KR101698698B1 - Parallel-flow type heat exchanger and air conditioner equipped with same - Google Patents

Abstract

The parallel flow type heat exchanger 1 has two vertical direction header pipes 2 and 3 and a plurality of horizontal direction flat tubes 4 connecting the header pipes. A plurality of horizontal flat tubes are also grouped into a plurality of groups, each of which constitutes a refrigerant path through which refrigerant flows from one side of the vertical header pipe to the other. The upper limit of the number of the flat tubes constituting the one-turn refrigerant pass is determined by a predetermined equation.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel-type heat exchanger and an air conditioner having the same,

The present invention relates to a side flow type parallel-flow heat exchanger and an air conditioner equipped with the same.

A parallel flow type heat exchanger in which a plurality of flat tubes are disposed between a plurality of header pipes to allow a plurality of refrigerant passages in the flat tubes to communicate with the inside of a header pipe and fins such as a corrugated fin are arranged between flat tubes, Outdoor unit of a car air conditioner or a building air conditioner.

An example of the structure of a parallel flow type heat exchanger is shown in Fig. 1, the upper side of the drawing corresponds to the upper side of the heat exchanger, and the lower side of the drawing corresponds to the lower side of the heat exchanger. The parallel flow type heat exchanger 1 is a side flow type and has two vertical direction header pipes 2 and 3 and a plurality of horizontal direction flat tubes 4 arranged therebetween. The header pipes 2 and 3 are arranged in parallel at intervals in the horizontal direction, and the flat tubes 4 are arranged at a predetermined pitch in the vertical direction. Since the heat exchanger 1 is installed at various angles in accordance with the design request in the step of actually mounting it on the device, the terms "vertical direction" and "horizontal direction" in this specification are not strictly interpreted. It should be understood as a simple directional reference.

The flattened tube 4 is an elongated molded product formed by extruding a metal. As shown in FIG. 2, a refrigerant passage 5 for circulating a refrigerant is formed inside. Since the flattened tube 4 is arranged so as to horizontally form the extrusion forming direction in the longitudinal direction, the refrigerant flow direction of the refrigerant passage 5 is also horizontal. A plurality of coolant passages (4) are arranged in the left and right direction in FIG. 2 in which the cross-sectional shapes and the cross-sectional areas are equivalent. Therefore, the vertical section of the flattened tube 4 has a harmonic shape. Each refrigerant passage (5) communicates with the inside of the header pipes (2, 3).

A pin (6) is provided on the flat surface of the flat tube (4). As the pin 6, a corrugated fin is used here, but it may be a plate pin. A side plate 7 is disposed on the outer side of the uppermost and lowermost one of the pins 6 arranged in the vertical direction.

The header pipes 2 and 3, the flat tube 4, the pin 6 and the side plate 7 all contain a metal having a good thermal conductivity such as aluminum and the flat tube 4 is connected to the header pipes 2 and 3 The pin 6 is fixed to the flat tube 4 and the side plate 7 is fixed to the pin 6 by brazing or welding.

The inside of the header pipe 2 is divided into three sections S1, S2 and S3 by two partition plates P1 and P2. The partition plates P1 and P2 divide the plurality of flat tubes 4 into three flat tube groups. A plurality of flat tubes 4 are connected to the sections S1, S2, and S3, respectively.

The inside of the header pipe 3 is partitioned into two sections S4 and S5 by one partition plate P3. The partition plate P3 divides the plurality of flat tubes 4 into two flat tube groups. A plurality of flat tubes 4 are connected to the divisions S4 and S5, respectively.

A refrigerant inlet / outlet pipe 8 is connected to the section S1. A refrigerant inlet / outlet pipe 9 is connected to the section S3.

The function of the heat exchanger 1 is as follows. When the heat exchanger 1 is used as a condenser, the refrigerant is supplied to the compartment S1 through the refrigerant inlet pipe 8. The refrigerant entering the section S1 flows through the plurality of flat tubes 4 connecting the section S1 and the section S4 to the section S4. A flat tube group including the plurality of flat tubes (4) constitutes a refrigerant pass A. The refrigerant pass A is symbolized by a block arrow. Other refrigerant passes are also symbolized by block arrows.

