U.S. patent application number 13/519371 was filed with the patent office on 2012-11-15 for heat transfer pipe for heat exchanger, heat exchanger, refrigeration cycle apparatus, and air-conditioning apparatus.
This patent application is currently assigned to MITSUBISHI ELECTIRC CORPORATION. Invention is credited to Akira Ishibashi, Sangmu Lee, Takuya Matsuda, Toru Onoda.
Application Number | 20120285190 13/519371 |
Document ID | / |
Family ID | 44304159 |
Filed Date | 2012-11-15 |
United States Patent
Application |
20120285190 |
Kind Code |
A1 |
Lee; Sangmu ; et
al. |
November 15, 2012 |
HEAT TRANSFER PIPE FOR HEAT EXCHANGER, HEAT EXCHANGER,
REFRIGERATION CYCLE APPARATUS, AND AIR-CONDITIONING APPARATUS
Abstract
A heat transfer pipe for a heat exchanger including high threads
and low threads that are lower than the high threads. The high
threads and the low threads are provided at respective prescribed
heights in a helical manner in a pipe axial direction on an inner
surface of a pipe, the high threads are formed with 11 to 19
threads, the low threads are formed with 3 to 6 threads between
each pair of the high threads, the high threads before expansion of
the pipe each have a trapezoidal shape in cross-section so that a
crest before the expansion of the pipe is flat, and a ratio W1/D of
a tip width W1 of the crest portion after the expansion of the pipe
to an outer diameter of the heat transfer pipe is 0.011 to 0.040.
Further, the high threads before the expansion of the pipe are
higher by 0.04 mm or more than the low threads.
Inventors: |
Lee; Sangmu; (Tokyo, JP)
; Onoda; Toru; (Tokyo, JP) ; Matsuda; Takuya;
(Tokyo, JP) ; Ishibashi; Akira; (Tokyo,
JP) |
Assignee: |
MITSUBISHI ELECTIRC
CORPORATION
Chiyoda-ku, Tokyo
JP
|
Family ID: |
44304159 |
Appl. No.: |
13/519371 |
Filed: |
January 7, 2011 |
PCT Filed: |
January 7, 2011 |
PCT NO: |
PCT/JP2011/000048 |
371 Date: |
June 27, 2012 |
Current U.S.
Class: |
62/238.6 ;
165/104.21; 62/498 |
Current CPC
Class: |
F28F 1/32 20130101; F28D
2021/0071 20130101; F28F 2275/125 20130101; F28D 2021/007 20130101;
F28F 1/40 20130101; F28D 1/0477 20130101; F25B 39/00 20130101 |
Class at
Publication: |
62/238.6 ;
165/104.21; 62/498 |
International
Class: |
F28D 15/02 20060101
F28D015/02; F25B 29/00 20060101 F25B029/00; F25B 1/00 20060101
F25B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 13, 2010 |
JP |
2010-005355 |
Claims
1. A heat transfer pipe for a heat exchanger, comprising: high
threads; and low threads that are lower than the high threads,
wherein the high threads and the low threads are provided at
respective prescribed heights in a helical manner in a pipe axial
direction on a pipe inner surface, the high threads are formed with
11 to 19 threads, the low threads are formed of 3 to 6 threads
between each pair of the high threads, the high threads before
expansion of the pipe each have a trapezoidal shape in a
cross-section such that a crest thereof is flat, ratio of a tip
width of the crest portion after the expansion of the pipe to an
outer diameter of the heat transfer pipe is 0.011 to 0.040, and a
curvature radius of the flat surface of the crest portion and one
side surface and a curvature radius of the flat surface of the
crest portion and the other side surface in each of the high
threads before the expansion of the pipe are 0.01 mm to 0.03
mm.
2. The heat transfer pipe for a heat exchanger of claim 1, wherein
the high threads before the expansion of the pipe are higher by
0.04 mm or more than the low threads.
3. (canceled)
4. The heat transfer pipe for a heat exchanger of claim 1, wherein
an apex angle of the high threads before the expansion of the pipe
is 15 to 30 degrees, and an apex angle of the low threads is 5 to
15 degrees.
5. The heat transfer pipe for a heat exchanger of claim 1, wherein
a curvature radius of crests of the low threads is 0.03 mm to 0.045
mm.
6. The heat transfer pipe for a heat exchanger of claim 1, wherein
a direction in which the threads extend relative to a pipe axial
direction makes 10 to 50 degrees.
7. A heat exchanger, comprising: a plurality of fins for exchanging
heat; and the heat transfer pipe of claim 1 that penetrates the
fins, wherein the heat transfer pipe is pressurized from an inner
surface to be expanded, and is fixed to the fins.
8. The heat exchanger of claim 7, wherein a height of the high
threads after the expansion of the pipe is 0.10 mm to 0.26 mm.
9. A refrigeration cycle apparatus, comprising: a refrigerant
circuit including a compressor that compresses a refrigerant, a
condenser that condenses the refrigerant by heat exchange, an
expansion means for decompressing the condensed refrigerant, and an
evaporator that evaporates the decompressed refrigerant by heat
exchange to circulate the refrigerant, the refrigerant circuit
being connected by piping, the refrigeration cycle apparatus,
wherein the heat exchanger of claim 7 is provided to both or either
one of the condenser and the evaporator.
10. The refrigeration cycle apparatus of claim 9, wherein as the
refrigerant, either one of an HC single refrigerant, a mixed
refrigerant including HC, R32, R410A, R407C, tetrafluoropropene, a
non-azeotropic refrigerant mixture consisting of HFC refrigerant
having a boiling point that is lower than the tetrafluoropropene,
or carbon dioxide is used.
