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To address the problem of lubricant entrainment within the refrigerant system components such as an evaporator and suction line, a control is provided to periodically, substantially and intermittently increase the refrigerant flow through these components to thereby carry the trapped lubricant back

To address the problem of lubricant entrainment within the refrigerant system components such as an evaporator and suction line, a control is provided to periodically, substantially and intermittently increase the refrigerant flow through these components to thereby carry the trapped lubricant back to the compressor. The increased flow of refrigerant can be accomplished by periodically throttling and then unthrottling either an expansion device or a suction modulation valve to cause instantaneous pressure buildup within a respective section of the vapor compression system and subsequent increase of the refrigerant flow through the above-referenced components such as an evaporator and suction line. Suggested time intervals of both the throttling and unthrottling states are provided, as well as the frequency of occurrence for subsequent oil return cycles.

대표청구항 ▼

1. A method of operating a refrigerant system having a compressor, a condenser, an expansion device, an evaporator and a suction modulation valve, comprising the steps of: operating the system in a normal conventional mode of operation to provide refrigerant flow through the evaporator at a normal r

1. A method of operating a refrigerant system having a compressor, a condenser, an expansion device, an evaporator and a suction modulation valve, comprising the steps of: operating the system in a normal conventional mode of operation to provide refrigerant flow through the evaporator at a normal rate determined by a thermal demand on the refrigerant system; andperiodically, substantially and intermittently increasing the flow of refrigerant through the evaporator such that the flow rate exceeds the normal flow rate to thereby flush out lubricant that has been entrained in the evaporator or suction line wherein said step of increasing the refrigerant flow is accomplished by first throttling one of the expansion device and the suction modulation valve and unthrottling the other of the expansion device and the suction modulation valve to temporarily build up pressure in the condenser and then unthrottling the throttled one of the expansion device and the suction modulation valve to provide a blast of refrigerant through the evaporator. 2. The method as set forth in claim 1 wherein said step of increasing the refrigerant flow is accomplished by first throttling the suction modulation valve and unthrottling the expansion device to build up pressure in the evaporator and then unthrottling the suction modulation valve to cause a blast of refrigerant through the evaporator. 3. The method as set forth in claim 1 wherein said step of increasing the refrigerant flow is accomplished by first throttling the expansion device and unthrottling the suction modulation valve to build up pressure in the condenser and then unthrottling the expansion device to cause a blast of refrigerant through the evaporator. 4. The method as set forth in claim 3 wherein the throttling position of the expansion device corresponds to a fully closed position. 5. The method as set forth in claim 3 wherein the unthrottling position of the expansion device corresponds to a fully open position. 6. The method as set forth in claim 2 wherein the throttling position of the suction modulation valve corresponds to a fully closed position. 7. The method as set forth in claim 2 wherein the unthrottling position of the suction modulation valve corresponds to a fully open position. 8. The method as set forth in claim 1 wherein initiation of an oil return cycle is determined based on a timer setting. 9. The method as set forth in claim 1 wherein initiation of an oil return cycle is determined based on refrigerant system operational and environmental parameters. 10. The method as set forth in claim 9 wherein said operational and environmental parameters are selected from the group consisting of a compressor suction pressure, saturation suction temperature, compressor suction temperature, compressor discharge pressure, compressor saturation discharge temperature, compressor discharge temperature, ambient temperature, indoor temperature, compressor current, compressor power draw. 11. The method as set forth in claim 3 wherein the expansion device is throttled for a period of 1-5 seconds. 12. The method as set forth in claim 3 wherein the expansion device is unthrottled for a period of 10-30 seconds. 13. The method as set forth in claim 3 wherein said throttling and unthrottling steps of the expansion device are repeated 1-10times in succession. 14. The method as set forth in claim 3 further including the steps of repeating the oil return process every 2-5 hours. 15. The method as set forth in claim 2 wherein the suction modulation valve is throttled for a period of 1-5 seconds. 16. The method as set forth in claim 2 wherein the suction modulation valve is unthrottled for a period of 10-30 seconds. 17. The method as set forth in claim 2 wherein said throttling and unthrottling steps are repeated 1-10 times in succession. 18. The method as set forth in claim 2 and including the steps of repeating the oil return process every 2-5 hours. 19. A vapor compression system, comprising: a compressor for receiving refrigerant vapor with lubricant entrained therein and compressing the refrigerant vapor;a condenser for receiving the compressed refrigerant vapor with lubricant entrained therein and condensing at least a portion of the refrigerant vapor;an expansion device for receiving the condensed refrigerant with lubricant entrained therein and expanding the refrigerant to a lower pressure and temperature;an evaporator for receiving the refrigerant with the lubricant entrained therein from the expansion device and passing it to the compressor while retaining a portion of the lubricant;a suction modulation valve disposed in a suction line establishing refrigerant flow communication between the evaporator and the compressor; anda control for causing a periodic, substantial and intermittent increase in the flow of refrigerant through the evaporator to flush out lubricant that has entrained therein, said control operative to provide a blast of refrigerant through the evaporator by first throttling one of the expansion device and the suction modulation valve and unthrottling the other of the expansion device and the suction modulation valve and then unthrottling the throttled one of the expansion device and the suction modulation valve. 20. A method of operating a vapor compression system including a compressor, a condenser, an expansion device and an evaporator, wherein a lubricant is entrained within the refrigerant and the refrigerant and lubricant mixture is circulated throughout the system, comprising the step of: periodically providing a blast of refrigerant through the evaporator by causing a substantial increase in the refrigerant flow rate through the evaporator to remove lubricant that has entrained therein by first throttling the expansion device to temporarily build up pressure in the condenser and then unthrottling the expansion device. 21. The method as set forth in claim 20 wherein the expansion device is throttled for a period of 1-5 seconds. 22. The method as set forth in claim 20 wherein the expansion device is unthrottled for a period of 10-30 seconds. 23. The method as set forth in claim 20 wherein said throttling and unthrottling steps of the expansion device are repeated 1-10 times in succession. 24. The method as set forth in claim 20 wherein said expansion device is opened for a period of 20-40 seconds. 25. A method of operating a vapor compression system including a compressor, a condenser, an expansion device, an evaporator and a suction modulation valve, wherein a lubricant is entrained within the refrigerant and the refrigerant and lubricant mixture is circulated throughout the system, comprising the step of: periodically providing a blast of refrigerant through the evaporator by causing a substantial increase in the refrigerant flow rate through the evaporator to remove lubricant that has entrained therein, wherein said step of increasing the refrigerant flow is accomplished by one of first throttling the suction modulation valve to build up pressure in the evaporator and then unthrottling the suction modulation valve and first throttling the expansion device to build up pressure in the condenser and then unthrottling the expansion device. 26. The method as set forth in claim 25 wherein said step of increasing the refrigerant flow is accomplished by first throttling the suction modulation valve and unthrottling the expansion device to build up pressure in the evaporator and then unthrottling the suction modulation valve to cause a blast of refrigerant through the evaporator. 27. The method as set forth in claim 25 wherein said step of increasing the refrigerant flow is accomplished by first throttling the expansion device and unthrottling the suction modulation valve to build up pressure in the condenser and then unthrottling the expansion device to cause a blast of refrigerant through the evaporator. 28. The method as set forth in claim 25 further including the steps of repeating the oil return process every 2-5 hours. 29. The method as set forth in claim 26 wherein the suction modulation valve is throttled for a period of 1-5 seconds. 30. The method as set forth in claim 26 wherein said suction modulation valve is unthrottled for a period of 10-30 seconds. 31. The method as set forth in claim 25 wherein said throttling and unthrottling steps of the suction modulation valve are repeated 1-10 times in succession. 32. The method as set forth in claim 25 further including the steps of repeating the oil return process every 2-5 hours. 33. The method as set forth in claim 25 wherein the suction modulation valve is opened for a period of 20-40 seconds.