Vapor Compression Cycle Air Conditioning: Design and Transient Simulation

This paper describes the application of the general purpose SINDA/FLUINT thermohydraulic analyzer to the modeling of vapor compression (VC) cycles such as those commonly used in automotive climate control and building HVAC systems. The software is able to simulate transient operation of vapor compression cycles, predicting pressures, coefficients of performance, and condenser/evaporator liquid positions in a closed two-phase system with a fixed fluid charge. The program can also be used to size components, to estimate the impact of tolerances and other variations, and to help estimate uncertainties given limited test data. SINDA/FLUINT (Ref 1) has a user base numbering in the thousands. It has several graphical user interfaces, preprocessors, and postprocessors; has strong links to CAD and structural tools; and has built-in optimization, data correlation, parametric analysis, reliability estimation, and robust design tools. Nonetheless, widespread application to vapor compression cycles is comparatively recent (Ref 2), and is largely due to an increased demand for transient modeling of air conditioning systems. Toward this requirement, SINDA/FLUINT’s unique abilities to analyze transient two-phase phenomena have been recognized as being critical to achieving accurate performance predictions. INTRODUCTION: SINDA/FLUINT SINDA/FLUINT is the standard in the aerospace industry for heat transfer and fluid flow analysis of thermal control systems. Because of its general formulation, it is also used in other aerospace specialties such as environmental control (ECLSS) and liquid propulsion, and in terrestrial industries such as electronics packaging, automotive, refrigeration, and power generation. SINDA/FLUINT is used to design and simulate thermal/fluid systems that can be represented in networks corresponding to finite difference, finite element, and/or lumped parameter equations. In addition to conduction, convection, and radiation heat transfer, the program can model steady or unsteady singleand two-phase flow networks, including nonreacting mixtures and nonequilibrium phenomena.