11. An air-conditioning apparatus, comprising the refrigeration
cycle apparatus of claim 9 that carries out cooling or heating of a
conditioned space.
Description
TECHNICAL FIELD
[0001] The present invention is related to a heat transfer pipe for
a heat exchanger having a groove on the inner surface of the pipe,
a heat exchanger, a refrigeration cycle apparatus, and an
air-conditioning apparatus.
BACKGROUND ART
[0002] Conventionally, in a heat exchanger used in a refrigeration
apparatus, an air-conditioning apparatus, a heat pump, and the
like, typically, a plurality of fins aligned at prescribed
intervals are provided with through holes, and a heat transfer pipe
that has grooves formed in its inner surface is disposed in the
through holes. The heat transfer pipe becomes a portion of a
refrigerant circuit in a refrigeration cycle apparatus and a
refrigerant (fluid) is made to flow in the pipe.
[0003] The grooves on the inner surface of the pipe are fabricated
such that the pipe axial direction and the direction in which the
grooves extend form a fixed angle. Herein, concavities and
convexities are created on the inner surface of the pipe by the
formation of the grooves. The space in the concavity is called a
groove portion and the convexity formed by the sidewalls of
adjacent grooves is called a thread portion.
[0004] A refrigerant that flows through such a heat transfer pipe
changes phase (condenses or evaporates) by heat exchange with the
air outside of the heat transfer pipe or the like. In order to
carry out the phase change effectively, the heat transfer
performance of the heat transfer pipe is improved by increasing the
surface area in the pipe, by a fluid stirring effect by the groove
portions, by a liquid film retaining effect between the groove
portions by the capillary action of the groove portions, and the
like (for example, refer to Patent Literature 1).
CITATION LIST
Patent Literature
[0005] Patent Literature 1: Japanese Unexamined Patent Application,
First Publication No. 60-142195 (page 2 and FIG. 1)
SUMMARY OF INVENTION
Technical Problem
[0006] The heat transfer pipe as described in the above Patent
Literature 1 is generally made of metal of copper or copper alloy.
In the manufacture of the heat exchanger, a mechanical pipe
expanding technique is used in which pipe expanding balls are
pushed into the pipe to expand the heat transfer pipe from the
inside, and thus the fins and the heat transfer pipe are adhered
and fixed. However, when expanding the pipe, there have been
problems in that the thread portions falls over due to the pipe
expanding balls, leading to reduction in adherence between the fins
and the heat transfer pipe. Further, the pressure loss in the pipe
increases causing a drop in the heat transfer performance.
[0007] The present invention has been made to solve the above
problems, and an object of the present invention is to provide a
heat transfer pipe for a heat exchanger in which the adherence
between the heat transfer pipe and the fins is improved and a
prescribed heat transfer performance can be obtained without
increasing the pressure loss in the pipe, as well as providing a
heat exchanger using this heat transfer pipe, a refrigeration cycle
apparatus using the heat exchanger, and an air-conditioning
apparatus using the refrigeration cycle apparatus.
Solution to Problem
[0008] A heat transfer pipe for a heat exchanger according to the
present invention includes high threads and low threads that are
lower than the high threads, in which the high threads and the low
threads are provided at respective prescribed heights in a helical
manner in a pipe axial direction on a pipe inner surface, the high
threads are formed with 11 to 19 threads, the low threads are
formed of 3 to 6 threads between each pair of the high threads, the
high threads before expansion of the pipe each have a trapezoidal
shape in cross-section such that a crest thereof is flat, and a
ratio of a tip width of the crest portion after the expansion of
the pipe to an outer diameter of the heat transfer pipe is 0.011 to
0.040.
[0009] The heat exchanger according to the present invention
includes a plurality of fins for exchanging heat; and any of the
above heat transfer pipes that penetrates the fins, in which the
heat transfer pipe is pressurized from an inner surface side, is
expanded, and is fixed to the fins.
[0010] The refrigeration cycle apparatus according to the present
invention includes a refrigerant circuit including a compressor
that compresses a refrigerant, a condenser that condenses the
refrigerant by heat exchange, an expansion means for decompressing
the condensed refrigerant, and an evaporator that evaporates the
decompressed refrigerant by heat exchange connected by piping to
circulate the refrigerant, in which any of the above heat exchanger
is provided to both or either one of the condenser and the
evaporator.
[0011] The air-conditioning apparatus of the present invention in
which the refrigeration cycle apparatus carries out cooling/heating
of a conditioned space
Advantageous Effects of Invention
[0012] According to the heat transfer pipe for a heat exchanger of
the present invention, when expanding the heat transfer pipe by the
mechanical pipe expanding technique, although pipe expanding balls
contact the high threads and the crest portions are crushed flat,
the crest portions do not fall over, and compared to a conventional
heat transfer pipe, the heat transfer performance in the pipe can
be increased without increasing the pressure loss. Further, the
outer surface of the heat transfer pipe is fabricated into a
polygonal shape, springback of the heat transfer pipe is
suppressed, and the adherence between the heat transfer pipe and
the fins can be improved.
[0013] In addition, a highly efficient heat exchanger,
refrigeration cycle apparatus, and air-conditioning apparatus can
be provided using this heat transfer pipe.
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1 is a perspective view of a heat exchanger according
to Embodiment 1 of the present invention, and a cross-sectional
side view when the heat exchanger is cut parallel to a fin
surface.
[0015] FIG. 2 is an enlarged cross-sectional view of portion A of
the heat transfer pipe in FIG. 1 before pipe expansion and after
pipe expansion.
