Patent Publication Number: US-2013240176-A1

Title: Heat pump

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority to Korean Patent Application No. 10-2012-0013872 filed in Korea on Feb. 10, 2012, which is hereby incorporated by reference. 
     BACKGROUND 
     1. Field 
     A heat pump is disclosed herein. 
     2. Background 
     Heat pumps are known. However, they suffer from various disadvantages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein: 
         FIG. 1  is a schematic diagram of a heat pump according to an embodiment; 
         FIG. 2  is a schematic diagram of an outdoor heat exchanger and an outdoor fan of the heat pump of  FIG. 1 ; 
         FIG. 3  is a graph comparing heat-exchange performance of the outdoor heat exchanger of the heat pump of  FIGS. 1-2  with those of a hydrophilic double-row heat exchanger and a water-repellent double-row heat exchanger; 
         FIG. 4  is a graph comparing pressure loss of the outdoor heat exchanger of the heat pump of  FIGS. 1-2  with those of a hydrophilic double-row heat exchanger and a water-repellent double-row heat exchanger; and 
         FIG. 5  is a graph comparing frost formation time of the outdoor heat exchanger of the heat pump of  FIGS. 1-2  with those of a hydrophilic double-row heat exchanger and a water-repellent double-row heat exchanger. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments are shown. Embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope to those skilled in the art. Where possible, like numbers refer to like elements throughout, and repetitive disclosure has been omitted. 
     In general, a heat pump is a device that includes a compressor, an outdoor heat exchanger, an expansion mechanism, and an indoor heat exchanger. Such a heat exchanger may be used to cool or heat the inside of a room or to supply hot water. 
     In a cooling operation of the heat pump, the outdoor heat exchanger may function as a condenser and the indoor heat exchanger may function as an evaporator. In a heating operation of the heat pump, the indoor heat exchanger may function as a condenser and the outdoor heat exchanger may function as an evaporator. 
     In the heating operation of the heat pump, frost may form on a surface of the outdoor heat exchanger. In this case, a defrosting heater that applies heat to the outdoor heat exchanger may be installed to prevent the frost from forming on the surface of the outdoor heat exchanger, or the frost formed on the surface of the outdoor heat exchanger may be removed by changing the heating operation of the heat pump to the cooling operation. 
     Recently, technologies for performing water-repellent coating or hydrophilic coating on an outdoor or indoor heat exchanger have been developed. 
       FIG. 1  is a schematic diagram of a heat pump according to an embodiment. Referring to  FIG. 1 , the heat pump  1  may include a compressor  2  that compresses a refrigerant, and an outdoor heat exchanger  4  that performs a heat exchange between the refrigerant and outdoor air. 
     The outdoor heat exchanger  4  may condense or evaporate the refrigerant by performing a heat exchange between the refrigerant and the outdoor air moved by an outdoor fan  5 . The outdoor fan  5  may move the outdoor air to the outdoor heat exchanger  4 , being placed together with the outdoor heat exchanger  4  at an outside of a room. 
     The heat pump  1  may further include an indoor heat exchanger  6 , in which refrigerant may be heat-exchanged with indoor air or heat-exchanged with a liquid heat medium, such as an antifreezing solution or water. 
     The heat pump may be a heat-pump type air conditioner or a heat-pump type hot-water supply apparatus. In the case of the heat-pump type air conditioner, the indoor air may be heat-exchanged with the refrigerant in the indoor heat exchanger  6  and then provided to an inside of a room, thereby changing an indoor temperature. In the case of the heat-pump type hot-water supply apparatus, the liquid heat medium, such as water or antifreezing solution, may be heat-exchanged with the refrigerant in the indoor heat exchanger  6  and then used to supply hot water. 
     In the case of the heat-pump type air conditioner, the indoor heat exchanger  6  may be a fin-tube heat exchanger including a refrigerant tube, through which the refrigerant may pass, and at least one fin coupled to the refrigerant tube, so that the indoor air may be heat-exchanged with the refrigerant by contacting the fin-tube heat exchanger. The indoor heat exchanger  6  may condense or evaporate the refrigerant by performing a heat exchange between the indoor air moved by an indoor fan  7  and the refrigerant passing through the indoor heat exchanger  6 . 
