Patent Publication Number: US-11378286-B2

Title: Outdoor unit

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a U.S. national stage application of International Application No. PCT/JP2017/021642, filed on Jun. 12, 2017, the contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to outdoor units, and in particular, relates to an outdoor unit including a heat sink that promotes dissipation of heat from a controller. 
     BACKGROUND 
     An outdoor unit of a refrigeration cycle apparatus includes a control board that controls, for example, a compressor. On the control board, for example, an inverter is mounted. The inverter includes a semiconductor device for driving an electric motor of a compressor. The inverter generates heat when the inverter drives the electric motor of the compressor. Heat generation of the inverter reduces the life of, for example, the semiconductor device included in the inverter. Heat generation of the inverter further causes another device mounted on the control board to generate heat, thus reducing the life of the device. For this reason, some outdoor units of refrigeration cycle apparatuses include a heat sink to promote dissipation of heat from a control board. However, for example, in a case where such a refrigeration cycle apparatus is operated in the summer, the temperature of the control board is highly likely to rise beyond an allowable temperature range even though the heat sink dissipates heat from the control board. 
     A developed refrigeration cycle apparatus includes a heat sink that is cooled by using refrigerant reduced in pressure by an expansion valve (refer to Patent Literature 1, for example). The refrigeration cycle apparatus disclosed in Patent Literature 1 includes a cooling pipe that helps heat dissipation of the heat sink. The cooling pipe is disposed downstream of the expansion valve in a refrigerant flow direction and is located upstream of an evaporator in the refrigerant flow direction. The heat sink of the refrigeration cycle apparatus disclosed in Patent Literature 1 receives cooling energy through the cooling pipe from the refrigerant cooled by the expansion valve and leaving the expansion valve. 
     PATENT LITERATURE 
     Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2012-127591 
     The cooling pipe included in the refrigeration cycle apparatus disclosed in Patent Literature 1 can help cool the heat sink. However, the cooling pipe included in the refrigeration cycle apparatus disclosed in Patent Literature 1 causes part of the refrigerant leaving the expansion valve to evaporate in the cooling pipe. Evaporation of the refrigerant cools the evaporator. Evaporation of part of the refrigerant leaving the expansion valve in the cooling pipe results in a reduction in amount of evaporation of the refrigerant in the evaporator. In other words, the evaporation of part of the refrigerant leaving the expansion valve in the cooling pipe results in a reduction in difference between the enthalpy of the refrigerant leaving the evaporator and the enthalpy of the refrigerant entering the evaporator. Disadvantageously, the cooling pipe included in the refrigeration cycle apparatus disclosed in Patent Literature 1 causes a reduction in cooling capacity. 
     SUMMARY 
     The present invention has been made to solve the above-described problem, and aims to provide an outdoor unit that facilitates heat dissipation of a heat sink while reducing or eliminating a reduction in cooling capacity. 
     An outdoor unit according to an embodiment of the present invention includes a casing including an air passage, an outdoor fan disposed in the air passage, a compressor disposed in the casing, an outdoor heat exchanger disposed in the casing and including fins and a heat transfer tube connected to the fins, a control board disposed in the casing and including a control unit that controls the compressor, and a heat sink disposed in the air passage in the casing and being in contact with the control board. The heat transfer tube of the outdoor heat exchanger includes a first region in which gas refrigerant or two-phase gas-liquid refrigerant flows when the outdoor heat exchanger is used as a condenser and a second region that is located downstream of the first region in a refrigerant flow direction and in which single-phase liquid refrigerant flows. The heat sink is disposed downstream of the outdoor heat exchanger in an air flow direction in the air passage. The heat sink is located at a first distance from the first region and is located at a second distance from the second region. The second distance is shorter than the first distance. 
     The outdoor unit according to an embodiment of the present invention includes no component like the cooling pipe described in Patent Literature 1. Such a configuration can reduce or eliminate a reduction in amount of evaporation of the refrigerant in the outdoor heat exchanger. Thus, the outdoor unit according to an embodiment of the present invention can reduce or eliminate a reduction in cooling capacity. In the outdoor unit according to an embodiment of the present invention, the second distance between the heat sink and the second region is shorter than the first distance between the heat sink and the first region. This arrangement reduces or eliminates a rise in temperature of air to be supplied to the heat sink. Thus, the outdoor unit according to an embodiment of the present invention facilitates heat dissipation of the heat sink. The outdoor unit according to an embodiment of the present invention therefore facilitates heat dissipation of the heat sink while reducing or eliminating a reduction in cooling capacity. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating, for example, a refrigerant circuit configuration of a refrigeration cycle apparatus  100  including an outdoor unit  101  according to Embodiment 1. 
         FIG. 2  is a schematic diagram illustrating, for example, the outdoor unit  101  according to Embodiment 1. 
         FIG. 3  is an exploded perspective view of the outdoor unit  101  according to Embodiment 1. 
         FIG. 4  is a schematic diagram of the outdoor unit  101  according to Embodiment 1 as viewed from the front of an air outlet  11 B of the outdoor unit  101 . 
         FIG. 5  is a schematic diagram of the outdoor unit  101  according to Embodiment 1 as viewed from above the outdoor unit  101 . 
         FIG. 6  is a perspective view of a heat sink Hs and a control board Cnt 1  included in the outdoor unit  101  according to Embodiment 1. 
         FIG. 7  is a functional block diagram of a control unit  60  included in the outdoor unit  101  according to Embodiment 1. 
