Multi-stage refrigeration apparatus and method

Claim 11

The method of claim 5, further including the step of continually adjusting the capacity of the second compressor so as to minimize the combined energy consumed by the compressors.

Claim 14

A method of achieving refrigeration as described in claim 6, further including the steps of controlling the speed of the third compressor so that the energy consumed by the compressors in the system is minimum.

Claim 15

A closed loop refrigeration system having a reservoir containing therein liquid and gaseous refrigerant at an intermediate pressure, comprising; (a) an evaporator having an inlet and outlet end, the evaporator connected to the reservoir at the inlet end for receiving liquid refrigerant therefrom and expanding it to a low pressure gaseous state; (b) a first compressor connected between the reservoir and the evaporator for compressing the low pressure gaseous refrigerant to the intermediate pressure and discharging it into the liquid contained in the reservoir; (c) a second compressor having an inlet and outlet end, the inlet end of the compressor connected to the reservoir, the compressor compressing the gaseous refrigerant from the reservoir to a condensing high pressure; (d) a condenser having an inlet and outlet end, the inlet end of the condenser connected to the outlet end of the second compressor for receiving high pressure gaseous refrigerant therefrom, the condenser condensing the high pressure gaseous refrigerant into a liquid; and (e) a control valve connected between the outlet end of the condenser and the reservoir for controllably discharging the liquid refrigerant from the condenser to the reservoir.

Claim 16

A closed loop refrigeration system having a reservoir containing therein liquid and gaseous refrigerant at an intermediate pressure, comprising; (a) an evaporator having an inlet and outlet end, the evaporator connected to the reservoir at the inlet end for receiving liquid refrigerant therefrom and expanding it to a low pressure gaseous state; (b) a first compressor connected between the reservoir and the evaporator for compressing the low pressure gaseous refrigerant to the intermediate pressure and discharging it into the liquid contained in the reservoir; (c) a second compressor having an inlet and outlet end, the inlet end of the compressor connected to the reservoir, the compressor compressing the gaseous refrigerant from the reservoir to a condensing high pressure; (d) a condenser having an inlet and outlet end, the inlet end of the condenser connected to the outlet end of the second compressor for receiving high pressure gaseous refrigerant therefrom, the condenser condensing the high pressure gaseous refrigerant into a liquid; and (e) a control valve connected between the outlet end of the condenser and the reservoir for controllably discharging the liquid refrigerant from the condenser to the reservoir.

Claim 17

The refrigeration system of claim 9 further comprising: (a) temperature sensors for generating electrical signals representative of the condenser liquid refrigerant and ambient temperatures; and (b) a micro-controller circuit electrically coupled to the sensors for receiving the electrical signals and computing the temperature difference between the liquid condenser and ambient temperatures, the micro-controller circuit also connected to the control valve for controlling the liquid refrigerant flow therethrough, said micro-controller circuit causing the control valve to increase the liquid refrigerant flow therethrough when the temperature difference is below a predetermined value and to decrease the flow when the temperature difference is above the predetermined value.

Claim 18

The system of claim 10 wherein the microprocessor is also connected to the second compressor, said micro-controller circuit continually adjusting the capacity of the second compressor so as to maintain the energy consumed by the first and second compressors at a minimum.

Claim 19

A refrigeration system having a reservoir which contains liquid and gaseous refrigerant at a pressure P i , comprising: (a) a first and second evaporator connected to the reservoir for receiving separate amounts of liquid refrigerant from the reservoir, said first and second evaporators expanding the liquid refrigerant to gaseous refrigerant at pressures P 1 and P m respectively, where P l <P m <P i ; (b) a first and second compressor, each having an inlet and outlet end, the inlet ends respectively connected to the first and second evaporators for receiving gaseous refrigerant from their respective evaporators, said first and second compressors compressing the gaseous refrigerant from their respective evaporators to pressures P i and a condensing high pressure P h respectively, where P p <P i , said first compressor discharging the gaseous refrigerant at pressure P i to the reservoir; (c) a third compressor having an inlet and outlet end, the inlet end of the third compressor connected to the reservoir for receiving gaseous refrigerant from the reservoir and compressing it to the high condensing pressure P h ; (d) a condenser having an inlet and outlet end, the inlet end of the condenser connected to the outlet ends of the second and third compressors, said condenser receiving the gaseous refrigerant from the second and third condensers and condensing it to a liquid; and (e) a flow control valve connected to the outlet end of the condenser and the reservoir for controllably discharging the liquid refrigerant from the condenser to the reservoir.

