Patent Publication Number: US-5839292-A

Title: Defroster for heat pump

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a defroster for a heat pump and, more particularly, to a defroster for heat pump for removing frost which falls on an evaporator during heating of the heat pump. 
     2. Discussion of the Related Art 
     Generally, a heat pump is capable of both heating and air conditioning operations. If the surface temperature of a heat exchanger(e.g. an evaporator) is lower than a dew-point of the outside air and is below zero, frost is formed on the heat exchanger of the heat pump. The possibility of frost formation is substantially increased when the temperature of the outside air is below 5° C. and the humidity of the outside air is above 65%. 
     FIG. 1 illustrates a heating operation cycle of a conventional heat pump. A high-temperature and high-pressure refrigerant is discharged from a compressor 9 and sent to a condenser by way of a four direction valve 14. The heat of the refrigerant is emitted at the condenser of an inside unit 15 into outside air supplied by a blowing fan 17. The condensed refrigerant is evaporated at an evaporator 1 of an outside unit after the pressure of the refrigerant is reduced by passing the refrigerant through a capillary tube 8. At the evaporator 1, the refrigerant absorbs heat from the outside air supplied by the blowing fan 17. The interior of a room is warmed up as the refrigerant circulates between the compressor 9 and the evaporator 1 repeatedly. 
     However, this conventional heat pump is disadvantageous in that frost falls on the evaporator 1 of the heat pump if a dew-point temperature of the supplied outside air is higher than a temperature of the refrigerant and the temperature of the outside air is below zero. The frost on the evaporator turns to ice within a few minutes and obstructs the supply of outside air generated by the blowing fan 17. The evaporator 1 stops functioning as the supply of the outside air is stopped. When evaporation is stopped the refrigerant flow is reduced and the pressure of the condenser 15 (the high-pressure portion) is also reduced. The reduction of the pressure leads to a drop in the condensing temperature, so that the heat pump cannot supply a sufficient amount of heat for heating a room. To defrost the evaporator, a user must change from the heating operation to the air-conditioning operation. The evaporator of the heating operation is used as a condenser during the air-conditioning operation, so that heat emitted from the condenser of the air-conditioning operation removes the frost. This results in cool air entering the interior of the room. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a defroster for a heat pump. 
     It is an object of the present invention to provide a defroster for a heat pump which removes frost formed on an evaporator without interrupting a heating operation of the heat pump. 
     To accomplish the object of the present invention, there is provided a defroster for a heat pump. The defroster includes refrigerant drawing means for drawing out a high-temperature refrigerant from an outlet of a compressor, the refrigerant circulating in the heat pump, and refrigerant distributing means installed at an inlet of an evaporator for supplying both a refrigerant coming from a condenser and the high-temperature refrigerant into the evaporator in separated states. 
     The refrigerant drawing means includes a bypass tube branching off at the outlet of the compressor for inducing the refrigerant, and an on-off valve for selectively inducing the refrigerant into the bypass tube. 
     The refrigerant distributing means alternately sends the two kinds of refrigerant into an upper portion and a lower portion of the evaporator. 
     The refrigerant distributing means includes a cylindrical converting valve, a first inlet tube formed at an upper portion of the a cylindrical converting valve for receiving refrigerant drawn by the refrigerant drawing means, a first outlet tube level with the first inlet tube for emitting refrigerant into the upper portion of evaporator, a second inlet tube formed at an lower portion of the a cylindrical converting valve for receiving refrigerant coming from a condenser, a second outlet tube level with the second inlet tube for emitting refrigerant into the lower portion of the evaporator; and a converting plate rotating in the cylindrical converting valve for connecting the first inlet tube with the first outlet tube while connecting the second inlet tube with the second outlet tube, or for connecting the first inlet tube with the second outlet tube while connecting the second inlet tube with the first outlet tube. 
     The refrigerant distributing means alternately may send the two kinds of refrigerant into an upper portion, a middle portion, and a lower portion of the evaporator. 
     The defroster for a heat pump also can include a check valve installed at an outlet of the evaporator for preventing refrigerant from flowing backward. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and/or other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawing, in which: 
     FIG. 1 is a configuration view illustrating a heating operation cycle of a conventional heat pump; 
     FIG. 2 is a configuration view illustrating a heating operation cycle of a heat pump in accordance with an embodiment of the present invention; 
     FIG. 3 is a P-h chart in accordance with the embodiment of FIG. 2; 
     FIG. 4a is a view illustrating a main operation of the embodiment of FIG. 2 when defrosting frost on an upper portion of the evaporator; 
     FIG. 4b is a view illustrating a main operation of the embodiment of FIG. 2 when defrosting frost on a lower portion of the evaporator; 
     FIG. 5a is a view illustrating operation of a converting valve of the embodiment of FIG. 2 when defrosting frost on the upper portion of the evaporator; 
     FIG. 5b is a view illustrating operation of a converting valve of the embodiment of FIG. 2 when defrosting frost on the lower portion of the evaporator; and 
     FIG. 6 illustrates another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A first embodiment of the invention will be described in detail with reference to FIGS. 2 to 5. 