         FIG. 8  is a diagram illustrating an arrangement of various components included in the outdoor unit  101  according to Embodiment 1. 
         FIG. 9  is a schematic diagram illustrating the configuration of an outdoor heat exchanger  3  and flows of refrigerant through the outdoor heat exchanger  3 . 
         FIG. 10  is a diagram illustrating Modification of the outdoor unit  101  according to Embodiment 1. 
         FIG. 11  is an exploded perspective view of an outdoor unit  101  according to Embodiment 2. 
         FIG. 12  is a diagram illustrating an arrangement of various components included in the outdoor unit  101  according to Embodiment 2. 
         FIG. 13  is a diagram illustrating an arrangement of various components included in an outdoor unit according to Embodiment 3. 
         FIG. 14  is a functional block diagram of a control unit  60  included in the outdoor unit according to Embodiment 3. 
         FIG. 15  is a flowchart of a control process for the outdoor unit according to Embodiment 3. 
         FIG. 16  is a schematic diagram of an outdoor heat exchanger of an outdoor unit according to Embodiment 4. 
         FIG. 17  is a diagram illustrating an outdoor heat exchanger of an outdoor unit according to Modification 1 of Embodiment 4. 
         FIG. 18  is a diagram illustrating an outdoor heat exchanger of an outdoor unit according to Modification 2 of Embodiment 4. 
         FIG. 19  is a diagram illustrating an outdoor heat exchanger of an outdoor unit according to Modification 3 of Embodiment 4. 
         FIG. 20  is a diagram illustrating an outdoor heat exchanger of an outdoor unit according to Modification 4 of Embodiment 4. 
         FIG. 21  is a diagram illustrating an outdoor heat exchanger of an outdoor unit according to Modification 5 of Embodiment 4. 
     
    
    
     DETAILED DESCRIPTION 
     Outdoor units  101  according to embodiments of the present invention will be described with reference to, for example, the drawings. Note that components designated by the same reference signs in the following drawings including  FIG. 1  are the same components or equivalents. This note applies to the entire description of the embodiments described below. 
     Embodiment 1 
       FIG. 1  is a diagram illustrating, for example, a refrigerant circuit configuration of a refrigeration cycle apparatus  100  including an outdoor unit  101  according to Embodiment 1. In  FIG. 1 , an arrow AR 1  represents a refrigerant flow direction in a heating operation of the refrigeration cycle apparatus  100  and an arrow AR 2  represents the refrigerant flow direction in a cooling operation of the refrigeration cycle apparatus  100 .  FIG. 2  is a schematic diagram illustrating, for example, the outdoor unit  101  according to Embodiment 1. Embodiment 1 will be described as an example that the refrigeration cycle apparatus  100  is an air-conditioning apparatus. 
     The refrigeration cycle apparatus  100  includes the outdoor unit  101  and an indoor unit  102 . The outdoor unit  101  and the indoor unit  102  are connected by refrigerant pipes P. The outdoor unit  101  includes a compressor  1  that compresses refrigerant, a four-way valve  2  that switches passages, an expansion device  4  that reduces the pressure of the refrigerant, an outdoor heat exchanger  3  that exchanges heat between the refrigerant and air, and an outdoor fan  3 A that supplies the air to the outdoor heat exchanger  3 . The indoor unit  102  includes an indoor heat exchanger  5  that exchanges heat between the refrigerant and air and an indoor fan  5 A that supplies the air to the indoor heat exchanger  5 . 
     The refrigeration cycle apparatus  100  includes a control board Cnt 1  disposed in the outdoor unit  101  and a control board Cnt 2  disposed in the indoor unit  102 . The control board Cnt 1  and the control board Cnt 2  are connected by a communication line (not illustrated) to establish communication. The refrigeration cycle apparatus  100  includes a heat sink Hs attached to the control board Cnt 1  and a first sensor SE 1  mounted on the heat sink Hs. The first sensor SE 1  measures the temperature of the heat sink Hs. The refrigeration cycle apparatus  100  further includes a second sensor SE 2  to measure an outdoor air temperature, a third sensor SE 3  to measure the temperature of the outdoor heat exchanger  3 , and a fourth sensor SE 4  to measure the temperature of the indoor heat exchanger  5 . In addition, the refrigeration cycle apparatus  100  includes a fifth sensor SE 5  to measure an indoor air temperature and a sixth sensor SE 6  to measure the temperature of the refrigerant discharged from the compressor  1 . 
       FIG. 3  is an exploded perspective view of the outdoor unit  101  according to Embodiment 1. 
       FIG. 4  is a schematic diagram of the outdoor unit  101  according to Embodiment 1 as viewed from the front of an air outlet  11 B of the outdoor unit  101 . 
       FIG. 5  is a schematic diagram of the outdoor unit  101  according to Embodiment 1 as viewed from above the outdoor unit  101 . As illustrated in  FIGS. 3 to 5 , the term “Z direction” as used herein refers to a height direction of the outdoor unit  101 , the term “Y direction” refers to an air flow direction in which the air passes through the outdoor unit  101 , and the term “X direction” refers to a direction orthogonal to the Z direction and the Y direction. The X direction and the Y direction are parallel to a horizontal plane. 
