GB2557822A

GB2557822A - Air heat exchanger and outdoor unit

Info

Publication number: GB2557822A
Application number: GB1805619.2A
Authority: GB
Inventors: Ishida Kazuyuki; Okoshi Yasushi; Ito Takuya; Hikone Takahito
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2015-10-19
Filing date: 2015-10-19
Publication date: 2018-06-27
Anticipated expiration: 2035-10-19
Also published as: JPWO2017068632A1; WO2017068632A1; GB201805619D0; JP6469245B2; GB2557822B

Abstract

An air heat exchanger and an outdoor unit having greater fin strength, lower wind resistance, and higher heat exchange efficiency. The air heat exchanger and the outdoor unit are provided with: a plurality of first heat exchangers comprising a plurality of rough-surface fins and a heat-transfer pipe through which a coolant is channeled, the heat-transfer pipe being inserted through the plurality of rough-surface fins; and a second heat exchanger comprising a plurality of smooth fins and a heat-transfer pipe through which a coolant is channeled, the heat-transfer pipe being inserted through the plurality of smooth fins, the second heat exchanger being adjacent to the plurality of first heat exchangers. The first heat exchangers curve toward the second heat exchanger side, and the second heat exchanger curves to the same side as the first heat exchangers.

Description

(56) Documents Cited:

WO 2014/024221 A1 JP 2008261611 A JPS63167078

JP 2014114983 A JP 2008128553 A (58) Field of Search:

INT CL F24F, F28F

Other: Jitsuyo Shinan Koho 1922-1996; Jitsuyo Shinan Toroku Koho 1996-2015; Kokai Jitsuyo Shinan Koho 1971-2015; Toroku Jitsuyo Shinan Koho 1994-2015 (71) Applicant(s):

Mitsubishi Electric Corporation (Incorporated in Japan)

7-3 Marunouchi 2-chome, Chiyoda-ku, Tokyo 100-8310, Japan (72) Inventor(s):

Kazuyuki Ishida Yasushi Okoshi Takuya Ito Takahito Hikone (74) Agent and/or Address for Service:

Mewburn Ellis LLP

City Tower, 40 Basinghall Street, LONDON, Greater London, EC2V 5DE, United Kingdom (54) Title of the Invention: Air heat exchanger and outdoor unit Abstract Title: Air heat exchanger and outdoor unit (57) An air heat exchanger and an outdoor unit having greater fin strength, lower wind resistance, and higher heat exchange efficiency. The air heat exchanger and the outdoor unit are provided with: a plurality of first heat exchangers comprising a plurality of rough-surface fins and a heat-transfer pipe through which a coolant is channeled, the heat-transfer pipe being inserted through the plurality of rough-surface fins; and a second heat exchanger comprising a plurality of smooth fins and a heat-transfer pipe through which a coolant is channeled, the heat-transfer pipe being inserted through the plurality of smooth fins, the second heat exchanger being adjacent to the plurality of first heat exchangers. The first heat exchangers curve toward the second heat exchanger side, and the second heat exchanger curves to the same side as the first heat exchangers.

[04]

(a I (h)

1/7

FIG. 1

2/7

FIG. 2

3/7

FIG. 3

( a ί ib)

4/7

FIG. 4

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FIG. 5

(b)

6/7

FIG. 6

5

/ 's i LX

5

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FIG. 7

LOW ◄— UNIT EFFICIENCY —► HIGH

LOW ◄ COMPRESSORE CAPACITY

HIGH

DESCRIPTION

Title of Invention

AIR HEAT EXCHANGER AND OUTDOOR UNIT

Technical Field [0001]

The present invention relates to an air heat exchanger and an outdoor unit and, more specifically, to the structure of an air heat exchanger that is used in a large outdoor unit.

Background Art [0002]

For example, in cold/hot water supply systems employed in buildings such as office buildings, air-conditioning apparatuses, serving as heat load sources, are provided in respective rooms, and cold/hot water produced in a cold/hot heat source apparatus is supplied thereto. The cold/hot heat source apparatus produces cold water or hot water by exchanging heat with the outside air by using an air heat exchanger of a heat-pump-type refrigeration cycle. Patent Literature 1 discloses a technique, which is an example of a cold/hot water supply system, in which cold/hot water is produced, and the cold/hot water is used to condition air in a facility and to regulate water temperature in a pool.

