US20150107803A1

US20150107803A1 - Heat exchanger and air-conditioning apparatus having the same

Info

Publication number: US20150107803A1
Application number: US14/399,979
Authority: US
Inventors: Ryoichi Ikeda; Akio Murata; Nobuaki Miyake; Hiroki Okazawa; Wataru Suzuki; Takuya Matsuda
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2012-08-08
Filing date: 2012-08-08
Publication date: 2015-04-23
Also published as: JPWO2014024221A1; EP2884211A1; WO2014024221A1; CN104321610A; EP2884211A4

Abstract

A heat exchanger includes a plurality of fins stacked with a predetermined fin pitch between them, and a plurality of heat transfer tubes which extend through the fins in the stack direction and have a flat cross-sectional shape, wherein the fins have a plurality of notches in a shape corresponding to the cross-sectional shape of the heat transfer tube on an end portion in the longitudinal direction, a collar is formed on an edge of the plurality of notches, the heat transfer tubes are inserted into the notches, a fin pitch between a portion of the plurality of fins is larger than a fin pitch between the other portion of the fins, and the larger fin pitch is larger than at least the height of the collar.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage application of PCT/JP2012/005041 filed on Aug. 8, 2012, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a heat exchanger and an air-conditioning apparatus having the same.

BACKGROUND

In the conventional heat exchangers for air-conditioning apparatuses, a plate fin tube configuration is commonly used. The plate fin tube configuration ensures close contact between fins and heat transfer tubes, which is necessary to ensure a given heat transfer performance of the heat exchangers, by stacking a plurality of strip-shaped aluminum fins having circular holes with a predetermined fin pitch between them, inserting a plurality of copper or aluminum heat transfer tubes having a circular cross-section into the stacked fins (to be also referred to as a group of fins hereinafter) in the direction in which the fins are stacked, and then increasing the inner diameter of the heat transfer tubes by using a hydraulic or mechanical tube expander (see, for example, Patent Literature 1).
In order to increase the contact area of the fins and the heat transfer tubes, cylindrical collars are formed on each of the edges of the circular holes of the fins by burring. Further, slits may be formed in the flat portions of the fins between the circular holes so as to improve the heat exchange performance between the fins and the air flowing between the fins. Circular holes, collars and slits are sequentially formed on the fin by placing a progressive die having a plurality of processes on a press machine, and operating the press machine continuously while supplying a strip-shaped aluminum hoop (see, for example, Patent Literature 2). After the circular holes, collars and slits are formed on the hoop by press working, the fins are formed by cutting the hoop into strips with a desired length.
Then, a predetermined number of fins are stacked with the collars being in contact with the adjacent fins. After that, a plurality of long heat transfer tubes having a U-shaped portion called a hair pin are inserted into the fins and expanded. Since both stacking of the fins and insertion of the circular tubes are performed by using the collars as a reference, the fins are stacked and fixed with an equal interval of the height of the collar (see, for example, Patent Literature 3). A plurality of heat transfer tubes are connected by brazing at their end portions to U-bends, which are bent in a U shape and serve as circular pipes for pipe connection, and components such as a distributor so that a continuous refrigerant flow passage which has a plurality of folded portions is formed in a group of fins. The group of fins including the heat transfer tubes with the pipes connected at their end portions may be formed in an L shape or a U shape. In forming, for example, a U-shaped heat exchanger, the group of fins are bent in an L shape twice, and accordingly, the heat exchanger having a group of fins with a U-shaped overall structure and heat transfer tubes with a U-shaped internal structure is formed (see, for example, Patent Literature 4). Even in the heat exchanger after the bending, the fins remain the same on its three faces (straight portions) forming the U-shaped structure as before bending, and are stacked with a constant interval of the height of the collar.
Recently, in air-conditioning apparatuses, in light of increasingly serious energy issues, intense competition takes place in terms of energy saving and cost reduction. Accordingly, for the above-described heat exchanger, the shapes of heat transfer tubes and fins, the fin pitch, and the materials of heat transfer tubes and fins are still under study for improvements. Further, measures have also been proposed to change the fin pitch depending on the internal structure of the air-conditioning apparatus (see, for example, Patent Literatures 5, 6 and 7).

PATENT LITERATURE

Patent Literature 1: Japanese Examined Patent Application Publication No. 58-13249 (pages 3 & 4, FIGS. 1-3)
Patent Literature 2: Japanese Examined Patent Application Publication No. 58-9358 (pages 2 & 3, FIGS. 1-5)
Patent Literature 3: Japanese Examined Patent Application Publication No. 3-80571 (page 9, FIGS. 1 & 2)
Patent Literature 4: Japanese Patent No. 4417620 (page 15, FIG. 20)
Patent Literature 5: Japanese Unexamined Patent Application Publication No. 63-233296 (page 2)
Patent Literature 6: Japanese Unexamined Patent Application Publication No. 2004-245531 (page 3)
Patent Literature 7: Japanese Unexamined Patent Application Publication No. 2008-8541 (page 7, FIG. 3)

As described above, conventional heat exchangers are manufactured by a process of stacking a plurality of fins on which the collars are formed on the edges of the circular holes, and a process of inserting the heat transfer tubes having a circular cross-section into the circular holes of the stacked fins, and expanding the heat transfer tubes. As a result, the pitch between adjacent fins in the conventional heat exchangers is constant as the height of the collar formed by burring. It is, therefore, difficult to change the fin pitch in a partial area in the conventional heat exchangers, in accordance with the internal structure or the like of the air-conditioning apparatus to improve the performance of the air-conditioning apparatus. Accordingly, the air-conditioning apparatus having the conventional heat exchanger has a problem that the cost is expensive with respect to the heat exchanger performance.
For example, the outdoor unit of the air-conditioning apparatus accommodates accommodation objects such as a compressor cover (a cover which accommodates the compressor) and a control panel. Accordingly, the air flow resistance in the heat exchanger varies depending on the positions of the accommodation objects. However, it is difficult for the conventional heat exchanger to change the fin pitch in a partial area of the heat exchanger, in accordance with the air flow resistance at different positions of the heat exchanger, since the fin pitch is defined by the height of the collar.
Note that a configuration for changing the fin pitch in a partial area of the heat exchanger has also been proposed by, for example, dividing the heat exchanger or using fins of different collar heights. However, in order to form a heat exchanger with such a configuration, a plurality of types of progressive dies for the fins need to be prepared in accordance with the height of the collar. Alternatively, a die having a mechanism for accommodating the burring heights is required. As a result, when a plurality of types of dies are provided, the cost of dies is expensive or the manufacturing cost of the fins is expensive because of a complicated process of replacing the dies. Further, when a die having a mechanism for accommodating the burring heights is used, the costs of the die and the press machine are expensive since the die is complicated and large, and thus the press machine is large. In addition, assembling a heat exchanger having such a configuration costs a lot since fins having different collar heights need to be stacked at predetermined positions. Further, due to a practical limit defined by constraints of the die size or the like, only two or three types of fins having different collar heights can be used. Accordingly, it is practically difficult to form a heat exchanger having such a configuration.
Alternatively, in order to avoid such a problem, a method for manufacturing a heat exchanger by using a collar having a height lower than the fin pitch (stacking interval) and not stacking fins with reference to the collar height is also possible. However, in manufacturing a conventional heat exchanger by this method, in the conventional heat exchanger in which heat transfer tubes having a circular cross-section are inserted into circular holes defined in fins, there is a problem that each fin is set at a wrong position when the heat transfer tubes are inserted into a group of fins stacked with a predetermined fin pitch between them, and a desired fin pitch between adjacent fins cannot be formed. Therefore, when the conventional heat exchanger is manufactured by this method, each fin needs to be mounted one by one on the heat transfer tubes. However, in mounting the fins one by one on the heat transfer tubes to manufacture a conventional heat exchanger, it is necessary to insert the heat transfer tubes into the circular holes of each fin, and move the fins in a long stroke in the axial direction of the heat transfer tube to a desired position. Alternatively, it is practically difficult to manufacture a conventional heat exchanger by using a collar having a height lower than the fin pitch (stacking interval) and not stacking the fins with reference to the collar height.