     The outdoor unit  101  includes a casing  100   a  including an air passage SP 1  and a compressor chamber SP 2 . The casing  100   a  contains the compressor  1 , the outdoor heat exchanger  3 , and the outdoor fan  3 A. The casing  100   a  includes a first panel  10  disposed above the outdoor heat exchanger  3  and the outdoor fan  3 A, a second panel  11  having the air outlet  11 B, and a third panel  12  separating the compressor chamber SP 2  from a space outside the outdoor unit  101 . The casing  100   a  further includes a partition  15  separating the air passage SP 1  from the compressor chamber SP 2 . In addition, the casing  100   a  includes a bottom plate  14  supporting, for example, the compressor  1  and the outdoor heat exchanger  3 . Additionally, the casing  100   a  includes a cover  13  to cover valves  17 . A fan grille  11 A is attached to the second panel  11 . 
     The outdoor unit  101  includes the valves  17  and a valve mounting plate  18  on which the valves  17  are mounted. The valves  17  are connected to ends of the refrigerant pipes P (refer to  FIGS. 1 and 2 ). 
     The outdoor unit  101  includes a motor support  3 A 1  supporting the outdoor fan  3 A. The motor support  3 A 1  is attached to the outdoor heat exchanger  3 . The outdoor fan  3 A includes a plurality of blades  3 B 1 , a boss  3 B 2 , an electric motor  3 C, and a shaft  3 D. The blades  3 B 1  radially extend from the boss  3 B 2 . A first end of the shaft  3 D is fixed to the boss  3 B 2  and a second end of the shaft  3 D is fixed to the electric motor  3 C. The electric motor  3 C is attached to the motor support  3 A 1 . 
     The partition  15  separates the air passage SP 1  containing, for example, the outdoor heat exchanger  3  and the outdoor fan  3 A, from the compressor chamber SP 2  containing, for example, the compressor  1 . A mounting plate  16  is fixed to the partition  15 . The control board Cnt 1  is attached to the mounting plate  16 . The mounting plate  16 , the heat sink Hs, and the control board Cnt 1  are arranged in the air passage SP 1 . The heat sink Hs is in contact with the control board Cnt 1 . The heat sink Hs, which is in contact with the control board Cnt 1 , promotes dissipation of heat from the control board Cnt 1 . The heat sink Hs is disposed downstream in the air flow direction in the air passage SP 1 . This arrangement causes the heat sink Hs to be supplied with the air while the outdoor fan  3 A is operating, thus facilitating heat dissipation of the heat sink Hs. The air to be supplied to the heat sink Hs passes through the outdoor heat exchanger  3 . While the refrigeration cycle apparatus  100  is performing the cooling operation, the outdoor heat exchanger  3  is used as a condenser. Consequently, the air passing through the outdoor heat exchanger  3  increases in temperature in the cooling operation of the refrigeration cycle apparatus  100 . In the refrigeration cycle apparatus  100 , the air with a small increase in temperature is supplied to the heat sink Hs to further facilitate heat dissipation of the heat sink Hs. 
       FIG. 6  is a perspective view of the heat sink Hs and the control board Cnt 1  included in the outdoor unit  101  according to Embodiment 1. 
     The control board Cnt 1  includes an inverter E including a semiconductor device. Examples of the semiconductor device of the inverter E include a power semiconductor device. The inverter E is configured to drive an electric motor disposed at the compressor  1 . The inverter E is electrically connected to a power supply circuit and a circuit including the electric motor of the compressor  1 . Higher outdoor air temperature conditions result in proportionately higher thermal loads in rooms. For this reason, in a case where the refrigeration cycle apparatus  100  performs the cooling operation under high outdoor air temperature conditions, the control board Cnt 1  typically sets a rotation frequency of the compressor  1  to a high value. Consequently, the indoor unit  102  enables the indoor air temperature to immediately approach a set temperature for an indoor space. Increasing the rotation frequency of the compressor  1  increases a current (primary current) in the power supply circuit accordingly. In the case where the refrigeration cycle apparatus  100  performs the cooling operation under high outdoor air temperature conditions, the amount of heat generated from the inverter E increases. 
     An increase in amount of heat generated from the inverter E causes an increase in temperature of the semiconductor device included in the inverter E, thus reducing the life of the inverter E. In addition, heat generation of the inverter E causes an increase in temperature of a device in proximity to the inverter E, thus reducing the life of the device. For this reason, the heat sink Hs is disposed at the inverter E. This arrangement promotes dissipation of heat from the inverter E. As the heat sink Hs is disposed in the air passage SP 1 , the heat sink Hs is supplied with the air, thus further facilitating heat dissipation of the heat sink Hs. 
       FIG. 7  is a functional block diagram of a control unit  60  included in the outdoor unit  101  according to Embodiment 1. 
     The control board Cnt 1  includes the control unit  60 . The control unit  60  includes a memory  61  to store various pieces of information, an input unit  62  to receive a sensor signal, a processing unit  63  to perform various operations, and an output unit  64  to output a control signal for controlling, for example, the compressor  1 . 
     The input unit  62  receives sensor signals from the first sensor SE 1 , the second sensor SE 2 , the third sensor SE 3 , and the sixth sensor SE 6 . The input unit  62  further receives information output from a control unit  70  included in the control board Cnt 2  disposed in the indoor unit  102 . The processing unit  63  includes an operation control section  63 A. The operation control section  63 A generates a control signal for controlling, for example, the compressor  1 , on the basis of the information acquired from the input unit  62 . The output unit  64  outputs the control signal generated by the processing unit  63  to the compressor  1 , for example. 
