NT-87-05-2 -- Prediction of Cyclic Heat Pump Performance with a Fully Distributed Model and a Comparison with Experimental Data PDF

A dynamic model of vapor compression heat pumps is presented. Due to the importance of thermal expansion and compressibility effects, a detailed mathematical treatment is given of the condenser, evaporator, and accumulator. A brief description is presented of the solution methodology employed in the complete heat pump model. Lumped-parameter models were developed for the expansion device, natural-gas-fueled IC engine, and compressor (open and hermetic). However, due to space limitations, these models will not be presented. Since inclusion of an appropriate void fraction model was found to be essential in determining the detailed refrigerant mass distribution, this topic is also discussed. Simulation results and experimental data are favorably compared for transient operation of a hermetic water-to-water heat pump and an airto- 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 ongoing work in the area of heat pump simulation and applications.

Units: I-P