U.S. patent application number 14/648343 was filed with the patent office on 2015-11-12 for double-pipe heat exchanger and refrigeration cycle system.
This patent application is currently assigned to MITSUBISHI ELECTRIC CORPORATION. The applicant listed for this patent is Yohei KATO, Satoru YANACHI. Invention is credited to Yohei KATO, Satoru YANACHI.
Application Number | 20150323263 14/648343 |
Document ID | / |
Family ID | 50933884 |
Filed Date | 2015-11-12 |
United States Patent
Application |
20150323263 |
Kind Code |
A1 |
YANACHI; Satoru ; et
al. |
November 12, 2015 |
DOUBLE-PIPE HEAT EXCHANGER AND REFRIGERATION CYCLE SYSTEM
Abstract
In a double-pipe heat exchanger, a groove non-forming range is
set as a non-groove surface in each of, in an inner surface of a
heat transfer area increasing pipe, an inner surface of a part of
the heat transfer area increasing pipe, which is held in close
contact with an inner surface of an outer pipe, and a part of the
inner surface of the outer pipe, which defines a second flow path
in cooperation with an outer surface of the heat transfer area
increasing pipe.
Inventors: |
YANACHI; Satoru; (Tokyo,
JP) ; KATO; Yohei; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
YANACHI; Satoru
KATO; Yohei |
Tokyo
Tokyo |
|
JP
JP |
|
|
Assignee: |
MITSUBISHI ELECTRIC
CORPORATION
Tokyo
JP
|
Family ID: |
50933884 |
Appl. No.: |
14/648343 |
Filed: |
December 11, 2012 |
PCT Filed: |
December 11, 2012 |
PCT NO: |
PCT/JP2012/082080 |
371 Date: |
May 29, 2015 |
Current U.S.
Class: |
165/154 |
Current CPC
Class: |
F28F 1/022 20130101;
F28F 1/40 20130101; F25B 39/00 20130101; F28F 1/105 20130101; F28F
1/20 20130101; F28F 13/185 20130101; F25B 2400/13 20130101; F28F
13/12 20130101; F25B 2339/047 20130101; F28D 7/106 20130101 |
International
Class: |
F28F 1/02 20060101
F28F001/02 |
Claims
1. A double-pipe heat exchanger, comprising: an outer pipe; an
inner pipe inserted to an inner side of the outer pipe, the inner
pipe forming an annular region between the outer pipe and the inner
pipe, and forming a first flow path in an inner side thereof; and a
heat transfer area increasing pipe arranged on the inner side of
the outer pipe and an outer side of the inner pipe, the heat
transfer area increasing pipe having projections and depressions in
a radial direction, and forming a second flow path in the annular
region, wherein a non-groove surface is set in each of, in an inner
surface of a part of the heat transfer area increasing pipe, which
is held in close contact with an inner surface of the outer pipe,
and a part of the inner surface of the outer pipe, which defines
the second flow path in cooperation with an outer surface of the
heat transfer area increasing pipe, and wherein grooves are formed
in at least a part or an entirety of a part excluding the
non-groove surface from wall surface forming the second flow
path.
2. A double-pipe heat exchanger according to claim 1, wherein the
non-groove surface is formed on each of a part of the inner surface
of the outer pipe, which is held in close contact with the outer
surface of the heat transfer area increasing pipe, a part of the
outer surface of the heat transfer area increasing pipe, which is
held in close contact with the inner surface of the outer pipe, a
part of the outer surface of the inner pipe, which is held in close
contact with the inner surface of the heat transfer area increasing
pipe, and a part of the inner surface of the heat transfer area
increasing pipe, which is held in close contact with the outer
surface of the inner pipe.
3. A double-pipe heat exchanger according to claim 1, wherein,
after the grooves are formed in the heat transfer area increasing
pipe, the heat transfer area increasing pipe is inserted to the
annular region between the outer pipe and the inner pipe, and the
outer pipe is reduced in diameter or the inner pipe is increased in
diameter so that the heat transfer area increasing pipe is
supported by the outer pipe and the inner pipe.
4. A double-pipe heat exchanger according to claim 1, wherein the
inner pipe and the outer pipe are brazed to the heat transfer area
increasing pipe.
5. A double-pipe heat exchanger according to claim 4, wherein the
heat transfer area increasing pipe comprises a cladding material
having a brazing material covered on a surface thereof.