[0003]

Typically, fins used in air heat exchangers are provided with cut-and-raised portions to cause turbulence and thus to improve the heat-exchange efficiency. Furthermore, for example, as disclosed in Patent Literature 2, it is proposed to improve water drainage by recesses-and-projections formed on fins and thus to suppress an increase in air-sending resistance due to deposited condensation water. Citation List

Patent Literature [0004]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2002-13838

Patent Literature 2: Japanese Unexamined Patent Application Publication No. 54-153366

Summary of Invention

Technical Problem [0005]

When the cold/hot water supply system in Patent Literature 1 is employed in buildings such as office buildings, because an outdoor unit is installed in a small space in a rooftop or other places, the air heat exchanger accommodated in the outdoor unit needs to be bent and reduced in size. However, if the air heat exchanger is bent, fins located on the inner side of the bent portion are brought close to one another, and thus, the bending angle is limited. This is because, if the fins are brought close to one another, the cut-and-raised parts provided on the fins may lie down or come into contact with one another, increasing the air-sending resistance. Because an increase in air-sending resistance increases the power consumption of a fan, cold/hot water supply systems employed in office buildings or other buildings in which a measure to improve the energy efficiency while reducing the compressor capacity is taken relatively decrease the energy efficiency.

[0006]

When fins provided with recesses-and-projections, as in Patent Literature 2, are employed, as a result of the fins being bent, a stress concentration occurs in the fins, which may decrease the strength of the fins. As a result, the fins may be bent in an unwanted direction, thus closing the spaces between the fins and increasing the air-sending resistance.

[0007]

The present invention has been made to overcome the above-described problems, and an object thereof is to provide an air heat exchanger and an outdoor unit in which the strength of fins is maintained and the air-sending resistance is reduced, even through the size thereof is reduced.

Solution to Problem [0008]

An air heat exchanger of one embodiment of the present invention includes a plurality of first heat exchangers each including a plurality of rough-surface fins and a heat transfer tube extending through the plurality of rough-surface fins, refrigerant flowing through the heat transfer tube; and a second heat exchanger provided adjacent to the plurality of first heat exchangers, the second heat exchanger including a plurality of smooth fins and a heat transfer tube extending through the smooth fins, the refrigerant flowing through the heat transfer tube. The first heat exchangers are bent toward the second heat exchanger, and the second heat exchanger is bent toward a same side as a side to which the first heat exchangers are bent. Advantageous Effects of Invention [0009]

According to the air heat exchanger of one embodiment of the present invention, because the first heat exchangers and the second heat exchanger are bent toward the second heat exchanger, which include the smooth fins, a stress concentration does not occur at the bent portion, and the smooth fins that are brought close to one another due to sharp bending do not come into contact with one another. Hence, even when the air heat exchanger is made compact, it is possible to prevent decrease in the strength of the fins and to reduce the power consumption of a fan. Furthermore, because the first heat exchangers include the rough-surface fins provided with the recesses-and-projections, it is possible to maintain high heatexchange efficiency.

Brief Description of Drawings [0010] [Fig. 1] Fig. 1 shows a refrigeration cycle device accommodated in an outdoor unit according to Embodiment.

[Fig. 2] Fig. 2 is a schematic plan view of an air heat exchanger of the outdoor unit in Fig. 1.

[Fig. 3] Fig. 3 includes the air heat exchanger in Fig. 2 and an enlarged side view of the air heat exchanger in Fig. 2, as viewed in the direction indicated by the arrow.

[Fig. 4] Fig. 4 includes the air heat exchanger in Fig. 2 and an enlarged side view of the air heat exchanger in Fig. 2, as viewed in the direction indicated by the arrow.

[Fig. 5] Fig. 5 includes an enlarged side view of a straight portion of a heat exchanger according to a modification, as viewed in the direction indicated by the arrow.

[Fig. 6] Fig. 6 includes an enlarged side view of a bent portion of the heat exchanger according to the modification, as viewed in the direction indicated by the arrow.

[Fig. 7] Fig. 7 is a scatter diagram showing a result of the performance evaluation of the air heat exchanger according to Embodiment.

