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  Monitoring system for detecting low-charge condition in a heat-exchange systemUSPTO Application #: 20070256434Title: Monitoring system for detecting low-charge condition in a heat-exchange system Abstract: A monitoring system for detecting a low-charge condition in a heat-exchange system is provided. The monitoring system has a first set of sensors located at the outlet of a compressor of the heat-exchange system. The first set of sensors monitor a plurality of first parameters. Based on the plurality of first parameters, a processor determines the low-charge condition in the heat-exchange system. (end of abstract) Agent: Daimlerchrysler Intellectual Capital Corporation Cims 483-02-19 - Auburn Hills, MI, US Inventors: Kwangtaek Hong, Gary L. Baker USPTO Applicaton #: 20070256434 - Class: 062149000 (USPTO) Related Patent Categories: Refrigeration, Automatic Control, Withdrawing Or Adding Refrigerant From Or To Normally Closed System The Patent Description & Claims data below is from USPTO Patent Application 20070256434. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention generally relates to a heat-exchange system. More particularly, the present invention relates to a monitoring system for the heat-exchange system. BACKGROUND OF THE INVENTION [0002] A heat-exchange system such as an air-conditioning system or a refrigeration system helps to maintain a constant temperature of the surrounding environment. The heat-exchange system works with a specified amount of refrigerant and a specified amount of lubricating fluid. It maintains temperature of the environment by exchanging heat with the surroundings. The exchange of heat may include either heating or cooling the environment. However, the exchange of heat can reduce significantly if the amount of refrigerant is less than the specified amount. This condition is referred to as a low-charge condition. The exchange of heat can also reduce significantly if the heat-exchange system is overheated due to lack of proper lubrication. This condition is referred to as a low-lube condition. The low-charge condition and the low-lube condition may be caused due to leakage of refrigerant or due to leakage of lubricating fluid from the heat-exchange system. This adversely affects the performance of the heat-exchange system as its capacity to transfer heat is reduced. Thus, the heat-exchange system may take more time to cool or to heat the surroundings to a certain temperature, thereby increasing the fuel consumption. The low-lube condition can also damage the moving parts of the heat-exchange system such as a compressor due to lack of proper lubrication. Operating the compressor in a low-charge condition or a low-lube condition for a long period may cause excessive wear and may finally lead to a breakdown of the compressor. Further, the leakage of refrigerants, such as chlorofluorocarbons, may damage the environment by depleting the ozone layer. Thus, it is imperative to detect the low-charge and low-lube condition accurately and reliably to prevent the above-mentioned problems. [0003] In an existing method for detecting a low-charge condition in a heat-exchange system, a sensor is installed at the outlet of a condenser. The sensor measures the temperature and pressure of the refrigerant at the outlet of a condenser. Based on the temperature and pressure, a sub-cool is calculated to detect a low-charge condition. However, such a system can reliably detect a low-charge condition only when the heat-exchange system employs a fixed displacement compressor. When a variable displacement compressor is employed, which is nowadays common in air-conditioners in automobiles, the temperature measured by the sensor is very close to ambient temperature. Thus, the sub-cool cannot be measured accurately and reliably. Further, the detection of the low-charge condition becomes even more difficult and unreliable in mid-ambient conditions (60-70 deg. F.). [0004] In the light of the foregoing discussion, there is a need for a system which can accurately detect a low-charge and a low-lube condition in a heat-exchange system. The system should be capable of detecting the low-charge condition in a variable displacement compressor such as those employed in automobiles. Further, the system should be able to reliably detect the low-charge condition in mid-ambient conditions. SUMMARY OF THE INVENTION [0005] It is an object of the present invention to accurately detect a low-charge in a heat-exchange system. [0006] Another object of the present invention is to accurately detect a low-lube condition in a heat-exchange system. [0007] Another object of the present invention is to detect a low-charge condition even when the heat-exchange system employs a variable displacement compressor, such as in air-conditioners in automobiles. [0008] Yet another object of the present invention is to reliably detect a low-charge condition when a heat-exchange system is operating in mid-ambient conditions. [0009] Yet another object of the