[0016] FIG. 3 is an explanatory diagram showing the expanded state
of the heat transfer pipe of FIG. 1 during pipe expansion by a
mechanical pipe expanding technique.
[0017] FIG. 4 is a diagram showing the relationship between the
number of high threads and the heat exchange rate in the heat
transfer pipe according to Embodiment 1.
[0018] FIG. 5 is a diagram showing the relationship between the
ratio of the tip width of the high threads after pipe expansion to
the outer diameter of the heat transfer pipe and the heat exchange
rate in the heat transfer pipe according to Embodiment 1.
[0019] FIG. 6 is a cross-sectional view showing a pipe inner
surface shape after pipe expansion of a heat transfer pipe
according to Embodiment 2 of the present invention.
[0020] FIG. 7 is a diagram showing the relationship between the
difference between the groove portion and the thread portion after
pipe expansion and the heat exchange rate in the heat transfer pipe
according to Embodiment 2.
[0021] FIG. 8 is a cross-sectional front view of a pipe inner
surface of a heat transfer pipe according to Embodiment 3 of the
present invention.
[0022] FIG. 9 is a diagram showing the relationship between a lead
angle of a helical groove and the heat exchange rate in the heat
transfer pipe according to Embodiment 3.
[0023] FIG. 10 is a cross-sectional view showing a pipe inner
surface shape of a heat transfer pipe according to Embodiment 4 of
the present invention.
[0024] FIG. 11 is a diagram showing the relationship between the
apex angle of the high threads and the heat exchange rate in the
heat transfer pipe according to Embodiment 4.
[0025] FIG. 12 is a system circuit diagram of an air-conditioning
apparatus according to Embodiment 5 of the present invention.
DESCRIPTION OF EMBODIMENTS
Embodiment 1
[0026] A heat exchanger in FIG. 1 is a fin-tube heat exchanger
widely used as an evaporator and condenser in a refrigeration
apparatus, an air-conditioning apparatus, and the like.
[0027] The heat exchanger 1 is constituted by a plurality of fins
10 for a heat exchanger and a heat transfer pipe 20. Through holes
11 are provided in each of the plurality of fins 10 that are
aligned at prescribed intervals, and the heat transfer pipe 20
penetrates through the through holes 11. The heat transfer pipe 20
becomes a portion of a refrigerant circuit in a refrigeration cycle
apparatus. By transferring heat between the refrigerant flowing
within the heat transfer pipe 20 and the air flowing outside via
the fins 10, the heat transfer area expands and heat exchange
between the refrigerant and the air can be efficiently
performed.
[0028] As shown in FIG. 2, the pipe inner surface of the heat
transfer pipe 20 is provided with groove portions 21 and thread
portions 22 made by groove formation, and as also shown in FIG. 2,
the thread portions 22 is further constituted by two types of
thread portion, high threads 22a and low threads 22b. A plurality
of low threads 22b is formed between the high threads 22a. The high
threads 22a each have a trapezoidal shape in cross-section so that
their crests before pipe expansion (FIG. 2(b)) are flat, and a
ratio (W1/D) of a tip width W1 of the crest portions of the high
threads 22a after pipe expansion (FIG. 2(a)) to an outer diameter D
of the heat transfer pipe 20 is 0.011 to 0.040. A height t1 of the
low threads 22b before pipe expansion is lower by t3, that is, 0.04
mm or greater, than a height t2 of the high threads 22a. However,
if the difference between the high threads 22a and the low threads
22b is too great (even if the low threads 22b are too low), the
heat performance may be reduced due to a reduction in the surface
area in the pipe or the like, and thus in Embodiment 1, the
difference is close to 0.04 mm.
[0029] In FIG. 3, in the heat exchanger 1, a pipe is first bent at
a middle portion in the longitudinal direction into a hairpin shape
with a prescribed bending pitch. A plurality of hairpin pipes that
will become the heat transfer pipe 20 are created. Next, the
hairpin pipes are inserted through the through holes 11 of the fins
10, and then the hairpin pipes are expanded by a mechanical pipe
expanding technique to form the heat transfer pipe 20. The heat
transfer pipe 20 is then closely adhered and fixed to the fins 10.
The mechanical pipe expanding technique is a method in which a rod
31, which has on its front tip a pipe expanding ball 30 whose
diameter is slightly larger than that of the inner diameter of the
heat transfer pipe 20, is passed through the inside of the heat
transfer pipe 20 to closely adhere the heat transfer pipe 20 to the
fins 10 by expanding the outer diameter of the heat transfer pipe
20.
[0030] When pipe expanding by the mechanical pipe expanding
technique, since the pipe expanding ball 30 makes contact with the
high threads 22a, the crest portions of the high threads 22a are
crushed flat to lower the height of the threads. On the other hand,
since the crest portions of the low threads 22b are lower than the
crushed height portion of 0.04 m, their shapes do not change (refer
to FIG. 2). Not as in the known art, since pressure from the
insertion of the pipe expanding ball 30 is not applied to all of
the thread portion in the pipe when expanding the pipe, but rather
only to the high threads 22a, the outer surface of the heat
transfer pipe 20 is fabricated into a polygonal shape, and
springback of the heat transfer pipe 20 can be suppressed. Thereby,
the adherence between the heat transfer pipe 20 and the fins 10 can
be improved, and the efficiency of heat exchange can be
increased.
[0031] FIG. 4 shows a relationship between the number of high
threads 22a and the heat exchange rate. On the inner surface of the
heat transfer pipe 20, 11 to 19 high threads 22a are continuously
formed in a helical manner in the axial direction, and 3 to 6 low
threads 22b are formed between a high thread 22a and a high thread
22a.