     In the case of the heat-pump type hot-water supply apparatus, the indoor heat exchanger  6  may be provided with a first flow path, through which the refrigerant may pass, and a second flow path, through which the liquid heat medium may pass. The indoor heat exchanger  6  may be a double-tube heat exchanger, a plate-type heat exchanger, or a shell-tube type heat exchanger, in which the refrigerant in the first flow path and the liquid heat medium in the second flow path may be heat-exchanged with a heat transfer member interposed therebetween. The liquid heat medium may be heat-exchanged with the refrigerant through the heat transfer member while passing through the second flow path. 
     The indoor heat exchanger  6  may be connected to a water tank (or hot-water tank) (not shown) through a liquid heat medium circulation flow path. The liquid heat medium moved in the water tank (or hot-water tank) may evaporate or condense the refrigerant while passing through the second flow path of the indoor heat exchanger  6 . 
     The heat pump  1  may further include an expansion mechanism  8  that expands the refrigerant, installed between the indoor heat exchanger  6  and the outdoor heat exchanger  4 . Additionally, the heat pump  1  may include a flow switch  10 . The flow switch  10  may allow the refrigerant to be circulated in the order of the compressor  2 , the outdoor heat exchanger  4 , the expansion mechanism  8 , and the indoor heat exchanger  6 , or may allow the refrigerant to be circulated in the order of the compressor  2 , the indoor heat exchanger  6 , the expansion mechanism  8 , and the outdoor heat exchanger  4 . 
     The flow switch  10  may include a 4-way valve that switches a moving direction of the refrigerant, or may include a plurality of open/close valves that switches the moving direction of the refrigerant. Hereinafter, an embodiment will be described using a 4-way valve to switch the moving direction of the refrigerant; however, embodiments are not so limited. 
     In the heat pump  1 , the compressor  2 , the outdoor heat exchanger  4 , the outdoor fan  5 , the expansion mechanism  8 , and the flow switch  10  may be installed in an outdoor device O, and the indoor heat exchanger  6  and the indoor fan  7  may be installed in an indoor device I. The heat pump  1  may include cooling and heating operations, or may include cooling, heating, and defrosting operations. Alternatively, the heat pump may include heating and defrosting operations. 
     The cooling operation may be an operation in which the indoor heat exchanger  6  cools the liquid heat medium or indoor air. In the cooling operation, the refrigerant compressed in the compressor  2  may move or flow to the outdoor heat exchanger  4 , sequentially passing through the expansion mechanism  8  and the indoor heat exchanger  6 , and may then be collected by the compressor  2 . In the cooling operation, the refrigerant may be condensed by being heat-exchanged with the outdoor air in the outdoor heat exchanger  4 , and may be evaporated by being heat-exchanged with the indoor air or liquid heat medium in the indoor heat exchanger  6 . 
     The heating operation may be an operation in which the indoor heat exchanger  6  heats the liquid heat medium or indoor air. In the heating operation, the refrigerant compressed in the compressor  2  may move or flow to the indoor heat exchanger  6 , sequentially passing through the expansion mechanism  8  and the outdoor heat exchanger  4 , and may then be collected by the compressor  2 . In the heating operation, the refrigerant may be condensed by being heat-exchanged with the indoor air or liquid heat medium in the indoor heat exchanger  6 , and evaporated by being heat-exchanged with the outdoor air in the outdoor heat exchanger  4 . 
     The defrosting operation may be an operation in which the refrigerant compressed in the compressor  2  is moved to the outdoor heat exchanger  4  so as to defrost or melt frost formed on the surface of the outdoor heat exchanger  4 . In the defrosting operation, the refrigerant compressed in the compressor  2  may move or flow to the outdoor heat exchanger  4 , sequentially passing through the expansion mechanism  8  and the indoor heat exchanger  6 , and may then be collected by the compressor  2 . In the defrosting operation, a portion of the refrigerant compressed in the compressor  2  may partially defrost or melt frost formed on the surface of the outdoor heat exchanger  4  while passing through a portion of the flow paths of the outdoor heat exchanger  4 . The rest of the refrigerant compressed in the compressor  2  may sequentially pass through the indoor heat exchanger  6  and the expansion mechanism  8 , pass through the remaining flow paths of the outdoor heat exchanger  4 , and may then be collected by the compressor  2 . 