     FIGS. 4 and 5 show a cylindrical converting valve 3 installed on a side of an evaporator 1. The converting valve 3 has a converting plate 2 that rotates at a right angle. When defrosting an upper portion or a lower portion of the evaporator 1, the converting plate 2 rotates at a right angle. The converting valve 3 also has a first inlet tube 4, a second inlet tube 5, a first outlet tube 6, and a second outlet tube 7 located on its sides. The first inlet tube 4 is coupled to a supplementary capillary tube 12, and the second inlet tube 5 is coupled to a capillary tube 8. The first outlet tube 6 is coupled to the upper portion of the evaporator 1, and the second outlet tube 7 is coupled to the lower portion of the evaporator 1. 
     A bypass tube 10 is located between the first inlet tube 4 and an outlet of a compressor 9. The bypass induces a high-temperature and high-pressure refrigerant into the evaporator 1. The refrigerant is circulated along a passage formed in a heat pump while converting its states into liquid or gas. The bypass tube 10 has an on-off valve 11 that selectively induces the high-temperature and high-pressure refrigerant into the bypass tube 10. The bypass tube 10 is coupled to the supplementary capillary tube 12 which turns the high-temperature and high-pressure refrigerant into a refrigerant having a suitable temperature and pressure. 
     A check valve 13 is located at an outlet of the evaporator 1 for preventing refrigerant from flowing backward. 
     FIGS. 2 and 5 illustrate the operation of the first embodiment. If the on-off valve 11 is turned on, a portion of the refrigerant goes into the first inlet 4 of the converting valve 3 through the supplementary capillary tube 12 in which a gas refrigerant having a high-temperature and high-pressure is turned into a refrigerant having a temperature and proper pressure. In the meantime, a majority of the refrigerant goes into the second inlet 5 of the converting valve 3 through the compressor 9, the condenser 15, and the capillary tube 8. The function of the capillary tube 8 is to expand the refrigerant that goes through the capillary. 
     The refrigerant entering a first inlet 4 is in the state of a high-temperature gas and the refrigerant entering the second inlet 5 is in the state of a two phase mixture, that is, a saturated refrigerant. As shown in FIG. 5, the two kinds of refrigerant go into the interior of the converting valve 3 without mixing, for defrosting the upper portion or the lower portion of the evaporator 1. During defrosting of the upper portion as shown FIG. 5a, the high-temperature refrigerant goes into the first outlet tube 6 while the saturated refrigerant goes into the second outlet tube 7. During defrosting of the lower portion as shown FIG. 5b, the high-temperature refrigerant goes into the second outlet tube 7 while the saturated refrigerant goes into the first outlet tube 6. As the converting plate 2 in the converting valve 3 rotates at a right angle, the upper portion and the lower portion of the evaporator 1 are defrosted periodically. 
     FIGS. 4a and 4b shows that the direction of the refrigerant flow is changed periodically according to the portion that is defrosted. Because frost is uniformly distributed on the surface of the evaporator 1, the upper or the lower portion of the evaporator 1 is selected randomly. The selected portion is first defrosted, and then the other portion is defrosted, alternating continuously. Defrosting periodically not only prevents frost from growing, but also removes frost. 
     When the heat pump is operated in a normal mode, the on-off valve 11 of the bypass tube 10 is turned off. 
     The function of the capillary tube 8 is to keep pressure on the inlet tube 4. The inlet tube 4 must have a saturated pressure in which a temperature of the refrigerant is 0° C. to 5° C. 
     The function of the check valve 13 is to prevent the refrigerant from flowing to the evaporator 1. The check valve 13 performs its function if the pressure at the inlet of the compressor 9 is higher than a pressure at the outlet of the evaporator 1 after: (i) the refrigerant passes through the bypass tube 10 and through the evaporator 1, and (ii) the refrigerant passes through the capillary tube 8 and through the evaporator 1. 
     FIG. 3 is a P-h chart which shows a main cycle and a bypass cycle of the refrigerant in accordance with the embodiment of the present invention. The refrigerant of the main cycle passes through evaporation, compression, condensation and expansion process. The refrigerant of the bypass cycle passes a process in which the high-temperature and the high-pressure refrigerant is expanded without a condensation process. The temperature of the refrigerant of the bypass cycle is dropped to remove frost while passing through the evaporator 1. 
     FIG. 6 illustrates another embodiment of the present invention, in which the evaporator 1 includes 3 paths. If frost falls on a surface of the evaporator 1, the on-off valve 11 is turned on and the bypass tube 10 induces the refrigerant. First, an upper portion 1a is defrosted while middle and lower portions 1b,1c are used for normal evaporation. Second, the middle portion 1b is defrosted, according to the rotation of the converting plate 2, while the upper and the lower portions 1a,1c are used for normal evaporation. Finally, the lower portion 1c is defrosted according to the rotation of the converting plate 2, while the upper and the middle portions 1a,1b are used for normal evaporation. If necessary, evaporation can be divided into a smaller portion than that of the first or the second evaporation. 
     As described above, the defroster removes frost which falls on the evaporator without interrupting a heating operation of the heat pump. Also, the heat pump can supply sufficient heat for heating a room because the evaporator functions normally. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in a defroster for heat pump of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.