[0032] The reason that the number of high threads 22a of the heat
transfer pipe 20 is set in the range of 11 to 19, as in the above
heat exchanger 1, is that during pipe expansion, while the pipe
expanding ball 30 contacts the high threads 22a so that their crest
portions are crushed flat by about 0.04 mm to lower the height of
the threads, if the number of high threads 22a of the heat transfer
pipe 20 is lower than 11, the crest portions of the low threads 22b
will also be crushed flat, thereby decreasing the heat transfer
performance in the pipe. Further, if the number of high threads is
greater than 19, the number of low threads 22b will be reduced,
thereby decreasing the heat transfer performance in the pipe.
[0033] In the heat transfer pipe 20 after pipe expansion, the ratio
(W1/D) of the tip width W1 of the crest portions of the high
threads 22a to the outer diameter D of the heat transfer pipe 20 is
0.011 to 0.040 (refer to FIG. 2).
[0034] FIG. 5 shows a relationship between the ratio (W1/D) of the
tip width W1 of the high threads 22a after pipe expansion to the
outer diameter D of the heat transfer pipe 20 and the heat exchange
rate. If the ratio (W1/D) of the tip width W1 after pipe expansion
to the outer diameter D of the heat transfer pipe 20 is set to be
0.011 or less, when pipe expanding using the pipe expanding ball
30, the upper crest portions becomes crushed and the insertion
pressure becomes weak. Therefore, the pipe expansion of the heat
transfer pipe 20 becomes insufficient, the adherence between the
heat transfer pipe 20 and the fins 10 is hindered, and reduction in
the heat exchange rate becomes prominent. If the ratio (W1/D) of
the tip width W1 to the outer diameter D of the heat transfer pipe
20 is set to be 0.040 or greater, the cross-section area of the
groove portion 21 decreases, and thus the liquid film of the
refrigerant becomes thick which leads to a remarkable reduction in
the heat transfer coefficient.
[0035] On the other hand, if the curvature radius R1 of the tip
portions (crests) of the low threads 22b is set to 0.03 mm to 0.035
mm, the bottom width of the thread becomes narrow and the overall
thread is formed narrowly. Thereby, the heat transfer area
increases and the heat transfer coefficient in the pipe is improved
(refer to FIG. 2).
[0036] The high threads 22a each have a trapezoidal shape in
cross-section so that their crests before pipe expansion are flat,
the pressure of the crests becomes smaller, and the amount that the
crests are crushed is reduced. However, if the curvature radii of
the flat surface and both side surfaces of the crests are 0.01 mm
or less, the manufacturing cost of the heat transfer pipe 20 may
increase. Thus, it is preferable for the curvature radii of the
flat surface and both side surfaces of the crests to be 0.01 to
0.03 mm.
[0037] As described above, according to the heat exchanger 1 of
Embodiment 1, thread portions 22 constituted by high threads 22a
and low threads 22b are formed in a helical manner in a pipe axial
direction on the pipe inner surface of the heat transfer pipe 20.
The high threads 22a that are formed with 11 to 19 threads at a
prescribed height each have a trapezoidal shape in cross-section so
that their crests before pipe expansion are flat, and the ratio
(W1/D) of the tip width W1 of the crest portions after pipe
expansion to the outer diameter D of the heat transfer pipe 20 is
0.011 to 0.040. The low threads 22b have a height that is lower
than the high threads 22a and are formed with 3 to 6 threads
between a high thread 22a and a high thread 22a, and the curvature
radius R1 of the crests of the low threads 22b is 0.03 mm to 0.045
mm. Therefore, the heat transfer performance in the heat transfer
pipe 20 can be improved. Further, since the pipe expanding ball 30
contacts only the high threads 22a to expand the pipe, the outer
surface of the heat transfer pipe 20 is fabricated into a polygonal
shape, and springback of the heat transfer pipe 20 is suppressed.
Thereby, the adherence between the heat transfer pipe 20 and the
fins 10 can be improved, and the heat exchange rate (ratio of the
amount of heat before and after passage through the heat transfer
pipe) can be increased so as to conserve energy. Further, the
amount of refrigerant within the refrigerant circuit can be reduced
while maintaining high efficiency and miniaturization can also be
achieved.
Embodiment 2
[0038] FIG. 6 shows a shape of a pipe inner surface of a heat
transfer pipe 20 according to Embodiment 2 of the present
invention. Constitution of a heat exchanger 1 is the same as that
in Embodiment 1. The same reference numerals as those used in
Embodiment 1 will be assigned to those parts that play an identical
or corresponding role (the same applies to the subsequent
Embodiments below). In Embodiment 2, a difference H between a
groove portion 21 and a thread portion 22 after pipe expansion will
be explained.
[0039] FIG. 7 shows a relationship between a difference between the
groove portion 21 and the thread portion 22 after pipe expansion
(high threads 22a after pipe expansion) and the heat exchange rate.
In the heat transfer pipe 20, as the difference H between the
groove portion 21 and the thread portion 22 after pipe expansion
increases, the surface area in the pipe increases, and thus the
heat transfer coefficient also increases. However, if the
difference H between the groove portion 21 and the thread portion
22 becomes larger than 0.26 mm, the amount of increase in the
pressure loss becomes greater than the amount of increase in the
heat transfer coefficient, and thus the heat exchange rate
decreases. On the other hand, if the difference H between the
groove portion 21 and the thread portion 22 is less than 0.1 mm,
the heat transfer coefficient does not improve. Therefore, in the
heat transfer pipe 20, the high threads 22a and low threads 22b are
formed so that the difference H between the groove portion 21 and
the thread portion 22 after pipe expansion becomes 0.1 mm to 0.26
mm.