SUMMARY

The present invention has been made to solve the above-mentioned problem, and has as its first object to provide a heat exchanger in which the fin pitch of a partial area can be changed without increasing the costs of a die for the fin, a press machine and assembly. The second object of this invention is to provide an energy saving and low-cost air-conditioning apparatus including the aforementioned heat exchanger, which costs little in terms of heat exchanger performance.
A heat exchanger according to the present invention includes a plurality of fins stacked with a predetermined fin pitch therebetween, and a plurality of heat transfer tubes which are disposed with a predetermined pitch therebetween in a longitudinal direction of the fins and extend through the fins in the direction in which the fins are stacked, wherein each of the plurality of heat transfer tubes has a flat cross-sectional shape, each of the plurality of fins includes a plurality of notches conforming to the cross-sectional shape of each heat transfer tube on an end portion of each fin in the longitudinal direction, each of the plurality of notches includes a collar formed on an edge thereof, the heat transfer tubes are respectively inserted into the notches, the plurality of fins include one set of fins having a fin pitch larger than a fin pitch of another set of fins, and the larger fin pitch is larger than at least a height of the collar corresponding to an amount of extension of the collar from a plate surface of the fin.
An air-conditioning apparatus according to the present invention includes a housing which is provided with an air inlet and an air outlet, the heat exchanger according to the present invention as disposed in the housing, and a fan disposed in the housing.
The heat exchanger according to the present invention has notches formed in the end portion of the fins in the longitudinal direction so that the heat transfer tubes are inserted into the notches. The fins can be mounted on the heat transfer tubes from the side face of the heat transfer tubes, and the fins can be mounted at a desired position by an end stroke. Accordingly, the heat exchanger can be manufactured without inserting the heat transfer tubes into a group of fins formed of the stacked fins which uses collars as a reference. That is, the fins having the same shape which do not require an expensive die or a press machine can be mounted at a desired position on the heat transfer tubes without labor of assembly. Accordingly, the heat exchanger in which the fin pitch of a partial area can be changed without increasing the cost of a die for the fin, the cost of press machine and the cost of assembly can be provided.
Since the air-conditioning apparatus according to the present invention includes the heat exchanger according to the present invention, the fins can be effectively distributed compared with the conventional device by changing the fin pitch of a partial area of the heat exchanger depending on the internal structure of the air-conditioning apparatus or the like (for example, by increasing the fin pitch of the area in which the air volume is smaller than the other area due to the presence of accommodation objects). Accordingly, the heat exchange efficiency can be improved with regard to the cost to performance ratio, and an energy saving and low-cost air-conditioning apparatus can be provided. Further, when the configuration of the present invention is applied to the air-conditioning apparatus which has a conventional performance and works without problem, the number of fins which becomes excessive due to the improvement in performance can be reduced, thereby allowing the size and price of the air-conditioning apparatus to be reduced while ensuring the same performance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an outdoor unit according to Embodiment 1 of the present invention.

FIG. 2 is a perspective view of an exemplary internal structure of the outdoor unit according to Embodiment 1 of the present invention.

FIG. 3 is a schematic view for explaining a compressor cover adjacent area in the outdoor unit according to Embodiment 1 of the present invention.

FIG. 4 is a graph showing the correlation between “an air volume Q in the compressor cover adjacent area 5” and “a ratio L/D of a distance L between the compressor cover adjacent area 5 and the compressor cover 7 to a diameter D of a propeller fan 9” in the outdoor unit according to Embodiment 1 of the present invention.

FIG. 5 is a graph showing the correlation between the fin pitch of the compressor cover adjacent area and the coefficient of performance of the outdoor unit according to Embodiment 1 of the present invention.

FIG. 6 is a schematic view for explaining the shape of components of the heat exchanger and a manufacturing method of the heat exchanger in the outdoor unit according to Embodiment 1 of the present invention.

FIG. 7 is a sectional plan view showing the heat exchanger and a control panel 8 in the outdoor unit according to Embodiment 2 of the present invention as seen from the perspective of the propeller fan.

FIG. 8 is a perspective view of an exemplary internal structure of the outdoor unit according to Embodiment 2 of the present invention.

FIG. 9 is a sectional plan view showing the heat exchanger in the outdoor unit according to Embodiment 3 of the present invention as seen from the perspective of the propeller fan.

FIG. 10 is a sectional plan view showing the heat exchanger in the outdoor unit according to Embodiment 4 of the present invention as seen from the perspective of the propeller fan.

FIG. 11 is a graph showing the relationship between the temperature efficiency ε and the heat exchanger performance AK.

FIG. 12 is a front view showing the positions of densely and sparsely arranged fins of the heat exchanger in the outdoor unit of the air-conditioning apparatus according to Embodiment 5 of the present invention.

