Abstract: A refrigeration system includes a refrigerant vapor compression unit including a compressor and one or more current sensors to determine a total system current draw. One or more pressure sensors are positioned to determine a refrigerant pressure in the refrigerant vapor compression unit. A controller compares the current draw on the system and the refrigerant pressure to selected acceptable ranges and determines a level of refrigerant charge in the refrigerant vapor compression unit. A method of determining a level of refrigerant charge in a refrigeration system includes measuring a refrigerant pressure in the refrigeration system and sensing a current draw of the refrigeration system. A level of refrigerant charge in the refrigeration system is calculated from the refrigerant pressure and the current draw.

Abstract: A flash tank economizer includes a sensor for sensing a condition indicative of pressure in the flash tank, and when that pressure is found to equal or exceed the critical pressure of the particular refrigerant being used, a controller responsively closes a valve in the economizer vapor line to shut off the economizer. A sensor is also provided to sense the pressure at the compressor mid-stage, and if that pressure is found to exceed the pressure in the flash tank, the controller causes the flow control device to function so as to prevent the flow of refrigerant from the compressor mid-stage to the flash tank. Provision is also made for selectively draining refrigerant from the flash tank to reduce the pressure therein from a supercritical to a subcritical condition.

Abstract: A carbon dioxide refrigerant vapor compression system and method of operating that system are provided. The refrigerant vapor compression system includes a compression device, a flash tank receiver disposed in the refrigerant circuit intermediate a refrigerant heat rejection heat exchanger and a refrigerant heat absorption heat exchanger, and a compressor unload circuit including a refrigerant line establishing refrigerant flow communication between an intermediate pressure stage of the compression device and the refrigerant circuit at a location downstream of the refrigerant heat absorption heat exchanger and upstream of a suction inlet to the compression device, and a unload circuit flow control device disposed in said unload circuit refrigerant line. In response to at least one system operating parameter sensed by at least one sensor, the controller selectively positions the unload flow control device to maintain the refrigerant vapor compression system operating below a preselected high pressure limit.

Abstract: A refrigerated cargo container includes a cargo container and a refrigeration unit. A plurality of refrigerant tubes are in fluid communication with the refrigeration unit and extend along a roof of the cargo container. The plurality of refrigeration tubes are configured to convey refrigerant there through and cool an interior of the cargo container via natural convection and thermal radiation. A method of cooling a cargo in a cargo container includes flowing a refrigerant through a plurality of refrigerant tubes disposed at a roof of the cargo container. Thermal energy is transferred from container air in the container to the refrigerant thereby cooling the container air. The container air is circulated via natural convection toward the cargo thereby cooling the cargo via thermal energy transfer to the container air. The container air is recirculated toward the plurality of refrigerant tubes.

Abstract: A refrigeration system includes a refrigerant vapor compression unit including a compressor and one or more current sensors to determine a total system current draw. One or more pressure sensors are positioned to determine a refrigerant pressure in the refrigerant vapor compression unit. A controller compares the current draw on the system and the refrigerant pressure to selected acceptable ranges and determines a level of refrigerant charge in the refrigerant vapor compression unit. A method of determining a level of refrigerant charge in a refrigeration system includes measuring a refrigerant pressure in the refrigeration system and sensing a current draw of the refrigeration system. A level of refrigerant charge in the refrigeration system is calculated from the refrigerant pressure and the current draw.

Abstract: A refrigerated cargo container includes a cargo container and a refrigeration unit. A plurality of refrigerant tubes are in fluid communication with the refrigeration unit and extend along a roof of the cargo container. The plurality of refrigeration tubes are configured to convey refrigerant there through and cool an interior of the cargo container via natural convection and thermal radiation. A method of cooling a cargo in a cargo container includes flowing a refrigerant through a plurality of refrigerant tubes disposed at a roof of the cargo container. Thermal energy is transferred from container air in the container to the refrigerant thereby cooling the container air. The container air is circulated via natural convection toward the cargo thereby cooling the cargo via thermal energy transfer to the container air. The container air is recirculated toward the plurality of refrigerant tubes.