[0040] According to the heat exchanger 1 of Embodiment 2 described
above, since the high threads 22a and the low threads 22b are
formed so that the difference H between the groove portion 21 and
the thread portion 22 after pipe expansion becomes 0.1 mm to 0.26
mm, the heat transfer performance in the heat transfer pipe 20 can
be improved.
Embodiment 3
[0041] FIG. 8 shows a shape of a pipe inner surface of a heat
transfer pipe 20 according to Embodiment 3 of the present
invention. An angle (lead angle or helix angle) .gamma. formed by a
straight line that is parallel to the pipe axial direction and a
direction in which the groove portion (helical groove) 21 (thread
portion 22) extend on the pipe inner surface of the heat transfer
pipe 20 is 10 to 50 degrees.
[0042] FIG. 9 shows a relationship between the lead angle .gamma.
of the groove portion (helical groove) 21 in the heat transfer pipe
20 and the heat exchange rate. Basically, the reason that the lead
angle .gamma. of the groove portion (helical groove) 21 in the heat
transfer pipe 20 is set in the range of 10 to 50 degrees is that if
the lower limit of the lead angle .gamma. of the groove portion
(helical groove) 21 is set to 10 degrees or less, there is a
remarkable reduction in the heat exchange rate, and if the upper
limit of the lead angle .gamma. of the groove portion (helical
groove) 21 is set to 50 degrees or more, the pressure loss in the
pipe increases. Thereby, a flow which flows over the groove portion
(helical groove) 21 does not easily occur and the heat exchange
rate can be improved without an increase in the pressure loss in
the pipe, and thus a highly efficient air-conditioner can be
obtained.
[0043] According to the heat exchanger 1 of Embodiment 3 described
above, threads are formed so that the lead angle .gamma. of the
groove portion (helical groove) 21 in the heat transfer pipe 20 is
10 to 50 degrees. Therefore, the heat transfer performance in the
heat transfer pipe 20 can be improved.
Embodiment 4
[0044] FIG. 10 shows a shape of a pipe inner surface of a heat
transfer pipe 20 according to Embodiment 4 of the present
invention. In a heat exchanger 1, an apex angle .alpha. of high
threads 22a of the heat transfer pipe 20 is 15 to 30 degrees, and
an apex angle .beta. of low threads 22b is 5 to 15 degrees.
[0045] Basically, as the apex angle of each thread portion
decreases, the heat transfer area of the entire heat transfer pipe
20 increases, and thus the heat transfer coefficient increases.
However, as shown in FIG. 11, if the apex angle .alpha. of the high
threads 22a becomes smaller than 15 degrees, since workability when
manufacturing the heat exchanger 1 decreases remarkably, the heat
exchange rate ultimately decreases. On the other hand, if the apex
angle .alpha. becomes larger than 30 degrees, since the
cross-section area of the groove portion 21 decreases leading to
the liquid film of refrigerant to overflow from the groove portion
21 and causing the liquid film to cover up to the crest portions,
the heat transfer coefficient decreases.
[0046] On the other hand, by setting the apex angle .beta. of the
low threads 22b to 5 to 15 degrees, the bottom width of the threads
is also formed narrowly, and the overall thread is formed narrowly.
Thereby, the heat transfer area is increased and the heat transfer
coefficient in the pipe is increased.
[0047] According to the heat transfer pipe 20 of Embodiment 4
described above, the high threads 22a and the low threads 22b are
formed so that the apex angle .alpha. of the high threads 22a is 15
to 30 degrees and the apex angle .beta. of the low threads 22b is 5
to 15 degrees. Therefore, the heat transfer performance in the heat
transfer pipe 20 can be improved.
Embodiment 5
[0048] FIG. 12 shows an air-conditioning apparatus that is a
refrigeration cycle apparatus according to Embodiment 5 of the
present invention. The air-conditioning apparatus includes a heat
source side unit (outdoor unit) 100 and a load side unit (indoor
unit) 200, and these units are connected by refrigerant piping to
constitute a refrigerant circuit for circulating a refrigerant.
Among the refrigerant piping, a piping in which a refrigerant of
gas flows is called a gas piping 300, and a piping in which a
refrigerant of liquid (liquid refrigerant, there are cases of a
gas-liquid two-phase refrigerant, also) flows is called a liquid
piping 400. Herein, the refrigerant used includes, for example, an
HC single refrigerant, a mixed refrigerant including an HC
refrigerant, R32, R410A, R407C, tetrafluoropropene (for example,
2,3,3,3-tetrafluoropropene), a non-azeotropic refrigerant mixture
consisting of HFC refrigerant having a boiling point that is lower
than the tetrafluoropropene, carbon dioxide, or the like.
[0049] In Embodiment 5, the heat source side unit 100 includes the
following devices (means) such as a compressor 101, an oil
separator 102, a four-way valve 103, a heat source side heat
exchanger 104, a heat source side fan 105, an accumulator 106, a
heat source side expansion device (expansion valve) 107,
refrigerant-to-refrigerant heat exchanger 108, a bypass expansion
device 109, and a heat source side control device 110.
[0050] The compressor 101 has an electric motor, sucks the
refrigerant and compresses it to a high-temperature high-pressure
gas state, and then conveys it to the refrigerant piping. Regarding
the operation control of the compressor 101, the compressor 101 is
equipped with, for example, a master-side inverter circuit, a
slave-side inverter circuit, and the like, and the capacity (the
amount of refrigerant sent out per unit time) of the compressor 101
can be finely changed by arbitrarily changing the operation
frequency.