Description of Embodiments [0011]

Embodiment

Fig. 1 shows a refrigeration cycle device accommodated in an outdoor unit 100 according to Embodiment. As shown in Fig. 1, in the outdoor unit 100, the refrigeration cycle device in which a compressor 1, an air heat exchanger 2, an expansion valve 4, and an evaporator 5 are connected by a refrigerant pipe 7 is accommodated in, for example, a rectangular-column-shaped casing 8. The air heat exchanger 2 is disposed at the upper part of the casing 8, together with a fan 3. The outdoor unit 100 is of a top-flow type and is disposed on, for example, the rooftop of a building.

[0012]

The air heat exchanger 2 is disposed inside the casing 8 so as to extend along an inner surface of the casing 8 and exchanges heat between the refrigerant flowing therein and the air passing therethrough. The fan 3 takes in the air from a side surface of the casing 8 and sends the air so as to discharge the air from the upper side while allowing the air to pass through the air heat exchanger 2. The evaporator 5 constitutes a cold/hot heat source apparatus. The refrigerant that has exchanged heat in the air heat exchanger 2 flows in the evaporator 5 and exchanges heat with water flowing through an inlet water pipe 6a and an outlet water pipe 6b disposed near the evaporator 5. The water flowing through the inlet water pipe 6a and the outlet water pipe 6b becomes cold/hot water as a result of the heat exchange and circulates through a facility.

[0013]

Fig. 2 is a schematic plan view of the air heat exchanger 2 of the outdoor unit 100 in Fig. 1. As shown in Fig. 2, the air heat exchanger 2 is of a type called fourrow air heat exchanger and is formed in a shape extending along an inner surface of the casing 8 of the outdoor unit 100. More specifically, the air heat exchanger 2 includes three rows of first heat exchangers 20 that are adjacent to one another and a second heat exchanger 25 that is adjacent to the first heat exchangers 20, is bent toward the second heat exchanger 25, and has a straight portion 2a extending along the inner surface of the casing 8 and a bent portion 2b bent along a corner of the casing 8. Note that the number of the bent portions 2b in the air heat exchanger 2 may be selected, as appropriate, according to the shape of the air heat exchanger 2. For example, when the air heat exchanger 2 is formed so as to extend along two side surfaces of the casing 8, one bent portion 2b is formed, whereas when the air heat exchanger 2 is formed so as to extend along three side surfaces of the casing 8, two bent portions 2b are formed. Furthermore, although the bent portion 2b in Fig. 2 is bent at right angle, the angle of the bent portion 2b is not limited, and the angle may be selected, as appropriate, according to the shape ofthe casing 8 or other factors. [0014]

A heat transfer tube is formed of a single pipe that is bent multiple times and thus has multiple stages in side view such that the air flowing in from the side surface of the casing 8 easily comes into contact therewith. Note that, in Fig. 2, a heat transfer tube and rough-surface fins are integrally shown as the first heat exchangers 20, and a heat transfer tube and smooth fins are integrally shown as the second heat exchanger 25, and these components are not individually shown.

[0015]

Fig. 3(a) is a schematic view of the air heat exchanger 2 in Fig. 2, and Fig. 3(b) is an enlarged side view of the air heat exchanger 2 in Fig. 2, as viewed from the direction indicated by the arrow. For convenience's sake, in Fig. 3(a), the left side and the right side of the air heat exchanger 2 in Fig. 2 are reversed. As shown in Fig. 3(b), on the outer side of the bent portion 2b of the air heat exchanger 2, for example, three rows of the first heat exchangers 20 are disposed in a layered manner. The first heat exchangers 20 are each formed of a heat transfer tube 21 and a plurality of rough-surface fins 22 through which the heat transfer tube 21 passes. The rough-surface fins 22 are fins provided with recesses-and-projections. Cut-and-raised parts 22a on the rough-surface fins 22 disturb the air flowing between the rough-surface fins 22, thus facilitating heat exchange. The rough-surface fins 22 are, for example, cross fins or other fins provided with a plurality of cut-and-raised parts 22a.

[0016]

Fig. 4(a) is a schematic view of the air heat exchanger 2 in Fig. 2, and Fig. 4(b) is an enlarged side view of the second heat exchanger 25 in the air heat exchanger 2 in Fig. 2, as viewed in the direction indicated by the arrow. As shown in Fig. 4, the second heat exchanger 25, which is adjacent to the plurality of first heat exchangers 20, is located on the inner side of the bent portion 2b of the air heat exchanger 2.