     If a defrosting start condition is satisfied during the heating operation, the heat pump  1  may perform the defrosting operation. If a defrosting end condition is satisfied, the heat pump  1  may return to the heating operation. 
     The defrosting condition may be a condition in which an accumulated time for which the heat pump  1  performs the heating operation and various conditions, such as outdoor temperature and suction superheat degree, satisfy the defrosting start condition. The defrosting end condition may be a condition in which the accumulated time for which the heat pump  1  performs the heating operation and various conditions, such as outdoor temperature and suction superheat degree, satisfy the defrosting end condition. 
     The flow switch  10  may move the refrigerant compressed in the compressor  2  to the outdoor heat exchanger  4  in the heating operation. If the defrosting start condition is satisfied, the flow switch  10  may move the refrigerant compressed in the compressor  2  to the indoor heat exchanger  6 . Then, when the heat pump returns to the heating operation, the flow switch  10  may move the refrigerant compressed in the compressor  2  to the outdoor heat exchanger  4 . 
       FIG. 2  is a schematic diagram of an outdoor heat exchanger and outdoor fan of the heat pump of  FIG. 1 . The outdoor device O may include a casing  13  in which an outdoor air inlet  11  and an outdoor air outlet  12  may be formed. 
     The outdoor heat exchanger  4  may include a plurality of heat exchange devices  16  and  18 . The plurality of heat exchange devices  16  and  18  may be disposed along a moving direction of the outdoor air. 
     The outdoor fan  5  may be installed in the casing  13 , and may blow the outdoor air so that the outdoor air may be sucked in through the outdoor air inlet  11 , sequentially pass through the plurality of heat exchange devices  16  and  18 , and then be exhausted through the outdoor air outlet  12 . The outdoor device O may include a barrier  14  that partitions an inside of the casing  13  into a blowing chamber  80   a , through which the outdoor air may pass, and a machine chamber  80   b , in which the compressor  2  may be installed. 
     The plurality of heat exchange devices  16  and  18  may include a front-row heat exchange device  16 , through which the outdoor air moved by the outdoor fan  5  may first pass, and a rear-row heat exchange device  18 , through which the outdoor air having passed through the front-row heat exchange device  16  may pass. Each of the front-row heat exchange device  16  and the rear-row exchange device  18  may be a fin-tube heat exchange device. The refrigerant may first pass through any one of the front-row heat exchange device  16  and the rear-row exchange device  18 , and may then pass through the other of the front-row heat exchange device  16  and the rear-row heat exchange device  18 . The refrigerant may be divided into refrigerants, respectively, passing through the front-row heat exchange device  16  and the rear-row exchange device  18 . The refrigerants, respectively, having passed through the front-row heat exchange device  16  and the rear-row exchange device  18  may be recombined. 
     The front-row heat exchange device  16  and the rear-row exchange device  18  may be disposed along the moving direction of the outdoor air. The front-row heat exchange device  16  and the rear-row exchange device  18  may be disposed to have a gap therebetween. The front-row heat exchange device  16  may be disposed closer to the outdoor air inlet  11  than the rear-row heat exchange device  18 . The rear-row heat exchange device  18  may be disposed closer to the outdoor air outlet  12  than the front-row heat exchange device  16 . The heat pump  1  may be configured so that the outdoor air inlet  11 , the front-row heat exchange device  16 , the rear-row heat exchange device  18 , the outdoor fan  5 , and the outdoor air outlet  12  are sequentially disposed in the moving direction of the outdoor air. 
     During rotation of the outdoor fan  5 , the outdoor air is sucked into the outdoor device O through the outdoor air inlet  11  and then passes through the front-row heat exchange device  16 . Subsequently, the outdoor air passes through the rear-row heat exchange device  18  and is then exhausted to the outside of the outdoor device O through the outdoor air outlet  12 . 
     The outdoor air sucked into the outdoor device O by the outdoor fan  5  may be primarily heat-exchanged with the refrigerant while passing through the front-row heat exchange device  16 . Then, the outdoor air may be secondarily heat-exchanged with the refrigerant while passing through the rear-row heat exchange device  18 . 
     Each of the front-row heat exchange device  16  and the rear-row exchange device  18  may include a refrigerant tube and at least one fin coupled to the refrigerant tube. The front-row heat exchange device  16  may include a front-row refrigerant tube  22  and at least one front-row fin  24  coupled to the front-row refrigerant tube  22 . The rear-row exchange device  18  may include a rear-row refrigerant tube  32  and at least one rear-row fin  34  coupled to the rear-row refrigerant tube  32 . 