[0051] The oil separator 102 separates lubricant oil that has mixed
with the refrigerant and has been discharged from the compressor
101. The separated lubricant oil is returned to the compressor 101.
The four-way valve 103 switches the flow of refrigerant according
to whether the air-conditioning apparatus is in cooling operation
or heating operation, based on instructions from the heat source
side control device 110. The heat source side heat exchanger 104 is
constituted by the heat exchanger 1 explained in Embodiments 1 to
4, and exchanges heat with the refrigerant and air (outside air).
For example, during heating operation, the heat source side heat
exchanger 104 functions as an evaporator to exchange heat between a
low pressure refrigerant that has flowed in via the heat source
side expansion device 107 and air, and evaporates and gasifies the
refrigerant. Further, during cooling operation, the heat source
side heat exchanger 104 functions as a condenser to exchange heat
between a refrigerant that has been compressed in the compressor
101 and that has flowed in from the four-way valve 103 side and
air, and condenses and liquefies the refrigerant. The heat source
side fan 105 is provided to the heat source side heat exchanger 104
in order to efficiently carry out heat exchange between the
refrigerant and air. The heat source side fan 105 can also have an
inverter circuit (not illustrated) so that the rotational speed of
the fan can be finely changed by arbitrarily changing the operation
frequency of the fan motor.
[0052] The refrigerant-to-refrigerant heat exchanger 108 exchanges
heat between a refrigerant flowing through the main passage of the
refrigerant circuit and the refrigerant that has branched from the
main passage and that had its flow regulated by the bypass
expansion device (expansion valve) 109. When it is necessary to
supercool the refrigerant, particularly during cooling operation,
the refrigerant-to-refrigerant heat exchanger 108 supercools the
refrigerant and supplies it to the load side unit 200. The
refrigerant-to-refrigerant heat exchanger 108 is also constituted
by the heat exchanger 1 explained in Embodiments 1 to 4.
[0053] Liquid that flows through the bypass expansion device 109 is
returned to the accumulator (liquid separator) 106 via a bypass
piping. The accumulator 106 is, for example, a means for retaining
excess liquid refrigerant. The heat source side control device 110
is constituted by, for example, a microcomputer or the like, and
can communicate via wires or wirelessly with a load side control
device 204. For example, the heat source side control device 110
performs operational control of the entire air-conditioning
apparatus by controlling each means in the air-conditioning
apparatus, such as operation frequency control of the compressor
101 by inverter circuit control, based on data related to detection
of various detection means (sensors) within the air-conditioning
apparatus.
[0054] Meanwhile, the load side unit 200 is constituted by a load
side heat exchanger 201, an expansion device (expansion valve) 202,
a load side fan 203, and the load side control device 204. The load
side heat exchanger 201 is also constituted by the heat exchanger 1
explained in Embodiments 1 to 4, and exchanges heat between the
refrigerant and air in a space subject to air-conditioning. For
example, during heating operation, the load side heat exchanger 201
functions as a condenser, exchanges heat between the refrigerant
that has flowed in from the gas piping 300 and air, condenses and
liquefies the refrigerant (or turns the refrigerant into a
gas-liquid two-phase refrigerant), and discharges it to the liquid
piping 400 side. On the other hand, during cooling operation, the
load side heat exchanger 201 functions as an evaporator, exchanges
heat between the refrigerant that has been turned into a low
pressure state by the load side expansion device 202 and air,
causes the refrigerant to take away heat from the air and evaporate
and gasify itself, and discharges it to the gas piping 300 side.
Further, the load side fan 203 for regulating the flow of air that
performs heat exchange is provided to the load side unit 200. The
operation speed of the load side fan 203 is determined by, for
example, a user setting. The load side expansion device 202
regulates the pressure of the refrigerant within the load side heat
exchanger 201 by changing the opening degree.
[0055] The load side control device 204 is also constituted by a
microcomputer or the like, and can, for example, communicate via
wires or wirelessly with the heat source side control device 110.
The load side control device 204 controls each device (means) of
the load side unit 200 so that, for example, the indoors reaches a
certain temperature, based on instructions from the heat source
side control device 110 or instructions from a resident or the
like. The load side control device 204 also sends signal containing
data related to detection of the detection means disposed in the
load side unit 200.
[0056] Next, the operation of the air-conditioning apparatus will
be explained. First, the basic refrigerant circulation in the
refrigerant circuit during cooling operation will be explained. A
high-temperature high-pressure gas refrigerant discharged from the
compressor 101 by the drive operation of the compressor 101 is
condensed while passing through the heat source side heat exchanger
104 via the four-way valve 103, turns into a liquid refrigerant,
and flows out of the heat source side unit 100. The refrigerant
that has flowed into the load side unit 200 through the liquid
piping 400, which is a low-temperature low-pressure liquid
refrigerant whose pressure has been controlled by the regulation of
the opening degree of the load side expansion device 202, flows
through the load side heat exchanger 201, is evaporated, and flows
out of the load side heat exchanger 201. The refrigerant then flows
into the heat source side unit 100 through the gas piping 300, is
sucked into the compressor 101 via the four-way valve 103 and the
accumulator 106, and is compressed again and discharged, thereby
completing a circulation.
