Refrigeration – Processes – Compressing – condensing and evaporating
Patent
1996-07-10
1998-10-06
Wayner, William E.
Refrigeration
Processes
Compressing, condensing and evaporating
621963, 62197, F25B 500, F25B 4100
Patent
active
058160558
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a refrigeration system having a rotary screw compressor, a condenser, first pressure reducing means, an economizer, second pressure reducing means and an evaporator, which elements are connected by channel means in the mentioned sequence and by channel means connecting the evaporator to a low pressure inlet of the compressor port to form a closed loop for a refrigerant and further having economizer channel means selectively connecting the economizer to a closed working chamber of the compressor and adjustable valve means in the economizer channel means.
The present invention also relates to a method for regulating the refrigeration capacity of such a system.
BACKGROUND OF THE INVENTION
The use of an economizer is frequently applied in order to increase the refrigeration capacity of a refrigeration system. When using an economizer a part of the refrigerant is withdrawn from the main loop and is evaporated. The refrigerant evaporated in the economizer is then led to a closed working chamber of the compressor at an intermediate pressure level. The heat required for evaporating the refrigerant is taken from the remaining refrigerant in the main loop, which thereby is subcooled. This is done in a heat exchanger or in a flash tank. By the subcooling of the refrigerant in the main loop the enthalpy difference across the evaporator increases. The components of the system, in particular the compressor, thus can be made smaller and consequently less expensive to manufacture.
In many applications the refrigeration demand may vary widely, which makes it desirable to vary the refrigeration capacity correspondingly. This can be accomplished in various ways; by measures directly affecting the operation of the compressor, by measures affecting the conditions of the flow of refrigerant through the evaporator or by a combination of such measures.
Although the present invention contemplates such a combined regulation in a preferred embodiment the main concept of the invention concerns regulating by means affecting the conditions of the flow of refrigerant through the evaporator. Examples of such systems are disclosed in U.S. Pat. No. 2,388,556, U.S. Pat. No. 4,899,555, U.S. Pat. No. 4,947,655, U.S. Pat. No. 5,062,274 and U.S. Pat. No. 5,095,712. Common to these systems is that the flow of refrigerant withdrawn from the main loop is regulated before it enters the economizer when it still is in the liquid state.
The regulation according to these known systems, however, in some cases requires additional means to attain a satisfactory solution, and in most cases this requires the use of more than one compressor.
SUMMARY OF THE INVENTION
The object of the present invention is to attain a refrigeration system whose refrigeration capacity can be simply and reliably regulated.
According to the present invention a refrigeration system includes a continuously adjustable valve for regulating the mass flow of gaseous refrigerant through the economizer channel, which adjustable valve are governed by sensor for sensing the value of at least one parameter of the refrigerant in the closed loop, which parameter is indicative of the required refrigeration capacity.
Also according to the present invention, a method for regulating the refrigeration capacity, whereby the mass flow of gaseous refrigerant through the economizer channel is continuously regulated by adjustable valve, and whereby the value of at least one parameter of the refrigerant in said closed loop, which parameter is indicative of the required refrigeration capacity, is sensed by a sensor and the sensed value is used to govern the adjustable valve.
The presence of the adjustable valve in the channel from the economizer to the compressor is not novel as such. In the above cited U.S. Pat. No. 4,899,555 and U.S. Pat. No. 4,947,655 as well as in U.S. Pat. No. 3,827,250, U.S. Pat. No. 4,727,725 and U.S. Pat No. 4,748,831 valve means are provided in the channel, but none of these references discloses that the valve means
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Svenska Rotor Maskiner AB
Wayner William E.
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