Abstract: Preventing freezing in a heat exchanger can include passing first and second cooling fluids through the heat exchanger, monitoring a temperature and/or pressure of the second cooling fluid entering the heat exchanger, heating the second cooling fluid entering the heat exchanger by opening a valve when the monitored temperature and/or monitored pressure is below a trigger temperature and/or trigger pressure, and closing the valve when a condition is met. The first cooling fluid can have a first freezing temperature and the second cooling fluid can have a second, lower freezing temperature. Opening the valve can cause the second cooling fluid, in gaseous phase, to mix with the second cooling fluid, in liquid phase, upstream of the heat exchanger.

Abstract: The present disclosure relates to a method for controlling a level of superheat during a pump mode of operation of a refrigeration system, wherein the refrigeration system can operate in either the pump mode or a compressor mode, and has an electronically controlled expansion valve (EEV). A controller obtains a stored, predetermined pump differential pressure range able to be produced by a pump of the system. The controller also obtains a stored, predetermined superheat range, and detects a superheat level. When the detected superheat level is outside of the superheat temperature range, the controller commands adjusting at least one of the EEV and a speed of the pump based on whether the detected superheat level is above or below the superheat range, and whether a current pump differential pressure is above or below the predetermined pump differential pressure range.

Abstract: In an aspect, a cooling system has a cooling circuit that includes an evaporator, a condenser, a compressor, a sub-cooler and an expansion device configured in a direct expansion cooling circuit with the sub-cooler coupled in series between an outlet of the condenser and an inlet of the expansion device. The condenser has a micro-channel cooling coil and the sub-cooler has a fin-and-tube cooling coil. In an aspect, the fin-and-tube cooling coil of the sub-cooler has a total hydraulic volume equivalent to the total hydraulic volume of the micro-channel cooling coil of the condenser but the fin-and-tube cooling coil of the sub-cooler has a face area more than two times smaller than a face area of the micro-channel cooling coil of the condenser.

Abstract: The present disclosure relates to a method for controlling a level of superheat during a pump mode of operation of a refrigeration system, wherein the refrigeration system can operate in either the pump mode or a compressor mode, and has an electronically controlled expansion valve (EEV). A controller obtains a stored, predetermined pump differential pressure range able to be produced by a pump of the system. The controller also obtains a stored, predetermined superheat range, and detects a superheat level. When the detected superheat level is outside of the superheat temperature range, the controller commands adjusting at least one of the EEV and a speed of the pump based on whether the detected superheat level is above or below the superheat range, and whether a current pump differential pressure is above or below the predetermined pump differential pressure range.

Abstract: In an aspect, a cooling system has a cooling circuit that includes an evaporator, a condenser, a compressor, a sub-cooler and an expansion device configured in a direct expansion cooling circuit with the sub-cooler coupled in series between an outlet of the condenser and an inlet of the expansion device. The condenser has a micro-channel cooling coil and the sub-cooler has a fin-and-tube cooling coil. In an aspect, the fin-and-tube cooling coil of the sub-cooler has a total hydraulic volume equivalent to the total hydraulic volume of the micro-channel cooling coil of the condenser but the fin-and-tube cooling coil of the sub-cooler has a face area more than two times smaller than a face area of the micro-channel cooling coil of the condenser.

Abstract: In a cooling system having a plurality of identical cooling circuits, fault detection is determined by a controller if monitored operating parameters of the cooling circuits differ from each other by an appreciable amount. In an aspect, the controller uses a comparison of the operating parameters of a cooling circuit to a snapshot of the operating parameters of that cooling circuit taken after the cooling circuit is determined to be operating properly after start-up. In an aspect, the controller uses known operating parameters of a cooling circuit and a system model of the cooling circuit to calculate remaining operating parameters of the cooling circuit (system model operating parameters) and uses a comparison of the system model operating parameters to the monitored operating parameters.