EP4711684A1

EP4711684A1 - Air conditioning device

Info

Publication number: EP4711684A1
Application number: EP25783915.9A
Authority: EP
Inventors: Shota AGO; Hiroyuki Nakano
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2024-07-24
Filing date: 2025-05-12
Publication date: 2026-03-18
Also published as: JP2026017832A; WO2026023203A1; JP7799212B1

Abstract

An air conditioner includes: a heat exchanger (40) including a heat transfer tube (27) made of aluminum or an aluminum alloy and a tube sheet (26) made of aluminum or an aluminum alloy; a drain pan (60) configured to receive water generated in the heat exchanger (40); and an antimicrobial agent (71) for leaching out cations of a metal having a lower ionization tendency than aluminum, the antimicrobial agent (71) being placed in the drain pan (60). The tube sheet (26) includes a plurality of first connection holes (S1) to which the heat transfer tube (27) is connected, and a lowermost first connection hole (SA), which is located lowermost among the plurality of first connection holes (S1), is located above a water level of the drain pan (60).

Description

TECHNICAL FIELD

The present disclosure relates to an air conditioner.

BACKGROUND ART

An air conditioner described in Patent Document 1 includes an antimicrobial member disposed in a drain pan. The antimicrobial member is filled with an antimicrobial agent. The antimicrobial agent leaches into the drain water in the drain pan, reducing the growth of bacteria and mold generated in the drain pan. Patent Document 1 discloses using, as the antimicrobial agent, an inorganic antimicrobial agent, which contains mainly an inorganic compound, such as compounds of silver, copper, zinc, or tin.

CITATION LIST

PATENT DOCUMENT

Patent Document 1: Japanese Unexamined Patent Publication No. 2006-170478

SUMMARY OF THE INVENTION

TECHNICAL PROBLEM

In recent years, aluminum has been attracting attention as a material for components of a heat exchanger from the viewpoints of weight reduction, improvement in heat transfer coefficient, cost reduction, and the like. However, in a case where: the components of a heat exchanger are made of aluminum; and an antimicrobial agent containing such an inorganic compound, as described above, is used therein, a connection portion between a tube sheet and a heat transfer tube of the heat exchanger may corrode due to the difference in ionization tendency if the connection portion becomes immersed in drain water containing cations leached out from the antimicrobial agent. As a result, the connection portion may loosen, leading to a connection failure between the tube sheet and the heat transfer tube.
An object of the present disclosure is to provide an air conditioner capable of reducing the occurrence of a connection failure between a tube sheet and a heat transfer tube.

