US 5,655,379 AGranted

Refrigerant level control in a refrigeration system

AssigneeGeneral Electric Company

InventorsHeinz Jaster, Frank Joseph Bowden

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Abstract

A refrigeration system includes a phase separator disposed in flow communication with a pulse width modulated solenoid valve. A thermistor is disposed in the phase separator and is submerged in either refrigerant liquid or refrigerant vapor during operation, with the electrical resistance thereof correspondingly changing. In an exemplary embodiment, a second thermistor is used in conjunction with the first thermistor and is disposed in the vapor inside the phase separator to provide a reference. By comparing voltage developed across the two thermistors during operation it may be determined whether one or both of the thermistors are submersed in the vapor. The duty cycle of the valve may therefore be increased when one of the thermistors is submerged in the liquid, and decreased when both thermistors are submersed in the vapor.

Claims9

Dependent claims

A refrigeration system having refrigerant level control capabilities comprising:

an evaporator;
a phase separator coupled to said evaporator via a conduit, said phase separator having an upper portion and a lower portion for containing a refrigerant in two phases, a liquid refrigerant disposed at a variable level therein and a vapor refrigerant disposed above said liquid level;
a control valve disposed in said conduit so as to control flow of said liquid refrigerant therethrough;
a first temperature sensor disposed in said upper portion of said phase separator for exposure to said vapor refrigerant;
a second temperature sensor disposed in said lower portion of said phase separator for alternative exposure to either said liquid refrigerant or vapor refrigerant as said liquid level varies;
a controller coupled to said control valve, to said first temperature sensor, and to said second temperature sensor wherein said controller senses a relative change in temperature between said first and second temperature sensors and, responsive to the sensed relative change said controller generates a control signal to said control valve to vary the duty cycle of said control valve;
and
said controller being adapted to generate said control signal to said control valve so as to decrease the duty cycle of said valve when said sensed relative change in temperature between said first and second temperature sensors is approximately zero and so as to increase the duty cycle of said valve when said sensed relative change in temperature between said first and second temperature sensors is relatively large compared to said value that is approximately zero.

5 more elements

A refrigeration system comprising:

a compressor, a condenser, a phase separator, a pulse width modulated solenoid valve, and an evaporator disposed in serial flow communication in a closed loop for circulating a refrigerant therethrough;
said phase separator including said refrigerant in two phases, with refrigerant liquid being disposed at a variable level therein, and refrigerant vapor being disposed above said liquid level;
a first thermistor disposed in a lower portion of said phase separator for being submerged in said liquid or vapor as said liquid level varies;
a reference second thermistor disposed in an upper portion of said phase separator for being submerged in said vapor;
a controller operatively coupled to said valve and said first and said second thermistors, and being effective for increasing duty cycle of said valve upon sensed increase in said liquid level, and decreasing said duty cycle upon sensed decrease in said liquid level;
a first means operatively coupled to said first and second thermistors for measuring said change in electrical resistance and producing a change signal indicative thereof;
a second means operatively joined to said first means for producing a liquid level signal indicative of said liquid level;
third means for generating a periodic ramp signal;
and
fourth means operatively coupled to said second and third means for receiving said level and ramp signal, and being effective for producing a pulse width modulated control signal having a long pulse to increase said duty cycle, and a short pulse relative to said long pulse to decrease said duty cycle, and said fourth means being operatively joined to said valve for controlling refrigerant flowrate therethrough;
and
said first means is operatively coupled to both said first and second thermistors so that said change signal has a low value when both said first and second thermistors are submerged in said vapor, and a high value relative to said low value when said first thermistor is submerged in said liquid and said second thermistor is submerged in said vapor.

9 more elements

Dependencies are inferred from the claim text.