     A water-repellent coating or a hydrophilic coating may be coated on both the front-row heat exchange device  16  and the rear-row exchange device  18 . According to one embodiment, when considering heat exchange performance, pressure loss, and frost formation time, the water-repellent coating may be coated on any one of the two heat exchange devices  16  and  18  and the hydrophilic coating may be coated on the other of the two heat exchange devices  16  and  18 , in comparison to a case in which the water-repellent coating or hydrophilic coating is coated on both the heat exchange devices  16  and  18 . In the outdoor heat exchanger  4 , a lot of frost may be formed on the front-row heat exchange device  16 , through which the outdoor air first passes, rather than the rear-row heat exchange device  18 . A heat transfer amount of the rear-row heat exchange device  18  may be relatively smaller than that of the rear-row heat exchange device  16 . Hence, the water-repellent coating may be coated on the front-row heat exchange device  16 , and the hydrophilic coating may be coated on the rear-row heat exchange device  18 . 
     A water-repellent coating layer X may be formed or coated on at least one surface of the front-row heat exchange device  16 , which the outdoor air contacts, and a hydrophilic coating layer Y may be formed or coated on at least one surface of the rear-row heat exchange device  18 , which the outdoor air contacts. For the front-row heat exchange device  16 , the water-repellent coating may be coated on the fin (front-row fin)  24 . For the rear-row heat exchange unit  18 , the hydrophilic coating may be coated on the fin (rear-row fin)  34 . 
     The water-repellent coating layer X may be formed or coated on at least one outer surface of the fin  24  of the front-row heat exchange device  16 . The water-repellent coating may be formed or coated on the front-row heat exchange device  16 , so that the at least one outer surface of the fin  24  is covered by the water-repellent coating layer X. The water-repellent coating layer X may be coated on both (first and second side) surfaces of the fin  24  of the front-row heat exchange device  16 . The water-repellent coating layer X may be coated on front and rear ends of the fin  24  of the front-row heat exchange device  16 . 
     The hydrophilic coating layer Y may be formed or coated on at least one outer surface of the rear-row heat exchange device  18 . The hydrophilic coating layer Y may be formed or coated on the rear-row heat exchange device  18 , so that at least one outer surface of the fin  34  of the rear-row heat exchange device  18  is covered by the hydrophilic coating layer Y. The hydrophilic coating layer Y may be coated on both (first and second side) surfaces of the fin  34  of the rear-row heat exchange device  18 . The water-repellent coating layer X may be coated on front and rear ends of the fin  34  of the rear-row heat exchange device  18 . 
     The water-repellent coating layer X and the hydrophilic coating layer Y may not be formed together on one heat exchange device, and moreover, may be spaced apart from each other. A rear end of the water-repellent coating layer X may be spaced apart from a front end of the hydrophilic coating layer Y in the moving direction of the outdoor air. 
     In a case in which the water-repellent coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18 , condensate water generated on the surface of each heat exchange device may form as a drop of water. Therefore, the pressure loss of the entire outdoor heat exchanger  4  may be enlarged, and a load of the outdoor fan  5  may be increased. Accordingly, a decrease in amount of air and degradation of performance may result. 
     On the other hand, in a case in which the hydrophilic coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18 , frost due to the condense water may easily form on the surface of each heat exchange device. Therefore, a frost formation time may be shortened, and the defrosting operation frequently required. 
     The outdoor heat exchanger  4  according to embodiments disclosed herein, in which the water-repellent coating is coated on the front-row heat exchange device  16  and the hydrophilic coating is coated on the rear-row heat exchange device  18 , has a higher heat transfer performance than a case in which the water-repellent coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18 , and has a lower heat transfer performance than a case in which the hydrophilic coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18 . 
     The outdoor heat exchanger  4  according to embodiments disclosed herein, in which the water-repellent coating is coated on the front-row heat exchange device  16  and the hydrophilic coating is coated on the rear-row heat exchange device  18 , has a lower pressure loss than a case in which the water-repellent coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18 , and has a higher pressure loss than a case in which the hydrophilic coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18 . 
