Patent Application
20080034772
Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
As shown in
The compressor 302 compresses a refrigerant vapor and delivers the vapor to the condenser 304 through a discharge line (and the reversing valve arrangement 350 if operated as a heat pump). The compressor 302 is preferably a reciprocating compressor. However, it is to be understood that the compressor 302 can be any suitable type of compressor, e.g., scroll compressor, rotary compressor, screw compressor, swag link compressor, turbine compressor, or any other suitable compressor. The refrigerant vapor delivered by the compressor 302 to the condenser 304 enters into a heat exchange relationship with a fluid, e.g., air or water, but preferably air, and undergoes a phase change to a refrigerant liquid as a result of the heat exchange relationship with the fluid. The condensed liquid refrigerant from condenser 304 flows through an expansion device (not shown) to the evaporator 306.
The condensed liquid refrigerant delivered to the evaporator 306 enters into a heat exchange relationship with a fluid, e.g., air or water, but preferably air, and undergoes a phase change to a refrigerant vapor as a result of the heat exchange relationship with the fluid. The vapor refrigerant in the evaporator 306 exits the evaporator 306 and returns to the compressor 302 by a suction line to complete the cycle (and the reversing valve arrangement 350 if operated as a heat pump). It is to be understood that any suitable configuration of condenser 304 and evaporator 306 can be used in the system 300, provided that the appropriate phase change of the refrigerant in the condenser 304 and evaporator 306 is obtained. The HVAC or refrigeration system 300 can include many other features that are not shown in
Referring now to
If the temperature set point is not satisfied in Step 404, the control proceeds to Step 408, where the compressor is started (if necessary) and the control valve is in the open position to operate the compressor at partial or reduced capacity. Preferably, the partial capacity of the compressor can range from about 70% of full capacity to about 90% of full capacity. As the compressor operates, the pressure within the compressor housing builds if the heating or cooling demand is not being satisfied, thereby creating a need for higher capacity from the compressor. In Step 410, the pressure in the compressor is compared to a predetermined set point of pressure differential between the suction inlet and the discharge outlet of the compressor. In an alternate embodiment, the pressure in the compressor is compared to a predetermined pressure set point, e.g., suction pressure set point or discharge pressure set point, rather than the differential pressure of the suction inlet and discharge outlet of the compressor. If the pressure differential in the compressor is less than the predetermined pressure differential set point, the control returns to Step 408 to continue operating at partial capacity. Otherwise, the control proceeds to Step 412 to operate the compressor at full capacity.
In a preferred embodiment, the pressure control valve within the compressor housing is calibrated to perform the comparison Step 410 and to close from the open position to operate the compressor at full capacity when the pressure differential of the compressor reaches the predetermined pressure differential set point. When the pressure differential set point is reached, the control valve activates and closes, which generates full capacity in the compressor. The compressor operates at full capacity until the predetermined temperature set point is reached in Step 414. If the predetermined temperature set point is not satisfied in Step 414, the control returns to Step 412 to continue operating the compressor at full capacity. However, if the predetermined temperature set point has been satisfied in Step 414, the compressor is shut down at Step 406 and the process begins again at Step 402. Once the compressor is operating at full capacity, the control valve prevents any switching to the lower capacity until after the compressor has been shut down.
In an alternate embodiment of the invention, the control valve can be arranged to permit operation of the compressor in full capacity mode when the control valve is in the open position and in partial capacity mode when the control valve is in the closed position. In addition, the control valve can be located in any suitable location within the compressor to control the capacity during operation.
The control valve is activated only by pressure levels within the compressor regardless of the temperature levels within the compressor or surrounding the system. The transition between partial and full capacity occurs almost instantaneously with the control valve moving from the open to the closed position. The almost instantaneous switch from the open to the closed position essentially eliminates a transitional range where the valve is neither fully open nor fully closed.
As illustrated in
Thus, by adjusting the location of the opening 484 relative to the bottom dead center position of the reciprocating piston 336, the reciprocating compressor 416 achieves a desired capacity modulation. Also, by adjusting the biasing force exerted by the biasing member 470, the reciprocating compressor 416 controls the discharge pressure at which valve member 464 prevents flow through the flow passage 454. Accordingly, the system efficiency of an air-conditioning or refrigeration system can be improved by optimizing the combination of the degree of capacity modulation and the pressure at which the valve member 464 prevents flow through the flow passage 454. Preferably, the location of the opening 484 is adjusted to obtain the desired reduced capacity percentage of full capacity. The valve member may be any suitable valve configuration or multiple valve configuration.
An alternate embodiment of the invention includes a system with no suction pressure channel 483 connected to the low-pressure side of the valve member 404. This embodiment allows for a transitional period between the open position and the closed position of the valve member 404. In one embodiment, the compressor pressure differential is at 0 psi on start-up and builds pressure in the compressor while operating in a reduced capacity mode. Once the compressor reaches the lower limit (e.g., 114 psi) of the predetermined differential pressure range, the control valve begins to close and reaches the fully closed position at the upper limit (e.g., 129 psi) of the predetermined differential pressure range. The pressure in the compressor continues to build until a full capacity steady state differential pressure (e.g., 145 psi) is obtained in the compressor. This transitional period exists during the time it takes the valve member to switch between the open position and the closed position.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