6. A refrigeration cycle system, comprising the double-pipe heat
exchanger of claim 1, wherein heat is exchanged between
refrigerants in the double-pipe heat exchanger.
7. A refrigeration cycle system, comprising the double-pipe heat
exchanger of claim 1, wherein heat is exchanged between a
refrigerant and water or between a refrigerant and brine in the
double-pipe heat exchanger.
8. A double-pipe heat exchanger according to claim 1, wherein a
groove forming candidate range comprises a part excluding the
groove non-forming range from a part of the inner surface of the
heat transfer area increasing pipe, which defines the second flow
path in cooperation with an outer surface of the inner pipe, a part
of the outer surface of the heat transfer area increasing pipe,
which defines the second flow path in cooperation with the inner
surface of the outer pipe, and a part of the outer surface of the
inner pipe, which defines the second flow path in cooperation with
the inner surface of the heat transfer area increasing pipe.
9. A double-pipe heat exchanger according to claim 1, wherein
grooves extend along a flow direction.
Description
TECHNICAL FIELD
[0001] The present invention relates to a double-pipe heat
exchanger in which two flow paths are formed by combining circular
pipes having different pipe diameters, and to a refrigeration cycle
system using the double-pipe heat exchanger.
BACKGROUND ART
[0002] In the double-pipe heat exchanger, a circular pipe having a
small diameter (hereinafter described as an inner pipe) is inserted
to a circular pipe having a large diameter (hereinafter described
as an outer pipe). An inside of the inner pipe is defined as a
first flow path, and a part on an outer side of the inner pipe and
an inner side of the outer pipe is defined as a second flow path so
that heat is exchanged between a first fluid inside the first flow
path and a second fluid inside the second flow path.
[0003] Further, as an effort to enhance heat transfer performance
in such a double-pipe heat exchanger, a structure disclosed in, for
example, Patent Literature 1 is known. That is, in Patent
Literature 1, there is proposed a method of enhancing the heat
transfer performance due to an effect of an increase in heat
transfer area, which is obtained by inserting a heat transfer area
increasing pipe having a multilobed lateral cross section to an
inside of an annular second flow path defined between the outer
side of the cylindrical inner pipe and the inner side of the
cylindrical outer pipe.
CITATION LIST
Patent Literature
[0004] [PTL 1] JP 2012-063067 A
SUMMARY OF INVENTION
Technical Problem
[0005] Patent Literature 1 merely discloses the effort to increase
the heat transfer area. Hence, the inventors of the present
invention focus on suitably transferring heat when the heat is
exchanged in a two-phase refrigerant.
[0006] The present invention has been made in view of the above,
and it is therefore an object thereof to provide a double-pipe heat
exchanger capable of enhancing heat exchange performance when a
two-phase flow flows in a second flow path, or the like.
Solution to Problem
[0007] In order to achieve the above-mentioned object, according to
one embodiment of the present invention, there is provided a
double-pipe heat exchanger, including: an outer pipe; an inner pipe
inserted to an inner side of the outer pipe, the inner pipe forming
an annular region between the outer pipe and the inner pipe, and
forming a first flow path in an inner side thereof; and a heat
transfer area increasing pipe arranged on the inner side of the
outer pipe and an outer side of the inner pipe, the heat transfer
area increasing pipe having projections and depressions in a radial
direction, and forming a second flow path in the annular region, in
which a groove non-forming range is set in each of, in an inner
surface of the heat transfer area increasing pipe, an inner surface
of a part of the heat transfer area increasing pipe, which is held
in close contact with an inner surface of the outer pipe, and a
part of the inner surface of the outer pipe, which defines the
second flow path in cooperation with an outer surface of the heat
transfer area increasing pipe, and the groove non-forming range
includes a non-groove surface, in which a groove forming candidate
range includes a part excluding the groove non-forming range from a
part of the inner surface of the heat transfer area increasing
pipe, which defines the second flow path in cooperation with the
outer surface of the inner pipe, a part of the outer surface of the
heat transfer area increasing pipe, which defines the second flow
path in cooperation with the inner surface of the outer pipe, and a
part of an outer surface of the inner pipe, which defines the
second flow path in cooperation with the inner surface of the heat
transfer area increasing pipe, and in which grooves extending along
a flow direction are formed in at least part or an entirety of the
groove forming candidate range.
