Heating And Defrosting Methods And Apparatus

Abstract

A heat pump includes a compressor 1 , a condenser 2 , an expansion valve 3 , an evaporator 4 and a heat exchanger 6 a . The heat exchanger 6 a is located immediately downstream of the expansion valve 3 and upstream of the evaporator 4 . A controller 8 monitors one or more variables which predict may be about to occur by means of a sensor 11 . When this is predicted the heat exchanger 6 a will receive hot refrigerant through line 17 from the high pressure side of the compressor 1 so as to heat the refrigerant entering the evaporator 4 until ice formation is no longer likely. In an alternative embodiment, the heat exchanger may utilise an electric element to heat the refrigerant before it enters the evaporator. The heat exchanger 6 a can preferably utilise a helically corrugated tube in order to enhance its heat exchange characteristics.

1 . A heat pump apparatus comprising an evaporator means, a control means in communication with at least one sensor means adapted to measure one or more variables representative of a temperature of an outer surface of the evaporator means, and a heat exchanger means operable to add heat from a working fluid from a high pressure side of the heat pump apparatus to the working fluid entering the evaporator means, wherein the control means is operatively connected with the heat exchanger means to add the heat when the control means determines that the temperature of the outer surface of the evaporator means is below a pre-selected temperature, thereby reducing or substantially eliminating the formation of ice on the outer surface of the evaporator means.  
   
   
       2 . A heat pump apparatus comprising an evaporator means, a control means in communication with at least one sensor means adapted to measure one or more variables representative of a temperature of an outer surface of the evaporator means, and a heat exchanger means comprising a heating element positioned upstream of the evaporator means and downstream of an expansion means of the heat pump apparatus, the heat exchanger means operable to add heat to a working fluid entering the evaporator, wherein the control means is operatively connected with the heat exchanger means so that when the control means determines that the temperature of the outer surface of the evaporator means is below a pre-selected temperature, the heat exchanger means adds heat to the working fluid thereby reducing or substantially eliminating formation of ice on the outer surface of the evaporator means, and wherein the heat exchanger comprises a helically corrugated tube positioned within an outer housing, and the working fluid being heated is caused to flow over the tube and between the tube and the outer housing.  
   
   
       3 . The heat pump apparatus as claimed in  claim 1  wherein the at least one sensor means comprises a temperature sensor adapted to measure the temperature of the outer surface of the evaporator means.  
   
   
       4 . The heat pump apparatus as claimed in  claim 1  wherein the at least one sensor means comprises a temperature sensor adapted to measure the temperature of the working fluid exiting the evaporator means.  
   
   
       5 . The heat pump apparatus as claimed in  claim 1  wherein the at least one sensor means comprises a temperature sensor adapted to measure the temperature of the environment surrounding the evaporator means.  
   
   
       6 . The heat pump apparatus as claimed in  claim 1  wherein the at least one sensor means comprises a pressure sensor adapted to measure the pressure of the working fluid exiting the evaporator means.  
   
   
       7 . The heat pump apparatus as claimed in  claim 2  wherein the heat exchanger means comprises an electric heating element.  
   
   
       8 . The heat pump apparatus as claimed in  claim 7  wherein the electric heating element extends through the helically corrugated tube.  
   
   
       9 . The heat pump apparatus as claimed in  claim 8  wherein the helically corrugated tube forms part of an electrical circuit of the electric heating element.  
   
   
       10 . The heat pump apparatus as claimed in  claim 1  further comprising a compressor and a condenser and where the heat exchanger means obtains heat from the working fluid between the compressor and the condenser to transfer the heat to the working fluid entering the evaporator means.  
   
   
       11 . The heat pump apparatus as claimed in  claim 2  wherein the pre-selected temperature is between about 4° C. and 0° C.  
   
   
       12 . The heat pump apparatus as claimed in  claim 1  wherein the heat exchanger means comprises a helically corrugated tube positioned in an outer housing, the working fluid from the high pressure side being caused to flow through the tube to add heat to the working fluid caused to flow over the tube and between the tube and the outer housing.  
   