SOLUTION TO THE PROBLEM

An air conditioner of a first aspect includes: a heat exchanger (40) including a heat transfer tube (27) made of aluminum or an aluminum alloy and a tube sheet (26) made of aluminum or an aluminum alloy; a drain pan (60) configured to receive water generated in the heat exchanger (40); and an antimicrobial agent (71) for leaching out cations of a metal having a lower ionization tendency than aluminum, the antimicrobial agent (71) being placed in the drain pan (60). The tube sheet (26) includes a plurality of first connection holes (S1) to which the heat transfer tube (27) is connected, and a lowermost first connection hole (SA), which is located lowermost among the plurality of first connection holes (S1), is located above a water level of the drain pan (60).
In the first aspect, it is possible to reduce the occurrence of a connection failure between the tube sheet (26) and the heat transfer tube (27).
A second aspect is an embodiment of the first aspect. In the second aspect, the heat transfer tube (27) is fixed to the first connection holes (S1) of the tube sheet (26) solely by a tube expansion force of the heat transfer tube (27).
In the second aspect, since the lowermost first connection hole (SA), which is located lowermost among the plurality of first connection holes (S1), is located at a position higher than the water level of the drain pan (60), it is possible to reduce the occurrence of a connection failure between the tube sheet (26) and the heat transfer tube (27), and therefore, even if the heat transfer tube (27) is fixed to the first connection holes (S1) of the tube sheet (26) solely by the tube expansion force of the heat transfer tube (27), it is possible to effectively maintain the state in which the heat transfer tube (27) is fixed to the tube sheet (26).
A third aspect is an embodiment of the first or second aspect. In the third aspect, the heat exchanger (40) includes a fin (F), the fin (F) includes a second connection hole (T) to which the heat transfer tube (27) is connected, a raised burring portion is provided around the second connection hole (T) of the fin (F), and no raised burring portion is provided around the first connection holes (S1) of the tube sheet (26).
In the third aspect, since the lowermost first connection hole (SA), which is located lowermost among the plurality of first connection holes (S1), is located at a position higher than the water level of the drain pan (60), it is possible to reduce the occurrence of a connection failure between the tube sheet (26) and the heat transfer tube (27), and therefore, even if no raised burring portion is provided around the first connection holes (S1), it is possible to effectively maintain the state in which the heat transfer tube (27) is fixed to the tube sheet (26).
A fourth aspect is an embodiment of any one of the first to third aspects. In the fourth aspect, the heat exchanger (40) includes a fin (F), and the tube sheet (26) has a higher ionization tendency than the fin (F).
In the fourth aspect, since the lowermost first connection hole (SA), which is located lowermost among the plurality of first connection holes (S1), is located at a position higher than the water level of the drain pan (60), it is possible to reduce the occurrence of a connection failure between the tube sheet (26) and the heat transfer tube (27), and therefore, even if the tube sheet (26) has a higher ionization tendency than the fin (F), it is possible to effectively maintain the state in which the heat transfer tube (27) is fixed to the tube sheet (26).
A fifth aspect is an embodiment of any one of the first to fourth aspects. In the fifth aspect, the heat exchanger (40) includes a fin (F), a protective layer is provided on a surface of the fin (F), and no protective layer is provided on a surface of the tube sheet (26).
In the fifth aspect, since the lowermost first connection hole (SA), which is located lowermost among the plurality of first connection holes (S1), is located at a position higher than the water level of the drain pan (60), it is possible to reduce the occurrence of a connection failure between the tube sheet (26) and the heat transfer tube (27), and therefore, even if no protective layer is provided on a surface of the tube sheet (26), it is possible to effectively maintain the state in which the heat transfer tube (27) is fixed to the tube sheet (26).
A sixth aspect is an embodiment of any one of the first to fifth aspects. In the sixth aspect, the air conditioner further includes a metal plate (Z) that is provided on a bottom surface (68) of the drain pan (60) and has a lower ionization tendency than aluminum.
In the sixth aspect, it is possible to reduce the generation of a slimy substance or slime on the bottom surface (68) of the drain pan (60).
A seventh aspect is an embodiment of any one of the first to sixth aspects. In the seventh aspect, the air conditioner further includes a metal particle-containing body that is provided on a bottom surface (68) of the drain pan (60) and contains a metal particle with a lower ionization tendency than aluminum.
In the seventh aspect, it is possible to reduce the generation of a slimy substance or slime on the bottom surface (68) of the drain pan (60).
An eighth aspect is an embodiment of the sixth aspect. In the eighth aspect, the metal plate (Z) is located at a position closer to a drain port (V) of the drain pan (60) than the antimicrobial agent (71) is located.
In the eighth aspect, the antimicrobial effect of the metal plate (Z) can help reduce clogging of the drain port (V) caused by slime.
A ninth aspect is an embodiment of the seventh aspect. In the ninth aspect, the metal particle-containing body is located at a position closer to a drain port (V) of the drain pan (60) than the antimicrobial agent (71) is located.
In the ninth aspect, the antimicrobial effect on a surface of the metal particle-containing body can help reduce clogging of the drain port (V) caused by slime.
A tenth aspect is an embodiment of any one of the first to ninth aspects. In the tenth aspect, the air conditioner further includes a housing portion (80) that houses the antimicrobial agent (71), and the housing portion (80) has a shape that tapers downward.
In the tenth aspect, water containing cations leached out from the antimicrobial agent (71) can reduce corrosion of the connection portion between the tube sheet (26) and the heat transfer tube (27).
An eleventh aspect is an embodiment of any one of the first to tenth aspects. In the eleventh aspect, the air conditioner further includes a housing portion (80) for housing the antimicrobial agent (71), the housing portion (80) includes a leaching portion (H) that allows cations leached out from the antimicrobial agent (71) to move to an outside of the housing portion (80), and the lowermost first connection hole (SA), which is located lowermost among the plurality of first connection holes (S1), is located at a position higher than an upper end of the leaching portion (H).
In the eleventh aspect, water containing cations leached out from the antimicrobial agent (71) can reduce corrosion of the connection portion between the tube sheet (26) and the heat transfer tube (27).
A twelfth aspect is an embodiment of any one of the first to eleventh aspects. In the twelfth aspect, the antimicrobial agent (71) is disposed near a center of the drain pan (60) in its longitudinal direction.
In the twelfth aspect, cations leached out from the antimicrobial agent (71) can be distributed over a wide area within the drain pan (60).
A thirteenth aspect is an embodiment of any one of the first to twelfth aspects. In the thirteenth aspect, a plurality of heat transfer tubes (27), each of which is identical to the heat transfer tube (27), are connected to the tube sheet (26), and a distance (Y) between adjacent ones of the plurality of first connection holes (S1) is 8 mm or more and 17 mm or less.
In the thirteenth aspect, the heat exchanger (40) has an improved evaporator efficiency effectively, and therefore, a large amount of water generated by dehumidification is sent from the heat exchanger (40) to the drain pan (60). However, the water in the drain pan (60) can be subjected to antimicrobial treatment performed by cations leached out from the antimicrobial agent (71), and thus the risk of generation of a slimy substance or slime in the drain pan (60) can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] FIG. 1 is a schematic piping system diagram of an air conditioner according to an embodiment.
[FIG. 2] FIG. 2 is a front view of an indoor unit.
[FIG. 3] FIG. 3 is a vertical sectional view of the indoor unit, showing the internal structure of the indoor unit cut at a position where a fin exists.
[FIG. 4] FIG. 4 is a vertical sectional view of the indoor unit, showing the internal structure of the indoor unit cut at a position where a tube sheet exists.
[FIG. 5] FIG. 5 is an enlarged vertical sectional view of part of the internal structure of the indoor unit, including a drain pan and its vicinity.
[FIG. 6] FIG. 6 is a perspective view of the drain pan.
[FIG. 7] FIG. 7 is a perspective view of part of the drain pan.
[FIG. 8] FIG. 8 is a perspective view of an appearance of a case.
[FIG. 9] FIG. 9 is a perspective view of a variation of the drain pan.
[FIG. 10] FIG. 10A is a graph showing the relationship between the distance between adjacent heat transfer tubes and the evaporator efficiency. FIG. 10B is a diagram illustrating the distance between adjacent heat transfer tubes.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described in detail below with reference to the drawings. The present disclosure is not limited to the embodiments shown below, and various changes can be made within the scope without departing from the technical concept of the present disclosure. Since each of the drawings is intended to illustrate the present disclosure conceptually, dimensions, ratios, or numbers may be exaggerated or simplified as necessary for ease of understanding. The same reference characters denote the same or equivalent components in each embodiment, example, and variation, as well as the drawings. Thus, detailed descriptions of such components, descriptions of advantages associated therewith, and other related explanations will not be repeated.