[0057] The basic refrigerant circulation in the refrigerant circuit
during heating operation will now be explained. A high temperature,
high-pressure gas refrigerant discharged from the compressor 101 by
the drive operation of the compressor 101 flows into the load side
unit 200 from the four-way valve 103 through the gas piping 300. In
the load side unit 200, the pressure of the refrigerant is adjusted
by regulation of the opening degree of the load side expansion
device 202. The refrigerant is condensed while passing through the
load side heat exchanger 201 and flows out of the load side unit
200 being turned into a liquid state or gas-liquid two-phase state
at intermediate pressure. The pressure of the refrigerant that has
flowed into the heat source side unit 100 through the liquid piping
400 is adjusted by regulation of the opening degree of the heat
source side expansion device 107. The refrigerant is made to
evaporate while passing through the heat source side heat exchanger
104, turns into a gas refrigerant, is sucked into the compressor
101 via the four-way valve 103 and the accumulator 106, is
compressed and discharged as described above, thereby completing a
circulation.
[0058] According to the air-conditioning apparatus of Embodiment 5
explained above, the heat source side heat exchanger 104 of the
heat source side unit 100, the refrigerant-to-refrigerant heat
exchanger 108, and the load side heat exchanger 201 of the load
side unit 200 are constituted by the heat exchanger 1 of
Embodiments 1 to 4, which has a high heat exchange rate, as an
evaporator or a condenser. Therefore, the COP (coefficient of
performance: energy efficiency ratio, performance factor) and the
like can be improved, and energy can be conserved.
[0059] In Embodiment 5 described above, the application of the heat
exchanger according to the present invention in an air-conditioning
apparatus was explained. However, the present invention is not
limited to such an apparatus, and the invention can be applied to
other refrigeration cycle apparatuses that include a heat exchanger
that functions as an evaporator and a condenser and that
constitutes a refrigerant circuit such as a refrigeration apparatus
and heat pump system.
Examples
[0060] Below, examples of the present invention will be explained
with comparison to comparative examples that deviate from the scope
of the present invention. As shown in Table 1, heat exchangers 1
were fabricated, wherein the outer diameter is 7 mm, the bottom
thickness of the groove 21 is 0.25 mm, the lead angle is 30
degrees, and the number of high threads 22a is 11 or 19 (Examples 1
and 2). Further, as comparative examples, heat exchangers were
fabricated, wherein the outer diameter is 7 mm, the bottom
thickness of the groove is 0.25 mm, and the number of high threads
is 6 or 30 (Comparative Examples 1 and 2).
TABLE-US-00001 TABLE 1 Thread Number Outer Bottom Lead (High Heat
Diameter Thickness Angle Threads) Exchange (mm) (mm) (degrees) (--)
Rate (%) Comparative 7 0.25 30 6 99 Example 1 Example 1 7 0.25 30
11 101.3 Example 2 7 0.25 30 19 101 Comparative 7 0.25 30 30 99.5
Example 2
[0061] As is clear from Table 1, the heat exchange rate of the heat
exchangers 1 in Example 1 and Example 2 was 101.3% and 101%,
respectively, and the heat exchange rate of the heat exchangers in
Comparative Example 1 and Comparative Example 2 was 99% and 99.5%,
respectively. The heat exchangers 1 in Example 1 and Example 2 have
a higher heat exchange rate compared to the heat exchangers in both
of Comparative Examples 1 and 2, and the heat transfer performance
in the pipe showed improvement.
[0062] Next, as shown in Table 2, heat exchangers 1 were
fabricated, wherein the outer diameter is 7 mm, the bottom
thickness of the grooves 21 is 0.25 mm, the lead angle is 30
degrees, and the ratio (W1/D) of the tip width W1 of the high
threads 22a to the outer diameter D of the heat transfer pipe 20 is
0.011, 0.020, or 0.040 (Examples 3, 4, and 5). Further, as
comparative examples, heat exchangers were fabricated, wherein the
outer diameter is 7 mm, the bottom thickness of the grooves is 0.25
mm, the lead angle is 30 degrees, and the ratio (W1/D) of the tip
width of the high threads to the outer diameter of the heat
transfer pipe is 0.005 or 0.050 (Comparative Examples 3 and 4).
TABLE-US-00002 TABLE 2 Tip Width of High Threads Outer Bottom to
Outer Diam- Thick- Lead Diameter of Heat eter ness Angle Heat
Transfer Exchange (mm) (mm) (degrees) Pipe (--) Rate (%)
Comparative 7 0.25 30 0.005 99.2 Example 3 Example 3 7 0.25 30
0.011 101.2 Example 4 7 0.25 30 0.02 101.8 Example 5 7 0.25 30 0.04
101 Comparative 7 0.25 30 0.05 98 Example 4
[0063] As is clear from Table 2, the heat exchange rate of the heat
exchangers 1 in Example 3, Example 4, and Example 5 was 101.2%,
101.8%, and 101%, respectively, and the heat exchange rate of the
heat exchangers in Comparative Example 3 and Comparative Example 4
was 99.2% and 98%, respectively. The heat exchangers 1 in Example
3, Example 4, and Example 5 have a higher heat exchange rate
compared to the heat exchangers in both of Comparative Examples 3
and 4, and the heat transfer performance within the pipe showed
improvement.
[0064] Next, as shown in Table 3, heat exchangers 1 were
fabricated, wherein the outer diameter is 7 mm, the bottom
thickness of the grooves 21 is 0.25 mm, the lead angle is 30
degrees, and the groove depth after pipe expansion is 0.1 mm or
0.26 mm (Examples 6 and 7). Further, as comparative examples, heat
exchangers were fabricated, wherein the outer diameter is 7 mm, the
bottom thickness of the grooves is 0.25 mm, the lead angle is 30
degrees, and the groove depth after pipe expansion is 0.05 mm or
0.3 mm (Comparative Examples 5 and 6).