Advantageous Effects of Invention
[0008] According to the one embodiment of the present invention, it
is possible to enhance the heat exchange performance when the
two-phase flow flows in the second flow path.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a view for illustrating an internal structure of a
double-pipe heat exchanger according to a first embodiment of the
present invention in a direction orthogonal to a pipe axis.
[0010] FIG. 2 is a sectional view of the double-pipe heat exchanger
taken along the line II-II of FIG. 1.
[0011] FIG. 3 is a view for illustrating a second flow path of FIG.
2 in an enlarged manner.
[0012] FIG. 4 is a view for illustrating a part of FIG. 3, in which
an outer pipe, a heat transfer area increasing pipe, and an inner
pipe are separated from each other for the sake of
illustration.
[0013] FIG. 5 is a view for illustrating Example 1 of the
refrigeration cycle system using the double-pipe heat
exchanger.
[0014] FIG. 6 is a view for illustrating Example 2 of the
refrigeration cycle system using the double-pipe heat
exchanger.
[0015] FIG. 7 is a view for illustrating Example 3 of the
refrigeration cycle system using the double-pipe heat
exchanger.
[0016] FIG. 8 is a view for illustrating Example 4 of the
refrigeration cycle system using the double-pipe heat
exchanger.
[0017] FIG. 9 is a view according to a second embodiment of the
present invention, for illustrating in the same manner as in FIG.
3.
[0018] FIG. 10 is a view according to a third embodiment of the
present invention, for illustrating in the same manner as in FIG.
3.
DESCRIPTION OF EMBODIMENTS
[0019] Now, embodiments of the present invention are described with
reference to the accompanying drawings. Note that, in the drawings,
the same reference symbols indicate the same or corresponding
parts.
First Embodiment
[0020] FIG. 1 is a view for illustrating an internal structure of a
double-pipe heat exchanger according to a first embodiment of the
present invention in a direction orthogonal to a pipe axis. FIG. 2
is a sectional view of the double-pipe heat exchanger taken along
the line II-II of FIG. 1. Note that, for the sake of clarity of
illustration, the illustration of a heat transfer area increasing
pipe described later is omitted in FIG. 1. A double-pipe heat
exchanger 1 has a double pipe structure in which an inner pipe 5,
which is a circular pipe having a relatively small diameter, is
concentrically inserted to an inner side of an outer pipe 3, which
is a circular pipe having a relatively large diameter. An inner
space of the inner pipe 5 functions as a first flow path 7. On the
other hand, a heat transfer area increasing pipe 11 is accommodated
in an annular region 9 on an outer side of the inner pipe 5 and the
inner side of the outer pipe 3.
[0021] The heat transfer area increasing pipe 11 has a plurality of
projecting portions 13 and a plurality of depressed portions 15 as
relative projections and depressions in a radial direction. As
illustrated in a lateral cross section of FIG. 2, the plurality of
projecting portions 13 are radially formed to project toward a
radially outer side of the heat transfer area increasing pipe 11.
Further, the plurality of projecting portions 13 are arranged at
substantially equal intervals in a circumferential direction. On
the other hand, the plurality of depressed portions 15 are each
positioned between a corresponding pair of the projecting portions
13 in the circumferential direction. Those depressed portions 15
are also positioned at substantially equal intervals in the
circumferential direction. Therefore, when viewing the entire heat
transfer area increasing pipe 11, the plurality of projecting
portions 13 and the plurality of depressed portions 15 are
alternately positioned in the circumferential direction.
[0022] In the present invention, various modes are conceivable as a
projection shape of the projecting portion and a depression shape
of the depressed portion when viewed in the lateral cross section
of FIG. 2 for illustrating the heat transfer area increasing pipe.
