A heat pump apparatus includes: a compressor including a motor; an inverter that applies a desired voltage to the motor; a current detector that detects current flowing to the motor; a drive-signal generation unit that generates a drive signal for the inverter; a magnetic-pole position estimation unit that changes a voltage phase of a voltage command value for a high-frequency voltage, and estimates a maximum-heat-amount acquisition magnetic-pole position when the generation unit applies the high-frequency voltage to the motor to heat the compressor; a steady heating control unit that determines an amplitude and voltage phase of the voltage command value from the maximum-heat-amount acquisition magnetic-pole position and a defined necessary amount of heat when the generation unit applies the high-frequency voltage to the motor to heat the compressor; and a control switching determination unit that causes one of the estimation unit and the heating control unit to operate.

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.

A heat pump includes a refrigerant loop. The refrigerant loop includes a compressor, a first condenser, a vapor generator having a first region and a second region, a first expansion valve, a second expansion valve, and a first evaporator. A branching point is positioned between the first condenser and the vapor generator. The branching point diverts a portion of a first heat exchange fluid circulating through the refrigerant loop to the vapor generator. The first expansion valve is positioned between the branching point and the vapor generator. An outlet vapor generator is coupled to a mid-pressure inlet port of the compressor.

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 refrigeration cycle apparatus (1) is capable of performing a refrigeration cycle using a small-GWP refrigerant. The refrigeration cycle apparatus (1) includes a refrigerant circuit (10) and a refrigerant enclosed in the refrigerant circuit (10). The refrigerant circuit includes a compressor (21), a condenser (23), a decompressing section (24), and an evaporator (31). The refrigerant contains at least 1,2-difluoroethylene.

A refrigeration appliance with multiple storage compartments has a refrigerant circuit with a first expansion valve, a first heat exchanger, a second expansion valve, and a second heat exchanger connected in series between pressure and suction connections of a compressor. Each heat exchanger is associated with at least one storage compartment in order to control its temperature. A control unit controls the compressor rotational speed and positions of the expansion valves. The control unit has a continuously linear regulator for each storage compartment with a P-component for estimating a required temperature control output using a difference between actual and target temperatures. A model computing unit ascertains a target evaporation temperature for a first storage compartment controlled by the first heat exchanger, and for a second storage compartment controlled by the second heat exchanger. The heat exchangers are operated by selecting the compressor rotational speed and the valve positions of the expansion valves.

A pressure relief arrangement in refrigerant circuits with one high-pressure side and one low-pressure side, which is characterized in that the high-pressure side is fluidically connected with the low-pressure side of the refrigerant circuit via an overpressure relief device, wherein the overpressure relief device causes pressure reduction of the overpressure in the case of overpressure on the high-pressure side and fluid flows from the high-pressure side to the low-pressure side of the refrigerant circuit.

A drive device for an AC motor includes: an adaptive observation unit that adaptively estimates an angular velocity of a rotor of an AC motor; a speed control unit that determines a first torque command with which an angular velocity command matches an average value of an estimated angular velocity; a phase lead amount calculation unit that calculates, based on a disturbance frequency, a phase lead amount of a transfer function from a true angular velocity to a model deviation; a vibration suppression control unit that determines, based on a frequency of load torque pulsations, the model deviation, and the phase lead amount, a second torque command with which speed pulsations in the AC motor are suppressed; and a torque control unit that controls a torque of the AC motor based on the first torque command and the second torque command.

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.