(1) Overall Configuration of Air Conditioner

FIG. 1 is a schematic piping system diagram of an air conditioner (10). The air conditioner (10) controls the temperature of air in a target space. The target space is an indoor space. The air conditioner (10) performs a cooling operation and a heating operation. In the cooling operation, the air conditioner (10) cools the air in the indoor space. In the heating operation, the air conditioner (10) heats the air in the indoor space.
The air conditioner (10) includes a refrigerant circuit (11). The refrigerant circuit (11) is filled with a refrigerant. The refrigerant circuit (11) circulates the refrigerant therethrough to perform a refrigeration cycle. The refrigerant circuit (11) is filled with a flammable refrigerant. The refrigerant in this example contains difluoromethane (R32). The refrigerant may contain propane (R290), which is a highly flammable natural refrigerant. The natural refrigerant is a refrigerant having an ozone depletion potential of zero, having a low global warming potential, and having a small impact on the environment.
The air conditioner (10) includes an outdoor unit (20), an indoor unit (30), a first connection pipe (12), and a second connection pipe (13). The air conditioner (10) is a pair-type air conditioner including one outdoor unit (20) and one indoor unit (30). The outdoor unit (20) includes a compressor (21), an outdoor heat exchanger (22), an expansion valve (23), a four-way switching valve (24), and an outdoor fan (25). The indoor unit (30) includes an indoor heat exchanger (40) and a cross-flow fan (50).

(1-1) Outdoor Unit

The outdoor unit (20) is installed in an outdoor space.
The compressor (21) compresses the refrigerant. The compressor (21) is a rotary compressor. The rotary compressor (21) is of an oscillation type, a rolling piston type, or a scroll type, for example.
The outdoor heat exchanger (22) exchanges heat between the refrigerant and outdoor air. The outdoor heat exchanger (22) is a fin-and-tube heat exchanger.
The outdoor fan (25) transfers outdoor air. The air transferred by the outdoor fan (25) passes through the outdoor heat exchanger (22). The outdoor fan (25) is a propeller fan.
The expansion valve (23) decompresses the refrigerant. The expansion valve (23) is an electronic or temperature-sensitive expansion valve.
The four-way switching valve (24) reverses the flow of the refrigerant in the refrigerant circuit (11). The four-way switching valve (24) switches between a first state indicated by a solid line in FIG. 1 and a second state indicated by a broken line in FIG. 1. The four-way switching valve (24) in the first state makes the discharge side of the compressor (21) and the gas side of the outdoor heat exchanger (22) communicate with each other, and simultaneously makes the suction side of the compressor (21) and the gas side of an indoor heat exchanger (40) communicate with each other. The four-way switching valve (24) in the second state makes the discharge side of the compressor (21) and the gas side of the indoor heat exchanger (40) communicate with each other, and simultaneously makes the suction side of the compressor (21) and the gas side of the outdoor heat exchanger (22) communicate with each other.

(1-2) Indoor Unit

The indoor unit (30) is installed in the indoor space.
The indoor heat exchanger (40) exchanges heat between the refrigerant and indoor air. The indoor heat exchanger (40) is a fin-and-tube heat exchanger.
The cross-flow fan (50) is an indoor fan that transfers indoor air. The air transferred by the cross-flow fan (50) passes through the indoor heat exchanger (40).

(1-3) First Connection Pipe and Second Connection Pipe

The first connection pipe (12) and the second connection pipe (13) connect the indoor unit (30) and the outdoor unit (20) to each other. The first connection pipe (12) is a gas pipe, and the second connection pipe (13) is a liquid pipe. The first connection pipe (12) is connected to a gas end of the indoor heat exchanger (40). The second connection pipe (13) is connected to a liquid end of the indoor heat exchanger (40).

(2) Details of Indoor Unit

FIG. 2 illustrates the indoor unit (30). FIG. 3 is a vertical sectional view of the indoor unit (30). In the following description, the terms "up," "down," "front," "rear," "left," and "right" refer to directions when the indoor unit (30) is viewed from the front.
The indoor unit (30) is provided on a wall surface. The indoor unit (30) is a wall-mounted air-conditioning indoor unit. The indoor unit (30) includes a casing (31), the indoor heat exchanger (40), a drain pan (60), and an antimicrobial portion (70).

