Patent Application
20070256434
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.
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.
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.).
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.
It is an object of the present invention to accurately detect a low-charge in a heat-exchange system.
Another object of the present invention is to accurately detect a low-lube condition in a heat-exchange system.
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.
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.
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.
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.
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:
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.
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.
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
In an embodiment of the present invention, the air-conditioning system can also include a second set of sensors 116. Second set of sensors 116 can monitor a plurality of second parameters associated with the air-conditioning system. Example of the plurality of second parameters include, a blower speed, a relative humidity, a temperature, an engine rotation per minute (RPM), and so forth. Based on the plurality of second parameters, the low-charge condition can be determined.
In an embodiment of the present invention, processor 112 can include comparator 114. Comparator 114 can ascertain a low-charge condition based on a comparison between a degree of superheat of the charge in heat-exchange system 100 and a pre-defined degree of superheat. The comparison is further described in detail in conjunction with
In an embodiment of the present invention, monitoring system 202 can also include second set of sensors 116. Second set of sensors 116 monitors a plurality of second parameters associated with heat-exchange system 100. The plurality of second parameter includes a blower speed, a relative humidity, a temperature, and an engine rotation per minute (RPM). The plurality of second parameters can be used to determine a low-charge condition in heat-exchange system 100.
In an embodiment of the present invention, a plurality of first parameters, associated with a lubricating fluid in heat-exchange system 100, is monitored. Examples of a first parameter include, but are not limited to, the pressure and temperature of the lubricating fluid. Based on the plurality of first parameters, a degree of superheat of the lubricating fluid is computed. Thereafter, a low-lube condition is ascertained based on a comparison between the degree of superheat of the lubricating fluid and a pre-defined degree of superheat.
An advantage of the monitoring system as described earlier is that it accurately detects a low-charge and a low-lube condition in a heat-exchange system. The monitoring system also detects the low-charge condition even when the heat-exchange system is employing a variable displacement compressor such as in air-conditioners fitted in automobiles. The monitoring system also reliably detects the low-charge condition in mid-ambient condition. Further, the monitoring system can be economically implemented in the heat-exchange systems.
While the various embodiments of the invention have been illustrated and described, it will be clear that the invention is not limited only to these embodiments. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the invention, as described in the claims.