DETAILED DESCRIPTION

Embodiment

1

A heat exchanger according to Embodiment 1 is formed to have a fin pitch that is larger in its partial area than in its other area, using an assembly method which is different from the conventional method and in which the fin pitch can be easily changed. Further, an air-conditioning apparatus according to Embodiment 1 includes the heat exchanger according to Embodiment 1 in which fins are positioned in an optimal density in accordance with the internal structure of the housing, thereby allowing for energy saving, cost reduction and price reduction while maintaining the same performance as that of the conventional apparatus.
A heat exchanger according to Embodiment 1, a manufacturing method of the heat exchanger according to Embodiment 1 and an air-conditioning apparatus according to Embodiment 1 will be described in detail below. The following description assumes, as the air-conditioning apparatus according to Embodiment 1, an outdoor unit on which the heat exchanger according to Embodiment 1 is mounted.
FIG. 1 is a perspective view of an outdoor unit according to Embodiment 1 of the present invention. FIG. 2 is a perspective view showing an exemplary internal structure of this outdoor unit. In order to facilitate understanding of the configuration of the outdoor unit according to Embodiment 1, FIG. 2 shows only accommodation objects which occupy a large part of the inner space of a housing and does not show accommodation objects such as refrigerant pipes, four-way valves and other valves.
An outdoor unit 101 according to Embodiment 1 is used for an industrial air-conditioning apparatus installed in buildings and factories. The outdoor unit 101 and an indoor unit (not shown) form a refrigeration cycle. The outdoor unit 101 accommodates accommodation objects such as a heat exchanger 1, a propeller fan 9, a compressor cover 7 which accommodates a compressor, and a control panel 8.
The housing 34 is formed by an almost square top face 35 a, an almost square bottom face 35 b and pillars (pillar members) 36 which connect the four corners of each of the top face 35 a and the bottom face 35 b. That is, the housing 34 is in an almost rectangular parallelepiped with its four side faces open. Three of the four open side faces serve as air inlets 34 a. A grid member or the like may be provided in the air inlets 34 a to prevent the user from inadvertently touching the heat exchanger 1 with, for example, his or her hand. Further, an almost cylindrical projection is formed on the top face of the housing 34. The top face and outer periphery of the projection are open and serve as an air outlet 34 b. The air outlet 34 b is provided with a fan guard 38 that guides air blown out from the air outlet 34 b.
As described above, the housing 34 having the above-mentioned configuration accommodates, for example, the heat exchanger 1, the propeller fan 9, the compressor cover 7 which accommodates the compressor, and the control panel 8.
The heat exchanger 1 is formed in a U shape, as viewed in a plan view, to face the air inlet 34 a which is open on its three side faces. That is, in the outdoor unit 101, the heat exchanger 1 is open to the environment in a large part except for the pillars 36 and the grid member disposed in the air inlet 34 a. The heat exchanger 1 is divided into three heat exchanger portions vertically aligned in stages (hereinafter, the three stages of heat exchanger portions will be referred to, where necessary, as a first stage heat exchanger 2, a second stage heat exchanger 3 and a third stage heat exchanger 4 which are numbered in ascending sequence from the top). Further, each of the first stage heat exchanger 2, the second stage heat exchanger 3 and the third stage heat exchanger 4 is divided into two columns of heat exchanger portions in the direction in which an air stream flows through the heat exchanger portions.
The above-described configuration of the heat exchanger 1 is merely an example. For example, the first stage heat exchanger 2, the second stage heat exchanger 3 and the third stage heat exchanger 4 may be integrally formed as the heat exchanger 1. The heat exchanger 1 may be formed as a single column heat exchanger. Alternatively, the heat exchanger 1 may be formed in an L shape, as seen in a plan view, when the air inlet 34 a is formed in its two adjacent side faces. The heat exchanger 1 need not necessarily be formed to have a bent portion. The heat exchanger 1 may be formed by combining the heat exchanger portions in a straight shape as seen in a plan view. The details of the heat exchanger 1 (the detailed configuration of fins and heat transfer tubes and a manufacturing method of the heat exchanger 1) will be described later.
The propeller fan 9 is disposed in the projection on the top face 35 a so that its circumferential portion faces the air outlet 34 b. That is, the outdoor unit 101 according to Embodiment 1 is configured to draw by suction the outside air from the air inlet 34 a formed in the side faces of the housing 34 by rotating the propeller fan 9, exchange heat between the drawn outside air and a refrigerant in the heat exchanger 1, and blow the outside air after heat exchange.
The compressor cover 7 and the control panel 8 are surrounded by the heat exchanger 1, as viewed in a plan view. That is, the compressor cover 7 and the control panel 8 are disposed in the flow passage of the outside air in the housing 34. More specifically, the compressor cover 7 is disposed in the lower portion of the housing 34 and is surrounded by the heat exchanger 1, as viewed in a plan view. The control panel 8 is disposed in the upper portion of the housing 34 and is surrounded by the heat exchanger 1, as viewed in a plan view. Further, the control panel 8 faces a portion of the side face of the housing 34, other than the air inlet 34 a. This side face is covered by a panel 37.
In the outdoor unit 101 according to Embodiment 1, the compressor cover 7 is adjacent to a part of the third stage heat exchanger 4 of the heat exchanger 1 (the adjacent area will be referred to as a compressor cover adjacent area 5 hereinafter). In other words, in the outdoor unit 101 according to Embodiment 1, the distance between the compressor cover adjacent area 5 of the third stage heat exchanger 4 and the compressor cover 7 is equal to or smaller than a predetermined distance. That is, in the heat exchanger 1, the air flow resistance in the compressor cover adjacent area 5 is higher than that in an area other than the former area (to be referred to as a compressor non-adjacent area 6 hereinafter), and the air volume in the compressor cover adjacent area 5 is smaller than that in the compressor non-adjacent area 6. Accordingly, in the heat exchanger 1 of Embodiment 1, the fin pitch of the compressor cover adjacent area 5 is larger than that of the compressor non-adjacent area 6.
In the outdoor unit 101 according to Embodiment 1 in which the heat exchanger 1 faces the air inlet 34 a formed in the side faces of the housing 34 and the propeller fan 9 faces the air outlet 34 b formed in the top face of the housing 34, it is advantageous that in the heat exchanger 1, the fin pitch of the compressor cover adjacent area 5 is larger than that of the compressor non-adjacent area 6 when the distance between the compressor cover adjacent area 5 of the third stage heat exchanger 4 and the compressor cover 7 is equal to or smaller than a predetermined distance (to be described later).
FIG. 3 is a schematic view for explaining the compressor cover adjacent area in the outdoor unit according to Embodiment 1 of the present invention. FIG. 3 is a sectional plan view showing the third stage heat exchanger 4 and the compressor cover 7 as seen from the perspective of the propeller fan 9.
As shown in FIG. 3, letting D be the diameter of the propeller fan 9, and L be the distance between the compressor cover adjacent area 5 and the compressor cover 7, the air volume takes values, shown in FIG. 4, in various portions of the third stage heat exchanger 4.
FIG. 4 is a graph showing the correlation between “an air volume Q in the compressor cover adjacent area 5” and “a ratio L/D of the distance L between the compressor cover adjacent area 5 and the compressor cover 7 to the diameter D of the propeller fan 9” in the outdoor unit according to Embodiment 1 of the present invention. A rotation speed N of the propeller fan 9 is constant.
As shown in FIG. 4, when L/D is 0.15 or less, it is found that the air flow resistance in the compressor cover adjacent area 5 is high and the air volume Q in the compressor cover adjacent area 5 is small. Accordingly, in the outdoor unit 101 according to Embodiment 1 in which the heat exchanger 1 faces the air inlet 34 a formed in the side faces of the housing 34 and the propeller fan 9 faces the air outlet 34 b formed in the top face of the housing 34, it is advantageous that in the heat exchanger 1, the fin pitch of the compressor cover adjacent area 5 is larger than that of the compressor non-adjacent area 6 when L/D is 0.15 or less.
Further, when the heat exchanger 1 is configured to have a fin pitch of the compressor cover adjacent area 5 larger than that of the compressor non-adjacent area 6, the fin pitch of the compressor cover adjacent area 5 is defined in, for example, the following way.
FIG. 5 is a graph showing the correlation between the fin pitch of the compressor cover adjacent area and the coefficient of performance of the outdoor unit according to Embodiment 1 of the present invention. The vertical axis in FIG. 5 represents the coefficient of performance (COP) of the air-conditioning apparatus which uses the outdoor unit 101. The horizontal axis in FIG. 5 represents the ratio k (=fp2/fp1) of a fin pitch fp2 of the compressor cover adjacent area 5 to a fin pitch fp1 of the compressor non-adjacent area 6.
As can be seen from FIG. 5, when k (=fp2/fp1)=1, that is, when the fin pitch fp2 of the compressor cover adjacent area 5 is the same as the fin pitch fp1 of the compressor non-adjacent area 6, the coefficient of performance (COP) of the air-conditioning apparatus which uses the outdoor unit 101 is close to a maximum value. Further, in a region with values of k close to k=1 (in which the fin pitch fp2 is close to the fin pitch fp1), the variation of the coefficient of performance (COP) is small regardless of a change in fin pitch fp2. As k (=fp2/fp1) increases, that is, as the fin pitch fp2 of the compressor cover adjacent area 5 becomes large relative to the fin pitch fp1 of the compressor non-adjacent area 6, the coefficient of performance (COP) of the air-conditioning apparatus which uses the outdoor unit 101 decreases. Accordingly, in Embodiment 1, in order to prevent the coefficient of performance (COP) of the air-conditioning apparatus which uses the outdoor unit 101 from excessively decreasing due to too large a fin pitch fp2 of the compressor cover adjacent area 5, the coefficient of performance (COP) of the air-conditioning apparatus which uses the outdoor unit 101 is set to, for example, 95% or more of the coefficient of performance (COP) of the air-conditioning apparatus which uses the outdoor unit 101 when k (=fp2/fp1)=1 (1<k≦b in FIG. 5).

