US 4,112,703 AGranted

Refrigeration control system

AssigneeBorg-Warner Corporation

InventorKenneth John Kountz

Life of this patent

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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 actuation of an electromechanical valve, such as a solenoid valve, interposed between the condenser and evaporator in the refrigeration system, the valve also serving as the system's expansion device. 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.

Claims18

Dependent claims

In a refrigeration system where refrigerant flows through a closed vapor cycle refrigeration circuit having in series an evaporator, a compressor and a condenser, a control system for controlling the operation of the refrigeration system to vary the effectiveness 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, including a first thermistor, for providing a space temperature electrical signal representing the actual ambient temperature in the space to be temperature controlled;
means, including a potentiometer, for providing a temperature set point electrical signal representing the desired temperature for the temperature controlled space;
means, including a second thermistor positioned adjacent to the evaporator outlet, for providing an evaporator outlet temperature electrical signal representing the actual temperature of the refrigerant at the evaporator outlet;
an electromechanical valve included in series with the refrigeration circuit between the condenser and evaporator for controlling the refrigerant flow rate through the circuit, said electromechanical valve also functioning as the expansion device in the refrigeration circuit;
and control means responsive to said space temperature electrical signal, said temperature set point electrical signal, and said evaporator outlet temperature electrical signal for varying the actuation of said electromechanical valve to modulate the refrigerant flowing through the evaporator to adjust the refrigerant temperature at the evaporator outlet to vary the evaporator effectiveness as required to maintain the controlled space at the desired temperature.

2 more elements

In a refrigeration system where refrigerant flows through a closed vapor cycle refrigeration circuit having in series an evaporator, a compressor and a condenser, a control system for regulating the refrigerant flow rate through the evaporator to vary the evaporator effectiveness 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 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;
an electromechanical valve included in series with the refrigeration circuit between the condenser and evaporator for controlling the refrigerant flow rate through the circuit;
and means responsive to said error signal for actuating said electromechanical valve 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.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/754,194Filed 27 Dec 1976
Granted: 12 Sep 1978
Term ends: Not estimatedThe source records don’t support an estimate.

Classification13 codes

B60H 1/3211
Control means therefor: for increasing the efficiency of a vehicle refrigeration cycle
F25B 41/347
By solenoids: with the valve member being opened and closed cyclically, e.g. with pulse width modulation
F25B 49/02
Arrangement or mounting of control or safety devices: for compression type machines, plants or systems
G05D 23/1931
Sensing the temperaure in different places in thermal relationship with one or more spaces: to control the temperature of one space