The refrigerant entering the zone S4 turns there, and is directed to the zone S2 through the plurality of flat tubes 4 connecting the zone S4 and the zone S2. A flat tube group including the plurality of flat tubes (4) constitutes a refrigerant pass B.

The refrigerant entering the zone S2 turns there, and is directed to the zone S5 through the plurality of flat tubes 4 connecting the zone S2 and the zone S5. A flat tube group including the plurality of flat tubes (4) constitutes a refrigerant pass (C).

The refrigerant entering the zone S5 turns there, and is directed to the zone S3 through the plurality of flat tubes 4 connecting the zone S5 and the zone S3. A flat tube group including the plurality of flat tubes (4) constitutes a refrigerant path (D). The refrigerant entering the zone S3 flows out from the refrigerant inlet / outlet pipe 9.

In this specification, the section from the refrigerant inlet pipe 8 or 9 to the first return portion or between the return portion and the next return portion is referred to as " one turn ". The refrigerant passes A, B, C, and D are all a one-turn refrigerant pass.

When the heat exchanger (1) is used as an evaporator, the refrigerant is supplied to the compartment (S3) through the refrigerant inlet / outlet pipe (9). The subsequent flow of refrigerant reverses the refrigerant path when the heat exchanger 1 is used as a condenser. The refrigerant passes through the refrigerant path D, the refrigerant path C, the refrigerant path B, and the refrigerant path A. The refrigerant enters the compartment S1 and flows out from the refrigerant inlet / outlet pipe 8.

In the parallel-flow type heat exchanger, various designs are designed in order to improve the performance. Examples thereof can be seen in Patent Documents 1 to 3.

In the parallel flow type heat exchanger described in Patent Document 1, a refrigerant passage having a fluid diameter in the range of 0.015 inch (about 0.38 millimeter) to 0.07 inch (about 1.78 millimeter) is disposed inside a plurality of flat tubes connecting two header pipes And a plurality of these are formed in parallel. The outline of the cross section of the coolant passage has at least one recessed portion which is formed at two or more relatively straight portions to be associated with each other and at a portion where the coolant passages meet. With this configuration, the front surface area of the air side blocked by the flat tube is small, and the air side heat transfer surface can be increased without increasing the air side pressure drop.

In the parallel flow type heat exchanger described in Patent Document 2, the height of the refrigerant passage in the flat tube is set to 0.35 mm to 0.8 mm. As a result, the sum of the lowered heat dissipation factor due to the ventilation resistance and the lowered heat dissipation performance due to the tube pressure loss is reduced, thereby enhancing the heat dissipation performance.

In the parallel-flow type heat exchanger described in Patent Document 3, the classification parameter? That is the ratio of the resistance parameter? Of the flat tube to the resistance parameter? Of the header pipe at the inlet side of the refrigerant is 0.5 or more. As a result, intensive flow of the refrigerant in the flat tube connected to the portion having the highest pressure in the refrigerant inlet port of the header pipe is prevented, the pressure applied to each of the flat tubes is uniformized to obtain a good sorted state, .

Japanese Patent Application Laid-Open No. 5-87752 Japanese Patent Application Laid-Open No. 2001-165532 Japanese Patent Application Laid-Open No. 2000-111274

In the case of using a parallel flow type heat exchanger as an evaporator, when a refrigerant flowing through a refrigerant path is considered, a state of "drifting" that a large amount of liquid refrigerant flows into some flat tubes and a large amount of refrigerant flows through the other flat tubes It is preferable not to occur. It is an object of the present invention to provide a parallel flow type heat exchanger of a side flow type in which an optimum design is implemented from the viewpoint of preventing the occurrence of drift with respect to the number of flat tubes constituting a refrigerant path. In particular, the present invention aims to optimize the number of flat tubes of a refrigerant path with a large ratio of gas refrigerant.

The parallel flow type heat exchanger according to the present invention includes two vertical direction header pipes and a plurality of horizontal direction flat tubes connecting the header pipes. The plurality of horizontal flat tubes are further grouped into a plurality of groups, each of which constitutes one turn of a refrigerant path through which refrigerant flows from one of the two vertical header pipes to the other. The upper limit of the number of the flat tubes constituting the one-turn refrigerant path is determined by the numerical value ± 2 obtained by the following equation (A).