As an example, the first embodiment is as follows. The heat
transfer area increasing pipe 11 includes a plurality of outer
close-contact portions 17, a plurality of inner close-contact
portions 19, and a plurality of continuous portions 21. As
illustrated in FIG. 2, outer surfaces 17a of the outer
close-contact portions 17 of the heat transfer area increasing pipe
11 and an inner surface 3b of the outer pipe 3 are held in close
contact with each other. In particular, in this embodiment, the
outer surface 17a and the inner surface 3b are held in surface
contact with each other. That is, the outer surface 17a of the
outer close-contact portion 17 of the heat transfer area increasing
pipe 11 has substantially the same curvature as that of the inner
surface 3b of the outer pipe 3. Similarly, inner surfaces 19b of
the inner close-contact portions 19 of the heat transfer area
increasing pipe 11 and an outer surface 5a of the inner pipe 5 are
held in close contact with each other. In particular, in this
embodiment, the inner surface 19b and the outer surface 5a are held
in surface contact with each other. That is, the inner surface 19b
of the inner close-contact portion 19 of the heat transfer area
increasing pipe 11 has substantially the same curvature as that of
the outer surface 5a of the inner pipe 5. Note that, this state of
having the same curvature may be obtained in a separated state of
each of the outer pipe 3, the inner pipe 5, and the heat transfer
area increasing pipe 11, or may be obtained in a state at the
completion of an assembly process that involves application of any
force from a center side of the double-pipe heat exchanger 1 or an
outer side thereof in the radial direction.
[0023] The continuous portions 21 are each positioned between the
adjacent outer close-contact portion 17 and inner close-contact
portion 19. In this embodiment, the plurality of outer
close-contact portions 17 are positioned at equal intervals in the
circumferential direction. The plurality of inner close-contact
portions 19 are also positioned at equal intervals in the
circumferential direction. When viewing the entire heat transfer
area increasing pipe 11, an arrangement mode in the order of the
outer close-contact portion 17, the continuous portion 21, the
inner close-contact portion 19, and the continuous portion 21 is
repeated in the circumferential direction. Note that, the
projecting portion 13 and the depressed portion 15 do not have a
definite boundary. The projecting portion 13 is formed by the outer
close-contact portion 17 and parts of the continuous portions 21,
which are closer to the outer side in the radial direction. The
depressed portion 15 is formed by the inner close-contact portion
19 and parts of the continuous portions 21, which are closer to an
inner side in the radial direction.
[0024] In the above-mentioned annular region 9, an inner side of
the projecting portion 13 and an outer side of the depressed
portion 15 each function as a second flow path 23. That is, the
second flow path 23 is defined in the annular region 9 by the heat
transfer area increasing pipe 11.
[0025] More specifically, the second flow path 23 has parts in two
modes. A first-mode part is defined by an inner surface 17b of the
outer close-contact portion 17, inner surfaces 21b of a
corresponding pair of the continuous portions 21, and the outer
surface 5a of the inner pipe 5. Further, a second-mode part is
defined by an outer surface 19a of the inner close-contact portion
19, outer surfaces 21a of a corresponding pair of the continuous
portions 21, and the inner surface 3b of the outer pipe 3. The
first-mode parts and the second-mode parts are alternately arrayed
in the circumferential direction.
[0026] In such a configuration, a first fluid flows in the first
flow path 7, and a second fluid flows in the second flow path 23.
The first fluid and the second fluid have different temperatures,
and heat is exchanged between the first fluid and the second fluid
through thermal conduction between the inner pipe 5 and the heat
transfer area increasing pipe 11.
[0027] In general, a heat exchange amount Q, a heat transfer area
A, a heat transfer coefficient K, and a temperature difference dT
between the first fluid and the second fluid have a relationship
represented by Expression (1).
[Math. 1]
Q=AKdT (1)
[0028] Further, the heat transfer coefficient K may be expressed by
Expression (2).
[ Math . 2 ] K = .lamda. L { 1 / ( .alpha. 1 d 1 ) + 1 / ( .alpha.
2 d 2 ) + 1 / ( 2 .lamda. ) ln ( d 10 / d 11 ) + R } ( 2 )
##EQU00001##
[0029] Note that, the meaning of each symbol is as follows.
.alpha.1: heat transfer coefficient of fluid 1, d1: hydraulic
diameter of flow path 1, .alpha.2: heat transfer coefficient of
flow path 2, d2: hydraulic diameter of flow path 2, .lamda.:
thermal conductivity of inner pipe, dio: outer diameter of inner
pipe, doi: inner diameter of inner pipe, R: thermal resistance
[0030] The above-mentioned heat transfer area increasing pipe 11
functions as a fin when held in contact with the inner pipe 5, and
hence the heat transfer area can be increased to increase a heat
exchange amount between the first fluid and the second fluid.