     Each functional part included in the control unit  60  is configured by dedicated hardware or a micro processing unit (MPU) that runs a program stored in the memory  61 . In a case where the control unit  60  is dedicated hardware, the control unit  60  corresponds to a single circuit, a composite circuit, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination of these circuits. The functional parts that the control unit  60  implements may be implemented by individual hardware components or may be implemented by a single hardware component. In a case where the control unit  60  is an MPU, the functions that the control unit  60  performs are achieved by software, firmware, or a combination of the software and the firmware. The software and the firmware are written as programs and the programs are stored in the memory  61 . The MPU reads the programs stored in the memory  61  and runs the programs, thus achieving the functions of the control unit  60 . The memory  61  is, for example, a nonvolatile or volatile semiconductor memory, such as a random access memory (RAM), a read-only memory (ROM), a flash memory, an erasable programmable read-only memory (EPROM), and an electrically erasable programmable read-only memory (EEPROM). 
       FIG. 8  is a diagram illustrating an arrangement of various components included in the outdoor unit  101  according to Embodiment 1.  FIG. 9  is a schematic diagram illustrating the configuration of the outdoor heat exchanger  3  and flows of the refrigerant through the outdoor heat exchanger  3 . A distributor (not illustrated) is attached to the outdoor heat exchanger  3 . The refrigerant leaving the distributor divides into two streams, refrigerant R 1  and refrigerant R 2 . The refrigerant R 1  enters an area Rg 1   a  of a heat transfer tube  3   a  and the refrigerant R 2  enters an area Rg 1   b  of the heat transfer tube  3   a.    
     The outdoor heat exchanger  3  includes the heat transfer tube  3   a  and a plurality of fins  3   b . The heat transfer tube  3   a  includes a first region Rg 1  in which gas refrigerant or two-phase gas-liquid refrigerant flows when the outdoor heat exchanger  3  is used as a condenser and a second region Rg 2  that is located downstream of the first region Rg 1  in the refrigerant flow direction and in which single-phase liquid refrigerant flows. In Embodiment 1, the first region Rg 1  includes the area Rg 1   a  and the area Rg 1   b . Both the area Rg 1   a  and the area Rg 1   b  are arranged upstream of the second region Rg 2  in the refrigerant flow direction. The heat transfer tube  3   a  includes the area Rg 1   a  and the area Rg 1   b  arranged parallel to each other. 
     The area Rg 1   a  of the first region Rg 1  includes an inlet IN 1  through which the refrigerant flows into the area and an outlet Out 1  through which the refrigerant flows out of the area. The inlet IN 1  is the most upstream portion of the area Rg 1   a  and the outlet Out 1  is the most downstream portion of the area Rg 1   a . The refrigerant R 1  that flows through the outdoor heat exchanger  3  passes through the inlet IN 1  and the outlet Out 1  of the area Rg 1   a  and enters a pipe  3   c.    
     The area Rg 1   b  of the first region Rg 1  includes an inlet IN 2  through which the refrigerant flows into the area and an outlet Out 2  through which the refrigerant flows out of the area. The inlet IN 2  is the most upstream portion of the area Rg 1   b  and the outlet Out 2  is the most downstream portion of the area Rg 1   b . The refrigerant R 2  that flows through the outdoor heat exchanger  3  passes through the inlet IN 2  and the outlet Out 2  of the area Rg 1   b  and enters the pipe  3   c . In the pipe  3   c , the refrigerant leaving the outlet Out 1  of the area Rg 1   a  joins the refrigerant leaving the outlet Out 2  of the area Rg 1   b.    
     The second region Rg 2  includes an inlet IN 3  through which the refrigerant flows into the region and an outlet Out 3  through which the refrigerant flows out of the region. The inlet IN 3  is the most upstream portion of the second region Rg 2  and the outlet Out 3  is the most downstream portion of the second region Rg 2 . Refrigerant R 3  that flows through the pipe  3   c  passes through the inlet IN 3  and the outlet Out 3  of the second region Rg 2 . In the case where the refrigeration cycle apparatus  100  is performing the cooling operation, refrigerant R 4  leaving the outlet Out 3  enters the expansion device  4  (refer to  FIG. 1 ). 
     The air, represented by Air, to be supplied to the heat sink Hs passes through the outdoor heat exchanger  3 . While the refrigeration cycle apparatus  100  is performing the cooling operation, the outdoor heat exchanger  3  is used as a condenser. Thus, the air Air increases in temperature by passing through the outdoor heat exchanger  3 . Since the control board Cnt 1  increases the rotation frequency of the compressor  1  as the outdoor air temperature becomes higher, a condensing temperature in the outdoor heat exchanger  3  rises with increasing outdoor air temperature. The higher the outdoor air temperature, the higher the temperature of the air Air to be supplied to the outdoor heat exchanger  3 . A higher outdoor air temperature makes it more difficult to help heat dissipation of the heat sink Hs. 
