can be enhanced.
[0044] In the vapor-compression type refrigerating machine in which
the pressure of refrigerant is isoentropically reduced by a
pressure reducing means such as an expansion valve (This cycle will
be referred to as an expansion valve cycle, hereinafter.),
refrigerant which has flowed out from the expansion valve flows
into the evaporator. On the other hand, in the ejector cycle, as
shown in FIG. 1, refrigerant which has flowed out from the ejector
40 flows into the gas-liquid separator 50, and liquid phase
refrigerant separated by the gas-liquid separator 50 is supplied to
the evaporator 30, and gas phase refrigerant separated by the
gas-liquid separator 50 is sucked into the compressor 10.
[0045] In other words, in the expansion valve cycle, there is one
refrigerant flow in which refrigerant circulates in the order of
compressor.fwdarw.radiator.fwdarw.expansion
valve.fwdarw.evaporator.fwdar- w.compressor. On the other hand, in
the ejector cycle, there are two refrigerant flows. In one flow,
refrigerant flows in the order of compressor 10.fwdarw.radiator
20.fwdarw.ejector 40.fwdarw.gas-liquid separator
50.fwdarw.compressor 10 (This flow will be referred to as a driving
flow, hereinafter.). In the other flow, refrigerant flows in the
order of gas-liquid separator 50.fwdarw.evaporator
30.fwdarw.ejector 40.fwdarw.gas-liquid separator 50 (This flow will
be referred to as a sucking flow, hereinafter.).
[0046] In this case, the driving flow is made to circulate by the
compressor 10. On the other hand, the sucking flow 10 is made to
circulate by a boosting action generated by the ejector 40, that
is, the sucking flow 10 is made to circulate by a pump action
generated by a difference in pressure between the outlet of
refrigerant of the ejector 40 and the inlet of liquid phase
refrigerant of the ejector 40. Accordingly, when a flow rate of the
driving flow is decreased and a boosting action generated by the
ejector 40 is reduced, a flow rate of refrigerant of the sucking
flow is decreased. Therefore, refrigerating machine oil, which has
flowed into the evaporator 30 together with liquid phase
refrigerant, tends to stay in the evaporator 30.
[0047] On the other hand, in the expansion cycle, refrigerant is
directly sucked from the evaporator by the compressor. Therefore,
even when a heat load is decreased, it is difficult for
refrigerating machine oil to stay in the evaporator compared with
the ejector cycle. Accordingly, it is especially effective for the
present invention to be applied to the evaporator 30 provided in
the ejector cycle.
[0048] In the above embodiment, the present invention is applied to
an evaporator provided in the ejector cycle. However, it should be
noted that the present invention is not limited to the above
specific embodiment. It is possible to apply the present invention
to an evaporator provided in the expansion valve cycle.
[0049] It is possible to apply the present invention to any type
evaporator 30, that is, the present invention can be applied to a
serpentine type heat exchanger in which the tube 31 is snaked.
Also, the present invention can be applied to a multi-flow type
heat exchanger composed of a plurality of tubes, header tanks and
others.
[0050] In the above embodiment, the vapor-compression type
refrigerating machine, in which the ejector of the present
invention is used, is applied to an air-conditioner for vehicle
use. However, the present invention is not limited to the above
specific application.
[0051] In the above embodiment, the present invention is applied to
an evaporator. However, it should be noted that the present
invention is not limited to the above specific embodiment. It is
possible to apply the present invention to a heat exchanger on the
high pressure side such as a radiator 20.
* * * * *