Details of Heat Exchanger 1

Next, details of the heat exchanger 1 will be described.
FIG. 6 is a schematic view for explaining the shape of components of the heat exchanger and a manufacturing method of the heat exchanger in the outdoor unit according to Embodiment 1 of the present invention.
The detailed configuration of the heat exchanger 1 will first be described with reference to FIG. 6.
The heat exchanger 1 is implemented in a fin tube heat exchanger including a plurality of fins 12 stacked with a predetermined fin pitch between them, and a plurality of heat transfer tubes 10 which are arranged in the longitudinal direction of the fins 12 with a predetermined interval between them and extend through the fins 12 in the direction in which the fins 12 are stacked.
The heat transfer tube 10 allows the refrigerant to flow through it so that the refrigerant exchanges heat with the air which flows through the gaps between adjacent fins 12. The heat transfer tube 10 has a flat cross-sectional shape (for example, an elliptical shape) and has an inner space divided by partitions into a plurality of flow passages (holes). Each heat transfer tube 10 is inserted into notches 13 of the fin 12 (to be described later) in the longitudinal direction of the cross-sectional shape.
The fin 12 is implemented using, for example, an almost rectangular plate. A plurality of notches 13 are formed in the end portion of the fin 12 in the longitudinal direction with a predetermined interval between them. As described above, the notches 13 are portions where the heat transfer tubes 10 are inserted and conform to the cross-sectional shape of the heat transfer tubes 10. In Embodiment 1, the notch 13 is formed as a U-shaped groove, and the opening width of its end portion is almost the same as the width of the heat transfer tube 10 (that is, the dimension of its cross-section in the widthwise direction). Further, collars 14 which extend almost perpendicularly to the plate surface of the fin 12 are formed on the edge of the notch 13 in order to increase the contact area of the fin 12 and the heat transfer tube 10 and ensure a given bonding strength of the fin 12 and the heat transfer tube 10. Further, the height of the collar 14 (the amount of extension of the collar 14 from the plate surface of the fin 12) is lower than at least the fin pitch of the compressor cover adjacent area 5, which is larger than that of the compressor non-adjacent area 6 of the heat exchanger 1. In addition, a plurality of slits (not shown) are formed in the surface of the fins 12 to be open in the direction in which an air stream flows through the gaps between adjacent fins 12 (that is, the widthwise direction of the fin 12). The formation of slits allows the temperature boundary layer on the surface of the fins 12 to be separated and updated, thereby improving the heat exchange efficiency between the fins 12 and the air which flows through the gaps between adjacent fins 12.
Moreover, according to various literatures, a heat exchanger which uses a combination of fins and heat transfer tubes having a flat cross-section and an inner space divided into a plurality of flow passages have a capacity/performance ratio which is equal to or higher than that of a conventional heat exchanger which uses a combination of fins and heat transfer tubes having a circular cross-section.
Next, a manufacturing method of the heat exchanger 1 will be described.
The fin 12 of the heat exchanger 1 is manufactured by cutting a thin plate (plate member) such as a thin aluminum plate wound around a reel in a hoop. Specifically, first, a plurality of pilot holes 15 are formed in the vicinities of the end portions of the thin plate in the direction in which the thin plate is fed. The thin plate is intermittently fed in a high speed press machine (see an arrow 16 of FIG. 6 which indicates a thin plate feeding operation) by a thin plate feeding mechanism of the high speed press machine by using the pilot holes 15 (for example, by inserting pins into the pilot holes 15). Further, the high speed press machine is provided with a progressive die to sequentially form opening holes on the thin plate as, for example, the notches 13, the collars 14, and the slits by press forming while the thin plate is intermittently fed in the high speed press machine. Accordingly, a series of fins 17, that is, a line of a plurality of the fins 12 is formed on the thin plate fed from the high speed press machine.
The series of fins 17 is separated by a cutting device, provided downstream of the high speed press machine, into the individual fins 12 (see an arrow 18 which indicates a cutting operation). The thus separated fins 12 are mounted on the heat transfer tubes 10 as follows.
Specifically, a manufacturing line of the heat exchanger 1 according to Embodiment 1 includes a table. A plurality of heat transfer tubes 10 are disposed on the upper surface of the table with a predetermined interval between them. The table is provided with a feed mechanism which is formed by, for example, a servo motor, a ball screw and a linear motion guide and is positioned by a pitch feeding operation in the axial direction of the heat transfer tube 10 (that is, the direction in which the fins 12 are stacked) (see an arrow 21 of FIG. 6 which indicates a pitch feeding operation). An insertion device which is formed by, for example, a cam and a servo is disposed above the table. The insertion device includes a holding mechanism that holds the fin 12 cut by the cutting device, and a rotation mechanism that rotates the fin 12 held by the holding mechanism so that the opening ends of the notches 13 face downwards.
Accordingly, when the insertion device holds the fin 12 cut by the cutting device, rotates the fin 12 held by the holding mechanism so that the opening ends of the notches 13 face downwards, and lowers the fin 12 toward the table, the upper portions of the heat transfer tubes 10 start to be inserted into the notches of the fin 12 from the side of their opening ends, the fin 12 is pushed until the bottom portions of the notches 13 come into contact with the upper portions of the heat transfer tubes 10, and the fin 12 is mounted on a plurality of heat transfer tubes 10 disposed on the table (see an arrow 19 of FIG. 6 which indicates a movement and rotation operation of the fin 12). While the insertion device repeats the mounting operation of the fin 12, that is, in the duration after one fin 12 is mounted on the heat transfer tubes 10 and the next fin 12 is mounted on the heat transfer tubes 10, the table is moved by a predetermined pitch in the axial direction of the heat transfer tube 10 so that the fin 12 is mounted on the heat transfer tubes 1 with a desired pitch from the last fin 12 as mounted on the heat transfer tubes 10.
The above-mentioned cutting operation 18 for the fin 12, the movement and rotation operation of the fin 12, and the pitch feeding operation 21 of the heat transfer tubes 10 are sequentially performed to follow the hoop feeding operation 16 of the high speed press machine while synchronizing the insertion device and a feed mechanism of the table with each other. A deviation in synchronization of the high speed press machine and the insertion device is reduced by sagging the thin plate in the supply passage of the thin plate in an area on the upstream side of the high speed press machine to provide a buffer of the material and changing the number of press strokes while detecting the amount of sagging.
Further, the amount of pitch movement of the above-mentioned pitch feeding operation 21 is set by a controller of the feed mechanism. Specifically, a large pitch movement amount is set for a group of fins 22 which forms the compressor cover adjacent area 5 with a small air volume in the heat exchanger 1. A small amount of pitch movement is set for a group of fins 23 which forms the compressor non-adjacent area 6 with a large air volume in the heat exchanger 1. By stacking a necessary number of fins 12 with such a pitch movement amount, a group of fins assembly portion 24 including the group of fins 22 stacked with a large fin pitch and the group of fins 23 stacked with a small fin pitch is completed (in FIG. 6, assembly is in progress).
The completed group of fins assembly portion 24 and the heat transfer tubes 10 are fixed to each other by brazing in a furnace by using a brazing material coated on the heat transfer tubes 10 in advance. Alternatively, the completed fin assembly 24 and the heat transfer tubes 10 are fixed to each other by bonding by using an adhesive applied to the portions defining the gaps between the heat transfer tubes 10 and the collars 14 of the fins 12. After that, two stacked group of fins assembly portions 24 are connected to pipes and bent in an L shape twice to form a U shape. Thus, assembly of the heat exchanger 1 (the first stage heat exchanger 2, the second stage heat exchanger 3, and the third stage heat exchanger 4) is completed.
As described above, according to Embodiment 1, the heat exchanger 1 (the first stage heat exchanger 2, the second stage heat exchanger 3, and the third stage heat exchanger 4) in which the fin pitch of the compressor cover adjacent area 5 is larger than that of the compressor non-adjacent area 6 is manufactured by positioning the heat transfer tubes 10 with a predetermined interval between them and mounting each fin 12 on the heat transfer tubes 10. Accordingly, unlike the conventional manufacturing method in which the heat transfer tubes having a circular cross-section are inserted into circular holes of the group of fins which is stacked in advance with reference to collars, the manufacturing method of the heat exchanger 1 according to Embodiment 1 needs neither complicated dies to change the height of collars nor a large press machine to change the fin pitch of a partial area of the heat exchanger 1. Further, the manufacturing method of the heat exchanger 1 according to Embodiment 1 can immediately change the fin pitch to different values by simply changing the controller command value of the pitch movement amount of the feed mechanism to change the fin pitch of a partial area of the heat exchanger 1.
The manufacturing method of the heat exchanger 1 according to Embodiment 1 is also different from the conventional manufacturing method of the heat exchanger in which the collar has a height lower than the fin pitch, and the fins are stacked without using the collars as a reference (the manufacturing method in which the heat transfer tubes are inserted into circular holes defined in each fin and the fin is moved by a long stroke in the axial direction of the heat transfer tube to a desired position). Since the fin 12 can be mounted on the heat transfer tube 10 from its side face, the stroke length after insertion of the heat transfer tube 10 into the notch 13 of the fin 12 and before the end of positioning of the fin 12 at a desired position can be shortened. Accordingly, in the manufacturing method of the heat exchanger 1 according to Embodiment 1, the fin can be mounted at a desired position on the heat transfer tube 10 with different fin pitches in a high speed operation which can follow the punching speed of a high speed press machine with a speed on the order of, for example, hundreds of SPM (Strokes Per Minute).
Further, the heat exchanger 1 in the outdoor unit 101 according to Embodiment 1 is formed such that the fin pitch of the compressor cover adjacent area 5 with a high air flow resistance and a small air volume is larger than that of the compressor non-adjacent area 6 with an air volume larger than that of the compressor cover adjacent area 5. That is, in the heat exchanger 1, the fin pitch of the area having a small air volume and a coefficient of performance (COP) which is not significantly affected by an increase in fin pitch. Accordingly, the heat exchanger 1 can keep the heat exchange efficiency in terms of cost performance higher than that of a heat exchanger having the same total number of fins as that of the heat exchanger 1 and the fin pitch between adjacent fins is the same in all fins. Therefore, it is possible to keep both the energy consumption and the cost of the outdoor unit 101 which includes the heat exchanger 1 lower than those in the conventional case. Further, when the configuration of the outdoor unit 101 according to Embodiment 1 is applied to an outdoor unit which requires only the conventional performance, the number of fins 12 which becomes excessive due to the improvement in performance can be reduced, thereby reducing the size and price of the outdoor unit while ensuring the same performance. The manufacturing time can also be reduced since the number of inserted fins is decreased.
In Embodiment 1, the fin pitch in a partial area (the compressor cover adjacent area 5) of only the third stage heat exchanger 4 is increased. However, when the compressor cover 7 is elongated in the height direction, the fin pitches in partial areas of the second stage heat exchanger 3 and the first stage heat exchanger 2 which are disposed higher than the third stage heat exchanger 4 may also be increased. Further, in Embodiment 1, the heat exchanger 1 is divided into three stages of heat exchanger portions (the first stage heat exchanger 2, the second stage heat exchanger 3 and the third stage heat exchanger 4). However, the heat exchanger 1 may be divided into two stages of heat exchanger portions or four or more stages of heat exchanger portions. It is needless to say that the above-mentioned effect can be achieved in those configurations as well.
Although Embodiment 1 assumes the compressor cover 7 as an accommodation object that increases the air flow resistance (that is, an accommodation object disposed in the vicinity of the heat exchanger 1), this is merely an example. When an accommodation object other than the compressor cover 7 is disposed in the vicinity of the heat exchanger 1, the above-mentioned effect can be achieved by increasing the fin pitch of an area in the vicinity of the accommodation object in the heat exchanger 1 to be larger than that of the remaining area.