     After the refrigerant enters the first region Rg 1 , the air Air receives the latent heat of condensation from the refrigerant and thus increases in temperature, causing the refrigerant to liquify. At this time, as the heat received from the refrigerant by the air Air is the latent heat, the temperature of the refrigerant remains unchanged. When the refrigerant leaving the first region Rg 1  enters the second region Rg 2 , the refrigerant is single-phase liquid. After the refrigerant enters the second region Rg 2 , the air Air receives sensible heat from the refrigerant and thus increases in temperature, resulting in a reduction in temperature of the refrigerant. Consequently, the temperature of the refrigerant flowing in the second region Rg 2  is lower than the temperature of the refrigerant flowing in the first region Rg 1 . The temperature of the air Air that has passed through the second region Rg 2  is therefore lower than the temperature of the air Air that has passed through the first region Rg 1 . The heat sink Hs is located at a first distance from the first region Rg 1  and is located at a second distance from the second region Rg 2 . The second distance is shorter than the first distance. This arrangement more effectively facilitates heat dissipation of the heat sink Hs than does an arrangement in which the second distance is longer than the first distance. 
     The second region Rg 2  is located at a level higher than is the first region Rg 1 . In Embodiment 1, the second region Rg 2  is located in the uppermost part of the outdoor heat exchanger  3 . A level at which an upper end of the second region Rg 2  is located is represented by a height coordinate h 1 . A level at which a lower end of the second region Rg 2  and an upper end of the first region Rg 1  are located is represented by a height coordinate h 2 . A level at which a lower end of the area Rg 1   a  and an upper end of the area Rg 1   b  are located is represented by a height coordinate h 3 . The heat sink Hs is located below the height coordinate h 1  and above the height coordinate h 2 . The control board Cnt 1  is also located below the height coordinate h 1  and above the height coordinate h 2 . The height coordinate h 1 , the height coordinate h 2 , and the height coordinate h 3  can be determined relative to, for example, the bottom plate  14 , as a reference. 
     The heat transfer tube  3   a  of the outdoor heat exchanger  3  includes a plurality of horizontal parts t parallel to a horizontal direction. The horizontal parts t are tube portions parallel to the horizontal plane. In Embodiment 1, the total number of horizontal parts t of the outdoor heat exchanger  3  is 48. The horizontal parts t include first horizontal parts nA arranged in the first region Rg 1  and second horizontal parts nB arranged in the second region Rg 2 . The first horizontal parts nA and the second horizontal parts nB are tube portions extending parallel to the horizontal plane. The number of horizontal parts in the area Rg 1   a  of the first region Rg 1  is 20. The number of horizontal parts in the area Rg 1   b  of the first region Rg 1  is 20. Thus, the total number of first horizontal parts nA is 40. The number of second horizontal parts nB is eight. The number of second horizontal parts nB is therefore less than the number of first horizontal parts nA. The reason why the number of second horizontal parts nB is eight will be described below. As illustrated in  FIG. 9 , the heat transfer tube  3   a  in the second region Rg 2  includes horizontal part n 1 , horizontal part n 2 , horizontal part n 3 , horizontal part n 4 , horizontal part n 5 , horizontal part n 6 , horizontal part n 7 , and horizontal part n 8 . Each of the horizontal parts n 1 , n 2 , n 3 , n 4 , n 5 , n 6 , n 7 , and n 8  is the second horizontal part nB. Thus, the number of second horizontal parts nB is eight. The first horizontal parts nA can be numbered in the same manner as for the second horizontal parts nB. The number of first horizontal parts nA is 40. When the refrigerant enters the inlet IN 3  of the second region Rg 2 , the refrigerant flows into the horizontal part n 1 . After the refrigerant flows through the horizontal part n 1 , the refrigerant flows through the horizontal part n 2 , the horizontal part n 3 , the horizontal part n 4 , the horizontal part n 5 , the horizontal part n 6 , the horizontal part n 7 , and the horizontal part n 8  in this order. 
     In the second region Rg 2 , the temperature of the single-phase liquid refrigerant is reduced to provide some degree of subcooling for the refrigerant. In the second region Rg 2 , it is only required that a predetermined degree of subcooling can be provided for the single-phase liquid refrigerant. In Embodiment 1, the number of second horizontal parts nB in the second region Rg 2  is less than the number of first horizontal parts nA in the first region Rg 1 . This arrangement further ensures that the refrigerant liquifies in the first region Rg 1 . As a result, this arrangement further ensures that the single-phase liquid refrigerant is supplied from the first region Rg 1  to the second region Rg 2 . 
       FIG. 10  is a diagram illustrating Modification of the outdoor unit  101  according to Embodiment 1. In Modification, the second region Rg 2  is interposed between the area Rg 1   a  and the area Rg 1   b  of the first region Rg 1 . A level at which the upper end of the area Rg 1   a  is located is represented by a height coordinate h 11 . A level at which the upper end of the second region Rg 2  and the lower end of the area Rg 1   a  are located is represented by a height coordinate h 12 . A level at which the lower end of the second region Rg 2  and the upper end of the area Rg 1   b  are located is represented by a height coordinate h 13 . The heat sink Hs is disposed below the height coordinate h 12  and above the height coordinate h 13 . The control board Cnt 1  is also disposed below the height coordinate h 12  and above the height coordinate h 13 . The height coordinate h 11 , the height coordinate h 12 , and the height coordinate h 13  can be determined relative to, for example, the bottom plate  14 , as a reference. In Modification, the heat sink Hs is disposed at the same level as a level of the boss  3 B 2  of the electric motor  3 C. The flow rate of the air Air flowing to the boss  3 B 2  is greater than the flow rate of the air Air flowing to distal ends of the blades  3 B 1 . This arrangement results in an increase in flow rate of the air Air to be supplied to the heat sink Hs in Modification, thus increasing the efficiency of heat dissipation of the heat sink Hs. 