(2-1) Casing

The casing (31) forms an outer contour of the indoor unit (30). An internal space (39) is formed inside the casing (31), and accommodates the indoor heat exchanger (40) and the cross-flow fan (50).
As shown in FIGS. 2 and 3, the casing (31) has a horizontally long box-like shape extending in a left-right direction. The casing (31) includes a front panel (32), a rear panel (33), a top panel (34), and a bottom panel (35).
The casing (31) has an intake opening (36). The intake opening (36) is provided at the top panel (34) of the casing (31). The intake opening (36) extends in the longitudinal direction of the casing (31) (i.e., in the left-right direction). Through the intake opening (36), air in the indoor space is taken into the internal space (39) of the casing (31).
The casing (31) has a blow-out opening (37). The blow-out opening (37) is provided at the bottom panel (35). The blow-out opening (37) extends in the longitudinal direction of the casing (31). Through the blow-out opening (37), air having flowed through a blow-out flow path (38) is blown out to the indoor space. At the blow-out opening (37), two flaps (55) are provided. The flaps (55) adjust the direction of the flow of air blown out from the blow-out opening (37).

(2-2) Indoor Heat Exchanger

The indoor heat exchanger (40) exchanges heat with air by using the refrigerant flowing through heat transfer tubes (27). As shown in FIGS. 2 to 4, the indoor heat exchanger (40) includes tube sheets (26), a plurality of heat transfer tubes (27), and a plurality of fins (F). The tube sheets (26), the heat transfer tubes (27), and the fins (F) are made of aluminum or an aluminum alloy. The tube sheets (26) support the heat transfer tubes (27) and the fins (F). The tube sheets (26) each have a plate-like shape. The tube sheets (26) each have a plurality of holes (S) extending therethrough. The fins (F) are disposed between the pair of tube sheets (26). In this embodiment, the pair of tube sheets (26) are disposed on both left and right sides of the of fins (F), respectively. The heat transfer tubes (27) extend in the left-right direction. Each of the heat transfer tubes (27) is connected to (inserted through) a corresponding one of the holes (S).
Among the holes (S), the holes (S) to which the heat transfer tubes (27) are connected may be referred to as first connection holes (S1). Among the holes (S), a hole (S) that does not correspond to the first connection hole (S1), i.e., a hole (S) that is open because no heat transfer tube (27) is connected may be referred to as an open hole (S2). The heat transfer tubes (27) may be connected to all of the holes (S), in which case all the holes (S) are the first connection holes (S1). Alternatively, the heat transfer tubes (27) may be connected to some of the holes (S), in which case the connected holes (S) of the holes (S) are the first connection holes (S1), and the remaining hole(s) (S) are the open hole(s) (S2).
The fins (F) each have a plate-like shape. The fins (F) are arranged at equal intervals along a direction of an axis O of the cross-flow fan (50) (i.e., along the left-right direction). Each of the fins (F) has a plurality of second connection holes (T) extending through the fin (F). The heat transfer tubes (27) are connected to (inserted through) the second connection holes (T). The interiors of the heat transfer tubes (27) form a flow path for the refrigerant. The heat transfer tubes (27) constitute a part of the refrigerant circuit (11).
The indoor heat exchanger (40) includes a front heat exchange unit (41) and a rear heat exchange unit (42). The indoor heat exchanger (40) further includes a front auxiliary heat exchange unit (43) and a rear auxiliary heat exchange unit (44). The front heat exchange unit (41), the rear heat exchange unit (42), the front auxiliary heat exchange unit (43), and the rear auxiliary heat exchange unit (44) are formed separately from each other.

(2-3) Drain Pan

The drain pan (60) is disposed below the indoor heat exchanger (40). Specifically, the drain pan (60) is disposed below the front heat exchange unit (41) and the front auxiliary heat exchange unit (43). The drain pan (60) receives water generated in the indoor heat exchanger (40) and consequently stores the water generated in the indoor heat exchanger (40). In the following, water stored in the drain pan (60) may be referred to as drain water.
As shown in FIGS. 5 and 6, the drain pan (60) has a horizontally long box-like shape extending in the left-right direction. The drain pan (60) includes a bottom plate (61), a front wall (62), a rear wall (63), a right wall (64), and a left wall (65). The left-right direction corresponds to the longitudinal direction of the drain pan (60). In other words, the left-right direction corresponds to the width or lateral direction of the drain pan (60). A front-rear direction is a direction perpendicular to the left-right direction and corresponds to the short-side direction of the drain pan (60). In other words, the front-rear direction corresponds to the depth direction of the drain pan (60). An up-down direction is a vertically up-down direction. The up-down direction is a direction perpendicular to the left-right direction and to the front-rear direction. In other words, the up-down direction corresponds to the height direction of the drain pan (60).
The bottom plate (61) includes a first bottom plate (61a) and a second bottom plate (61b). The first bottom plate (61a) and the second bottom plate (61b) are substantially rectangular. The first bottom plate (61a) is a substantially horizontal plate. The second bottom plate (61b) is formed so as to be inclined upward as it extends rearward from the rear end of the first bottom plate (61a).
The front wall (62) is formed so as to be inclined frontward as it extends upward from the front end of the first bottom plate (61a). The rear wall (63) extends upward from the rear end of the second bottom plate (61b). The right wall (64) is connected to the right end of the bottom plate (61). The left wall (65) is connected to the left end of the bottom plate (61).
The drain pan (60) is provided with a drain port (V) that allows communication between the inside and outside of the drain pan (60). Drain water is discharged to the outside of the drain pan (60) through the drain port (V). In this embodiment, the drain port (V) includes a first drain port (V1) and a second drain port (V2). The first drain port (V1) and the second drain port (V2) are holes to which drain hoses are connected. The first drain port (V1) is disposed at one end (left end) of the drain pan (60) in the left-right direction, and the second drain port (V2) is disposed at the other end (right end) of the drain pan (60) in the left-right direction. Drain water flows into a drain hose via the first drain port (V1) or the second drain port (V2) to which the drain hose is connected.
As shown in FIG. 7, the drain pan (60) is provided with a first fixing portion (66) and a second fixing portion (67) that fix the position of the antimicrobial portion (70). The first fixing portion (66) is provided at the center in the left-right direction at the upper end of the front wall (62). The first fixing portion (66) is formed as a recess at the upper end of the front wall (62). A first tongue portion (77c) (the details of this portion will be described later) of the antimicrobial portion (70) is fitted into the first fixing portion (66). The second fixing portion (67) is provided at the center in the left-right direction at the lower end of the front wall (62). The second fixing portion (67) includes a rectangular first plate (67a) extending rearward from the lower end of the front wall (62), and a second plate (67b) connected to the rear end of the first plate (67a) and extending in the left-right direction. A second tongue portion (77d) (the details of this portion will be described later) of the antimicrobial portion (70) is fitted to the second fixing portion (67).

