A fresh-air air conditioning system comprises: a first electromagnetic valve connected to a first interior heat exchanger, and the first electromagnetic valve is connected via a first accumulator to a compressor and a third electromagnetic valve; the third electromagnetic valve is connected via a second accumulator to the compressor and a second electromagnetic valve; and the second electromagnetic valve is connected to a second interior heat exchanger. When the first interior heat exchanger or the second interior heat exchanger is closed, the third electromagnetic valve opens so that the first accumulator and the second accumulator simultaneously communicate with the open one of the first interior heat exchanger or the second interior heat exchanger, avoiding poor oil return as a result of prolonged single-cylinder operation of the compressor, and ensuring the reliability of the compressor as well as interior comfort.

An HVAC system includes a face-split evaporator. The face-split evaporator includes a top evaporator circuit positioned above a bottom evaporator circuit. The system includes a first compressor associated with the top evaporator circuit, a second compressor associated with the bottom evaporator circuit, and a controller communicatively coupled to the first and second compressors. The controller receives a demand request, which includes a command to reduce power consumption by the HVAC system by a predefined percentage. In response to receiving the demand request, the second compressor is turned off thereby decreasing power consumption by at least the predefined percentage. A portion of a liquid condensate formed on a surface of the top evaporator circuit is allowed to fall on a surface of the bottom evaporator circuit such that a portion of a flow of air passing across the bottom evaporator is evaporatively cooled by the portion of the liquid condensate.

An HVAC system includes a compressor, condenser, and evaporator. A sensor measures a value associated with the refrigerant in the condenser or the evaporator, and a controller is communicatively coupled to the compressor and the sensor. The controller determines, based on an operational history the compressor, that pre-requisite criteria are satisfied for entering a sensor validation mode. After determining the pre-requisite criteria are satisfied, an initial sensor measurement value is determined. Following determining the initial sensor measurement value, the compressor is operated according to a sensor-validation mode. Following operating the compressor according to the sensor-validation mode for at least a minimum time, a current sensor measurement value is determined. The controller determines whether validation criteria are satisfied for the current sensor value. In response to determining that the validation criteria are satisfied, the controller determines that the sensor is validated.

In one instance, a multistage microchannel condenser is provided for use as an aspect of a heating, ventilating, and air conditioning (HVAC) system. The multistage microchannel condenser includes at least two pluralities of flat tubes having microchannels, each associated with a different refrigeration circuit, that are interspersed so that when only one refrigeration circuit is operational, the multistage microchannel condenser still does not have any substantial thermal dead spots. Manifolds are used on each end of the multistage microchannel condenser to fluidly couple members of the at least two pluralities of flat tubes such that the refrigerant in each refrigeration circuit remains separated while still using a majority of the area of the face of the multistage microchannel condenser. Other aspects are presented.

A refrigeration system includes a dedicated defrost-mode compressor that delivers high pressure, high temperature refrigerant to one or more evaporators to defrost the evaporators.

A refrigeration system includes an expansion valve downstream of one or more medium temperature compressors. The expansion valve is configured to decrease pressure of a portion of refrigerant output by the one or more medium temperature compressors. When defrost operation of an evaporator is indicated, the refrigerant with decreased pressure from the expansion valve is provided to the evaporator for at least a period of time sufficient to defrost the evaporator.

An gas-driven generator system for generating electric power from movement of a working liquid. The system includes a gas-driven generator that includes a liquid turbine system fluidically interposed between the lower end of an elongated gravitational distribution conduit and the lower ends of plural elongated buoyancy conduits. A heavy working liquid flows from the upper ends of the buoyancy conduits and is fed into the upper end of the elongated gravitational distribution conduit. Working liquid flows down the elongated gravitational distribution conduit to actuate the liquid turbine system. An injection of refrigerant gas into the working liquid in the plural elongated buoyancy conduits induces upward flow of the working liquid. The system includes a solar thermal heating system fluidically coupled to heat exchangers that transfer heat collected by the solar thermal heating system to the working liquid through a thermal transfer fluid circuit.

A refrigeration assembly includes a receiver tank, a heat exchanger, a first piping assembly, and a second piping assembly. The receiver tank has a fluid outlet and a fluid inlet that receives a working fluid. The heat exchanger is disposed within the receiver tank. The heat exchanger has coiled tubing that is fluidly coupled to the fluid inlet and to the fluid outlet. The first piping assembly is disposed between and is fluidly coupled to the fluid inlet and the coiled tubing. The first piping assembly has a first double riser and a first P-trap. The second piping assembly is disposed between and is fluidly coupled to the fluid outlet and the coiled tubing. The second piping assembly includes a second double riser and a second P-trap.

A plurality of scroll compressors with different fixed volume indexes are connected in fluid parallel circuit and configured to selectively operate to maximize isentropic efficiency at different condensing temperatures. Different quantities of scroll compressors of different volume indexes may be selected based upon typical climate or geographic location environmental conditions to attempt to maximize efficiency. A controller may selectively operate different combinations of the compressors of different volume indexes bases up load demands and condensing temperature conditions, which may be determined in a variety of ways.

A system for modulating hot gas reheat operation of a heating, ventilation, and/or air conditioning (HVAC) system with multiple compressors, wherein the HVAC system is configured to regulate air provided to multiple zones. The system includes a controller configured to respond to a call for dehumidification in the absence of a call for cooling by sequentially energizing a first compressor of the multiple compressors in a reheat mode of the first compressor, energizing a second compressor of the multiple compressors in a cooling mode of the second compressor, energizing a third compressor of the multiple compressors in a reheat mode of the third compressor initially at full capacity, and energizing a fourth compressor of the multiple compressors in a cooling mode of the fourth compressor.