   
       13 . (canceled)  
   
   
       14 . A method of operating a heat pump having an evaporator downstream of an expansion means, the method comprising obtaining heat as required from a working fluid on a high pressure side of the heat pump to transfer to the working fluid on a low pressure side of the heat pump, prior to the working fluid entering the evaporator to reduce or substantially prevent ice from forming on the outer surface of the evaporator.  
   
   
       15 . The method as claimed in  claim 14  wherein the method comprises measuring one or more variables representative of a temperature of an outer surface of the evaporator and adding the heat to the working fluid entering the evaporator when the one or more variables indicate that the temperature has dropped below a pre-selected minimum.  
   
   
       16 . The method as claimed in  claim 15  wherein the method further comprises providing a controller to determine when icing of the evaporator is imminent based on the measurement of one or more variables.  
   
   
       17 . The method as claimed in  claim 16  wherein the method comprises heating the working fluid entering the evaporator with an electric heating element.  
   
   
       18 . The method as claimed in  claim 17  wherein the high pressure side is between a compressor and a condenser of heat pump.  
   
   
       19 . The method as claimed in  claim 18  in which the low pressure side of the heat pump is provided with a heat exchanger; the method comprising providing the heat exchanger with a helically corrugated tube within an outer housing, the working fluid being caused to flow over the tube and between the outer housing to be heated before it enters the evaporator.  
   
   
       20 . The method as claimed in  claim 14  wherein the method comprises adding heat to the working fluid while the heat pump is in operation.  
   
   
       21 . (canceled)  
   
   
       22 . (canceled)  
   
   
       23 . The heat pump apparatus as claimed in  claim 2  wherein the at least one sensor means comprises a temperature sensor adapted to measure the temperature of the outer surface of the evaporator means.  
   
   
       24 . The heat pump apparatus as claimed in  claim 2  wherein the at least one sensor means comprises a temperature sensor adapted to measure the temperature of the working fluid exiting the evaporator means.  
   
   
       25 . The heat pump apparatus as claimed in  claim 2  wherein the at least one sensor means comprises a temperature sensor adapted to measure the temperature of the environment surrounding the evaporator means.  
   
   
       26 . The heat pump apparatus as claimed in  claim 2  wherein the at least one sensor means comprises a pressure sensor adapted to measure the pressure of the working fluid exiting the evaporator means.  
   
   
       27 . The heat pump apparatus as claimed in  claim 2  further comprising a compressor and a condenser and where the heat exchanger means obtains heat from the working fluid between the compressor and the condenser to transfer the heat to the working fluid entering the evaporator means.  
   
   
       28 . A heat pump apparatus comprising an evaporator, a controller in communication with at least one sensor adapted to measure one or more variables representative of a temperature of an outer surface of the evaporator, and a heat exchanger operable to add heat from a working fluid from a high pressure side of the heat pump apparatus to the working fluid entering the evaporator, wherein the controller is operatively connected with the heat exchanger to add the heat when the controller determines that the temperature of the outer surface of the evaporator is below a pre-selected temperature, thereby reducing or substantially eliminating the formation of ice on the outer surface of the evaporator.  
   
   
       29 . A heat pump apparatus comprising an evaporator, a controller in communication with at least one sensor adapted to measure one or more variables representative of a temperature of an outer surface of the evaporator, and a heat exchanger comprising a heating element positioned upstream of the evaporator and downstream of an expansion valve of the heat pump apparatus, the heat exchanger operable to add heat to a working fluid entering the evaporator, wherein the controller is operatively connected with the heat exchanger so that when the controller determines that the temperature of the outer surface of the evaporator is below a pre-selected temperature, the heat exchanger adds heat to the working fluid thereby reducing or substantially eliminating formation of ice on the outer surface of the evaporator, and wherein the heat exchanger comprises a helically corrugated tube positioned within an outer housing, and the working fluid being heated is caused to flow over the tube and between the tube and the outer housing.  
   
   
       30 . The heat pump apparatus as claimed in  claim 28  wherein the at least one sensor comprises a temperature sensor adapted to measure the temperature of the outer surface of the evaporator.  
   
