A refrigeration system includes a compressor having a first stage and a second stage; a heat rejecting heat exchanger including an inter-cooler and a gas cooler, the intercooler coupled to an outlet of the first stage and the gas cooler coupled to an outlet of the second stage; an unload valve coupled to an outlet of the intercooler and a suction port of the first stage; a flash tank coupled to an outlet of the gas cooler; a primary expansion device coupled to an outlet of the flash tank; a heat absorbing heat exchanger coupled to an outlet of the primary expansion device, an outlet of the heat absorbing heat exchanger coupled to the suction port of the first stage; and a controller for executing a startup process including controlling the unload valve to direct refrigerant from the intercooler to the suction port of the first stage.

A vapor compression system that includes a reheat coil that heats a supply air stream flowing across the reheat coil with a refrigerant. A fan forces an environmental air flow across a condenser to remove energy from the refrigerant. A controller adjusts a speed of the fan to control a flow of the refrigerant through the reheat coil.

A coolant cycle system for cooling a structure includes a two stage compressor configured to compress a coolant. The two stage compressor has a first stage with a first stage inlet and a first stage outlet and a second stage with a second stage inlet and a second stage outlet. The second stage is a high pressure stage relative to the first stage. A gas cooler has a coolant inlet fluidly connected to the second stage outlet and has a gas cooler outlet. The gas cooler outlet is fluidly connected to a heat exchanger and a fluid storage tank. The heat exchanger is configured to cool the fluid storage tank and has a heat exchanger coolant outlet fluidly connected to the second stage inlet. The fluid storage tank has a fluid storage tank outlet fluidly connected to a coolant inlet of an evaporator. A coolant outlet of the evaporator is fluidly connected to the first stage inlet of the compressor. The first stage outlet of the compressor is fluidly connected to the second stage inlet.

A predictive failure system for a cooling apparatus having sensors measuring operational components of a cooling apparatus to determine performance data and means to analyze the data to determine a performance profile, wherein anomalies in the performance profile are determined and the operator of the cooling apparatus is warned prior to failure of the operational components.

A refrigeration system includes a gas cooler/condenser configured to remove heat from a refrigerant, a temperature sensor configured to measure a temperature of the refrigerant leaving the gas cooler/condenser, a pressure sensor located along the high pressure conduit and configured to measure a pressure of the refrigerant leaving the gas cooler/condenser, a pressure control valve operable to regulate the pressure of the refrigerant leaving the gas cooler/condenser, and a controller. The controller is configured to determine whether the refrigerant leaving the gas cooler/condenser is in a subcritical region based on at least one of the measured temperature of the refrigerant or the measured pressure of the refrigerant. If the refrigerant leaving the gas cooler/condenser is not in the subcritical region, the controller is configured to add a pseudo-subcooling temperature value to the measured temperature of the refrigerant to calculate a summed temperature, calculate a supercritical pseudo-saturated pressure as a function of the summed temperature, and operate the pressure control valve to drive the pressure of the refrigerant leaving the gas cooler/condenser to the supercritical pseudo-saturated pressure corresponding to the summed temperature.

A refrigeration system includes a gas cooler/condenser configured to remove heat from a refrigerant, a temperature sensor configured to measure a temperature of the refrigerant leaving the gas cooler/condenser, a pressure sensor located along the high pressure conduit and configured to measure a pressure of the refrigerant leaving the gas cooler/condenser, a pressure control valve operable to regulate the pressure of the refrigerant leaving the gas cooler/condenser, and a controller. The controller is configured to determine whether the refrigerant leaving the gas cooler/condenser is in a subcritical region based on at least one of the measured temperature of the refrigerant or the measured pressure of the refrigerant. If the refrigerant leaving the gas cooler/condenser is not in the subcritical region, the controller is configured to add a pseudo-subcooling temperature value to the measured temperature of the refrigerant to calculate a summed temperature, calculate a supercritical pseudo-saturated pressure as a function of the summed temperature, and operate the pressure control valve to drive the pressure of the refrigerant leaving the gas cooler/condenser to the supercritical pseudo-saturated pressure corresponding to the summed temperature.

A coolant cycle system for cooling a structure includes a two stage compressor configured to compress a coolant. The two stage compressor has a first stage with a first stage inlet and a first stage outlet and a second stage with a second stage inlet and a second stage outlet. The second stage is a high pressure stage relative to the first stage. A gas cooler has a coolant inlet fluidly connected to the second stage outlet and has a gas cooler outlet. The gas cooler outlet is fluidly connected to a heat exchanger and a fluid storage tank. The heat exchanger is configured to cool the fluid storage tank and has a heat exchanger coolant outlet fluidly connected to the second stage inlet. The fluid storage tank has a fluid storage tank outlet fluidly connected to a coolant inlet of an evaporator. A coolant outlet of the evaporator is fluidly connected to the first stage inlet of the compressor. The first stage outlet of the compressor is fluidly connected to the second stage inlet.

A predictive failure system for a cooling apparatus having sensors measuring operational components of a cooling apparatus to determine performance data and means to analyze the data to determine a performance profile, wherein anomalies in the performance profile are determined and the operator of the cooling apparatus is warned prior to failure of the operational components.

In certain embodiments, a transcritical refrigeration system provides refrigeration by circulating carbon dioxide (CO.sub.2) refrigerant through the system. A flash tank of the transcritical refrigeration system is operable to supply the CO.sub.2 refrigerant, in liquid form, to a low temperature refrigeration case and a medium temperature refrigeration case. A low temperature compressor is operable to compress the CO.sub.2 refrigerant discharged from the low temperature refrigeration case. A medium temperature compressor, a parallel compressor, and an ejector are each operable to compress the CO.sub.2 refrigerant discharged from the medium temperature refrigeration case, the CO.sub.2 refrigerant discharged from the low temperature compressor, and/or CO.sub.2 flash gas discharged from the flash tank. A gas cooler is operable to cool the CO.sub.2 refrigerant discharged from the medium temperature compressor and the parallel compressor. A controller is operable to dynamically adjust a pressure set point for the flash tank.

A vehicle air conditioning apparatus is provided that can prevent temperature variations of the air after the heat exchange in a radiator to reliably control the temperature of the air supplied to the vehicle interior. During the heating operation and the heating and dehumidifying operation, target degree of supercooling SCt when target air-blowing temperature TAO is a predetermined temperature or higher is set to SCt1 that is greater than SCt2 when the target air-blowing temperature TAO is lower than the predetermined temperature. When amount of air Ga supplied from indoor fan 12 is lower than a predetermined value, the target degree of supercooling SCt is corrected, which is set such that the degree of supercooling is lower than target degree of supercooling corrected when the amount of air Ga supplied from the indoor fan 12 is a predetermined value or higher.