Embodiment 2

Embodiment 1 assumes, for example, that the fin pitch in the compressor cover adjacent area 5 which is adjacent to the compressor cover 7 is changed as an example of changing the fin pitch of a partial area of the heat exchanger 1. However, the area in which the fin pitch is changed is not limited to the compressor cover adjacent area 5. In addition to or instead of the compressor cover adjacent area 5, the fin pitch of the following areas of the heat exchanger 1 may be changed. Configurations which will not specifically be referred to in Embodiment 2 are the same as those in Embodiment 1, and elements with the same functions or configurations are denoted by the same reference numerals.
FIG. 7 is a sectional plan view showing the heat exchanger and the control panel in the outdoor unit according to Embodiment 2 of the present invention as seen from the perspective of the propeller fan.
Similarly to Embodiment 1, the control panel 8 is disposed on one side face of the housing 34 of the outdoor unit 101 according to Embodiment 2. Since the control panel 8 generates heat by operating the outdoor unit 101, the control panel 8 needs cooling during the operation of the outdoor unit 101. Accordingly, the outdoor unit 101 according to Embodiment 2 is configured to cool the control panel 8 by using an air flow generated by the action of the propeller fan 9.
In Embodiment 2, in order to improve the cooling effect of the control panel 8, the fin pitch on the end portions of the heat exchanger 1 located on the side of the control panel 8 is larger than that in an area of the heat exchanger 1 other than these end portions. Embodiment 2 also uses the heat exchanger 1 formed in a U shape similarly to Embodiment 1. Accordingly, the fin pitch on two end portions 25 of the U-shaped heat exchanger 1 is larger than that in an area of the heat exchanger 1 other than the two end portions 25.
How the cooling effect of the control panel 8 is improved by setting the fin pitch on the two end portions 25 of the heat exchanger 1 to be larger than that in an area of the heat exchanger 1 other than the two end portions 25 will be described below.
FIG. 8 is a perspective view of an exemplary internal structure of the outdoor unit 101 according to Embodiment 2 of the present invention. White arrows shown in FIG. 8 indicate an air flow inside the outdoor unit 101. In order to facilitate understanding of the air flow, accommodation objects other than the heat exchanger 1 and the propeller fan 9 are not illustrated in FIG. 8.
The air has the property of flowing along the wall surface. Accordingly, as shown in FIG. 8, in the outdoor unit 101 according to Embodiment 2 in which the heat exchanger 1 faces the air inlet 34 a formed in the side faces of the housing 34 and the propeller fan 9 faces the air outlet 34 b formed in the top face of the housing 34, the air which has passed through the heat exchanger 1 collects at the two end portions 25 of the heat exchanger 1 located in the vicinity of the panel 37, flows upwards along the two end portions 25 of the heat exchanger 1, and is exhausted from the air outlet 34 b through the propeller fan 9 on the top face of the housing 34.
In this configuration, the volume of air flowing from the two end portions 25 of the heat exchanger 1 can be set relatively large and the volume of air flowing along the two end portions 25 of the heat exchanger 1 can thus be set relatively large by setting the fin pitch at the two end portions 25 of the heat exchanger 1 to be larger than that of an area of the heat exchanger 1 other than the two end portions 25 to decrease the air flow resistance at the two end portions 25. Accordingly, the cooling effect of the control panel 8 can be improved by setting the fin pitch at the two end portions 25 of the heat exchanger 1 to be larger than that in an area of the heat exchanger 1 other than the two end portions 25.
Further, the amount of heat exchanged between the air which flows through the two end portions 25 and the refrigerant which flows through the heat exchanger 1 is decreased by increasing the fin pitch on the two end portions 25 of the heat exchanger 1 to be larger than the fin pitch of an area of the heat exchanger 1 other than the two end portions 25. As a result, during cooling operation, the temperature of the air which flows from the two end portions 25 of the heat exchanger 1, that is, the temperature of the air which flows along the two end portions 25 of the heat exchanger 1 can be decreased. Accordingly, during cooling operation, the cooling effect of the control panel 8 can be also improved by decreasing the temperature of the air.
In the outdoor unit 101 according to Embodiment 2, the control panel 8 is disposed on one side of the housing 34, and the fin pitch on the end portions of the heat exchanger 1 located on the side of the control panel 8 is formed to be larger than the fin pitch of an area of the heat exchanger 1 other than these end portions. Accordingly, the cooling air volume of the control panel 8 can be increased, thereby improving the cooling effect of the control panel 8.