TABLE-US-00003 TABLE 3 Groove Depth After Outer Bottom Pipe Heat
Diameter Thickness Lead Expansion Exchange (mm) (mm) Angle (mm)
Rate (%) Comparative 7 0.25 30 0.05 99 Example 5 Example 6 7 0.25
30 0.1 101.5 Example 7 7 0.25 30 0.26 101.2 Comparative 7 0.25 30
0.3 99.4 Example 6
[0065] As is clear from Table 3, the heat exchange rate of the heat
exchangers 1 in Example 6 and Example 7 was 101.5% and 101.2%,
respectively, and the heat exchange rate of the heat exchangers in
Comparative Example 5 and Comparative Example 6 was 99% and 99.4%,
respectively. The heat exchangers 1 in Example 6 and Example 7 have
a higher heat exchange rate compared to the heat exchangers in both
of Comparative Examples 5 and 6, and the heat transfer performance
in the pipe showed improvement.
[0066] Next, as shown in Table 4, heat exchangers 1 were
fabricated, wherein the outer diameter is 7 mm, the bottom
thickness of the grooves 21 is 0.25 mm, the apex angle is 30
degrees, and the lead angle .gamma. is 10 degrees, 30 degrees, or
50 degrees (Examples 8, 9, and 10). Further, as comparative
examples, heat exchangers were fabricated, wherein the outer
diameter is 7 mm, the bottom thickness of the grooves is 0.25 mm,
the apex angle is 30 degrees, and the lead angle is 5 degrees or 60
degrees (Comparative Examples 7 and 8).
TABLE-US-00004 TABLE 4 Outer Bottom Apex Lead Heat Diameter
Thickness Angle Angle Exchange (mm) (mm) (degrees) (degrees) Rate
(%) Comparative 7 0.25 30 5 99.2 Example 7 Example 8 7 0.25 30 10
100.9 Example 9 7 0.25 30 30 101.5 Example 10 7 0.25 30 50 100.8
Comparative 7 0.25 30 60 99.5 Example 8
[0067] As is clear from Table 4, the heat exchange rate of the heat
exchangers 1 in Example 8, Example 9, and Example 10 was 100.9%,
101.5%, and 101.8%, respectively, and the heat exchange rate of the
heat exchangers in Comparative Example 7 and Comparative Example 8
was 99.2% and 99.5%, respectively. The heat exchangers 1 in Example
8, Example 9, and Example 10 have a higher heat exchange rate
compared to the heat exchangers in both of Comparative Examples 7
and 8, and the heat transfer performance within the pipe showed
improvement.
[0068] Next, as shown in Table 5, heat exchangers 1 were
fabricated, wherein the outer diameter is 7 mm, the bottom
thickness of the grooves 21 is 0.25 mm, the lead angle is 30
degrees, and the apex angle .alpha. is 15 degrees or 30 degrees
(Examples 11 and 12). Further, as comparative examples, heat
exchangers were fabricated, wherein the outer diameter is 7 mm, the
bottom thickness is 0.25 mm, the lead angle is 30 degrees, and the
apex angle is 10 degrees or 40 degrees (Comparative Examples 9 and
10).
TABLE-US-00005 TABLE 5 Outer Bottom Lead Apex Heat Diameter
Thickness Angle Angle Exchange (mm) (mm) (degrees) (degrees) Rate
(%) Comparative 7 0.25 30 10 99 Example 9 Example 11 7 0.25 30 15
101 Example 12 7 0.25 30 30 101.3 Comparative 7 0.25 30 40 99.3
Example 10
[0069] As is clear from Table 5, the heat exchange rate of the heat
exchangers 1 in Example 11 and Example 12 was 101% and 101.3%,
respectively, and the heat exchange rate of the heat exchangers in
Comparative Example 9 and Comparative Example 10 was 99% and 99.3%,
respectively. The heat exchangers 1 in Example 11 and Example 12
have a higher heat exchange rate compared to the heat exchangers in
both of Comparative Examples 9 and 10, and the heat transfer
performance within the pipe showed improvement.
REFERENCE SIGNS LIST
[0070] 1 . . . heat exchanger; 10 . . . fin; 11 . . . through hole;
20 . . . heat transfer pipe; 21 . . . groove portion; 22 . . .
thread portion; 22a . . . high thread (thread portion); 22b . . .
low thread (thread portion); 30 . . . pipe expanding ball; 31 . . .
rod; 100 . . . heat source side unit; 101 . . . compressor; 102 . .
. oil separator; 103 . . . four-way valve; 104 . . . heat source
side heat exchanger; 105 . . . heat source side fan; 106 . . .
accumulator; 107 . . . heat source side expansion device; 108 . . .
refrigerant-to-refrigerant heat exchanger; 109 . . . bypass
expansion device; 110 . . . heat source side control device; 200 .
. . load side unit; 201 . . . load side heat exchanger; 202 . . .
load side expansion device; 203 . . . load side fan; 204 . . . load
side control device; 300 . . . gas piping; 400 . . . liquid piping;
.alpha. . . . apex angle of high thread; .beta. . . . apex angle of
low thread; .gamma. . . . direction in which the thread portion
extend relative to pipe axial direction (lead angle); D . . . outer
diameter of heat transfer pipe; H . . . height of high thread after
pipe expansion; R1 . . . curvature radius of crest of low thread;
W1 . . . tip width of crest portion of high thread after pipe
expansion.
* * * * *