Abstract: A heat exchanger (10) is provided including at least one aluminum alloy tube (12) and a plurality of aluminum fins (26) arrayed on the aluminum alloy tube. The aluminum tube may be supported by tube sheets (24) made of aluminum alloy.

Abstract: A refrigerant vapor compression system includes a flash tank economizer defining a separation chamber is disposed in the refrigerant circuit intermediate a refrigerant heat rejection heat exchanger and a refrigerant heat absorption heat exchanger. A primary expansion valve is interdisposed in the refrigerant circuit in operative association with and upstream of the refrigerant heat absorption heat exchanger and a secondary expansion valve is interdisposed in the refrigerant circuit in operative association and upstream of the flash tank economizer. A refrigerant vapor injection line establishes refrigerant flow communication between an upper portion of the separation chamber and an intermediate pressure stage of the system's compression device and a suction pressure portion of the refrigerant circuit.

Abstract: A refrigerant vapor compression system is provided that includes a refrigerant circuit and a lubricant cooler circuit. The lubricant cooler circuit is operatively associated with the compression device for cooling a lubricant associated with the compression device and includes a heat exchanger coil disposed downstream of the refrigerant heat absorption heat exchanger with respect to the flow of heating medium. The lubricant cooler heat exchanger defines a flow path for passing the lubricant in heat exchange relationship with the cooled heating medium leaving the refrigerant heat absorption heat exchanger.

Abstract: In a method of operating a compressor at startup, the compressor is rotated in reverse for a brief period of time. The compressor is of a type that does not compress liquid when rotated in reverse. The purpose is to boil off the liquid refrigerant from the oil by heating and agitating the mixture of oil and refrigerant in the oil sump. This results in a much more benign forward start as less refrigerant is drawn into the compressor pump and the amount of oil pumped out of the compressor on start up is minimized. Also, the viscosity of oil is increased and lubrication of the bearings is improved. After a short period of time reverse rotation is stopped and the compressor can start rotating in the forward direction. The short period of time of reverse rotation is varied based upon system conditions. In one embodiment, the variation can occur by reducing the reverse run time as ambient temperature increases.

Abstract: A refrigeration circuit having a system charge and a system charge storage area. The system charge area has a condenser having a set of micro-channel heat exchanger coils. The condenser is appropriately sized to receive a first volume of the system charge. There is a compressor for compressing the system charge from an expanded state to a compressed state. There is a sealed refrigerant charge holding area fluidly connected to the condenser and the compressor. The sealed refrigerant charge holding area is appropriately sized for storing a second volume of the system charge during a system pumpdown. A receiver is fluidly connected to the sealed refrigerant charge holding area. The receiver is appropriately sized to receive a third volume of the system charge during a system pumpdown.

Abstract: An activation indicator for a refrigeration system pressure relief valve is presented. In one embodiment, the indicator comprises a covering that covers an outlet passage of the pressure relief valve. The covering is at least partially displaceable by refrigerant as it exits the refrigeration system through the pressure relief valve. In another embodiment, sensors outputting a signal transmit an altered signal when the relief device releases refrigerant. A notification device is activated to indicate that the pressure relief device has activated.

Abstract: A refrigeration unit for a shipping container exposed to end loads and rack loads. The refrigeration unit has a frame, a back panel, a plurality of structural support brackets secured to the back panel, a condenser cover secured to the plurality of structural support brackets so that the condenser cover, the plurality of structural support brackets, the frame, and the back panel form a structural member sufficient to support end loads and rack loads. The refrigeration unit also has a condenser coil having a first end and a second end, a first coil support member secured to one of the structural support brackets and secured around the first end, and a second coil support member secured to one of the structural support brackets and secured around the second end. The first and second coil support members maintain the condenser coil unstressed from the end loads and rack loads.

Abstract: A refrigerant vapor compression system includes a hot gas bypass line establishing refrigerant vapor flow communication between the compression device and the refrigerant heat absorption heat exchanger, and bypassing the refrigerant heat rejection heat exchanger and the primary expansion device. A refrigerant vapor flow control device is interdisposed in the hot gas bypass line. The flow control device has at least a first open position in which refrigerant vapor flow may pass through the hot gas bypass line and a closed position in which refrigerant vapor flow may not pass through the hot gas bypass line.

Abstract: A refrigerant vapor compression system includes a flash tank disposed in the refrigerant circuit intermediate a refrigerant heat rejection heat exchanger and a refrigerant heat absorption heat exchanger. The flash tank has a shell defining an interior volume having an upper chamber, a lower chamber and a middle chamber. A first fluid passage establishes fluid communication between the middle chamber and the upper chamber and a second fluid passage establishing fluid communication between the middle chamber and the lower chamber. An inlet port opens to the middle chamber. A first outlet port opens to the upper chamber and a second outlet port opens to the lower chamber.

Abstract: A flash tank economizer includes a sensor for sensing a condition indicative of pressure in the flash tank, and when that pressure is found to equal or exceed the critical pressure of the particular refrigerant being used, a controller responsively closes a valve in the economizer vapor line to shut off the economizer. A sensor is also provided to sense the pressure at the compressor mid-stage, and if that pressure is found to exceed the pressure in the flash tank, the controller causes the flow control device to function so as to prevent the flow of refrigerant from the compressor mid-stage to the flash tank. Provision is also made for selectively draining refrigerant from the flash tank to reduce the pressure therein from a supercritical to a subcritical condition.

Abstract: A carbon dioxide refrigerant vapor compression system and method of operating that system are provided. The refrigerant vapor compression system includes a compression device, a flash tank receiver disposed in the refrigerant circuit intermediate a refrigerant heat rejection heat exchanger and a refrigerant heat absorption heat exchanger, and a compressor unload circuit including a refrigerant line establishing refrigerant flow communication between an intermediate pressure stage of the compression device and the refrigerant circuit at a location downstream of the refrigerant heat absorption heat exchanger and upstream of a suction inlet to the compression device, and a unload circuit flow control device disposed in said unload circuit refrigerant line. In response to at least one system operating parameter sensed by at least one sensor, the controller selectively positions the unload flow control device to maintain the refrigerant vapor compression system operating below a preselected high pressure limit.

Abstract: A refrigerant vapor compression system is provided that includes a refrigerant circuit and a lubricant cooler circuit. The lubricant cooler circuit is operatively associated with the compression device for cooling a lubricant associated with the compression device and includes a heat exchanger coil disposed downstream of the refrigerant heat absorption heat exchanger with respect to the flow of heating medium. The lubricant cooler heat exchanger defines a flow path for passing the lubricant in heat exchange relationship with the cooled heating medium leaving the refrigerant heat absorption heat exchanger.

Abstract: A refrigeration circuit having a system charge and a system charge storage area. The system charge area has a condenser having a set of micro-channel heat exchanger coils. The condenser is appropriately sized to receive a first volume of the system charge. There is a compressor for compressing the system charge from an expanded state to a compressed state. There is a sealed refrigerant charge holding area fluidly connected to the condenser and the compressor. The sealed refrigerant charge holding area is appropriately sized for storing a second volume of the system charge during a system pumpdown. A receiver is fluidly connected to the sealed refrigerant charge holding area. The receiver is appropriately sized to receive a third volume of the system charge during a system pumpdown.

Abstract: A refrigerant vapor compression system includes a flash tank economizer defining a separation chamber is disposed in the refrigerant circuit intermediate a refrigerant heat rejection heat exchanger and a refrigerant heat absorption heat exchanger. A primary expansion valve is interdisposed in the refrigerant circuit in operative association with and upstream of the refrigerant heat absorption heat exchanger and a secondary expansion valve is interdisposed in the refrigerant circuit in operative association and upstream of the flash tank economizer. A refrigerant vapor injection line establishes refrigerant flow communication between an upper portion of the separation chamber and an intermediate pressure stage of the system's compression device and a suction pressure portion of the refrigerant circuit.