Embodiment 3

The example of changing the fin pitch of a partial area of the heat exchanger 1 is not limited to those described in Embodiments 1 and 2. In addition to at least one of the configurations of Embodiments 1 and 2 or instead of them, the fin pitch of the following areas of the heat exchanger 1 may be changed. A configuration which is not specifically described in Embodiment 3 is the same as that of Embodiment 1 or Embodiment 2, and the identical functions or configurations are denoted by the same reference numerals.
FIG. 9 is a sectional plan view showing the heat exchanger in the outdoor unit according to Embodiment 3 of the present invention as seen from the perspective of the propeller fan. The white arrow in FIG. 9 indicates an air flow inside the outdoor unit 101.
The heat exchanger 1 according to Embodiment 3 is divided into two rows of the heat exchanger portions in the direction in which an air stream flows through the heat exchanger 1 (hereinafter, the heat exchanger portion disposed upstream in the air flow direction will be referred to as an outer heat exchanger 1 b and the heat exchanger portion disposed downstream in the air flow direction is referred to as an inner heat exchanger 1 a). The fin pitch of the inner heat exchanger 1 a which is part of the heat exchanger 1 is formed to be larger than the fin pitch of the outer heat exchanger 1 b.
As shown in FIG. 9, the air which flows through the heat exchanger 1 and is exhausted from the propeller fan 9 is first flows through the outer heat exchanger 1 b and then flows through the inner heat exchanger 1 a. Assuming that the temperature of the refrigerant which flows through the heat exchanger 1 is constant, the temperature of the air changes after heat exchange in the outer heat exchanger 1 b, and the temperature difference between the air which flows from the outer heat exchanger 1 b and the refrigerant which flows through the heat exchanger 1 decreases. That is, the temperature difference between the air which flows through the inner heat exchanger 1 a and the refrigerant which flows through the heat exchanger 1 (that is, the inner heat exchanger 1 a) is small, and accordingly, the heat exchange amount becomes small.
Accordingly, in Embodiment 3, the fin pitch of the inner heat exchanger 1 a which has the heat exchange amount smaller than the outer heat exchanger 1 b is formed to be larger than that of the outer heat exchanger 1 b.
As described above, in the outdoor unit 101 having the configuration of Embodiment 3, it is possible to reduce the size and price of the outdoor unit 101 while maintaining the same performance as that of the conventional device by decreasing the insertion number of fins of the inner heat exchanger 1 a which has a small heat exchange amount and a low contribution to the heat exchange.
In Embodiment 3, the heat exchanger 1 is divided into two rows of the heat exchanger portions in the direction in which an air stream flows through the heat exchanger 1. However, as a matter of course, the heat exchanger 1 may be divided into three or more rows of the heat exchanger portions in the direction in which an air stream flows through the heat exchanger 1. In at least two of those heat exchanger portions, when the fin pitch of the heat exchanger portion disposed downstream is larger than that of the heat exchanger portion disposed upstream, the effect of Embodiment 3 can be achieved.
Although Embodiment 3 assumes the outdoor unit 101 including the heat exchanger 1 in which the inner heat exchanger 1 a has a fin pitch larger than that of the outer heat exchanger 1 b, the outdoor unit 101 may be equipped with a heat exchanger 1 in which the outer heat exchanger 1 b has a fin pitch larger than that of the inner heat exchanger 1 a. This configuration is particularly advantageous when the outdoor unit 101 is installed in a cold climate environment where frost is often formed.
When the conventional outdoor unit in which the same fin pitch is used for the outer heat exchanger and the inner heat exchanger is installed in a cold climate environment where frost is formed on the heat exchanger, the larger amount of frost is formed on the outer heat exchanger compared to the inner heat exchanger, and the frost is unevenly distributed. Accordingly, there is a problem that the air flow passage between the fins in the outer heat exchanger is blocked at early time, and the heating performance of the air-conditioning apparatus having the outdoor unit is impaired. Since the air first flows through the outer heat exchanger and then the inner heat exchanger, the larger amount of frost is formed on the outer heat exchanger where an absolute humidity of the air is high.
Accordingly, in a modification example of Embodiment 3, the fin pitch of the outer heat exchanger 1 b which has the larger frost formation than the inner heat exchanger 1 a is formed to be larger than the inner heat exchanger 1 a. With this configuration of the heat exchanger 1, the frost is evenly distributed on the inner heat exchanger 1 a and the outer heat exchanger 1 b, and blockage of the air flow passage between the fins may be delayed, thereby improving the heating performance of the air-conditioning apparatus which includes the outdoor unit 101.
In the modification example of Embodiment 3, the heat exchanger 1 is divided into two rows of the heat exchanger portions in the direction in which an air stream flows through the heat exchanger 1. However, as a matter of course, the heat exchanger 1 may be divided into three or more rows of the heat exchanger portions in the direction in which an air stream flows through the heat exchanger 1. In at least two of those heat exchanger portions, the fin pitch of the heat exchanger portion disposed upstream may be larger than that of the heat exchanger portion disposed downstream. With this configuration, the frost is evenly distributed on the heat exchanger 1, and blockage of the air flow passage between the fins may be delayed, thereby improving the heating performance of the air-conditioning apparatus which includes the outdoor unit 101.

