Modeling Adjustable Throat-Area Expansion Valves

Adjustable throat-area expansion valves (ATAEV), including thermostatic and electric expansion valves, are used commonly in air conditioning equipment and lead to improved system performance as compared with the use of fixed orifice expansion devices. However, ATAEV modeling literature is limited. Typically, a TXV is modeled by specifying the superheat entering the compressor or empirically correlating experimental data. In order to model system behavior more accurately and effectively over a wide range of conditions, more accurate ATAEV models are necessary and a more general modeling methodology is desired. The current paper presents a general model format that utilizes manufacturers’ rating data. Model structures for three types of valve geometries are derived. Two model formats and parameter estimation procedures using manufacturer performance rating data were considered. The proposed methods are validated using experimental data and compared with results in the literature. Both experimental validation and theoretical analysis demonstrate that the proposed methods are more accurate and more generic than other methods presented in the literature.