[0031] In this case, a flowing state of a refrigerant in a case
where a gas-liquid two-phase flow flows in the second flow path 23
is described referring to FIG. 3 and also to FIG. 4. FIG. 3 is a
view in the same manner as in FIG. 2, for illustrating the second
flow path in an enlarged manner. FIG. 4 is a view for illustrating
a part of FIG. 3, in which the outer pipe, the heat transfer area
increasing pipe, and the inner pipe are separated from each other
for the sake of illustration. In this case, in general, in the
two-phase flow, a liquid refrigerant having a higher heat transfer
coefficient is held in close contact with a pipe wall, and a gas
refrigerant having a lower heat transfer coefficient flows in a
portion away from the pipe wall. That is, the liquid refrigerant
concentrates on wall surfaces indicated by reference symbols 3b,
5a, 17b, 19a, 21a, and 21b in FIG. 3.
[0032] In view of the above, the present invention sets a groove
non-forming range and a groove forming candidate range as described
below. A non-groove surface is formed in the groove non-forming
range, and grooves extending along a flow direction are formed in
at least a part or the entirety of the groove forming candidate
range. The first embodiment is an example of a case where the
grooves are formed in the entirety of the groove forming candidate
range.
[0033] The groove non-forming range and the groove forming
candidate range are described in detail. Specifically, the groove
non-forming range corresponds to, in an inner surface of the heat
transfer area increasing pipe 11, an inner surface of a part of the
heat transfer area increasing pipe 11, which is held in close
contact with the inner surface 3b of the outer pipe 3 (inner
surface 17b of the outer close-contact portion 17). In addition,
the groove non-forming range also corresponds to a part of the
inner surface 3b of the outer pipe 3, which defines the second flow
path 23 in cooperation with an outer surface of the heat transfer
area increasing pipe 11. Grooves 25 described later are not formed
in each of those groove non-forming ranges.
[0034] Further, the groove forming candidate range is formed by a
part excluding the above-mentioned groove non-forming range (inner
surface 17b of the outer close-contact portion 17) from a part of
the inner surface of the heat transfer area increasing pipe 11,
which defines the second flow path 23 in cooperation with the outer
surface 5a of the inner pipe 5 (inner surfaces 21b of the
continuous portions 21), a part of the outer surface of the heat
transfer area increasing pipe 11, which defines the second flow
path 23 in cooperation with the inner surface 3b of the outer pipe
3 (outer surfaces 21a of the continuous portions 21 and the outer
surface 19a of the inner close-contact portion 19), and a part of
the outer surface 5a of the inner pipe 5, which defines the second
flow path 23 in cooperation with the inner surface of the heat
transfer area increasing pipe 11.
[0035] In the first embodiment, the grooves are not formed in the
groove non-forming range as described above, and the grooves are
formed in the entirety of the groove forming candidate range. More
specific description is given below. The grooves 25 are formed in
each of the part of the outer surface 5a of the inner pipe 5, which
defines the second flow path 23 in cooperation with the outer
close-contact portion 17 and the pair of the continuous portions
21, the outer surface 19a of the inner close-contact portion 19 of
the heat transfer area increasing pipe 11, and the outer surfaces
21a and the inner surfaces 21b of the continuous portions 21.
Further, the non-groove surface is formed on each of the inner
surface 17b of the outer close-contact portion 17 and the part of
the inner surface 3b of the outer pipe 3, which defines the second
flow path 23 in cooperation with the inner close-contact portion 19
and the pair of the continuous portions 21. Note that, although not
particularly limited as the present invention, in the first
embodiment, the non-groove surface is formed on each of the outer
surface 17a of the outer close-contact portion 17 of the heat
transfer area increasing pipe 11 and a part of the inner surface 3b
of the outer pipe 3, which is held in close contact with the outer
surface 17a. In addition, the non-groove surface is formed on each
of the inner surface 19b of the inner close-contact portion 19 and
a part of the outer surface 5a of the inner pipe 5, which is held
in close contact with the inner surface 19b.
[0036] The grooves 25 are formed in a mode of extending along the
flow direction so as to allow the refrigerant to flow smoothly in
the flow direction. Note that, the grooves are schematically
illustrated in FIG. 3 and FIG. 4, and further, in FIG. 2, the
illustration of the grooves is omitted for the sake of clarity of
illustration.