(3) Antimicrobial Portion

As shown in FIGS. 3 to 6, the antimicrobial portion (70) is disposed in the drain pan (60). The antimicrobial portion (70) is disposed near the front wall (62) of the drain pan (60). The antimicrobial portion (70) includes an antimicrobial agent (71) and a case (72) that houses the antimicrobial agent (71). The antimicrobial agent (71) has an antimicrobial effect on drain water. In this embodiment, the term "antimicrobial" encompasses killing bacteria and reducing or removing bacteria. The case (72) includes a housing portion (80) and a lid portion (73). The housing portion (80) houses the antimicrobial agent (71). The housing portion (80) (the antimicrobial agent (71)) is disposed near the center of the drain pan (60) in the left-right direction.
The housing portion (80) has a shape that tapers downward. That is, the housing portion (80) has a shape such that the cross-sectional area of the housing portion (80) perpendicular to the up-down direction decreases downward.
As shown in FIGS. 5 and 8, the housing portion (80) has a hollow box-like shape with an open top. The open top of the housing portion (80) is closed by the lid portion (73) when the lid portion (73) is attached.
The housing portion (80) has a plurality of holes (H) that are in communication with the inside and the outside of the housing portion (80). The holes (H) are formed in front and side surfaces (84, 86, 87) and a bottom (81) of the housing portion (80). The antimicrobial agent (71) is in the form of a plurality of granules. The antimicrobial agent (71) contains a metal having a lower ionization tendency than aluminum. The antimicrobial agent (71) contains, for example, silver, copper, stainless steel, and/or zinc. Upon contact with drain water, cations of the metal having a lower ionization tendency than aluminum are leached out from the antimicrobial agent (71).
The housing portion (80) is provided with a flange portion (92). The flange portion (92) is provided with the second tongue portion (77d). The second tongue portion (77d) has a slit (79) extending from the lower end toward the upper end of the second tongue portion (77d). The first plate (67a) of the second fixing portion (67) is inserted into the slit (79).
The lid portion (73) includes a hook (77). The hook (77) includes a base portion (77a), an arm portion (77b), and the first tongue portion (77c). The base portion (77a) extends upward from a front portion of the lid portion (73). The arm portion (77b) extends substantially horizontally from the upper end of the base portion (77a) toward the front wall (62) of the drain pan (60). The first tongue portion (77c) extends downward from the rear end of the arm portion (77b). A groove (78) is formed at a connection portion between the first tongue portion (77c) and the arm portion (77b). The groove (78) is disposed such that the groove (78) and the first fixing portion (66) are engaged with each other.
Drain water flows into and out of the housing portion (80) through the holes (H). Drain water enters the inside of the housing portion (80) through the holes (H), and as a result, the drain water comes into contact with the antimicrobial agent (71) within the housing portion (80). Consequently, cations of the metal having a lower ionization tendency than aluminum are leached out from the antimicrobial agent (71), and the cations flow into the drain pan (60) (i.e., to the outside of the housing portion (80)) through the holes (H). Thus, the antimicrobial effect can be exerted on the drain water by the cations. As a result, generation of a slimy substance or slime in the drain pan (60) can be reduced. The holes (H) are an example of a leaching portion.

(4) Features

The tube sheets (26) have the first connection holes (S1) to which the heat transfer tubes (27) are connected. The lowermost first connection hole (SA), which is located lowermost among the first connection holes (S1), is located above the water level of the drain pan (60). The water level of the drain pan (60) refers to the position of the upper end of the drain port (V) of the drain pan (60) in the up-down direction (in this embodiment, the position of the upper end of the annular two-dot-dash line indicating the drain port (V) in FIG. 4). In the case where the drain port (V) includes a plurality of drain ports (e.g., the first drain port (V1) and the second drain port (V2)) as in this embodiment, the water level of the drain pan (60) refers to the position of the upper end of the uppermost drain port (V), which is located uppermost among the plurality of drain ports in the up-down direction.