When the parallel-flow type heat exchanger is used in an outdoor unit of an air conditioner,

When the parallel-flow type heat exchanger is used in an indoor unit of an air conditioner,

Where n is the number of flat tubes constituting one turn of the refrigerant path, Q is the rated capacity and W is the unit. Q uses the heating rating capability in the case of an outdoor unit, and the cooling capability in the case of an indoor unit.

When the parallel flow type heat exchanger having the above configuration is used in the outdoor unit of the air conditioner, it is preferable that the lower limit of the number of the flat tubes constituting the one-turn refrigerant path is determined by the following expression (B).

Where α = 0.0161, β = 8.86, d is the hydraulic diameter and m is the unit, A 'is the cross-sectional area of the refrigerant passage of one flat tube, and m2 is the unit.

When the parallel-flow heat exchanger of the above configuration is used in the indoor unit of the air conditioner, it is preferable that the lower limit of the number of the flat tubes constituting the one-turn refrigerant pass is determined by the following expression (B).

Where α = 0.0228, β = 6.62, d is the hydraulic diameter and m is the unit, A 'is the cross-sectional area of the refrigerant passage of one flat tube, and m2 is the unit.

Further, the present invention is an air conditioner in which the above-described parallel-flow type heat exchanger is installed in an outdoor unit or an indoor unit.

According to the present invention, it is possible to obtain a side flow type parallel-flow heat exchanger that does not cause drift, depending on the amount of circulation of the refrigerant.

1 is a schematic configuration diagram of a parallel flow type heat exchanger of a side flow type.
2 is a cross-sectional view taken along the line II-II in Fig.
3 is a table of specifications of the test sample of the flat tube.
Fig. 4 is a table showing the relationship between the refrigerant circulation amount and the number of flat tubes which do not cause drift. Fig.
5 is a graph showing the relationship between the refrigerant circulation amount and the number of flat tubes.
6 is a graph showing the relationship between the cooling capacity and the refrigerant circulation amount.
7 is a graph showing the relationship between the heating capacity and the refrigerant circulation amount.
8 is a graph of the optimum number of flat tubes pertaining to the outdoor unit of the air conditioner.
Fig. 9 is a graph of the optimal number of flat tubes pertaining to the indoor unit of the air conditioner.
10 is a graph showing the relationship between the refrigerant circulation amount and the suction pressure.
11 is a graph showing the relationship between the refrigerant circulation amount and the number of flat tubes.
12 is a graph showing the relationship between the number of flat tubes in the outdoor unit heat exchanger and the heating rating capability.
13 is a graph showing the relationship between the number of flat tubes in the indoor heat exchanger and the cooling rating capability.
Fig. 14 is a schematic configuration of an air conditioner equipped with a parallel-type heat exchanger according to the present invention, showing a state at the time of heating operation.
Fig. 15 is a schematic configuration of an air conditioner equipped with a parallel-type heat exchanger according to the present invention, showing a state during cooling operation.

The parallel flow type heat exchanger 1 of the side flow type shown in Fig. 1 and the number of the flat tubes 4 constituting the refrigerant path are set by the following method is a parallel flow type heat exchanger according to the present invention . However, the number of refrigerant passes is not limited to four. More than that, and less than that.

First, the upper limit of the number of the flat tubes 4 constituting the one-turn refrigerant path is obtained. The upper limit value is obtained from the following equation (A).

When the parallel-flow type heat exchanger is used in an outdoor unit of an air conditioner,

When the parallel-flow type heat exchanger is used in an indoor unit of an air conditioner,

Where n is the number of flat tubes constituting one turn of the refrigerant path, Q is the rated capacity and W is the unit.

Equation A was derived from the test. The table of Fig. 3 shows the specifications of the flat tubes examined in the test. The specimen a has a width of 16.2 mm, a thickness of 1.9 mm, and a refrigerant passage sectional area of 13 mm 2. The specimen b has a width of 13.9 mm, a thickness of 1.9 mm, and a refrigerant passage sectional area of 11 mm 2. The sample c has a width of 16.2 mm, a thickness of 1.6 mm, and a refrigerant passage sectional area of 11 mm 2. The specimen d has a width of 19.2 mm, a thickness of 1.9 mm, and a refrigerant passage sectional area of 14 mm 2.