The second heat exchanger 25 includes a heat transfer tube 21 and a plurality of smooth fins 27 through which the heat transfer tube 21 passes. The smooth fins 27 are flat, plate-shaped fins, and the resistance of the air flowing through the smooth fins 27 is lower than the resistance of the air flowing through the rough-surface fins

22. The smooth fins 27 are, for example, ring fins or other fins having no recessesand-projections, such as the cut-and-raised parts, in the surfaces.

[0017]

As in the related art, when solely the first heat exchangers 20, in which the rough-surface fins 22 are arranged, are disposed in the air heat exchanger 2, because the first heat exchanger 20 having the rough-surface fins 22 is located also on the inner side of the bent portion 2b, the rough-surface fins 22 are brought close to one another. In this configuration, the flow of air is inhibited, the air-sending efficiency is decreased by the cut-and-raised parts 22a, and consequently, the heatexchange efficiency is decreased. If the bent portion 2b is made less sharp to maintain the shape of the rough-surface fins 22, the size of the overall outdoor unit increases, thus increasing the area occupied, which is undesirable.

[0018]

In contrast, in the configuration of Embodiment, the second heat exchanger 25, which has the smooth fins 27, is provided on the inner side of the bent portion 2b. Because the smooth fins 27 are not provided with cut-out portions or recesses-andprojections, even though the smooth fins 27 are brought close to one another at the bent portion 2b, the flow of air is not excessively inhibited. Furthermore, even if the angle of the bent portion 2b is sharp, because the smooth fins 27 are unlikely to come into contact with one another, and a local stress concentration in the smooth fins 27 is suppressed, the strength of the smooth fins 27 is maintained high. Hence, even when the air heat exchanger 2 is bent and accommodated in the casing 8, it is possible to obtain high air-sending efficiency while maintaining the heat exchange capacity. In the outdoor unit 100 accommodating this air heat exchanger 2, the area occupied by the outdoor unit 100 is small.

[0019] [Modification]

Fig. 5(a) is a schematic view of an air heat exchanger 30 according to a modification, and Fig. 5(b) is an enlarged side view of straight portions 30a of the air heat exchanger 30 in Fig. 5(a), as viewed in the direction indicated by the arrow. Furthermore, Fig. 6(a) is a schematic view of the air heat exchanger 30 according to the modification, and Fig. 6(b) is an enlarged side view of a bent portion 30b of the air heat exchanger 30 in Fig. 6(a), as viewed in the direction indicated by the arrow. As shown in Figs. 5 and 6, in this modification, the air heat exchanger 30 includes three rows of first heat exchangers 31 and a second heat exchanger 35 located on the inner side thereof. Among them, the straight portions 30a of the first heat exchangers 31 include the rough-surface fins 22. Furthermore, in the second heat exchanger 35, the smooth fins 27 are provided at the bent portion 30b, and the roughsurface fins 22 are provided at the straight portion 30a.

[0020]

Because the second heat exchanger 35 has the smooth fins 27 at the bent portion 30b, an increase in air-sending resistance due to the smooth fins 27 being adjacent to one another is suppressed. Furthermore, because the rough-surface fins 22 are provided at the straight portion 30a of the second heat exchanger 35, the air is disturbed, and thus, heat exchange is facilitated. In this way, by using the smooth fins 27 only in the area where the air-sending resistance may be increased and by using the rough-surface fins 22 in the other areas, it is possible to maintain high heat-exchange efficiency with the rough-surface fins 22 while reducing the airsending resistance with the smooth fins 27.

[0021]

Note that, besides the above-described configuration, a configuration in which, for example, different types of fins are disposed in the stage direction of the second heat exchanger 25 may be employed. Furthermore, the recesses-and-projections formed on the rough-surface fins 22 are not limited to the cut-and-raised parts 22a, and, for example, a configuration in which small projections are attached may also be employed.

[0022] [Performance Evaluation]

In a performance evaluation, an evaluation was performed on the basis of indexes defined by Integrated Part Load Value, abbreviated as IPLV. IPLV defines, as indexes, the coefficients of performance of a refrigerator at four different loads and evaluates the energy efficiency of the refrigerator on the basis of the operating ratio at the respective loads. As the evaluation targets, a related-art air heat exchanger having four rows of the first heat exchangers 20 that are bent, and the air heat exchanger 2 according to Embodiment having three rows of the first heat exchangers 20 and one row of the second heat exchanger 25 that are bent toward the second heat exchanger 25 were employed.