(5) Advantageous Effects

As described above, the lowermost first connection hole (SA), which is located lowermost among the plurality of first connection holes (S1), is located above the water level of the drain pan (60) (see FIG. 4). This allows drain water to be discharged to the outside of the drain pan (60) through the drain port (V) before the drain water reaches the lowermost first connection hole (SA). This can reduce immersion of the connection portions (the first connection holes (S1)) between the tube sheets (26) and the heat transfer tubes (27) in drain water containing cations leached out from the antimicrobial agent (71). As a result, corrosion (electrolytic corrosion) of the connection portions between the tube sheets (26) and the heat transfer tubes (27) can be reduced, and therefore, it is possible to reduce the occurrence of connection failures between the tube sheets (26) and the heat transfer tubes (27).
If a connection failure occurs between a tube sheet (26) and a heat transfer tube (27), a gap may be created between the corresponding first connection hole (S1) of the tube sheet (26) and the heat transfer tube (27), allowing drain water containing cations leached out from the antimicrobial agent (71) to enter and remain in the gap. However, in the above configuration, the increase in the risk of corrosion of the heat transfer tube (27) caused by the remaining water can be minimized.
The housing portion (80) has a shape that tapers downward (see FIGS. 5 and 8). Even when the housing portion (80) has a tapered shape, that is, a shape such that the contact area between drain water and the housing portion (80) increases as the water level of the drain pan (60) rises, to allow more cations to be leached out from the antimicrobial agent (71), it is possible to reduce corrosion of the connection portions between the tube sheets (26) and the heat transfer tubes (27) caused by the drain water containing cations leached out from the antimicrobial agent (71), because the lowermost first connection hole (SA) is located at a position higher than the water level of the drain pan (60), making it less likely that the connection portions between the tube sheets (26) and the heat transfer tubes (27) become immersed in the water.
The antimicrobial agent (71) is disposed near the center of the drain pan (60) in its longitudinal direction (see FIG. 6). Due to this, cations leached out from the antimicrobial agent (71) are less likely to remain in a localized area of the drain pan (60), and the cations can be distributed over a wide area within the drain pan (60).
While the embodiments and variations have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims (for example, variations (A) to (J) described below).

(A) The heat transfer tubes (27) may be fixed to the first connection holes (S1) of the tube sheets (26) solely by the tube expansion force of the heat transfer tubes (27) (see FIG. 4). In this configuration, since the lowermost first connection hole (SA) is located at a position higher than the water level of the drain pan (60), it is possible to reduce the occurrence of connection failures between the tube sheets (26) and the heat transfer tubes (27), and therefore, even if the heat transfer tubes (27) are fixed to the first connection holes (S1) of the tube sheets (26) solely by the tube expansion force of the heat transfer tubes (27), it is possible to effectively maintain the state in which the heat transfer tubes (27) are fixed to the tube sheets (26).
(B) No raised burring portion may be provided around the first connection holes (S1) of the tube sheets (26), whereas a raised burring portion is provided around each of the second connection holes (T) of the fins (F) (see FIGS. 3 and 4). In this configuration, since the lowermost first connection hole (SA) is located at a position higher than the water level of the drain pan (60), it is possible to reduce the occurrence of connection failures between the tube sheets (26) and the heat transfer tubes (27), and therefore, even if no raised burring portion is provided around the first connection holes, it is possible to effectively maintain the state in which the heat transfer tubes (27) are fixed to the tube sheets (26).
(C) The tube sheets (26) may have an ionization tendency higher than the fins (F). In this case, the tube sheets (26) are made of aluminum or an aluminum alloy, while the fins (F) are made of, for example, copper or stainless steel. In this configuration, since the lowermost first connection hole (SA) is located at a position higher than the water level of the drain pan (60), it is possible to reduce the occurrence of connection failures between the tube sheets (26) and the heat transfer tubes (27), and therefore, even if the tube sheets (26) have an ionization tendency higher than the fins (F), it is possible to effectively maintain the state in which the heat transfer tubes (27) are fixed to the tube sheets (26).
(D) No protective layer may be provided on the surfaces of the tube sheets (26), whereas protective layers are provided on the surfaces of the fins (F). A protective layer is a film that covers an object to prevent the object from galvanic corrosion. Such protective layers include not only a layer (sacrificial layer) having a lower potential than the object on which the protective layer is provided, but also a resin coating layer. In this embodiment, sacrificial layers formed using zinc thermal spraying, for example, are provided on the surfaces of the fins (F) made of aluminum or an aluminum alloy. On the other hand, the surfaces of the tube sheets (26) made of aluminum or an aluminum alloy are not provided with protective layers and are exposed. In this configuration, since the lowermost first connection hole (SA) is located at a position higher than the water level of the drain pan (60), it is possible to reduce the occurrence of connection failures between the tube sheets (26) and the heat transfer tubes (27), and therefore, even if no protective layer is formed on the surfaces of the tube sheets (26), it is possible to effectively maintain the state in which the heat transfer tubes (27) are fixed to the tube sheets (26).
(E) As shown in FIG. 9, the indoor unit (30) (antimicrobial portion (70)) may further include a metal plate (Z) that is a plate-shaped metal. The metal plate (Z) contains a metal having a lower ionization tendency than aluminum. The metal plate (Z) includes, for example, silver, copper, stainless steel, and/or zinc. The metal plate (Z) is provided on a bottom surface (68) of the drain pan (60). The metal plate (Z) is fixed to the bottom surface (68) of the drain pan (60) using a screw or adhesive tape (including double-sided tape), for example. Upon contact with drain water, cations of the metal with a lower ionization tendency than aluminum are leached out from the metal plate (Z). Thus, the cations leached out from the metal plate (Z) can locally apply antimicrobial treatment to the drain water in the vicinity of the bottom surface (68) of the drain pan (60), where a slimy substance or slime is likely to be generated. Accordingly, the generation of a slimy substance or slime can be effectively reduced.
(F) The metal plate (Z) may be located at a position closer to the drain port (V) than the antimicrobial agent (71) is located. For example, as shown in FIG. 9, when the first drain port (V1) is located at the left end of the drain pan (60) and the second drain port (V2) is located at the right end of the drain pan (60), the antimicrobial agent (71) may be located near the center of the drain pan (60) in the left-right direction, a first metal plate (Z1) may be located near the left end of the drain pan (60), and a second metal plate (Z2) may be located near the right end of the drain pan (60). This allows the metal plate (Z) to exert its antimicrobial effect in the vicinity of the drain port (V), thereby reducing clogging of the drain port (V) caused by slime.
(G) The indoor unit (30) (antimicrobial portion (70)) may further include a metal particle-containing body. The metal particle-containing body includes metal particles (metal powder). The metal particles include a metal having a lower ionization tendency than aluminum. The metal particles include, for example, silver, copper, stainless steel, and/or zinc. The metal particle-containing body is provided on the bottom surface (68) of the drain pan (60).