   
       31 . The heat pump apparatus as claimed in  claim 28  wherein the at least one sensor comprises a temperature sensor adapted to measure the temperature of the working fluid exiting the evaporator.  
   
   
       32 . The heat pump apparatus as claimed in  claim 28  wherein the at least one sensor comprises a temperature sensor adapted to measure the temperature of the environment surrounding the evaporator.  
   
   
       33 . The heat pump apparatus as claimed in  claim 28  wherein the at least one sensor comprises a pressure sensor adapted to measure the pressure of the working fluid exiting the evaporator.  
   
   
       34 . The heat pump apparatus as claimed in  claim 29  wherein the heat exchanger comprises an electric heating element.  
   
   
       35 . The heat pump apparatus as claimed in  claim 34  wherein the electric heating element extends through the helically corrugated tube.  
   
   
       36 . The heat pump apparatus as claimed in  claim 35  wherein the helically corrugated tube forms part of an electrical circuit of the electric heating element.  
   
   
       37 . The heat pump apparatus as claimed in  claim 28  further comprising a compressor and a condenser and where the heat exchanger obtains heat from the working fluid between the compressor and the condenser to transfer the heat to the working fluid entering the evaporator.  
   
   
       38 . The heat pump apparatus as claimed in  claim 29  wherein the pre-selected temperature is between about 4° C. and 0° C.  
   
   
       39 . The heat pump apparatus as claimed in  claim 28  wherein the heat exchanger comprises a helically corrugated tube positioned in an outer housing, the working fluid from the high pressure side being caused to flow through the tube to add heat to the working fluid caused to flow over the tube and between the tube and the outer housing.  
   
   
       40 . A method of operating a heat pump having an evaporator downstream of an expansion valve, the method comprising obtaining heat as required from a working fluid on a high pressure side of the heat pump to transfer to the working fluid on a low pressure side of the heat pump, prior to the working fluid entering the evaporator to reduce or substantially prevent ice from forming on the outer surface of the evaporator.  
   
   
       41 . The method as claimed in  claim 40  wherein the method comprises measuring one or more variables representative of a temperature of an outer surface of the evaporator and adding the heat to the working fluid entering the evaporator when the one or more variables indicate that the temperature has dropped below a pre-selected minimum.  
   
   
       42 . The method as claimed in  claim 41  wherein the method further comprises providing a controller to determine when icing of the evaporator is imminent based on the measurement of one or more variables.  
   
   
       43 . The method as claimed in  claim 42  wherein the method comprises heating the working fluid entering the evaporator with an electric heating element.  
   
   
       44 . The method as claimed in  claim 43  wherein the high pressure side is between a compressor and a condenser of heat pump.  
   
   
       45 . The method as claimed in  claim 44  in which the low pressure side of the heat pump is provided with a heat exchanger; the method comprising providing the heat exchanger with a helically corrugated tube within an outer housing, the working fluid being caused to flow over the tube and between the outer housing to be heated before it enters the evaporator.  
   
   
       46 . The method as claimed in  claim 40  wherein the method comprises adding heat to the working fluid while the heat pump is in operation.  
   
   
       47 . The heat pump apparatus as claimed in  claim 29  wherein the at least one sensor comprises a temperature sensor adapted to measure the temperature of the outer surface of the evaporator.  
   
   
       48 . The heat pump apparatus as claimed in  claim 29  wherein the at least one sensor comprises a temperature sensor adapted to measure the temperature of the working fluid exiting the evaporator.  
   
   
       49 . The heat pump apparatus as claimed in  claim 29  wherein the at least one sensor comprises a temperature sensor adapted to measure the temperature of the environment surrounding the evaporator.  
   
   
       50 . The heat pump apparatus as claimed in  claim 29  wherein the at least one sensor comprises a pressure sensor adapted to measure the pressure of the working fluid exiting the evaporator.  
   
   
       51 . The heat pump apparatus as claimed in  claim 29  further comprising a compressor and a condenser and where the heat exchanger obtains heat from the working fluid between the compressor and the condenser to transfer the heat to the working fluid entering the evaporator.