Claim 20

A refrigeration system having a reservoir which contains liquid and gaseous refrigerant at a pressure P i , comprising: (a) a first and second evaporator connected to the reservoir for receiving separate amounts of liquid refrigerant from the reservoir, said first and second evaporators expanding the liquid refrigerant to gaseous refrigerant at pressures P 1 and P m respectively, where P l <P m <P i ; (b) a first and second compressor, each having an inlet and outlet end, the inlet ends respectively connected to the first and second evaporators for receiving gaseous refrigerant from their respective evaporators, said first and second compressors compressing the gaseous refrigerant from their respective evaporators to pressures P i and a condensing high pressure P h respectively, where P p <P i , said first compressor discharging the gaseous refrigerant at pressure P i to the reservoir; (c) a third compressor having an inlet and outlet end, the inlet end of the third compressor connected to the reservoir for receiving gaseous refrigerant from the reservoir and compressing it to the high condensing pressure P h ; (d) a condenser having an inlet and outlet end, the inlet end of the condenser connected to the outlet ends of the second and third compressors, said condenser receiving the gaseous refrigerant from the second and third condensers and condensing it to a liquid; and (e) a flow control valve connected to the outlet end of the condenser and the reservoir for controllably discharging the liquid refrigerant from the condenser to the reservoir.

Claim 21

The refrigeration system of claim 9 further comprising a control circuit electrically coupled to both the compressors for continually controlling the capacity of one of the compressors so as to minimize the combined energy consumed by the compressors.

Claim 22

The refrigeration system of claim 12, wherein the control circuit is a microprocessor based circuit.

Claim 23

The refrigeration system of claim 12 further comprising: (a) a first temperature sensor connected to the condenser for providing an electrical signal representative of the liquid refrigerant temperature therein; (b) a second temperature sensor placed near the condenser for providing an electrical signal representative of the ambient temperature; and (c) a control circuit electrically coupled to the first and second temperature sensor, said control circuit determining the temperature difference between the ambient temperature and the condensed liquid refrigerant temperature and causing the control valve to increase the liquid discharge therethrough when the temperature difference is below a predetermined valve and decreasing the discharge when the temperature difference is greater than the predetermined value.

Claim 24

The refrigeration system of claim 12 further comprising: (a) a pressure transducer connected to the reservoir for providing an electrical signal representative of the intermediate pressure; (b) a first watt transducer connected to the first compressor for providing an electrical signal corresponding to the energy consumed by the first compressor; (c) a second watt transducer connected to the third compressor for providing an electrical signal corresponding to the energy consumed by the third compressor; (d) a control circuit connected to the pressure transducer, the first and second watt transducers, and the third compressor, said control circuit computing the combined energy consumed by the first and second compressors and in response thereto adjusting the speed of the second compressor so that the combined energy consumption is the least.

Claim 25

A control circuit for optimizing energy consumption in a two compression stage closed loop refrigeration system wherein a first compressor in the first stage compresses a gaseous refrigerant from a low pressure to an intermediate pressure while a second compressor in the second stage compresses the gaseous refrigerant from the intermediate to a high condenser pressure, comprising a control circuit which includes: (a) a circuit electrically coupled to the first and second compressors for increasing and decreasing the capacity of one of the compressors; (b) a circuit electrically connected to the compressors for measuring the combined energy consumed by the first and second compressors each time the speed of a compressor is charged; (c) a comparator for comparing the combined energy consumption between the successive energy consumption measurements; and (d) a decision making circuit coupled to the comparator and the compressors for increasing and decreasing the capacity of one of the compressors as a function of the successive energy consumption measurements.

