Air conditioning system employing dual cycle

Abstract

An air conditioning unit including a compressor-expander employing a vaned rotor defining enclosed compartments which become smaller in the compressor and larger in the expander as the shaft rotates, for positive compression and expansion. A primary heat exchanger having an associated separator-sump is connected between the compressor outlet port and the expander inlet port for dissipation of heat. A secondary heat exchanger is connected between the expander outlet port and compressor inlet port for absorption of heat and to complete a closed loop. The loop is charged with a main refrigerant in the form of a non-condensing gas, such as air, plus an auxiliary refrigerant mixed with oil, the auxiliary refrigerant being chosen (a) to have appreciable heat of vaporization and (b) to be capable of liquifaction at the pressure and temperature existing in the primary heat exchanger and evaporation at the pressure and temperature existing in the secondary heat exchanger. A spray nozzle, fed from the sump via a first conduit, is provided at the inlet of the secondary heat exchanger so that droplets of auxiliary refrigerant are sprayed into the gas discharged from the expander for vaporization in the secondary heat exchanger. A booster pump is optionally used to feed a stream of auxiliary refrigerant, plus oil, from the sump to the unit via a second conduit for purposes of lubrication and cooling.