A refrigeration system is provided and includes a common suction line, a common discharge line, first and second high-side compressors disposed in parallel to receive low-pressure refrigerant from the common suction line and to direct high-pressure refrigerant to the common discharge line, a first pipe connected to the first and second high-side compressors at vertical heights at which an oil supply is required to remain higher and a second pipe connected to the first and second high-side compressors at vertical heights sufficient to maintain gas pressure balance between the first and second high-side compressors.

Air conditioner units and methods of operating the same are provided. A method of operating an air conditioner unit includes determining a fan speed as a function of a compressor speed of a variable speed compressor of the air conditioner unit. The method also includes activating a variable speed fan of the air conditioner unit at the fan speed. An air conditioner unit may include a controller, and the controller may be configured for performing the method.

A refrigeration appliance has at least a first and a second temperature zone and a refrigerant circuit that includes a compressor, a first evaporator for cooling the first temperature zone and a second evaporator for cooling the second temperature zone. The first evaporator is serially connected downstream of the second evaporator in the refrigerant circuit, and a controllable throttle point is arranged upstream of the first evaporator and downstream of the second evaporator in the refrigerant circuit. A compressor controller is configured to control the rotational speed of the compressor on the basis of the temperature in the first temperature zone.

Disclosed are a carbon dioxide overlapping type heating system and a control method therefor. The heating system comprises a low-temperature stage loop, a high-temperature stage loop and a heat supply loop, wherein a low-temperature stage compressor (3) and a high-temperature stage compressor (7) are both variable-frequency compressors; and a water pump (10) is a variable-frequency water pump.

A method of operating a chiller system includes receiving an input from at least one sensor associated with a compressor of the chiller system, determining that the compressor is experiencing a surge or rotating stall event, adjusting at least one operating parameter associated with a heat rejection heat exchanger of the chiller system in response to determining that the compressor is experiencing the surge or rotating stall event, and reducing a condenser saturation temperature by adjusting the at least one operating parameter.

An oil return control method for a multi-split air conditioner and a system accomplishing the same includes: calculating an average exhaust pressure within an oil return period Pd_AVG; determining whether the average exhaust pressure Pd_AVG≥the set threshold Pd.sub.threshold; if Pd_AVG≥Pd.sub.threshold, maintaining the multi-split air conditioner working in heating mode to ensure an acceptable oil return performance without affecting the air conditioning effect of indoor unit in heating mode; if Pd_AVG<Pd.sub.threshold, switching the multi-split air conditioner to cooling mode, stopping a fan within those power-on indoor units and entering into a cooling oil return process and switching the multi-split air conditioner back to heating mode until the cooling oil return process ends.

A heat exchanger for a heating, ventilation, air conditioning, and refrigeration (HVAC&R) system includes a base portion having a first plurality of channels extending therethrough and a second plurality of channels extending therethrough. The heat exchanger further includes a first manifold and a second manifold, where the first plurality of channels extends from the first manifold to the second manifold, and a third manifold and a fourth manifold, where the second plurality of channels extends from the third manifold to the fourth manifold. The heat exchanger further includes a single part having the base portion, the first manifold, the second manifold, the third manifold, and the fourth manifold.

A hybrid shellfish cooling system employs both DC and AC cooling units that use both solar power and AC electrical supply as energy sources. As temperature control and uniform temperature distribution in the cooling system are critical factors in reducing vibrio growth on raw oysters and reducing energy consumption, the hybrid shellfish cooling system is equipped with a specially configured divider that optimizes airflow through the cooling system interior cabinet to achieve uniform temperature distribution in six individual internal compartments inside of the cooling system. Test results indicated that an average of 130 min. cooling was required to reach the suggested oyster temperatures of 7.2° C. and meet the cooling time requirement (i.e., 10 h or less). Airflow is further optimized via fan location and airflow direction, whereby a circulation fan located on the lower part of the 12-volt DC section with an air supply from the 12-volt DC section to the 110-volt AC section provides the optimal condition to achieve relatively uniform temperature distribution.

According to various aspects, exemplary embodiments are disclosed of chiller systems including thermoelectric modules, and corresponding control methods. In an exemplary embodiment, a compressor chiller system generally includes a refrigerant loop having a refrigerant fluid, a compressor connected in the refrigerant loop to compress the refrigerant fluid, and a condenser connected in the refrigerant loop to receive the compressed refrigerant fluid from the compressor and to condense the compressed refrigerant fluid. The system also includes a heat transfer component connected in the refrigerant loop to receive the condensed refrigerant fluid from the condenser, and a coolant loop having a coolant fluid. The heat transfer component is connected in the coolant loop to transfer heat from the coolant fluid to the condensed refrigerant fluid. The system further includes a thermoelectric module connected in the coolant loop. The thermoelectric module is adapted to transfer heat into and/or out of the coolant fluid.

An air conditioning apparatus includes an indoor unit and an outdoor unit. The outdoor unit includes a compressor that compresses a refrigerant and a motor drive apparatus that drives the compressor. The motor drive apparatus includes an inverter that converts a direct-current voltage into an alternating-current voltage and a motor that operates on the alternating-current voltage from the inverter. The motor includes six stator windings that are each openable at both ends. The motor drive apparatus further includes a connection state switching unit that includes a function of switching a connection state of the six stator windings of the motor among at least four types of connection states.