     The outdoor heat exchanger  4  according to embodiments disclosed herein, in which the water-repellent coating is coated on the front-row heat exchange device  16  and the hydrophilic coating is coated on the rear-row heat exchange device  18 , has a shorter frost formation time than a case in which the water-repellent coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18 , and has a longer frost formation time than a case in which the hydrophilic coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18 . 
     Hereinafter, for convenience of illustration, an outdoor heat exchanger in which the water-repellent coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18  may be referred to as a water-repellent double-row heat exchanger, and an outdoor heat exchanger in which the hydrophilic coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18  may be referred to as a hydrophilic double-row heat exchanger. 
     Hereinafter, operation of embodiments configured as described above will be described as follows. 
     First, in a cooling operation, the refrigerant may be circulated in the order of the compressor  2 , the outdoor heat exchanger  4 , the expansion mechanism  8 , the indoor heat exchanger  6 , and the compressor  2 . The refrigerant compressed in the compressor  2  may be condensed while passing through the front-row heat exchange device  16  and the rear-row heat exchange device  18 . The condensed refrigerant may be expanded in the expansion mechanism  8 . The expanded refrigerant may be evaporated while passing through the indoor heat exchanger  6  and then flow into the compressor  2 . 
     In a heating operation, the refrigerant may be circulated in the order of the compressor  2 , the indoor heat exchanger  6 , the expansion mechanism  8 , the outdoor heat exchanger  4 , and the compressor  2 . The refrigerant compressed in the compressor  2  may be condensed while passing through the indoor heat exchanger  6 . The condensed refrigerant may be expanded in the expansion mechanism  8 . The expanded refrigerant may be evaporated while passing through the front-row heat exchange device  16  and the rear-row heat exchange device  18  and then flow into the compressor  2 . 
     The outdoor air may be heat-exchanged with the refrigerant of the front-row heat exchange device  16  and the rear-row heat exchange device  18  while sequentially passing through the front-row heat exchange device  16  and the rear-row heat exchange device  18 . When passing through the front-row heat exchange device  16 , the outdoor air may pass between the fins  24  on which the water-repellent coating layer X may be coated. Then, when passing through the rear-row heat exchange device  18 , the outdoor air may pass between the fins  34  on which the hydrophilic coating layer Y may be coated. 
     In the heating operation, the condensed water may form as a drop of water on the water-repellent coating layer X of the front-row heat exchange device  16 , and therefore, the pressure loss of the front-row heat exchange device  16  may be large. However, the condensed water may be widely spread on the hydrophilic coating layer Y of the rear-row heat exchange device  18 , and therefore, the pressure loss of the rear-row heat exchange device  18  may be small. In this case, the pressure loss of the entire outdoor heat exchanger  4  may be smaller than the case in which the water-repellent coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18 . 
       FIG. 3  is a graph comparing heat-exchange performance of the outdoor heat exchanger of the heat pump of  FIGS. 1-2  with those of a hydrophilic double-row heat exchanger and a water-repellent double-row heat exchanger.  FIG. 4  is a graph comparing pressure loss of the outdoor heat exchanger of the heat pump of  FIGS. 1-2  with those of a hydrophilic double-row heat exchanger and a water-repellent double-row heat exchanger.  FIG. 5  is a graph comparing frost formation time of the outdoor heat exchanger of the heat pump of  FIGS. 1-2  with those of a hydrophilic double-row heat exchanger and a water-repellent double-row heat exchanger. 
     When assuming that the front-row heat exchange device  16  and the rear-row heat exchange device  18  have the same conditions and the same amount of outdoor air is moved therethrough,  FIGS. 3 to 5  illustrates results obtained by comparing heat exchange performances, pressure losses, and frost formation times when the hydrophilic coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18 , when the water-repellent coating is coated on both the front-row heat exchange device  16  and the rear-row heat exchange device  18 , and when the water-repellent coating is coated on the front-row heat exchange device  16  and the hydrophilic coating is coated on the rear-row heat exchange device  18 . 
     Referring to  FIG. 3 , when the outdoor heat exchanger  4  is configured as the water-repellent double-row heat exchanger, the heat exchange performance is lower by approximately 1.8% than that (approximately 100%) when the outdoor heat exchanger  4  is configured as the hydrophilic double-row heat exchanger. On the other hand, when the water-repellent coating is coated on the front-row heat exchange device  16  and the hydrophilic coating is coated on the rear-row heat exchange device  18 , the heat exchange performance is higher by approximately 1.1% than that when the outdoor heat exchanger  4  is configured as the water-repellent double-row heat exchanger. 
