Air-conditioning systems consume significant portions of energy in an automotive system, hence any improvement in performance or efficiency of automotive air-conditioning systems contribute to the energy efficiency and design economy of the vehicle. There has been massive research interest in improving the design of individual components of HVAC systems for efficiency and many of these improvements have already been implemented. However, due to the non-linear and dynamic nature of automotive air-conditioning and cooling systems, there is still room for improving the efficiency of the integrated unit by improving the control strategy for such systems instead of focusing on individual components alone.With the advancement in machine learning and programming capabilities there are now various novel control strategies and algorithms for non-linear systems in general. To apply these algorithms, black box models of the specific air-conditioning system are used from elaborate experimental data. Despite generating optimized control parameters, these methods provide little insight to the inner dynamics of the system and how they impact system behavior. For this reason, robust physics based dynamic model of automotive air-conditioning systems is required to formulate improved control strategies. The goal of this research is to develop a transient model of the automotive heat pump system for cabin space conditioning including the non-static time delay features of the thermal expansion valve used as expansion device. A modular trans-critical vapor compression system built at MSU sponsored by Ford was developed to run with sub-critical refrigerants for experimental validation of the model and system identification tests. From the understanding of the thermal expansion valve dynamics a method was developed to control an electronic expansion valve to perform exactly like or better than the specimen thermal expansion valve in the system. The heat pump cycle simulation model results matched with experimental results with an acceptable error margin and the system coefficient of performance with the developed controller strategy for the electronic expansion valve was found equivalent of the cycle with the specimen thermostatic expansion valve. This work will enable easy conversion from TXV to EXV systems by recommending hardware features and control parameters for similar performance level in automotive systems. Furthermore, generalized transfer functions of the components were developed for analysis and recommendation of improved control strategy in automotive air-conditioning systems using thermal and electronic expansion valves.
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