[0023]

Fig. 7 is a scatter diagram showing a result of the performance evaluation of the air heat exchanger 2 according to Embodiment. The horizontal axis shows the compressor capacity, and the vertical axis shows the unit efficiency. The unit efficiency indicates the energy efficiency of the air heat exchanger. Furthermore, in Fig. 7, diamond marks show the results obtained with the related-art air heat exchanger, and square marks show the results obtained with the air heat exchanger 2 according to Embodiment.

[0024]

As shown in Fig. 7, in both of the related-art heat exchanger and the air heat exchanger 2 according to Embodiment, when the partial load factor was reduced, the unit efficiency increased. This means that the higher the percentage at which the heat exchanger operates at a low partial load factor is, the higher the energy efficiency is, and the higher the percentage at which the heat exchanger operates at a high partial load factor is, the lower the energy efficiency is. At low (50% and 25%) partial load factors, the unit efficiency of the air heat exchanger 2 according to Embodiment showed larger values than that of the related-art air heat exchanger.

The reason for this is considered that, because the use of smooth fins in the second heat exchanger decreases the air-sending resistance, the power consumption of the fan decreases, and thus, the energy efficiency increases. This shows that, by providing the smooth fins in the second heat exchanger, which is on the inner side of the bent portion, the air heat exchanger 2 according to Embodiment obtains high energy efficiency. The structure of Embodiment was useful particularly when a lowload operation was assumed.

[0025]

In the above-described air heat exchanger 2 of the present invention, the second heat exchanger 25 having the flat, plate-shaped smooth fins 27a is located on the inner side of the bent portion 2b. With this configuration, a local stress concentration does not occur in the smooth fins 27 at the bent portion 2b, and the smooth fins 27 do not contact one another even though they are close to one another.

Hence, it is possible to prevent decrease in strength due to a local stress concentration while reducing the area occupied and to reduce the power consumption of the fan 3, thus improving the heat-exchange efficiency.

[0026]

Furthermore, by providing the rough-surface fins 22 in the areas other than the bent portion 2b of the second heat exchanger 25, it is possible to disturb the flow of air and thus to improve the heat-exchange efficiency.

[0027]

In particular, even when the rough-surface fins 22 provided with the cut-and10 raised parts 22a are used, high heat-exchange efficiency and air-sending efficiency are maintained.

Reference Signs List [0028] compressor 2, 30 air heat exchanger 2a, 30a straight portion 2b,

30b bent portion 3 fan 4 expansion valve 5 evaporator 6a inlet water pipe 6b outlet water pipe 7 refrigerant pipe 8 casing 20, 31 first heat exchanger 21 heat transfer tube 22 rough-surface fin 22a cut-and-raised parts 25,35 second heat exchanger 27 smooth fin 100 outdoor unit

Claims

CLAIMS [Claim 1]

An air heat exchanger comprising:

a plurality of first heat exchangers each including a plurality of rough-surface fins and a heat transfer tube extending through the plurality of rough-surface fins, the heat transfer tube being configured to allow refrigerant to flow through the heat transfer tube; and a second heat exchanger provided adjacent to the plurality of first heat exchangers, the second heat exchanger including a plurality of smooth fins and a heat transfer tube extending through the smooth fins, the heat transfer tube being configured to allow the refrigerant to flow through the heat transfer tube, the first heat exchangers being bent toward the second heat exchanger, the second heat exchanger being bent toward a same side as a side to which the first heat exchangers are bent.
[Claim 2]

The air heat exchanger of claim 1, wherein the heat transfer tube disposed in an area in which the second heat exchanger is not bent passes through the roughsurface fins.
[Claim 3]

The air heat exchanger of claim 1 or 2, wherein the rough-surface fins have cut-and-raised parts or recesses-and-projections.
[Claim 4]

An outdoor unit comprising a casing accommodating the air heat exchanger of any one of claims 1 to 3, a compressor configured to compress refrigerant gas, a fan configured to send air to the air heat exchanger, an expansion valve configured to control an amount of a refrigerant, and a water heat exchanger configured to exchange heat between water and the refrigerant, wherein the air heat exchanger is provided along two adjacent inner surfaces of the casing.