Study On Calculation Method Of Performance Of Thermal Vapor Compressor

Thermal vapour compressor (TVC) belongs to gas-ejectors using steam as the working fluid. It has been widely used recently to improve the energy utilization ratio and increase the gained output ratio (GOR) of Multi-effect Distillation (MED) System. And because a fixed structure TVC has only one optimum operating point, a kind of adjustable TVCs have been applied to fit for variable operating conditions. As an important element of MED, the performance of TVC should be well considered, but more researchers before have paid their attention to the ejector using in refrigeration system with the refrigerant as working fluid.In this paper, mathematical models, based on gas-dynamic theory, a kind of semi-empirical calculation method of ejector, including calculation of the design point and variable operating condition of ejector with ether cylindrical mixing tube or converging mixing tube have been presented. The results of the models have been compared with the data from the experimental results, the computational results and the data from the producing company of TVC to validate the models. And the results show reasonably good agreement with the latter ones. Furthermore, three kinds of the critical modes of operating condition of the ejector with cylindrical mixing tube and both two kinds of the critical modes of the ejector with converging mixing tube were considered in these models, therefore the models could predict the ejector performance in a wide operating condition range of TVC-MED.As an important proportion, the 1-D mathematical model of the adjustable ejector has been developed. The effects of the needle moving in the nozzle have been considered to be changes of consumption of the motive steam and the loss effect of the needle has been neglected. The empirical coefficient P is considered to be constant. The calculation results show much close to the data from the ejector producing company. As a result, the model is verified by the comparison of the average deviation of 4.5394%, and the deviation ranging from-7.34% to 21.35%. Furthermore the performance curves are calculated to analyze the performance of the adjustable ejector in the MED system and an analyses of the factors which effect the value ofμare also presented.