The metal particles may be contained in a water-soluble coating material. In this case, the metal particles may be provided on the bottom surface (68) of the drain pan (60), by applying the coating material to the bottom surface (68) of the drain pan (60). In this case, the coating material serves as the metal particle-containing body. Alternatively, the metal particles may be attached to a surface of a sealing material disposed on the bottom surface (68) of the drain pan (60). In this case, the sealing material serves as the metal particle-containing body. Alternatively, the metal particles may be kneaded or incorporated into the drain pan (60), to be disposed within the bottom surface (68) of the drain pan (60). In this case, the portion of the drain pan (60), into which the metal particles are incorporated, serves as the metal particle-containing body. Alternatively, the metal particles may be contained in a bag-shaped member having a mesh, such as a net, and disposed on the bottom surface (68) of the drain pan (60). In this case, the bag-shaped member serves as the metal particle-containing body.
When the metal particle-containing body is immersed in the drain water, cations of the metal with a lower ionization tendency are leached out from the metal particle-containing body into the drain water. Upon contact with the drain water, cations of the metal with a lower ionization tendency than aluminum are leached out from the metal particle-containing body (metal particles). Thus, the cations leached out from the metal particles can locally apply antimicrobial treatment to the drain water in the vicinity of the bottom surface (68) of the drain pan (60), where a slimy substance or slime is likely to be generated. Accordingly, the generation of a slimy substance or slime can be effectively reduced.

(H) The metal particle-containing body may be located at a position closer to the drain port (V) than the antimicrobial agent (71) is located. This allows the metal particles contained in the metal particle-containing body to exert the antimicrobial effect in the vicinity of the drain port (V), thereby reducing clogging of the drain port (V) caused by slime.
(I) The lowermost first connection hole (SA), which is located lowermost among the first connection holes (S1), may be located at a position higher than the upper end of the leaching portion. The upper end of the leaching portion corresponds to the upper end of a portion of the housing portion (80) that allows communication between the inside and the outside of the housing portion (80) and allows the drain water to flow between the inside and the outside of the housing portion (80). In this embodiment, the upper end of the leaching portion is the upper end of the uppermost hole (H), which is located uppermost among the plurality of holes (H) (see FIG. 8). This can reduce the likelihood of immersion of the connection portions (first connection holes (S1)) between the tube sheets (26) and the heat transfer tubes (27) in the drain water containing cations leached out from the antimicrobial agent (71) to the outside of the housing portion (80). It is therefore possible to reduce corrosion of the connection portions between the tube sheets (26) and the heat transfer tubes (27).
(J) As shown in FIGS. 10A and 10B, a distance (Y) between adjacent heat transfer tubes (27) may be 8 mm or more and 17 mm or less. The distance (Y) between adjacent heat transfer tubes (27) can also be said as the distance (Y) between adjacent first connection holes (S1). The inventors of the present application have confirmed the following through tests, for example. The evaporator efficiency increases as the distance (Y) between adjacent heat transfer tubes (27) decreases. However, if the distance (Y) between adjacent heat transfer tubes (27) is less than 8 mm, airflow resistance increases when air flows within the indoor heat exchanger (40), requiring the fan (50) to operate at a higher number of rotations, which in turn leads to increased power consumption of the fan (50). In comparison, the resulting improvement in evaporator efficiency is not sufficiently significant. The inventors of the present application have also confirmed that the evaporator efficiency falls below a desired level if the distance (Y) between adjacent heat transfer tubes (27) is greater than 17 mm. Accordingly, in order to effectively ensure the evaporator efficiency while considering the running costs of the air conditioner (10), the distance (Y) between adjacent heat transfer tubes (27) is set to 8 mm or more and 17 mm or less. In this configuration, although dehumidification is effectively performed by the heat exchanger (22), and as a result, a large amount of water generated due to dehumidification is sent from the heat exchanger (22) to the drain pan (60), the water in the drain pan (60) can be subjected to antimicrobial treatment performed by cations leached out from the antimicrobial agent (71). Thus, the risk of generation of a slimy substance or slime in the drain pan (60) can be reduced. The evaporator efficiency of the air conditioner (10) is expressed by a value obtained by dividing a value obtained by subtracting the wet-bulb temperature of the outlet air from the wet-bulb temperature of the inlet air (inlet-air WB - outlet-air WB) by a value obtained by subtracting the evaporation temperature from the wet-bulb temperature of the inlet air (inlet-air WB - evaporation temperature). That is, evaporator efficiency = (inlet-air WB - outlet-air WB)/(inlet-air WB - evaporation temperature), where WB is wet-bulb temperature.