[0037] Note that, it is conceivable that the heat transfer area
increasing pipe 11 is formed through press forming or a drawing
process. Therefore, in order to simplify the process, the grooves
25 are simultaneously formed at the time of the press forming or
the drawing process. Further, the heat transfer area increasing
pipe 11 having the grooves 25 formed therein is inserted to the
annular region 9 between the outer pipe 3 and the inner pipe 5, and
the outer pipe 3 is reduced in diameter or the inner pipe 5 is
increased in diameter. In this manner, the heat transfer area
increasing pipe 11 is supported by the outer pipe 3 and the inner
pipe 5.
[0038] Alternatively, as a method of further reliably holding the
inner pipe 5 and the outer pipe 3 in close contact with the heat
transfer area increasing pipe 11, a mode of joining respective
contact surfaces through brazing is also preferred. Specifically,
after the heat transfer area increasing pipe 11 is assembled to the
outer pipe 3 and the inner pipe 5, a brazing material is applied to
the contact surfaces, and the brazing material is melted through
brazing in a furnace or the like. In this manner, the contact
surfaces may be brazed to each other. Further, in a case where the
brazing material is difficult to be applied after the heat transfer
area increasing pipe 11 is assembled to the inner pipe 5 and the
outer pipe 3, the brazing may be performed using a cladding
material having the brazing material applied thereto in advance as
the heat transfer area increasing pipe 11.
[0039] According to the double-pipe heat exchanger 1 configured as
described above, the following excellent advantages can be
obtained. Of the parts that define the second flow path 23, a
predetermined part of the outer surface 5a of the inner pipe 5 and
the outer surface 19a of the inner close-contact portion 19 are
parts extremely close to the first flow path 7, and parts having
highest effectiveness as heat transfer surfaces. Further, the
continuous portion 21 is formed between the above-mentioned
first-mode part and second-mode part of the second flow path 23,
and inner and outer surfaces of the continuous portion 21 are
effective heat transfer surfaces when the continuous portion 21
exchanges heat between the second fluids of the first-mode part and
the second-mode part (internal relationship of the second flow path
23) by exerting an effect of the fin. Therefore, with the grooves
25 formed as described above, the liquid refrigerant can actively
be gathered on the inner and outer surfaces of the continuous
portion 21, and the predetermined part of the outer surface 5a of
the inner pipe 5 and the outer surface 19a of the inner
close-contact portion 19 that is held in close contact with the
inner pipe 5, which are closer to the first flow path 7. Further,
in addition to the above, the non-groove surface is formed on each
of a predetermined part of the inner surface 3b of the outer pipe 3
and the inner surface 17b of the outer close-contact portion 17,
which are farther from the first flow path 7 and have lower
effectiveness as heat transfer surfaces. With this, the liquid
refrigerant is less likely to gather on the non-groove surface
relative to the predetermined part of the outer surface 5a or the
outer surface 19a. As a countereffect, the liquid refrigerant is
assisted so as to gather on the predetermined part of the outer
surface 5a, the outer surface 19a, and the inner and outer surfaces
of the continuous portion 21. That is, the following matter is
prevented. Specifically, a large amount of the liquid refrigerant
having the higher heat transfer coefficient is supplied also to
each of the predetermined part of the inner surface 3b of the outer
pipe 3 and the inner surface 17b of the outer close-contact portion
17, which have the lower effectiveness as the heat transfer
surfaces, to thereby correspondingly reduce a supply amount of the
liquid refrigerant to each of the predetermined part of the outer
surface 5a, the outer surface 19a, and the inner and outer surfaces
of the continuous portion 21, which have the higher effectiveness
as the heat transfer surfaces. As described above, according to
this embodiment, even in the case where the gas-liquid two-phase
flow flows in the second flow path, heat exchange performance can
be enhanced by effectively utilizing the heat transfer
surfaces.
[0040] In addition, in the first embodiment, the non-groove surface
is formed on each of the outer surface 17a of the outer
close-contact portion 17 of the heat transfer area increasing pipe
11 and the part of the inner surface 3b of the outer pipe 3, which
is held in close contact with the outer surface 17a. Similarly, the
non-groove surface is formed on each of the inner surface 19b of
the inner close-contact portion 19 and the part of the outer
surface 5a of the inner pipe 5, which is held in close contact with
the inner surface 19b. Thus, close contact performance between the
heat transfer area increasing pipe 11 and each of the inner pipe 5
and the outer pipe 3 can be maintained high. Not only that,
particularly because the close contact performance between the
inner pipe 5 and the heat transfer area increasing pipe 11 is high,
an efficiency of the thermal conduction of the heat transfer area
increasing pipe 11 can be enhanced. Thus, the provision of the heat
transfer area increasing pipe 11 can efficiently be utilized.
