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  Heating and defrosting methods and apparatusUSPTO Application #: 20070199335Title: 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 6a. The heat exchanger 6a 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 6a 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 6a can preferably utilise a helically corrugated tube in order to enhance its heat exchange characteristics. (end of abstract)
Agent: Sheldon Mak Rose & Anderson PC - Pasadena, CA, US Inventor: Rodney Mitchell Innes USPTO Applicaton #: 20070199335 - Class: 062151000 (USPTO) Related Patent Categories: Refrigeration, Automatic Control, Preventing, Removing Or Handling Atmospheric Condensate, Defrosting The Patent Description & Claims data below is from USPTO Patent Application 20070199335. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention in one embodiment relates to heat pump apparatus and to methods of operating a heat pump, and in particular, but not exclusively, to heat pumps which reduce or eliminate icing of the evaporator. It does, however, have application wherever fluid heating may be required. BACKGROUND OF THE INVENTION [0002] The term "heat pump" is used herein to define a system which absorbs heat (heat energy), at one or more temperatures and emits heat at a higher temperature, and which includes, in order, a compressor to pump refrigerant vapor around a closed circuit, a condenser to extract heat from the vapor, thereby condensing the refrigerant, an expansion valve to expand the refrigerant to a gaseous phase, thereby causing the temperature of the refrigerant to fall, and an evaporator to allow the cool refrigerant vapor to absorb heat. [0003] The refrigerant then returns to the compressor and repeats the cycle. Elements such as accumulators and receivers may also be used to ensure that the fluid is in the correct phase before it proceeds around the cycle. [0004] It is to be understood that the term heat pump may be applied equally to such systems when used to remove heat from a space or medium, such as for the purposes of air conditioning and refrigeration, or to systems used for heating a space or medium, such as water or space heating. Typically a four-way valve will be included in the heat pump system before the compressor to change-over the condenser to an evaporator and vice versa. The terms "evaporator" and "condenser" are therefore used interchangeably herein depending on whether the heat pump is being used in its heating or cooling mode. Other uses such as the heating of a gas or other fluids will also be included. Such uses could include the heating of a fluid such as in a hydraulic system or in an engine where lowering of the viscosity of the fluid could be of benefit. Further uses could include the heating of a gas, such as a compressed gas before its release when its cooling could create problems. [0005] Heat pump technology is now very common and the savings gained through using this method for heating in addition to its more traditional role in air conditioning are now more widely appreciated. Many Governments and Authorities as well as Industry and Commerce are realizing the benefits. The need to save energy has become a priority around the world. [0006] A disadvantage of using current heat pumps for heating is that ice may form on the evaporator when the ambient temperature around the evaporator drops below a minimum temperature, typically around +10.degree. C. When this happens the efficiency of the heat pump reduces dramatically due to the low thermal conductivity of the ice reducing the rate at which heat can be absorbed by the evaporator. [0007] One of the options currently used to combat icing of the evaporator is the provision of electric heating elements attached to the evaporator or embedded within it. In such systems the heat pump may be stopped and the refrigerant pumped down to the receiver before the evaporator is heated. Failure to stop the device may lead to liquid refrigerant entering the compressor, which may damage or even destroy it. Once the heat pump has been stopped the heating elements defrost the coil until the ice is melted and the unit can be run again. The heating element may cycle on and off many times until the ambient temperature increases. [0008] A second method in use at present is a hot gas by-pass system. When the evaporator coil ices, a solenoid valve opens, and hot gas is directly injected into the evaporator just after the expansion device. This method of evaporator de-icing may affect the system's operation dramatically and performance may drop accordingly. [0009] A further method currently in use is to reverse the heat pump so that the functions of the evaporator and condenser are reversed. A disadvantage of this method is that the heat transfer path is reversed, and the element which the heat pump is intended to heat is instead cooled for the duration of the de-icing cycle. OBJECT OF THE INVENTION [0010] It is an object of a preferred embodiment of the present invention to provide a heat pump apparatus and/or a method of operating a heat pump which will overcome or ameliorate problems with such apparatus or methods at present. [0011] Other objects of the present invention may become apparent from the following description, which is given by way of example only. SUMMARY OF THE INVENTION [0012] According to a first aspect of the present invention there is provided a heat pump apparatus including 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 said evaporator means, and a heat exchanger means operable to add heat from a working fluid from a high pressure side of said heat pump apparatus to said working fluid entering said evaporator, wherein said control means is operatively connected with said heat exchanger means to add said heat when said control means determines that said temperature of said outer surface of said evaporator means is below a pre-selected temperature, thereby reducing or substantially eliminating formation of ice on said outer surface of said evaporator. [0013] Preferably, said heat exchanger means includes a helically corrugated tube positioned within an outer housing, said working fluid from said high pressure side being caused to flow through said tube to add heat to said working fluid caused to flow over said tube and between said tube and said outer housing. [0014] Optionally, said at least one sensor means includes a temperature sensor adapted to measure the temperature of said outer surface of said evaporator. [0015] Optionally, said at least one sensor means includes a temperature sensor adapted to measure the temperature of the working fluid exiting the evaporator. [0016] Optionally, said at least one sensor means includes a temperature sensor adapted to measure the temperature of the environment surrounding the evaporator. [0017] Optionally, said at least one sensor means includes a pressure sensor adapted to measure the pressure of the working fluid exiting the evaporator. [0018] Optionally, said heat exchanger means includes an electric heating element. [0019] Optionally, said heat exchanger means obtains heat from said working fluid between a compressor and a condenser of said heat pump apparatus to transfer said heat to said working fluid entering said evaporator means. [0020] Optionally, said pre-selected temperature is between about 4.degree. C. and 0.degree. C. Continue reading... Full patent description for Heating and defrosting methods and apparatus Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Heating and defrosting methods and apparatus patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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