The test was carried out as follows. The refrigerant is circulated in various numbers of flat tubes and whether or not drift has occurred is visually confirmed by thermography. The four kinds of the specimens shown in Fig. 3 were used, and the circulation amount was varied for each of the specimens to circulate the refrigerant. Fig. 4 is a table summarizing the maximum number of flat tubes in which no drift is observed (this condition may be referred to as " unspecified " in this specification) in the refrigerant circulation amount.

In the table of Fig. 4, Test 1 was used in Test 1. When the refrigerant circulation amount was 27.3 kg / h, the maximum number of untreated flows was 8. When the refrigerant circulation amount was 42.5 kg / h, the maximum number of untreated flows was 9. When the refrigerant circulation amount was 64.3 kg / h, the maximum number of untwisted streams was 10. When the refrigerant circulation amount was 63.2 kg / h, the maximum number of untwisted streams was 10.

In Test 2, the test piece b was used. When the refrigerant circulation amount was 20.9 kg / h, the maximum number of untreated flows was 9. When the refrigerant circulation amount was 22.1 kg / h, the maximum number of untreated flows was 8.

In Test 3, the test piece c was used. When the refrigerant circulation amount was 59.2 kg / h, the maximum number of untwisted streams was 10. When the refrigerant circulation amount was 48.8 kg / h, the maximum number of untreated products was 9. When the refrigerant circulation amount was 26.4 kg / h, the maximum number of untreated products was 8.

In Test 4, the test piece b was used. When the refrigerant circulation amount was 54.8 kg / h, the maximum number of untreated flows was 8. When the refrigerant circulation amount was 89.2 kg / h, the maximum number of untwisted streams was 8.

In Test 5, the sample d was used. When the refrigerant circulation amount was 26.6 kg / h, the maximum number of untwisted streams was 6. When the refrigerant circulation amount was 44.3 kg / h, the maximum number of untreated products was 9. When the refrigerant circulation amount was 67.3 kg / h, the maximum number of untreated products was 9.

The results of the test of FIG. 4 were plotted, and the graph of FIG. 5 was obtained. By drawing an approximate straight line, from an approximate expression of linear approximation,

± 2.

The refrigerant circulation amount m (kg / h) is generally set as a value proportional to the rated capacity of the product. The relationship between the refrigerant circulation amount and the capability is shown in Figs. 6 and 7. Fig.

If the heating rating capability Q (unit: W) is used to express in a mathematical expression,

.

If expressed in a mathematical expression using a cooling cooling capacity Q (unit: W)

.

The relationship between the rated capacity and the refrigerant circulation varies somewhat depending on the product. The refrigerant circulation amount is calculated from the following equation.

Circulation amount of refrigerant m = number of revolutions of compressor x suction pressure density x compressor volume

When used as a heat exchanger for an outdoor unit of an air conditioner, a parallel flow type heat exchanger serves as an evaporator during heating operation, and when used as an indoor heat exchanger of an air conditioner, serves as an evaporator during cooling operation.

Therefore, when the parallel flow type heat exchanger is used as a heat exchanger for an outdoor unit, as shown in FIG. 8, it can be understood from the above equations (a) and (b) that the number of flat tubes constituting one- The upper limit,

.

9, when the parallel-type heat exchanger is used as a heat exchanger for an indoor unit, the upper limit of the number of flat tubes constituting the refrigerant path for one turn from the above equations (a) and (c)

By setting the number to be +/- 2, it is possible to suppress the drift.

Subsequently, the lower limit of the number of the flat tubes 4 constituting each refrigerant path is obtained. If the outlet temperature of the heat exchanger

, The suction pressure is largely lowered as shown in Fig. That is, the suction pressure is drastically reduced with respect to the refrigerant circulation amount. This is due to the phase-out caused by the outlet temperature being below 0 캜.

If the temperature drop due to the pressure loss? P is T _Dp ,

. T _Rin is the inlet evaporation temperature of the refrigerant. The unit of pressure loss? P is Pa.

In other words,

. P _Rin is the inlet evaporation pressure, and P _lim is the saturation pressure of the refrigerant at 0 ° C.

here,

. is a friction coefficient between the inner wall of the flat tube 4 and the refrigerant. L is the length of the pipe and m is the unit. d is the hydraulic diameter and m is the unit. ρ is the refrigerant density in units of kg / m3. u is the flow rate of the refrigerant and m / s is the unit.

The flow velocity u is obtained from the following equation.