present invention is to provide a system for detecting a low-charge condition that can be economically implemented in a heat-exchange system. [0010] The present invention provides a monitoring system to detect a low-charge condition in a heat-exchange system. The monitoring system includes a first set of sensors and a processor. The first set of sensors is located at an outlet of a compressor of the heat-exchange system and monitors a plurality of first parameters. Based on the plurality of first parameters, the processor determines the low-charge condition in the heat-exchange system. BRIEF DESCRIPTION OF THE DRAWINGS [0011] The various embodiments of the invention will hereinafter be described in conjunction with the appended drawings, provided to illustrate and not to limit the invention, wherein like designations denote like elements, and in which: [0012] FIG. 1 shows a heat-exchange system, in accordance with an embodiment of the present invention; [0013] FIG. 2 shows a monitoring system for detecting a low-charge condition in a heat-exchange system, in accordance with an embodiment of the present invention; [0014] FIG. 3 is a flow-chart illustrating a method for detecting a low-charge condition in a heat-exchange system, in accordance with an embodiment of the present invention; and [0015] FIG. 4 represents a graph illustrating variation of degree of superheat with respect to time for different percentages of refrigerant, in accordance with an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS [0016] The present invention relates to a monitoring system for detecting a low-charge condition in a heat-exchange system. The monitoring system has a first set of sensors and a processor. The first set of sensors is located at an outlet of a compressor in the heat-exchange system. The first set of sensors monitors a plurality of first parameters. Based on the plurality of first parameters, the processor determines the low-charge condition. [0017] FIG. 1 shows a heat-exchange system 100, in accordance with an embodiment of the present invention. The examples of heat-exchange system 100 include, but are not limited to, an air-conditioning system and a refrigerator. Heat-exchange system 100 includes a compressor 102, at least one condenser-coil 104, at least one expansion-valve 106 and at least one evaporator-coil 108. Compressor 102 compresses a charge (or a refrigerant). It is lubricated using lubricating fluids such as silicon lubricants, synthetic lubricants, oils and greases. Examples of a compressor include, a reciprocating compressor, a rotary compressor, a screw compressor, a scroll a screw compressor, a centrifugal compressor, a screw compressor, and so forth. A charge is a chemical substance having a low boiling point that absorbs heat from the environment while evaporating. Examples of charge include, but are not limited to, ammonia, fluorocarbons, chlorofluorocarbons and carbon dioxide. Due to the compression, the temperature and pressure of the charge is raised. The charge flows into at least one condenser-coil 104 from compressor 102. In at least one condenser-coil 104, the charge condenses to a liquid state and thus dissipates heat to the environment. Thereafter, the charge flows through at least one expansion-valve 106 where its pressure drops quickly. The charge at low pressure, in at least one evaporator-coil 108, absorbs heat from the environment thereby producing a cooling effect. [0018] In an exemplary embodiment of the present invention, heat-exchange system 100 can be an air-conditioning system. The air-conditioning system can include a first set of sensors 110 located at an outlet of compressor 102 and a processor 112. First set of sensors 110 measures a plurality of first parameters such as pressure and temperature of refrigerant in the air-conditioning system. Based on the plurality of first parameters, processor 112 determines a low-charge condition in the air-conditioning system. In an embodiment of the present invention, processor 112 can calculate a degree of superheat to determine the low-charge condition based on the plurality of first parameters. A degree of superheat for a fluid at a specific pressure is defined as the difference between the temperature of the fluid and the saturation temperature of the fluid at the specific pressure. [0019] In an embodiment of the present invention, processor 112 can include a comparator 114. Comparator 114 can ascertain a low-charge condition based on a comparison between a degree of superheat of the refrigerant in the air-conditioning system and a pre-defined degree of superheat. The comparison is further described in detail in conjunction with FIG. 4. Continue reading... Full patent description for Monitoring system for detecting low-charge condition in a heat-exchange system Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Monitoring system for detecting low-charge condition in a heat-exchange system patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. 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