Temperature control system for refrigeration apparatus
First Claim
1. In a refrigeration system where refrigerant flows through a closed vapor cycle refrigeration circuit having an evaporator, a controlled displacement compressor, a condensor and a thermostatic expansion device, a control system for controlling the operation of the refrigeration system to vary the evaporator boiling pressure, and consequently the capacity of the evaporator, in order to maintain a substantially constant desired temperature in a space to which cooled air is supplied by the refrigeration system, comprising:
- means for providing a space temperature signal representing the actual ambient temperature in the space to be temperature controlled;
means for providing a temperature set point signal representing the desired temperature for the temperature controlled space;
means for providing an evaporator pressure signal representing the actual pressure of the refrigerant flowing through the evaporator;
and control means responsive to said space temperature signal, said temperature set point signal, and said evaporator pressure signal for varying the displacement of the controlled displacement compressor to modulate the refrigerant flowing through the evaporator to adjust the evaporator boiling pressure to vary the evaporator capacity as required to maintain the controlled space at the desired temperature.
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Accused Products
Abstract
A controlled space is maintained at a desired set point temperature by adjusting the evaporator boiling pressure in a refrigeration system, thereby controlling the evaporator capacity (namely, the amount of cooling imparted to the air supplied to the space) which is inversely proportional to the evaporator boiling pressure. When the space temperature tends to vary from the desired set point due, for example, to a changing heat load, the control system automatically changes the refrigerant flow through the evaporator to establish the evaporator boiling pressure (and hence the boiling temperature) at the control point required to cool the air sufficiently to maintain the controlled space at the desired temperature. More specifically, in response to a space temperature increase, the flow rate of the refrigerant increases to decrease the evaporator boiling pressure; and in response to a drop below the set point, the refrigerant flow decreases to increase the evaporator boiling pressure. Such control of the flow rate, and consequently the evaporator boiling pressure, is achieved by varying the displacement of a controlled displacement compressor included in the refrigeration system. When the heat load on the evaporator is constant, the refrigerant flow is automatically controlled in order to hold the evaporator boiling pressure fixed at the required control point.
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Citations
23 Claims
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1. In a refrigeration system where refrigerant flows through a closed vapor cycle refrigeration circuit having an evaporator, a controlled displacement compressor, a condensor and a thermostatic expansion device, a control system for controlling the operation of the refrigeration system to vary the evaporator boiling pressure, and consequently the capacity of the evaporator, in order to maintain a substantially constant desired temperature in a space to which cooled air is supplied by the refrigeration system, comprising:
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means for providing a space temperature signal representing the actual ambient temperature in the space to be temperature controlled; means for providing a temperature set point signal representing the desired temperature for the temperature controlled space; means for providing an evaporator pressure signal representing the actual pressure of the refrigerant flowing through the evaporator; and control means responsive to said space temperature signal, said temperature set point signal, and said evaporator pressure signal for varying the displacement of the controlled displacement compressor to modulate the refrigerant flowing through the evaporator to adjust the evaporator boiling pressure to vary the evaporator capacity as required to maintain the controlled space at the desired temperature. - View Dependent Claims (2, 3, 4, 5)
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6. In a refrigeration system where refrigerant flows through a closed vapor cycle refrigeration circuit having an evaporator, a controlled displacement compressor, a condenser and a thermostatic expansion device, a control system for regulating the refrigerant flow rate through the evaporator to vary the evaporator boiling pressure, and consequently the evaporator capacity, in order to maintain a substantially constant desired temperature in a space to which cooled air is supplied by the refirgeration system, comprising:
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means, including a temperature sensor located in the space to be temperature controlled, for providing a space temperature signal representing the actual ambient temperature therein; means, including an adjustable device, for providing a temperature set point signal representing the desired temperature for the temperature controlled space; means responsive to said space temperature signal and to said temperature set point signal for providing a pressure control point signal which represents a desired evaporator boiling pressure, referenced with respect to a predetermined desired minimum evaporator boiling pressure; means for providing an evaporator pressure signal representing the actual pressure of the refrigerant flowing through the evaporator; means responsive to said pressure control point signal and to said evaporator pressure signal for providing an error signal which varies as a function of the difference between the desired control point pressure and the actual evaporator pressure; and means reponsive to said error signal for varying the displacement of the controlled displacement compressor to modulate the refrigerant flowing through the evaporator to establish the evaporator boiling pressure at the desired control point, thereby to maintain the controlled space at the desired temperature. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification