An HVAC system includes a unit cooler, which includes a first evaporator coil, a second evaporator coil, and a blower. The HVAC system further includes a first sensor, a second sensor, a first valve, a second valve, and a controller. The controller actuates the blower to direct air to flow over the first evaporator coil and the second evaporator coil, receives measurements from the first sensor and the second sensor, initiates a defrost cycle for the first evaporator coil by transmitting instructions to close the first valve to prevent the flow of refrigerant into the first evaporator coil, transmits instructions to open the first valve when the defrost cycle for the first evaporator coil has terminated, and initiates a defrost cycle for the second evaporator coil by transmitting instructions to close the second valve to prevent the flow of refrigerant into the second evaporator coil.

Systems, apparatus and methods for efficiently operating a chiller plant while minimizing or eliminating the occurrence of centrifugal compressor surge. Taking into account chiller design specifications and current operating conditions, a compressor lift point at which surge is predicted to occur is established. Minima and maxima for various chiller setpoints that avoid or eliminate the occurrence of compressor surge are imposed on setpoints provided by a conventional optimizing chiller controller. The chiller system is operated in accordance with the resultant anti-surge setpoints. Energy savings is realized by modulating coolant tower flow to enable the compressor to operate at near-surge conditions while preventing the onset of actual surge.

A refrigerant circuit of a refrigeration apparatus performs a refrigeration cycle in which a high pressure is equal to or greater than the critical pressure of a refrigerant. The refrigeration apparatus performs at least a heat application operation in which an indoor heat exchanger of the refrigerant circuit functions as a radiator. A controller of the refrigeration apparatus controls the opening degree of the indoor expansion valve of the refrigerant circuit so that the temperature of the refrigerant at the outlet of the indoor heat exchanger reaches a predetermined reference temperature, in the heat application operation.

An air-conditioning apparatus includes a first indoor unit included in a single refrigeration cycle and an outdoor unit connected to the first indoor unit via a first refrigerant pipe, and the outdoor unit is included in the single refrigeration cycle. The first indoor unit is provided with a first refrigerant leakage sensor configured to detect leakage of refrigerant flowing through the first refrigerant pipe and a concentration of leaked refrigerant, and the outdoor unit includes a compressor configured to compress the refrigerant flowing through the first refrigerant pipe, a first flow control valve configured to adjust a flow rate of the refrigerant flowing through the first refrigerant pipe, and a control unit configured to stop the compressor and fully close the first flow control valve in a case where leakage of the refrigerant flowing through the first refrigerant pipe is detected by the first refrigerant leakage sensor, and configured to change, after the compressor is stopped and the first flow control valve is fully closed, an opening speed of the first flow control valve to a speed less than an opening speed of the first flow control valve adopted before the leakage of the refrigerant is detected.

A valve mechanism (14a, 14b, 63a, 63b, 90) includes: a valve body (80, 95); a first flow path (81) located opposite a distal end (80a, 95b) of the valve body (80, 95); a driver (85) configured to move the valve body (80, 95) to a first position where the distal end (80a, 95b) of the valve body (80, 95) closes the first flow path (81) and a second position where the distal end (80a, 95b) of the valve body (80) opens the first flow path (81); and a second flow path (82) configured to communicate with the first flow path (81) when the valve body (80) is at the second position. The high-pressure flow path (I1, I2, O2, O3, 48) causes the high-pressure refrigerant to always flow through the second flow path (82) and first flow path (81) of the valve mechanism (14a, 14b, 63a, 63b, 90) in this order.

An air cooled oil-free centrifugal chiller system and method, the system comprising at least one AC condenser fan; at least one solar panel; at least one AC/DC convertible fan connected to the at least one solar panel; and a controller configured to determine when sufficient DC power is available and activating the at least one AC/DC convertible fan when sufficient DC power is available, and when DC power is not sufficient, activating the at least one AC condenser fan.

A heating mode control method of an air conditioner, comprises: obtaining an indoor temperature and calculating the difference between the indoor temperature and an indoor target temperature to obtain an indoor temperature difference as air conditioner running at heating mode; performing a coil temperature control process as the indoor temperature difference in a set indoor temperature difference range, wherein the coil temperature control process including: obtaining an indoor coil temperature and controlling the frequency of the compressor according to the indoor coil temperature and a coil target temperature. The application of the method can achieve the purpose of improving the heating effect by increasing the outlet air temperature, thus improving the heating performance of an air-conditioner.

In some embodiments, an air-cooled ammonia refrigeration system comprises: a plurality of air-cooled condensers, each having a heat exchanger and at least one axial fan and having a first operating state capable of condensing vaporous ammonia to form liquid ammonia; an evaporator coupled to the air-cooled condenser; a subcooler positioned between the air-cooled condenser and the evaporator; a compressor coupled to the evaporator; an oil cooler coupled to the compressor; and a plurality of valves coupled to the plurality of air-cooled condensers and having a first configuration corresponding to the first operating state of the plurality of air-cooled condensers, and a second configuration corresponding to a second operating state of one or more of the plurality of air-cooled condensers such that the one or more of the plurality of air-cooled condensers functions as an evaporator capable of evaporating liquid ammonia to form vaporous ammonia.

An air conditioning system includes a control unit, a circulation system, an AC-to-DC conversion unit, and a fan module. The control unit detects an area temperature, controls the compressor unit being in operation or not in operation according to the area temperature and a setting temperature set by the control unit, and control a rotation speed of the condensing fan according to a temperature difference between the area temperature and the setting temperature. When the area temperature is greater than the setting temperature, the control unit controls the compressor unit being in operation and control the condensing fan being in full-speed operation.

Disclosed herein are air conditioning systems comprising a refrigerant line configured to transport a refrigerant; a compressor in fluid communication with the suction line; and a controller in communication with a sensor configured to measure a characteristic of the refrigerant line. The compressor can be configured to move the refrigerant through the refrigerant line, and the refrigerant can have a first temperature at the outlet of the compressor. The controller configured to receive sensor data from the sensor indicative of a current value associated with the characteristic of the refrigerant line; determine, based at least partially on the sensor data, that the characteristic of the refrigerant line is above a predetermined threshold; and output instructions for the compressor to perform one or more corrective actions.