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 condenser and an automatic expansion device, a control system for regulating the refrigerant flow rate through 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, including a first 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 temperature control point signal which represents a desired evaporator refrigerant outlet temperature, referenced with respect to a predetermined desired minimum evaporator outlet temperature;
means, including a second temperature sensor positioned adjacent to the evaporator outlet, for providing an evaporator outlet temperature signal representing the actual temperature of the refrigerant at the evaporator outlet;
means responsive to said temperature control point signal and to said evaporator outlet temperature signal for providing an error signal which varies as a function of the difference between the desired control point temperature and the actual evaporator outlet temperature;
and means responsive 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 outlet temperature at said control point, thereby to maintain the controlled space at the desired temperature.
1 Assignment
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Accused Products
Abstract
A controlled space is maintained at a desired set point temperature by adjusting the refrigerant temperature at the evaporator outlet in a refrigeration system, thereby controlling the evaporator effectiveness or capacity which is inversely proportional to the outlet temperature. When the space temperature tends to vary from the desired set point due to a changing heat load, the control system automatically changes the refrigerant flow through the evaporator to establish the evaporator outlet temperature at the control point required 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; and in response to a drop below the set point, the refrigerant flow decreases. Such control of the flow rate 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 controlled in order to hold the evaporator outlet temperature fixed at the required control point.
90 Citations
14 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 condenser and an automatic expansion device, a control system for regulating the refrigerant flow rate through 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, including a first 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 temperature control point signal which represents a desired evaporator refrigerant outlet temperature, referenced with respect to a predetermined desired minimum evaporator outlet temperature; means, including a second temperature sensor positioned adjacent to the evaporator outlet, for providing an evaporator outlet temperature signal representing the actual temperature of the refrigerant at the evaporator outlet; means responsive to said temperature control point signal and to said evaporator outlet temperature signal for providing an error signal which varies as a function of the difference between the desired control point temperature and the actual evaporator outlet temperature; and means responsive 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 outlet temperature at said control point, thereby to maintain the controlled space at the desired temperature. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification