Unsteady compressible two-phase flow model for predicting cyclic heat pump performance and a comparison with experimental data

Abstract A dynamic model of vapour compression heat pumps is presented. Due to the importance of thermal expansion and compressibility effects, a detailed mathematical treatment of the condenser, evaporator and accumulator is given. Brief descriptions of the modelling techniques used for the remaining heat pump components and the solution methodology employed in the complete heat pump model are presented. Lumped-parameter models were developed for the expansion device, natural-gas-fueled internal combustion engine and compressor (open and hermetic). Inclusion of an appropriate void fraction model was found to be essential in determining the spatial refrigerant mass distribution, therefore a discussion pertaining to this model is also given. Simulations results and experimental data are favourably compared for transient operation of a hermetic water-to-water heat pump and an air-to-air system with an open compressor. The spatial variations of temperature, enthalpy, mass flow rate and density are predicted at each point in time for the two heat exchangers. The refrigerant pressures in the condenser and evaporator are determined such that the boundary conditions for the governing set of parabolic partial differential equations are satisfied. The summary provides a list of on-going work in the area of heat pump simulation and applications.