A system and method are disclosed for cooling ambient air to be supplied as combustion air to a gas turbine. The system comprises a closed coolant loop direct expansion cooling system including a compressor for compressing a suitable working fluid, an expansion device downstream from the compressor for expanding the working fluid so as to cool a cooling coil. The cooling coil is in heat exchange relation with ambient air flowing to the gas turbine for lowering the temperature of the ambient air to a lower temperature such that combustion air delivered to the gas turbine is below the ambient temperature thereby to increase the efficiency of the gas turbine. A return line is provided for returning the working fluid to the compressor.

An air conditioner comprises: a refrigerant circuit configured to circulate refrigerant through a compressor, a condenser, an LEV and an evaporator; a first temperature sensor configured to sense the temperature of liquid refrigerant at the inlet port of the evaporator; and a controller configured to control the compressor and the LEV. In a case where a temperature sensed by the first temperature sensor is lower than a frosting reference temperature, the controller increases the opening degree of the LEV and also increases the operating frequency of the compressor as compared with a case where the temperature sensed by the first temperature sensor is higher than the frosting reference temperature.

In an embodiment, a method of preventing evaporator coil freeze in a heating, ventilation and air conditioning (HVAC) system includes determining a reference saturated suction temperate (SST) via a sensor disposed in relation to an evaporator coil in the HVAC system, where the HVAC system is operating in reheat dehumidification mode. The method also includes determining whether the reference SST is below a minimum SST threshold. The method also includes, responsive to a determination that the reference SST is below the minimum SST threshold, determining a decreased compressor speed. The method also includes modulating a variable-speed compressor in the HVAC system in correspondence to the decreased compressor speed.

A system includes a compressor for increasing the pressure of a refrigerant; a condenser heat exchanger arranged downstream of the compressor for receiving a high pressure refrigerant output from the compressor and for transferring heat from the high pressure refrigerant to a source of water; an expansion device for reducing the pressure of a refrigerant; and an evaporator heat exchanger for extracting heat from ambient air. The evaporator heat exchanger includes a first tube bank having a first inlet arranged to receive a high pressure refrigerant output from the condenser and a first outlet fluidly coupled to the expansion device; and a second tube bank having a second inlet arranged to receive a low pressure refrigerant output from the expansion device, and a second outlet fluidly coupled to an inlet of the compressor.

The disclosed technology includes systems and methods of reducing frost accumulation on a heat pump evaporator coil. The disclosed technology can include a heat pump assembly having an evaporator coil, a fan configured to direct air across the evaporator coil, a temperature sensor, and a controller configured to energize the fan to direct air across the evaporator coil when the temperature of the evaporator coil is below a threshold temperature.

A method of operating a refrigeration system. The method includes operating a multi-temperature refrigeration system that has a plurality of heat absorption heat exchangers in a single temperature mode. A number of the plurality of heat absorption heat exchangers are determined that require defrosting a single heat absorption heat exchanger is directed into a different operational state when the number of heat absorption heat exchangers that require defrosting is equal to one. E of the plurality of heat absorption heat exchangers is directed into a defrost mode when the number of heat absorption heat exchangers that requires defrosting is more than one.

A heat pump system includes a compression device 12, a heat rejecting heat exchanger 14, an expansion device 18 and a heat absorbing heat exchanger 16; wherein the expansion device 18 provides a controllable degree of expansion. The heat pump system is operated in accordance with a method including determining a temperature indicative of frosting conditions on an exterior surface of the heat absorbing heat exchanger 16; operating the heat pump system in a first mode if the temperature indicative of frosting conditions is above a threshold value, and operating the heat pump system in a second mode if the temperature indicative of frosting conditions is within a range of temperatures that is below the threshold value.

In other features, a refrigeration system is provided and includes a compressor motor, an inverter, a converter and a control module. The inverter is configured to convert a direct current (DC) bus voltage to an alternating current (AC) voltage and supply the AC voltage to the compressor motor. The converter is configured to convert a DC input voltage to the DC bus voltage. The control module is configured to obtain a parameter and in response to the parameter exceeding a predetermined threshold, reduce the DC bus voltage and at least one of (i) reduce a switching frequency, (ii) increase an amount of negative d-axis current of the compressor motor, or (iii) reduce a speed of the compressor motor.

A thermal management system includes a receiver configured to store a refrigerant fluid; a refrigeration system having a refrigerant fluid path that includes the receiver, and at least one evaporator disposed in the refrigerant fluid path. The refrigeration system is configured to receive the refrigerant fluid from the receiver through the refrigerant fluid path. The at least one evaporator is configured to receive the refrigerant fluid and to extract heat from at least one heat load having a specified thermal inertia that is in at least one of thermal conductive or convective contact with the at least one evaporator.

A heat exchanger is provided including a first manifold and a second manifold separated from one another. A plurality of tube segments arranged in a spaced parallel relationship fluidly couple the first and second manifold. The plurality of tube segments includes a bend defining a first slab and a second slab. The second slab is arranged at an angle to the first slab. The heat exchanger has a multi-pass configuration relative to an air flow including at least a first pass and a second pass. The first pass has a first flow orientation and the second pass has a second flow orientation. The second flow orientation is different from the first flow orientation.