[0041] Next, Examples of a refrigeration cycle system to which the
above-mentioned double-pipe heat exchanger 1 is applied are
described referring to FIG. 5 to FIG. 8.
[0042] As Example 1 of the refrigeration cycle system, a
refrigeration cycle system 101 illustrated in FIG. 5 includes, as
circuit main components, a compressor 103, a condenser 105, an
expansion valve 107, an evaporator 109, and the above-mentioned
double-pipe heat exchanger 1. In the double-pipe heat exchanger 1,
heat is exchanged between a high-pressure liquid refrigerant
(second fluid) from an outlet of the condenser 105 (before flowing
into an inlet of the expansion valve 107), and a low-pressure gas
refrigerant (first fluid) from an outlet of the evaporator 109
(before flowing into an inlet of the compressor 103). With the use
of the double-pipe heat exchanger 1 as described above, an inlet
temperature of the condenser 105 is increased. Thus, performance in
heating can be enhanced to enhance COP (value obtained by dividing
the performance by an input), or the liquid refrigerant can be
prevented from returning to the compressor.
[0043] Next, as Example 2 of the refrigeration cycle system, a
refrigeration cycle system 201 illustrated in FIG. 6 includes, as
circuit main components, the compressor 103, the condenser 105, a
first expansion valve 207a, a second expansion valve 207b, the
evaporator 109, and the above-mentioned double-pipe heat exchanger
1. The compressor 103, the condenser 105, the first expansion valve
207a, and the evaporator 109 construct a basic refrigeration cycle
circuit similarly to the case of Example 1. A bypass passage 211 is
further formed in the refrigeration cycle system 201. The bypass
passage 211 is connected at a first connecting point 213a to a part
from the outlet of the condenser 105 to an inlet of the first
expansion valve 207a, and is connected at a second connecting point
213b to a part from the outlet of the evaporator 109 to the inlet
of the compressor 103. The second expansion valve 207b is arranged
in the bypass passage 211.
[0044] In the double-pipe heat exchanger 1, heat is exchanged
between a high-pressure liquid refrigerant (first fluid) from the
outlet of the condenser 105 (before reaching the first connecting
point 213a), and an intermediate-pressure gas-liquid two-phase
refrigerant (second fluid) from the outlet of the second expansion
valve 207b of the bypass passage 211. The intermediate-pressure gas
refrigerant after undergoing the heat exchange in the double-pipe
heat exchanger 1 is sucked into the compressor 103. With the use of
the double-pipe heat exchanger as described above, a refrigerant
circulation amount in a downstream part with respect to the first
expansion valve 207a can be reduced to reduce pressure loss,
thereby enhancing the COP.
[0045] Next, as Example 3 of the refrigeration cycle system, a
refrigeration cycle system 301 illustrated in FIG. 7 includes, as
circuit main components, a compressor 303, the condenser 105, the
first expansion valve 207a, the second expansion valve 207b, the
evaporator 109, and the above-mentioned double-pipe heat exchanger
1. The compressor 303, the condenser 105, the first expansion valve
207a, and the evaporator 109 construct a basic refrigeration cycle
circuit similarly to the case of Example 1.
[0046] In the double-pipe heat exchanger 1, heat is exchanged
between a high-pressure liquid refrigerant (first fluid) from the
outlet of the condenser 105 (before reaching the first connecting
point 213a), and an intermediate-pressure gas-liquid two-phase
refrigerant (second fluid) from the outlet of the second expansion
valve 207b of the bypass passage 211. Further, the
intermediate-pressure gas refrigerant after undergoing the heat
exchange in the double-pipe heat exchanger 1 is caused to bypass
into the middle of a compressing part of the compressor 303. With
the use of the double-pipe heat exchanger as described above, a
refrigerant circulation amount in the downstream part with respect
to the first expansion valve 207a can be reduced, and a compressing
process can be performed in a plurality of stages to reduce an
input to the compressor, thereby enhancing the COP.