M is the refrigerant circulation amount and is in units of kg / s. A is the total cross-sectional area of the refrigerant passages of the plurality of flat tubes 4 constituting the one-turn refrigerant pass, and is expressed in m2.

therefore,

.

Here, when the sectional area of the refrigerant passage of one flat tube 4 is A '

. and n is the number of the flat tubes 4 constituting the one-turn refrigerant pass.

here,

From

.

here,

.

From the above equation

.

The refrigerant circulation amount m (kg / h), which is the unit difference of M, is generally set as a value proportional to the rated capacity of the product. therefore,

.

The relationship between the refrigerant circulation amount and the capability is shown in Figs. 6 and 7. Fig. The heating rating capacity Q (unit: W)

. That is,? = 0.0161 and? = 8.86.

Further, when expressed in a mathematical expression using the cooling cooling capacity Q (unit: W)

. That is,? = 0.0228 and? = 6.62.

The outdoor heat exchanger uses the heating rating capability, and the indoor heat exchanger uses the cooling rating power.

The relationship between the rated capacity and the refrigerant circulation varies somewhat depending on the product. The refrigerant circulation amount is calculated from the following equation.

Circulation amount of refrigerant m = number of revolutions of compressor x suction pressure density x compressor volume

The pressure loss is usually suppressed to 200 kPa or less. therefore,

The coefficient of friction lambda varies depending on the refrigerant circulation amount, the refrigerant pressure, the shape of the flattened tube, and the like. Generally, it is about 0.5 to 0.05 in the domestic air conditioner. The density rho varies depending on the pressure and the degree of drying of the refrigerant, but in the case of gas refrigerant, it is generally 20 to 70 kg / m3.

From the above, when unit conversion from M to m is performed

은,

silver,

If the calculation result of the upper limit number by the formula (A) exceeds the lower limit number, it is preferable to branch off at the inlet or in the middle of the heat exchanger.

은 최저값, 즉 1.4×10^-16을 사용하는 것이 바람직하다. Here, since it is preferable that the pressure loss is low,

Is preferably the lowest value, that is, 1.4 x 10 < ^{-16 &} gt ;.

therefore,

From the above, it is possible to obtain the lower limit of the number of the flat tubes 4 constituting the one-turn refrigerant path by the expression (B).

12 and 13 are graphs showing an example of the calculation result by the expression (B).

12 shows the relationship between the number of flat tubes in the outdoor unit heat exchanger and the heating rating capability. 13 shows the relationship between the number of flat tubes in the indoor heat exchanger and the cooling rating capability. In these graphs, the number of the flat tubes 4 constituting the one-turn refrigerant path is optimized in accordance with the rated capacity, and the lower limit of the number is shown.

The parallel flow type heat exchanger (1) can be mounted on a separate air conditioner. The separate air conditioner is composed of an outdoor unit and an indoor unit. The outdoor unit includes a compressor, a four-way valve, an expansion valve, an outdoor heat exchanger, an outdoor-side blower, and the like. The indoor unit includes an indoor heat exchanger, an indoor fan, and the like. The outdoor heat exchanger functions as an evaporator during heating operation and functions as a condenser during cooling operation. The indoor heat exchanger functions as a condenser at the time of heating operation and functions as an evaporator at the time of cooling operation.

The basic configuration of the separate air conditioner using the heat pump cycle as the refrigeration cycle is shown in Fig. The heat pump cycle 101 is constituted by connecting the compressor 102, the four-way valve 103, the outdoor heat exchanger 104, the low pressure expansion device 105 and the indoor heat exchanger 106 in the form of a loop . The compressor 102, the four-way valve 103, the heat exchanger 104, and the decompression expansion device 105 are housed in the housing of the outdoor unit. The heat exchanger 106 is accommodated in the housing of the indoor unit. The blower 107 on the outdoor side is combined with the heat exchanger 104. The heat exchanger 106 is combined with the blower 108 on the indoor side. The blower 107 includes a propeller fan. The blower 108 includes a cross flow fan.

The parallel-flow heat exchanger (1) according to the present invention can be used as a component of the heat exchanger (106) of the indoor unit. The heat exchanger 106 is a combination of the three heat exchangers 106A, 106B, and 106C as a roof covering the blower 108. [ Any one of the heat exchangers 106A, 106B, and 106C can be used as the parallel flow type heat exchanger 1. [

The parallel-flow type heat exchanger 1 according to the present invention can also be used as a heat exchanger 104 for an outdoor unit.