Embodiment 4

The example of changing the fin pitch of a partial area of the heat exchanger 1 is not limited to those described in Embodiments 1 to 3. In addition to at least one of the configurations of Embodiments 1 to 3 or instead of them, the fin pitch of the following areas of the heat exchanger 1 may be changed. A configuration which is not specifically described in Embodiment 4 is the same as that of Embodiments 1 to 3, and the identical functions or configurations are denoted by the same reference numerals.
FIG. 10 is a sectional plan view showing the heat exchanger in the outdoor unit according to Embodiment 4 of the present invention as seen from the perspective of the propeller fan.
The heat exchanger 1 according to Embodiment 4 is formed in a U shape as seen in a plan view. That is, the heat exchanger 1 is formed of two bent portions 29 and three straight portions 30 (a portion of the heat exchanger which is in a straight shape as seen in a plan view). In the heat exchanger 1 according Embodiment 4, the fin pitch of the bent portion 29 and the fin pitch of the straight portion 30 are different.
In a bending process of the heat exchanger 1, the fin 12 of the bent portion 29 may fall down or buckle. In this case, the fin pitch of the bent portion 29 of the heat exchanger 1 may be formed larger than the fin pitch of the straight portion 30 so as to achieve the air flow volume of the bent portion 29 even if the end portions of the fin 12 falls down or buckles during the bending process. Alternatively, the fin pitch of the bent portion 29 of the heat exchanger 1 may be formed smaller than the fin pitch of the straight portion 30, that is, the number of stack of the fins in the bent portion 29 may be increased so as to decrease the stress applied to each fin 12 during the bending process, thereby preventing the fin 12 from falling down or buckling and achieving the air flow volume of the bent portion 29.
As described above, with the configuration of the heat exchanger 1 of Embodiment 4, the air flow volume of the bent portion 29 may be achieved and heat exchange can be effectively performed at the bent portion 29. Accordingly, the heat exchange efficiency of the heat exchanger 1 can be improved, and the energy saved and small sized outdoor unit 101 may be provided.
Further, the following effect can also be achieved by increasing the fin pitch of the bent portion 29 of the heat exchanger 1 to be larger than the fin pitch of the straight portion 30.
In the heat exchanger 1 formed in a U shape as seen in a plan view, the fin pitch between adjacent fins 12 located on the inner side of the bent portion 29 is smaller than the fin pitch between adjacent fins 12 located on the outer side of the bent portion 29. Further, the pillars 36 are disposed on the outer circumferential side of the bent portion 29 (see FIG. 1). As a result, the air flow volume of the bent portion 29 becomes smaller than that of the straight portion 30, which causes a distribution of temperature efficiency of the bent portion 29 and the straight portion 30 (the bent portion 29 and the straight portion 30 are different in temperature efficiency). Specifically, in the conventional heat exchanger which is formed by bending, in a U shape as seen in a plan view, a heat exchanger having a uniform fin pitch, the difference in temperature efficiency between the bent portion and the straight portion is larger than that of the heat exchanger 1 according to Embodiment 4 in which the fin pitch of the bent portion 29 of the heat exchanger 1 is formed larger than the fin pitch of the straight portion 30.
With reference to FIG. 11, a temperature efficiency ε and a heat exchanger performance AK will be described.
FIG. 11 is a graph showing the relationship between the temperature efficiency ε and the heat exchanger performance AK. In FIG. 11, the temperature efficiency ε of the heat exchanger 1 according to Embodiment 4 (the heat exchanger 1 in which the fin pitch of the bent portion 29 of the heat exchanger 1 is formed larger than the fin pitch of the straight portion 30) is shown as a black circle. Further, the temperature efficiency ε of the conventional heat exchanger (the heat exchanger which is formed by bending the heat exchanger having the uniformly formed fin pitch in a U shape as seen in a plan view) is shown as a white circle. The heat exchanger 1 according to Embodiment 4 and the conventional heat exchanger have the same total number of fins.
The temperature efficiency ε (=(heat exchanger outlet air temperature−heat exchanger inlet air temperature)/(refrigerant saturation temperature−heat exchanger inlet air temperature)) tends to decrease as the air flow volume increases (as the air flow speed increases). Accordingly, in both the heat exchanger 1 according to Embodiment 4 and the conventional heat exchanger, the temperature efficiency (ε2, ε2′) of the bent portion is higher than the temperature efficiency (ε1, ε1′) of the straight portion. When focusing on the temperature efficiency of the straight portion, in the heat exchanger 1 according to Embodiment 4 and the conventional heat exchanger formed of the same number of fins, the heat exchanger 1 according to Embodiment 4 in which the fin pitch of the bent portion 29 of the heat exchanger 1 is formed larger than the fin pitch of the straight portion 30 has the temperature efficiency ε1′ which is higher than the temperature efficiency ε1 of the conventional heat exchanger. Further, when focusing on the temperature efficiency of the bent portion, in the heat exchanger 1 according to Embodiment 4 and the conventional heat exchanger formed of the same number of fins, the heat exchanger 1 according to Embodiment 4 in which the fin pitch of the bent portion 29 of the heat exchanger 1 is formed larger than the fin pitch of the straight portion 30 has the temperature efficiency ε2 which is smaller than the temperature efficiency ε2′ of the conventional heat exchanger.
As shown in FIG. 11, the heat exchanger performance AK (heat transfer performance) and the temperature efficiency ε have a property that the temperature efficiency ε gradually approaches 1 as the heat exchanger performance AK increases. Consequently, in the straight portion which has a large air flow volume, the temperature efficiency of the heat exchanger 1 according to Embodiment 4 is improved by the amount of ε1′−ε1 since the fin pitch is smaller than that of conventional heat exchanger. Further, in the bent portion which has a small air flow volume, the temperature efficiency of the heat exchanger 1 according to Embodiment 4 is decreased by the amount of ε2′-ε2 since the fin pitch is larger than that of conventional heat exchanger.
However, the temperature efficiency (ε1, ε1′) of the straight portion is smaller than the temperature efficiency (ε2, ε2′) of the straight portion, and, as described above, the temperature efficiency ε has a property that the temperature efficiency ε gradually approaches 1 as the heat exchanger performance AK increases. As a result, the improvement in temperature efficiency (ε1′−ε1) of the heat exchanger of Embodiment 4 is large, while the decrease in temperature efficiency (ε2′−ε2) of the heat exchanger of Embodiment 4 is significantly small.
That is, (ε1′−ε1)>(ε2′−ε2) is established.
Therefore, as shown in Embodiment 4, an average temperature efficiency of the heat exchanger 1 according to Embodiment 4, that is, the heat exchange efficiency of the entire heat exchanger 1 is significantly improved by increasing the fin pitch of the bent portion 29 having a high temperature efficiency ε and decreasing the fin pitch of the straight portion 30 having a low temperature efficiency ε.