     Advantageous effects of Embodiment 1 will be described below. The outdoor unit  101  includes no component like the cooling pipe described in Patent Literature 1. Such a configuration reduces or eliminates a reduction in amount of evaporation of the refrigerant in the outdoor heat exchanger  3  of the outdoor unit  101 . This configuration reduces or eliminates a reduction in cooling capacity of the outdoor unit  101 . 
     In Embodiment 1, the second distance between the heat sink Hs and the second region Rg 2  is shorter than the first distance between the heat sink Hs and the first region Rg 1 . This arrangement causes the flow rate of air supplied to the heat sink Hs through the second region Rg 2  to be greater than the flow rate of air supplied to the heat sink Hs through the first region Rg 1 . 
     In the cooling operation of the refrigeration cycle apparatus  100 , the outdoor heat exchanger  3  is used as a condenser. The air passing through the outdoor heat exchanger  3  receives the latent heat of condensation of the refrigerant flowing through the outdoor heat exchanger  3 . Thus, the air increases in temperature by passing through the outdoor heat exchanger  3 . The second region Rg 2  is located to receive single-phase liquid refrigerant. The refrigerant decreases in temperature by flowing in the second region Rg 2 . This operation reduces or eliminates a rise in temperature of the air supplied to the outdoor heat exchanger  3  when the air passes through the second region Rg 2 . As the heat sink Hs is supplied with the air of which a rise in temperature is reduced or eliminated, the outdoor unit  101  facilitates heat dissipation of the heat sink Hs. The outdoor unit  101  according to Embodiment 1 therefore facilitates the heat dissipation of the heat sink Hs while reducing or eliminating a reduction in cooling capacity. 
     Embodiment 2 
       FIG. 11  is an exploded perspective view of an outdoor unit  101  according to Embodiment 2.  FIG. 12  is a diagram illustrating an arrangement of various components included in the outdoor unit  101  according to Embodiment 2. In Embodiment 2, the same components as those in Embodiment 1 are designated by the same reference signs. The following description will focus on the difference between Embodiment 2 and Embodiment 1. In Embodiment 2, a shield  19  is added to the components in Embodiment 1. 
     The flow direction of the air Air passing through the outdoor heat exchanger  3  is not limited to a direction parallel to the Y direction. In other words, the air Air flowing through the first region Rg 1  may rise and be supplied to the heat sink Hs. As described in Embodiment 1, the temperature of the air Air leaving the second region Rg 2  is lower than the temperature of the air Air leaving the first region Rg 1 . When the air Air flowing through the first region Rg 1  rises and is supplied to the heat sink Hs, heat dissipation of the heat sink Hs is made difficult to be promoted. 
     The outdoor unit  101  according to Embodiment 2 includes the shield  19  that is plate-shaped and is disposed under the heat sink Hs. The shield  19  is disposed parallel to an X-Y plane. The shield  19  is secured to the partition  15 . The shield  19  is located at the same level as the height coordinate h 2  at which the lower end of the second region Rg 2  is located. 
     Advantageous effects of Embodiment 2 will be described below. As the outdoor unit  101  according to Embodiment 2 includes the shield  19 , such a configuration reduces or eliminates supply of the air Air through the first region Rg 1  to the heat sink Hs. Thus, the outdoor unit  101  according to Embodiment 2 more reliably facilitates heat dissipation of the heat sink Hs. 
     Embodiment 3 
       FIG. 13  is a diagram illustrating an arrangement of various components included in an outdoor unit according to Embodiment 3. In Embodiment 3, the same components as those in Embodiments 1 and 2 are designated by the same reference signs. The following description will focus on the difference between Embodiment 3 and Embodiments 1 and 2. In Embodiment 3, a flow switching device  20  is added to the components in Embodiment 1. Specifically, the outdoor unit according to Embodiment 3 includes the flow switching device  20  connected to the expansion device  4  for reducing the pressure of the refrigerant and the heat transfer tube  3   a.    
     The flow switching device  20  includes an inflow port a, a first outflow port b, and a second outflow port c. The inflow port a is connected to the most downstream portion of the heat transfer tube  3   a  in the first region Rg 1 . More specifically, the inflow port a is connected to the pipe  3   c . The first outflow port b is connected to the most upstream portion of the heat transfer tube  3   a  in the second region Rg 2 . More specifically, the first outflow port b is connected to the inlet IN 3  of the second region Rg 2  by a pipe  3   c   1 . The second outflow port c is connected to the expansion device  4 . More specifically, the second outflow port c is connected to a pipe  3   c   2 . The pipe  3   c   2  is connected to the outlet Out 3 . Furthermore, the pipe  3   c   2  is connected to the expansion device  4 . 
       FIG. 14  is a functional block diagram of a control unit  60  included in the outdoor unit according to Embodiment 3. The control unit  60  of the control board Cnt 1  adjusts the flow switching device  20  on the basis of the temperature of the heat sink Hs. Specifically, the control unit  60  acquires a sensor signal concerning the temperature of the heat sink Hs from the first sensor SE 1  (refer to  FIGS. 1, 4, and 5 ). The control unit  60  adjusts the flow switching device  20  on the basis of the acquired sensor signal. The first sensor SE 1  corresponds to a temperature sensor in the present invention. The processing unit  63  of the control unit  60  includes a determination section  63 B. The determination section  63 B is configured to compare the temperature of the heat sink Hs acquired from the first sensor SE 1  with a predetermined reference temperature. In Embodiment 3, the predetermined reference temperature includes a first reference temperature T 1  and a second reference temperature T 2  that is lower than the first reference temperature T 1 . The predetermined reference temperatures are stored in the memory  61 . The first reference temperature T 1  is a temperature set to avoid breakage of, for example, the inverter E. The second reference temperature T 2  is a reference temperature set to increase the life of, for example, the semiconductor device, rather than to avoid breakage of, for example, the inverter E. 
