Room Air Conditioner System Modeling

Increasingly stringent energy standards and the redesigning of room air conditioners for use with alternative refrigerants have highlighted the need for design and simulation models that are accurate, easy to modify, and flexible enough for a variety of design and simulation tasks. This report describes the latest version of the Air Conditioning and Refrigeration Center (ACRC) room air conditioner simulation model. The model is being continually improved using heat transfer and pressure drop correlations and other modifications which are added as a result of an ongoing experimental program. The governing equations are solved using the Newton-Raphson method, which allows the equations to be listed in an order-independent fashion. A specialized Newton-Raphson equation solving package was developed that allows model variables and parameters in the governing equations to be easily "swapped" for design purposes and includes automated uncertainty and sensitivity analyses. A two-stage approach toward room air conditioner instrumentation is an integral part of the plans for model validation and improvement. The first stage uses only air-side thermocouples, and the second stage introduces refrigerant-side thermocouples and pressure transducers. Comparison of data sets from the two stages allows the intrusive effects of the refrigerant-side instrumentation to be identified. Simultaneous measurements with air and refrigerant-side thermocouples make it possible to quantify the offset errors in surface thermocouple measurements of refrigerant temperatures. The first stage of the room air conditioner instrumentation has been completed, and a baseline data set has been taken. The predictions of each component model in the room air conditioner system model are compared with preliminary experimental results obtained from this non-intrusive instrumentation, and component models which require improvement are identified. Several appendices address details of the model and equation solver, modeling condenser condensate spray, and the uncertainty analysis methods and results.Air Conditioning and Refrigeration Center Project 4