Control system for low temperature refrigeration system

Claim 2

In a compression process for refrigeration using a mixture of refrigerants having different boiling points which process comprises the steps of compressing a vaporous mixture of refrigerants, partially condensing the compressed refrigerant vapors in a first condensation stage, separating the condensate into first liquid and first vapor phases, throttling said first liquid phase to a lower pressure, evaporating said throttled first liquid phase to absorb heat from and at least partially condense said separated first vapor phase, throttling the at least partially condensed vapors to a lower pressure, at least partially evaporating said throttled condensed vapors in an evaporator to produce the final refrigerating temperatures, mixing the refrigerant leaving said evaporator with the said throttled first liquid phase and closing the circuit by recycling the mixture of refrigerants to the compressing step, the improvement comprising by-passing the final throttling step feeding the evaporator when compression is commenced and continuing by by-pass said throttling step until the said refrigerants reach a predetermined operating condition.

Claim 3

The process of claim 1 wherein said final throttling step is by-passed until the discharge pressure is 10 to 150 psi more than the final discharge pressure of said process.

Claim 4

The process of claim 1 wherein said final throttling step is by-passed until the temperature of the refrigerant in said evaporator is within 5* to 100* F. of the lowest evaporator temperature for said process.

Claim 5

The process of claim 1 including at least one additional intermediate cooling stage subsequent to said first condensation stage and prior to separating the condensate into first liquid and first vapor phases, each said intermediate cooling step comprising the steps of separating the condensate from said first condensation stage into a vapor phase and a liquid phase, throttling the liquid phase to a lower pressure; evaporating the throttled liquid phase to absorb heat from and at least partially condense the separated vapor phase and mixing the evaporated liquid phase with said mixture of refrigerants being recycled from said final evaporator to said compressing step.

Claim 6

The process of claim 1 wherein said refRigerant mixture comprises two to six individual refrigerants.

Claim 7

The process of claim 1 in which any separated liquid phase is cooled by an exchange of heat with said recycling refrigerant returning to the compressing step prior to said evaporation of said separated and throttled liquid.

Claim 8

A compression refrigeration apparatus comprising: a. compression means for compressing a vaporous mixture of refrigerants having different boiling points; b. condenser means for at least partially condensing said compressed refrigerant vapors; c. at least one intermediate cooling stage, said stage comprising vapor-liquid separating means, throttling means for reducing the pressure on the separated liquid phase, heat exchanger means for at least partially condensing said separated vapor and evaporating said throttled liquid phase, circulation means for passing said at least partially condensed vapor to the next succeeding cooling stage, and circulation means for returning said evaporated liquid phase to said compressor means; d. final throttling means for reducing the pressure of the at least partially condensed vapors from said intermediate cooling stage; e. evaporator means for at least partially evaporating said throttled condensed vapors to produce the final refrigerating temperature; f. by-pass means interposed between said intermediate cooling stage and said evaporator said by-pass means having an open position and a closed position and adapted to move between said positions in response to predetermined operating characteristics of the refrigerants; and g. recycling means for returning the at least partially evaporated refrigerant mixture to said compressor means.

Claim 9

A compression refrigeration apparatus comprising: a. compression means for compressing a vaporous mixture of refrigerants having different boiling points; b. condenser means for at least partially condensing said compressed refrigerant vapors; c. at least one intermediate cooling stage, said stage comprising vapor-liquid separating means, throttling means for reducing the pressure on the separated liquid phase, heat exchanger means for at least partially condensing said separated vapor and evaporating said throttled liquid phase, circulation means for passing said at least partially condensed vapor to the next succeeding cooling stage, and circulation means for returning said evaporated liquid phase to said compressor means; d. final throttling means for reducing the pressure of the at least partially condensed vapors from said intermediate cooling stage; e. evaporator means for at least partially evaporating said throttled condensed vapors to produce the final refrigerating temperature; f. by-pass means interposed between said intermediate cooling stage and said evaporator said by-pass means having an open position and a closed position and adapted to move between said positions in response to predetermined operating characteristics of the refrigerants; and g. recycling means for returning the at least partially evaporated refrigerant mixture to said compressor means.

Claim 10

The apparatus of claim 7 wherein said by-pass means is a pressure actuated valve.

Claim 11

The apparatus of claim 8 wherein said valve is responsive to the discharge pressure of said apparatus.

Claim 12

The apparatus of claim 7 wherein said by-pass means is a temperature responsive valve.

Claim 13

The apparatus of claim 10 wherein said valve is a thermal expansion valve which is actuated by the evaporator temperature and pressure.

Claim 14

The apparatus of claim 7 which includes two to five successive intermediate cooling stages.

Claim 15

The apparatus of claim 7 including a series of mixing means for joining the recycling refrigerant mixture emanating from said evaporator means with the throttled separated liquid from each of said successive intermediate cooling stages prior to reaching said compression means.

Claim 16

The apparatus of claim 7 further including at least one auxiliary condenser means for permitting heat exchange between said recycling refrigerant mixture and said at least partially condensed vapors.

Claim 17

The apparatus of claim 7 further including at least one heat exchange means for permitting an exchange of heat between said separated liquid and said recycling refrigerant mixture.