       FIG. 15  is a flowchart of a control process for the outdoor unit according to Embodiment 3. In the following description on  FIG. 15 , the temperature of the heat sink Hs acquired from the first sensor SE 1  will be abbreviated to a temperature Tf of the heat sink Hs. The control unit  60  of the control board Cnt 1  acquires the temperature Tf of the heat sink Hs (step S 1 ). 
     The control unit  60  of the control board Cnt 1  determines whether the temperature Tf of the heat sink Hs is higher than the first reference temperature T 1  (step S 2 ). When the temperature Tf of the heat sink Hs is higher than the first reference temperature T 1 , the control unit  60  of the control board Cnt 1  closes the first outflow port b and opens the second outflow port c (step S 3 ). When the control process proceeds to step S 3 , it means avoiding breakage of, for example, the semiconductor device of the control board Cnt 1 . As the first outflow port b is closed, the refrigerant does not flow in the second region Rg 2 . Thus, the second region Rg 2  is not used as a condenser. This operation reduces or eliminates a rise in temperature of the air passing through the second region Rg 2 . In other words, the heat sink Hs is supplied with the air having substantially the same temperature as the outdoor air temperature. This operation increases the efficiency of heat dissipation of the heat sink Hs. 
     The control unit  60  of the control board Cnt 1  determines whether the temperature Tf of the heat sink Hs is at or below the first reference temperature T 1  and is above the second reference temperature T 2  (step S 4 ). When the temperature of the heat sink Hs is at or below the first reference temperature T 1  and is above the second reference temperature T 2 , the control unit  60  of the control board Cnt 1  opens the first outflow port b and the second outflow port c (step S 5 ). When the control process proceeds to step S 5 , it means that although, for example, the semiconductor device of the control board Cnt 1  is less likely to break, it is preferable to increase the efficiency of heat dissipation of the heat sink Hs. As the first outflow port b and the second outflow port c are opened, part of the refrigerant flows to the second region Rg 2  and the other refrigerant flows to the expansion device  4  in the cooling operation of the refrigeration cycle apparatus  100 . As part of the refrigerant flows in the second region Rg 2 , the second region Rg 2  is used as a condenser. This operation provides some degree of subcooling for the refrigerant. Furthermore, not the entire refrigerant flows in the second region Rg 2 . This operation reduces or eliminates a rise in temperature of the air passing through the second region Rg 2 . In other words, the heat sink Hs is supplied with the air of which a rise in temperature is reduced or eliminated. This operation increases the efficiency of heat dissipation of the heat sink Hs in step S 5 , though the efficiency in step S 5  is lower than the efficiency in step S 3 . 
     When the temperature of the heat sink Hs is at or below the second reference temperature T 2 , the control unit  60  of the control board Cnt 1  opens the first outflow port b and closes the second outflow port c (step S 6 ). When the control process proceeds to step S 6 , it means that, for example, the semiconductor device of the control board Cnt 1  is much less likely to break than the case in step S 5 . As the first outflow port b is opened and the second outflow port c is closed, the entire refrigerant leaving the first region Rg 1  enters the second region Rg 2 . This operation more reliably provides some degree of subcooling for the refrigerant. 
     Advantageous effects of Embodiment 3 will be described below. The control unit  60  adjusts the flow switching device  20  on the basis of the temperature Tf of the heat sink Hs. Specifically, the control unit  60  adjusts the flow switching device  20  as described in steps S 3  and S 5 , thereby avoiding breakage of, for example, the semiconductor device of the control board Cnt 1 . In addition, the control unit  60  adjusts the flow switching device  20  as described above in steps S 5  and S 6 , thereby increasing the efficiency of heat dissipation of the heat sink Hs. Additionally, the control unit  60  adjusts the flow switching device  20  as described above in step S 6 , thereby more reliably providing some degree of subcooling for the refrigerant. 
     Embodiment 4 
       FIG. 16  is a schematic diagram of an outdoor heat exchanger  30  of an outdoor unit according to Embodiment 4. In Embodiment 4, the same components as those in Embodiments 1 to 3 are designated by the same reference signs. The following description will focus on the difference between Embodiment 4 and Embodiments 1 to 3. In Embodiment 4, an air flow resistance in the second region Rg 2  is less than an air flow resistance in the first region Rg 1 . An air flow resistance correlates with a pressure loss. In other words, the greater the air flow resistance, the greater the pressure loss. The pressure loss can be expressed by the following mathematical formula.
 
Δ P=λ×Q   2   (Math.)
 
     In the mathematical formula, ΔP denotes the difference between a pressure on an upstream side of the outdoor heat exchanger  30  and a pressure on a downstream side of the outdoor heat exchanger  30 . In other words, ΔP denotes a pressure loss in the air passing through the outdoor heat exchanger  30 . In the mathematical formula, λ denotes a coefficient determined on the basis of, for example, the density of the air, the cross-sectional area of the outdoor heat exchanger  30  that is orthogonal to the air flow direction, and a resistance coefficient, and Q denotes the flow rate of the air passing through the outdoor heat exchanger  30 . 