Claim 26

A control circuit for optimizing energy consumption in a two compression stage closed loop refrigeration system wherein a first compressor in the first stage compresses a gaseous refrigerant from a low pressure to an intermediate pressure while a second compressor in the second stage compresses the gaseous refrigerant from the intermediate to a high condenser pressure, comprising a control circuit which includes: (a) a circuit electrically coupled to the first and second compressors for increasing and decreasing the capacity of one of the compressors; (b) a circuit electrically connected to the compressors for measuring the combined energy consumed by the first and second compressors each time the speed of a compressor is charged; (c) a comparator for comparing the combined energy consumption between the successive energy consumption measurements; and (d) a decision making circuit coupled to the comparator and the compressors for increasing and decreasing the capacity of one of the compressors as a function of the successive energy consumption measurements.

Claim 29

The method of claim 19 further comprising the step of compressing the gas from the reservoir and discharging that compressed gas into the condenser.

Claim 30

A refrigeration system having a reservoir for holding liquid and gas refrigerants, comprising: (a) a first evaporator coupled to the reservoir for receiving the liquid refrigerant therefrom and evaporating that refrigerant to a gas; (b) a condenser for condensing a gas refrigerant into a liquid refrigerant and discharging the liquid refrigerant into the reservoir; (c) a first compressor coupled to the first evaporator for compressing gas from the first evaporator and discharging that compressed gas into the condenser; (d) a second evaporator coupled to the reservoir for receiving the liquid refrigerant from the reservoir and evaporating that liquid refrigerant into a gas; (e) a second compressor coupled to the second evaporator and the reservoir for compressing the gas from the second evaporator and discharging that compressed gas into the reservoir; and (f) a third compressor coupled to the reservoir for compressing the gas from the reservoir and discharging that compressed gas into the condenser.

Claim 31

A refrigeration system having a reservoir for holding liquid and gas refrigerants, comprising: (a) a first evaporator coupled to the reservoir for receiving the liquid refrigerant therefrom and evaporating that refrigerant to a gas; (b) a condenser for condensing a gas refrigerant into a liquid refrigerant and discharging the liquid refrigerant into the reservoir; (c) a first compressor coupled to the first evaporator for compressing gas from the first evaporator and discharging that compressed gas into the condenser; (d) a second evaporator coupled to the reservoir for receiving the liquid refrigerant from the reservoir and evaporating that liquid refrigerant into a gas; (e) a second compressor coupled to the second evaporator and the reservoir for compressing the gas from the second evaporator and discharging that compressed gas into the reservoir; and (f) a third compressor coupled to the reservoir for compressing the gas from the reservoir and discharging that compressed gas into the condenser.

Claim 32

A closed loop refrigeration system having a receiver for holding a refrigerant in liquid and gaseous states, comprising: (a) a condenser coupled to the receiver for condensing compressed gas refrigerant into a liquid refrigerant and discharging the liquid refrigerant into the receiver; (b) an evaporator coupled to the receiver for receiving the liquid refrigerant therefrom and evaporating that liquid refrigerant to a gas; and (c) a compressor coupled to the receiver and the evaporator for compressing the gas refrigerant from the evaporator and discharging that compressed gas into the liquid contained in the receiver.

Claim 33

A closed loop refrigeration system having a receiver for holding a refrigerant in liquid and gaseous states, comprising: (a) a condenser coupled to the receiver for condensing compressed gas refrigerant into a liquid refrigerant and discharging the liquid refrigerant into the receiver; (b) an evaporator coupled to the receiver for receiving the liquid refrigerant therefrom and evaporating that liquid refrigerant to a gas; and (c) a compressor coupled to the receiver and the evaporator for compressing the gas refrigerant from the evaporator and discharging that compressed gas into the liquid contained in the receiver.