Multi-Temperature Heat Pump with Cascade Compressor Connection

 Object of the study is a multifunctional heat pump with several evaporators and condensers designed for simultaneous provision of technological processes with heat and cold. The aim of the work is the development and study of the scheme for this type of heat pumps, which ensures minimum irreversibility in the "compressor-gas coolers" chain, without the use of adjustable ejectors installed after evaporators and used as flow mixers. Obtained technical solution ensures the stabilization of heat pump coefficient of performance (COP) and prescribed thermal regimes of heat exchangers at a variable flow rate of the refrigerant. The novelty of the elaboration is inclusion of a compressor of the first stage with a serially connected intermediate heat exchanger and a control valve that are located before the compressor inlet of the second stage of the heat pump, which allows establishing rational pressure after the first stage of compressors. A scheme for the temperature regulation at the inlet of first stage compressors by regulating the flow through the primary circuits of the recuperative heat exchangers has been proposed. Control system of first stage compressor allows providing the required modes of operation of the heat pump. Exergetic analysis of the sections of the hydraulic circuit of heat pump located between the evaporators and gas coolers established that reduction of irreversible losses in the heat pump could be ensured due to optimal choice of the superheat value of gas after the evaporators.