     Referring to  FIG. 4 , when the outdoor heat exchanger  4  is configured as the water-repellent double-row heat exchanger, the pressure loss is higher by approximately 37% than that (approximately 100%) when the outdoor heat exchanger  4  is configured as the hydrophilic double-row heat exchanger. On the other hand, when the water-repellent coating is coated on the front-row heat exchange device  16  and the hydrophilic coating is coated on the rear-row heat exchange device  18 , the pressure loss is lower by approximately 16% than that when the outdoor heat exchanger  4  is configured as the water-repellent double-row heat exchanger. 
     Referring to  FIG. 5 , when the outdoor heat exchanger  4  is configured as the water-repellent double-row heat exchanger, the frost formation time is longer by approximately 68% than that (approximately 100%) when the outdoor heat exchanger  4  is configured as the hydrophilic double-row heat exchanger. On the other hand, when the water-repellent coating is coated on the front-row heat exchange device  16  and the hydrophilic coating is coated on the rear-row heat exchange device  18 , the frost formation time is shorter by approximately 23% than that when the outdoor heat exchanger  4  is configured as the water-repellent double-row heat exchanger, but is longer by approximately 45% than that when the outdoor heat exchanger  4  is configured as the hydrophilic double-row heat exchanger. That is, when the water-repellent coating is coated on the front-row heat exchange device  16  and the hydrophilic coating is coated on the rear-row heat exchange device  18 , the frost formation delay effect is lower than that when the outdoor heat exchanger  4  is configured as the water-repellent double-row heat exchanger, but is remarkably higher than that when the outdoor heat exchanger  4  is configured as the hydrophilic double-row heat exchanger. 
     When the water-repellent coating is coated on the front-row heat exchange device  16  and the hydrophilic coating is coated on the rear-row heat exchange device  18 , the frost formation delay effect is remarkably higher than that when the outdoor heat exchanger  4  is configured as the water-repellent double-row heat exchanger. When considering both heat exchange performance and the pressure loss, the entire performance of the outdoor heat exchanger  4  is higher than that of the water-repellent double-row heat exchanger or hydrophilic double-row heat exchanger. 
     In the heat pump according to embodiments, it is possible to delay frost formation time as compared with the hydrophilic double-row heat exchanger and to reduce pressure loss while enhancing heat exchange performance as compared with the water-repellent double-row heat exchanger. 
     Embodiments disclosed herein provide a heat pump capable of improving heating performance while delaying a frost formation time of an outdoor heat exchanger as long as possible. 
     Embodiments disclosed herein provide a heat pump that may include an outdoor heat exchanger in which a refrigerant is condensed by being heat-exchanged with outdoor air in a cooling operation and evaporated by being heat-exchanged with the outdoor air in a heating operation, and an outdoor fan that allows the outdoor air to be moved to the outdoor heat exchanger. In the heat pump, the outdoor heat exchanger may include a front-row heat exchange unit or device, through which the outdoor air moved by the outdoor fan may pass, and a rear-row heat exchange unit or device, through which the outdoor air passing through the front-row heat exchange unit may pass; a water-repellent coating layer formed on a surface of the front-row heat exchange unit, which the outdoor air contacts; and a hydrophilic coating layer formed on a surface of the rear-row heat exchange unit, which the outdoor air contacts. 
     Each of the front-row heat exchange unit and the rear-row heat exchange unit may include a refrigerant tube and at least one fin coupled to the refrigerant tube. The water-repellent coating layer may be formed on an outer surface of the fin of the front-row heat exchange unit. The hydrophilic coating layer may be formed on an outer surface of the fin of the rear-row heat exchange unit. 
     The water-repellent coating layer and the hydrophilic coating layer may be spaced apart from each other. The water-repellent coating layer may be formed on both surfaces of the fin of the front-row heat exchange unit, and the hydrophilic coating layer may be formed on both surfaces of the fin of the rear-row heat exchange unit. A rear end of the water-repellent coating layer may be separated from a front end of the hydrophilic coating layer in the moving direction of the outdoor air. 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.