The expressions such as "first," "second," "third," and so on described above are used to distinguish the terms to which these expressions are given, and do not limit the number and order of the terms. The embodiments, examples, variations, and the other embodiments may be combined and replaced with each other without deteriorating intended functions of the present disclosure.

INDUSTRIAL APPLICABILITY

As described above, the present disclosure is useful for an air conditioner.

DESCRIPTION OF REFERENCE CHARACTERS

10: Air Conditioner
26: Tube Sheet
27: Heat Transfer Tube
40: Heat Exchanger
60: Drain Pan
71: Antimicrobial Agent
S1: First Connection Hole
SA: Lowermost First Connection Hole

Claims

An air conditioner comprising:
a heat exchanger (40) including a heat transfer tube (27) made of aluminum or an aluminum alloy and a tube sheet (26) made of aluminum or an aluminum alloy;

a drain pan (60) configured to receive water generated in the heat exchanger (40); and

an antimicrobial agent (71) for leaching out cations of a metal having a lower ionization tendency than aluminum, the antimicrobial agent (71) being placed in the drain pan (60),

the tube sheet (26) including a plurality of first connection holes (S1) to which the heat transfer tube (27) is connected,

a lowermost first connection hole (SA), which is located lowermost among the plurality of first connection holes (S1), being located above a water level of the drain pan (60).
The air conditioner of claim 1, wherein
the heat transfer tube (27) is fixed to the first connection holes (S1) of the tube sheet (26) solely by a tube expansion force of the heat transfer tube (27).
The air conditioner of claim 1 or 2, wherein
the heat exchanger (40) includes a fin (F),

the fin (F) includes a second connection hole (T) to which the heat transfer tube (27) is connected,

a raised burring portion is provided around the second connection hole (T) of the fin (F), and

no raised burring portion is provided around the first connection holes (S1) of the tube sheet (26).
The air conditioner of any one of claims 1 to 3, wherein
the heat exchanger (40) includes a fin (F), and

the tube sheet (26) has a higher ionization tendency than the fin (F).
The air conditioner of any one of claims 1 to 4, wherein
the heat exchanger (40) includes a fin (F),

a protective layer is provided on a surface of the fin (F), and

no protective layer is provided on a surface of the tube sheet (26).
The air conditioner of any one of claims 1 to 5, further comprising a metal plate (Z) that is provided on a bottom surface (68) of the drain pan (60) and has a lower ionization tendency than aluminum.
The air conditioner of any one of claims 1 to 6, further comprising
a metal particle-containing body that is provided on a bottom surface (68) of the drain pan (60) and contains a metal particle with a lower ionization tendency than aluminum.
The air conditioner of to claim 6, wherein
the metal plate (Z) is located at a position closer to a drain port (V) of the drain pan (60) than the antimicrobial agent (71) is located.
The air conditioner of claim 7, wherein
the metal particle-containing body is located at a position closer to a drain port (V) of the drain pan (60) than the antimicrobial agent (71) is located.
The air conditioner of any one of claims 1 to 9, further comprising
a housing portion (80) that houses the antimicrobial agent (71), wherein

the housing portion (80) has a shape that tapers downward.
The air conditioner of any one of claims 1 to 10, further comprising
a housing portion (80) that houses the antimicrobial agent (71), wherein

the housing portion (80) includes a leaching portion (H) that allows cations leached out from the antimicrobial agent (71) to move to an outside of the housing portion (80), and

the lowermost first connection hole (SA), which is located lowermost among the plurality of first connection holes (S1), is located at a position higher than an upper end of the leaching portion (H).
The air conditioner of any one of claims 1 to 11, wherein
the antimicrobial agent (71) is disposed near a center of the drain pan (60) in its longitudinal direction.
The air conditioner of any one of claims 1 to 12, wherein
a plurality of heat transfer tubes (27), each of which is identical to the heat transfer tube (27), are connected to the tube sheet (26), and a distance (Y) between adjacent ones of the plurality of first connection holes (S1) is 8 mm or more and 17 mm or less.