A heat exchanger model for mixtures and pure refrigerant cycle simulations
Abstract This paper describes a heat exchanger simulation developed for transient and steady state cycle simulations of mixtures and pure components. The simulation focuses on air to refrigerant condensers and evaporators found in residential heat pumps. The refrigerant differential momentum, continuity, species and energy equations are solved for these components and the steady state results are verified experimentally. Ten different heat transfer correlations for condensation and evaporation are evaluated to determine which best reproduces experimental data. Of those tested Jung and Radermacher's (1989, Int. J. Heat Mass Transfer 32 2435–2446) heat transfer correlation worked the best for evaporation while Dobson et al.'s (1994, ACRC Project 37) correlation worked the best for condensation. The experimentally determined capacity of four cross flow heat exchangers operating as condensers and evaporators with four different refrigerants is compared to the simulation results. The capacities predicted by the simulation agreed with the experimental results within ±8.0%. Furthermore, the simulation is used to quantify the effects of using a zeotropic mixture, R-407C, with cross, parallel and counter flow heat exchangers. As compared to a typical cross flow heat exchanger at typical heat pump operating conditions, the simulation predits that a pure parallel flow heat exchanger can decrease capacity by as much as 8.3% while a pure counter flow heat exchanger can increase performance by up to 4.4%.