Embodiment 5

The example of changing the fin pitch of a partial area of the heat exchanger 1 is not limited to those described in Embodiments 1 to 4. In addition to at least one of the configurations of Embodiments 1 to 4 or instead of them, the fin pitch of the following areas of the heat exchanger 1 may be changed. A configuration which is not specifically described in Embodiment 5 is the same as that of Embodiments 1 to 3, and the identical functions or configurations are denoted by the same reference numerals.
FIG. 12 is a front view of an exemplary internal structure of the outdoor unit according to Embodiment 5 of the present invention. The accommodation objects other than the heat exchanger 1 and the propeller fan 9 are not illustrated in FIG. 12.
The heat exchanger 1 according to Embodiment 5 is divided into three stages of vertically aligned heat exchanger portions (the first stage heat exchanger 2, the second stage heat exchanger 3 and the third stage heat exchanger 4). The fin pitch 33 of the third stage heat exchanger 4 is larger than the fin pitch 32 of the second stage heat exchanger 3, and the fin pitch 32 of the second stage heat exchanger 3 is larger than the fin pitch 31 of the first stage heat exchanger 2.
In the outdoor unit 101 according to Embodiment 1 in which the heat exchanger 1 faces the air inlet 34 a formed in the side faces of the housing 34 and the propeller fan 9 faces the air outlet 34 b formed in the top face of the housing 34, the air volume varies depending on the distance from the propeller fan 9. Specifically, the air volume which passes through the third stage heat exchanger 4 is smaller than the air volume which passes through the first stage heat exchanger 2. Accordingly, in Embodiment 5, the fin pitch of the third stage heat exchanger 4 which has the heat exchange amount smaller than that of the first stage heat exchanger 2 is formed to be larger than that of the first stage heat exchanger 2.
As described above, it is possible to reduce the size and price of the air-conditioning apparatus while maintaining the same performance as that of the conventional apparatus by decreasing the insertion number of fins of the third stage heat exchanger 4 which has a small air volume and a low contribution to the heat exchange.
Further, in Embodiment 5, the heat exchanger 1 is divided into three stages of vertically aligned heat exchanger portions. However, the heat exchanger 1 may be divided into two stages of heat exchanger portions or four or more stages of heat exchanger portions. In at least two of those heat exchanger portions, when the fin pitch of the lower heat exchanger portion is formed to be smaller than the fin pitch of the upper heat exchanger portion, the effect of Embodiment 5 can be achieved.
In the above-mentioned Embodiments 1 to 5, the present invention has been described by taking, as an example, the outdoor unit 101 in which the air outlet 34 b is formed in the top face of the housing 34. However, the effect of Embodiments 1 to 5 can be achieved by applying the present invention to the outdoor unit in which the air outlet is formed in the side face of the housing.
In the above-mentioned Embodiments 1 to 5, the present invention has been described by taking, as an example, the heat exchanger 1 formed in a U shape as seen in a plan view. However, any shape of the heat exchanger may be used and the effect of Embodiments 1 to 5 can be achieved regardless of the shape of the heat exchanger.
In the above-mentioned Embodiments 1 to 5, the present invention has been described by taking, as an example, the outdoor unit 101 which includes a single heat exchanger 1 (including a plurality of heat exchanger portions). However, the effect of Embodiments 1 to 5 can be achieved in the outdoor unit which includes a plurality of heat exchangers 1.
In the above-mentioned Embodiments 1 to 5, the present invention has been described by taking, as an example, the outdoor unit 101 which includes a propeller fan 9. However, the effect of Embodiments 1 to 5 can be achieved in the outdoor unit which includes a fan other than the propeller fan 9.
In the above-mentioned Embodiments 1 to 5, the present invention is applied to the outdoor unit 101. However, as a matter of course, the present invention is also applicable to the indoor unit.

Claims

1. A heat exchanger comprising:

a plurality of fins stacked with a predetermined fin pitch therebetween; and

a plurality of heat transfer tubes which are disposed with a predetermined pitch therebetween in a longitudinal direction of the fins and extend through the fins in a direction in which the fins are stacked,

wherein each of the plurality of heat transfer tubes has a flat cross-sectional shape,

each of the plurality of fins includes a plurality of notches conforming to the cross-sectional shape of each heat transfer tube on an end portion of each fin in the longitudinal direction,

each of the plurality of notches includes a collar formed on an edge thereof,

the heat transfer tubes are respectively inserted into the notches,

the plurality of fins include one set of fins having a fin pitch larger than a fin pitch of another set of fins, and

the larger fin pitch is larger than at least a height of the collar corresponding to an amount of extension of the collar from a plate surface of the fin.

2. An air-conditioning apparatus comprising:

a housing which is provided with an air inlet and an air outlet;

the heat exchanger of claim 1 as disposed in the housing; and

a fan disposed in the housing.

3. The air-conditioning apparatus of claim 2, wherein

the housing accommodates an accommodation object in an air flow passage between the heat exchanger and the fan, and

in the heat exchanger, a fin pitch in an area having a distance from the accommodation object, which is not more than a predetermined distance, is the larger fin pitch.

4. The air-conditioning apparatus of claim 3, wherein

the housing is provided with the air inlet formed in at least one side face thereof and the air outlet formed in a top face thereof,

the heat exchanger faces the air inlet,

the fan includes a propeller fan and faces the air outlet, and

in the heat exchanger, a fin pitch in an area which satisfies L/D≦0.15 is the larger fin pitch, where D is a diameter of the propeller fan, and L is a distance between the heat exchanger and the accommodation object.

5. The air-conditioning apparatus of claim 3, wherein

in the heat exchanger, letting fp2 be the larger fin pitch, and fp1 be the fin pitch of the other set of fins,

the fin pitch fp2 is set so that a coefficient of performance of the air-conditioning apparatus equipped with the heat exchanger having both the fin pitches fp1 and fp2 in two fin areas respectively defined by the one set of fins and the other set of fins is not less than 95% of a coefficient of performance of an air-conditioning apparatus equipped with a heat exchanger having only the fin pitch fp1 in the two fin areas.

6. The air-conditioning apparatus of claim 3, wherein

the accommodation object includes a control panel which is disposed on one side face of the housing,

the air inlet is formed at least in a side face of the housing which is adjacent to the one side face thereof on which the control panel is disposed,

the heat exchanger faces the air inlet, and

the fin pitch on an end portion of the heat exchanger on a side of the control panel is the larger fin pitch.

7. The air-conditioning apparatus of claim 2, wherein

the heat exchanger is divided into a plurality of heat exchanger portions in a direction in which an air stream flows through the heat exchanger, and

in at least one of the plurality of divided heat exchanger portions, the fin pitch of the heat exchanger portion disposed on a downstream side is larger than the fin pitch of the heat exchanger portion disposed on an upstream side.

8. The air-conditioning apparatus of claim 2, wherein

in at least one of the plurality of divided heat exchanger portions, the fin pitch of the heat exchanger portion disposed on an upstream side is larger than the fin pitch of the heat exchanger portion disposed on a downstream side.

9. The air-conditioning apparatus of claim 2, wherein

the heat exchanger has a bent portion, and

the fin pitch between adjacent fins disposed at the bent portion is larger than the fin pitch between adjacent fins disposed at a straight portion of the heat exchanger.

10. The air-conditioning apparatus of claim 2, wherein

the heat exchanger has a bent portion, and

the fin pitch between adjacent fins disposed at a straight portion of the heat exchanger is larger than the fin pitch between adjacent fins disposed at the bent portion.

11. The air-conditioning apparatus of claim 2, wherein

the fan includes a propeller fan and faces the air outlet,

the heat exchanger faces the air inlet and is divided into a plurality of vertically aligned heat exchanger portions, and

in at least one of the plurality of divided heat exchanger portions, the fin pitch of the heat exchanger portion disposed at a lower position is larger than the fin pitch of the heat exchanger portion disposed at an upper position.

12. The heat exchanger of claim 1, wherein the fins and the heat transfer tubes are bonded to each other by one of brazing and adhesion.