     The fins  3   b  of the outdoor heat exchanger  30  include a first fin fn 1  to which the heat transfer tube  3   a  in the first region Rg 1  is fixed and a first fin fn 2  to which the heat transfer tube  3   a  in the first region Rg 1  is fixed and that faces the first fin fn 1  and is disposed at a distance corresponding to a fin pitch D 1  from the first fin fn 1 . The first fin fn 1  and the first fin fn 2  are any adjacent fins to which the heat transfer tube  3   a  in the first region Rg 1  is fixed. The fins  3   b  further include a second fin fn 3  to which the heat transfer tube  3   a  in the second region Rg 2  is fixed and a second fin fn 4  to which the heat transfer tube  3   a  in the second region Rg 2  is fixed and that faces the second fin fn 3  and is disposed at a distance corresponding to a fin pitch D 2  from the second fin fn 3 . The second fin fn 3  and the second fin fn 4  are any adjacent fins to which the heat transfer tube  3   a  in the second region Rg 2  is fixed. 
     Advantageous effects of Embodiment 4 will be described below. In Embodiment 4, the fin pitch D 2  is greater than the fin pitch D 1 . This arrangement causes the air flow resistance in the second region Rg 2  to be less than the air flow resistance in the first region Rg 1 . Thus, the flow rate of the air passing per unit area of the second region Rg 2  is greater than the flow rate of the air passing per unit area of the first region Rg 1 . This arrangement results in an increase in flow rate of the air to be supplied to the heat sink Hs, thus facilitating heat dissipation of the heat sink Hs. 
       FIG. 17  is a diagram illustrating an outdoor heat exchanger  31  of an outdoor unit according to Modification 1 of Embodiment 4. In the above-described arrangement in Embodiment 4, the fin pitch D 2  is greater than the fin pitch D 1 . The arrangement is not limited to the above-described one. As illustrated in  FIG. 17 , a pitch pt 2  of the heat transfer tube  3   a  in the second region Rg 2  in the Z direction may be greater than a pitch pt 1  of the heat transfer tube  3   a  in the first region Rg 1  in the Z direction. In Modification 1, an air flow resistance in the second region Rg 2  is less than an air flow resistance in the first region Rg 1  as in Embodiment 4. 
       FIG. 18  is a diagram illustrating an outdoor heat exchanger  32  of an outdoor unit according to Modification 2 of Embodiment 4. As illustrated in  FIG. 18 , a pitch pt 4  of the heat transfer tube  3   a  in the second region Rg 2  in the Y direction may be greater than a pitch pt 3  of the heat transfer tube  3   a  in the first region Rg 1  in the Y direction. In Modification 2, an air flow resistance in the second region Rg 2  is less than an air flow resistance in the first region Rg 1  as in Embodiment 4. 
       FIG. 19  is a diagram illustrating an outdoor heat exchanger  33  of an outdoor unit according to Modification 3 of Embodiment 4. As illustrated in  FIG. 19 , a width W 2  of the fins  3   b  in the second region Rg 2  in the Y direction may be less than a width W 1  of the fins  3   b  in the first region Rg 1  in the Y direction. In Modification 3, an air flow resistance in the second region Rg 2  is less than an air flow resistance in the first region Rg 1  as in Embodiment 4. 
       FIG. 20  is a diagram illustrating an outdoor heat exchanger  34  of an outdoor unit according to Modification 4 of Embodiment 4. As illustrated in  FIG. 20 , the number of columns of the heat transfer tube  3   a  in the second region Rg 2  in the Y direction may be less than the number of columns of the heat transfer tube  3   a  in the first region Rg 1  in the Y direction. In Modification 4, an air flow resistance in the second region Rg 2  is less than an air flow resistance in the first region Rg 1  as in Embodiment 4.  FIG. 20  illustrates an exemplary arrangement in which the number of columns of the heat transfer tube  3   a  in the second region Rg 2  in the Y direction is one and the number of columns of the heat transfer tube  3   a  in the first region Rg 1  in the Y direction is two. 
       FIG. 21  is a diagram illustrating an outdoor heat exchanger  35  of an outdoor unit according to Modification 5 of Embodiment 4. As illustrated in  FIG. 21 , the fins  3   b  in the first region Rg 1  have cut-raised portions  3   b   1  to promote heat exchange between the outdoor heat exchanger  35  and the air Air. The fins  3   b  in the second region Rg 2  have no cut-raised portions  3   b   1 . In other words, the fins  3   b  in the second region Rg 2  each have a flat surface. In Modification 5, an air flow resistance in the second region Rg 2  is less than an air flow resistance in the first region Rg 1  as in Embodiment 4. 
     In each of Modifications 1 to 5, the air flow resistance in the second region Rg 2  is less than the air flow resistance in the first region Rg 1  as in Embodiment 4. Thus, the flow rate of the air Air passing per unit area of the second region Rg 2  is greater than the flow rate of the air Air passing per unit area of the first region Rg 1 . This arrangement results in an increase in flow rate of the air Air to be supplied to the heat sink Hs, thus facilitating heat dissipation of the heat sink Hs. 
     Embodiment 1, Modification of Embodiment 1, Embodiment 2, Embodiment 3, Embodiment 4, and Modifications 1 to 5 of Embodiment 4 can be appropriately combined.