Fig. 14 shows a state at the time of heating operation. At this time, the high-temperature and high-pressure refrigerant discharged from the compressor 102 enters the heat exchanger 106 on the indoor side, radiates heat therefrom, and condenses. The refrigerant exiting the heat exchanger 106 enters the outdoor heat exchanger 104 from the decompression expansion device 105 and expands therefrom. After introducing heat from the outdoor air, the refrigerant returns to the compressor 102. The airflow generated by the blower 108 on the indoor side promotes the heat radiation from the heat exchanger 106 and the airflow generated by the blower 107 on the outdoor side promotes the heat absorption of the heat exchanger 104.

Fig. 15 shows a state at the time of cooling operation or during defrost operation. At this time, the four-way valve 103 is switched, and the flow of the refrigerant is reversed during the heating operation. That is, the high-temperature and high-pressure refrigerant discharged from the compressor 102 enters the heat exchanger 104 on the outdoor side, radiates heat therefrom, and condenses. The refrigerant exiting the heat exchanger 104 enters the indoor heat exchanger 106 from the decompression expansion device 105 and expands therefrom. After introducing heat from the room air, the refrigerant returns to the compressor 102. The airflow generated by the blower 107 on the outdoor side promotes the heat radiation from the heat exchanger 104 and the airflow generated by the blower 108 on the indoor side promotes the heat absorption of the heat exchanger 106.

Although the embodiment of the present invention has been described above, the scope of the present invention is not limited thereto, and various changes can be made without departing from the gist of the invention.

The present invention is widely applicable to a side flow type parallel-flow heat exchanger.

1: Heat exchanger
2, 3: header pipe
4: Flat tube
5: Refrigerant passage
6: pin
7: Side plate
A, B, C, D: refrigerant pass

Claims (5)

A side flow type parallel-flow heat exchanger,
Two vertical header pipes,
And a plurality of horizontal flat tubes connecting the header pipes,
The plurality of horizontal flat tubes are further grouped into a plurality of groups, each constituting a one-turn refrigerant path through which refrigerant flows from one of the two vertical header pipes to the other,
The refrigerant includes a gas and a liquid,
The parallel-flow type heat exchanger is used in an outdoor unit of an air conditioner,
The upper limit of the number of the flat tubes constituting the one-turn refrigerant path is determined by the numerical value ± 2 obtained by the following expression A,
Wherein the lower limit of the number of the flat tubes constituting the one-turn refrigerant pass is determined by the following expression (B).

(Where n is the number of flat tubes constituting a one-turn refrigerant pass, Q is the rated capacity and W is in units of? = 0.0161,? = 8.86, L is the length of the duct and m is the unit, d Is the hydraulic diameter and m is the unit, A 'is the cross-sectional area of the refrigerant passage of one flat tube, and m2 is the unit) A side flow type parallel-flow heat exchanger,
Two vertical header pipes,
And a plurality of horizontal flat tubes connecting the header pipes,
The plurality of horizontal flat tubes are further grouped into a plurality of groups, each constituting a one-turn refrigerant path through which refrigerant flows from one of the two vertical header pipes to the other,
The refrigerant includes a gas and a liquid,
The parallel flow type heat exchanger is used in an indoor unit of an air conditioner,
The upper limit of the number of the flat tubes constituting the one-turn refrigerant path is determined by the numerical value ± 2 obtained by the following expression A,
Wherein the lower limit of the number of the flat tubes constituting the one-turn refrigerant pass is determined by the following expression (B).

(Where n is the number of flat tubes constituting one turn of the refrigerant path, Q is the rated capacity and W is the unit, α = 0.0228, β = 6.62, L is the channel length and m is the unit, d Is the hydraulic diameter and m is the unit, A 'is the cross-sectional area of the refrigerant passage of one flat tube, and is in units of m2) Air conditioner,
An air conditioner in which the parallel flow type heat exchanger according to claim 1 is mounted on an outdoor unit of the air conditioner. Air conditioner,
An air conditioner in which the parallel flow type heat exchanger according to claim 2 is mounted on an indoor unit of the air conditioner.
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