MODELING AND SIMULATION OF A TRANSCRITICAL CO_2 HEAT PUMP SYSTEM WITH AN INTERNAL HEAT EXCHANGER

摘要

In this study, a transcritical carbon dioxide heat pump model consisting of five components (compressor, plate heat exchanger gas cooler, expansion device, finned-coil evaporator and tube-in-tube internal heat exchanger) is proposed. The detailed geometrical variation in each of the components and parametric influences of the fluids upon the system are taken into account. Computer code has been developed to evaluate both thermodynamic and transport properties for CO_2, water and air in each of the components correspondingly, as well as a solution algorithm for the system without imposing excessive constrains. Moreover, the proposed study aims not only to improve the existing models, but also to provide a better understanding in realizing the systemic performance of CO_2 as a working fluid. Furthermore, the results from this study may assist in the analysis and design of transcritical CO_2 systems.