[0047] In addition, a refrigeration cycle system 401 illustrated in
FIG. 8 uses the double-pipe heat exchanger 1 as a condenser itself
of the basic refrigeration cycle circuit. The refrigeration cycle
system 401 is an example of a system of exchanging heat between the
refrigerant (second fluid) in the general condenser of the
refrigeration cycle circuit and a fluid (first fluid), such as
water or brine, fed by a pump 415 in the double-pipe heat exchanger
1, to thereby supply hot water.
Second Embodiment
[0048] Next, a second embodiment of the present invention is
described. FIG. 9 is a view according to the second embodiment of
the present invention, for illustrating in the same manner as in
FIG. 3. The second embodiment is the same as the above-mentioned
first embodiment except for a part described below. Further, the
second embodiment is the same as the first embodiment also in that
the second embodiment may be carried out by the refrigeration cycle
system of FIG. 5 to FIG. 8.
[0049] A double-pipe heat exchanger 51 is an example in which the
grooves 25 extending along the flow direction are formed in at
least a part of the groove forming candidate range. That is, in the
second embodiment, as illustrated in FIG. 9, the grooves 25 are
only formed in the inner and outer surfaces of the continuous
portion 21, in the groove forming candidate range that corresponds
to the above-mentioned predetermined part of the outer surface 5a
of the inner pipe 5, the outer surface 19a of the inner
close-contact portion 19, and the inner and outer surfaces of the
continuous portion 21. In such a second embodiment, similarly to
the first embodiment, the liquid refrigerant can efficiently be
gathered on the inner and outer surfaces of the continuous portion
21, which have the higher effectiveness as the heat transfer
surfaces. Even when the gas-liquid two-phase flow flows in the
second flow path, the heat exchange performance can be enhanced by
effectively utilizing the heat transfer surfaces.
Third Embodiment
[0050] Next, a third embodiment of the present invention is
described. FIG. 10 is a view according to the third embodiment of
the present invention, for illustrating in the same manner as in
FIG. 3. The third embodiment is the same as the above-mentioned
first embodiment except for a part described below. Further, the
third embodiment is the same as the first embodiment also in that
the third embodiment may be carried out by the refrigeration cycle
system of FIG. 5 to FIG. 8.
[0051] A double-pipe heat exchanger 61 is also an example in which
the grooves 25 extending along the flow direction are formed in at
least a part of the groove forming candidate range. In the third
embodiment, as illustrated in FIG. 10, the grooves 25 are only
formed in the above-mentioned predetermined part of the outer
surface 5a of the inner pipe 5 and the outer surface 19a of the
inner close-contact portion 19, in the groove forming candidate
range that corresponds to the above-mentioned predetermined part of
the outer surface 5a of the inner pipe 5, the outer surface 19a of
the inner close-contact portion 19, and the inner and outer
surfaces of the continuous portion 21. In such a third embodiment,
similarly to the first embodiment, even when the gas-liquid
two-phase flow flows in the second flow path, the heat exchange
performance can be enhanced by effectively utilizing the heat
transfer surfaces.
[0052] Although the details of the present invention are
specifically described above with reference to the preferred
embodiments, it is apparent that persons skilled in the art may
adopt various modifications based on the basic technical concepts
and teachings of the present invention.
[0053] For example, the above-mentioned first embodiment may be
modified so that the grooves 25 are formed also in the outer
surface 17a of the outer close-contact portion 17 of the heat
transfer area increasing pipe 11. With such a modification, the
grooves 25 are formed in the entire outer surface of the heat
transfer area increasing pipe 11 as a uniform process. Thus,
facilitation of manufacture due to the uniformity of the process
can be achieved. Further, even with such a modification, the outer
surface 17a of the outer close-contact portion 17 of the heat
transfer area increasing pipe 11, which is held in close contact
with the outer pipe 3, is less important as the heat transfer
surface. The modification does not lower the effectiveness of the
present invention from the viewpoint of utilization of the heat
transfer surface. That is, easiness of the manufacture can be
enhanced while suitably maintaining effective utility of the heat
transfer surface of the present invention.
REFERENCE SIGNS LIST
[0054] 1, 51, 61 double-pipe heat exchanger, 3 outer pipe, 5 inner
pipe, 7 first flow path, 9 annular region, 11 heat transfer area
increasing pipe, 23 second flow path, 25 groove, 101, 201, 301, 401
refrigeration cycle system
* * * * *