Investigation On Cyclic Characteristics Of Zeotropic Mixtures In Moderate And High Temperature Heat Pumps According To The Relation Between Temperature And Enthalpy

To satisfy the need of saving energy and protecting environment, and utilize the industrial waste heat, the system of moderate and high temperature heat pump is researched with its cyclic properties in theory and by experiments.It is carried on the theoretical and experimental researches on temperature gliding of zeotropic mixtures during phase change. Proper proportion among each component can obtain linear variation between temperature and enthalpy in two phase region in order to approach the Lorenz Cycle. With appropriate matching of temperature differences between mixtures and heat-transfer fluids, it can reduce irreversible losses and improve efficiency. From the view of the temperature and enthalpy relation during phase change in binary mixtures, the theoretical investigations and computations are carried out for the two binary mixtures composed of R22 and R142b which are named W1 (mass ratio: R22/R142b, 0.5/0.5) and W2 (mass ratio: R22/R142b, 0.26/0.74). From the theoretical results, the COP of W2 is a little better than W1, but the temperature and enthalpy relation is non-linear for W2 in two phase region. The experimental researches are carried on for the two mixtures in different working conditions, and the results show that their values of COP get close. At the same time, the differences are very small in their thermodynamics perfections. Therefore, it has to analyze the components'proportion specially for binary mixtures in order to avoid reducing the selection range of working fluids and causing the losses of economy or other costs just because of a little improvement of efficiency.From the selection by theoretical computation, ZM1 (R125/R152a/R245fa) is tested in different working conditions and compared with W2. The experimental data indicate that they reach the same level in supplying temperatures and output of heat. But the pressure level of ZM1 is higher than W2, while the COP is lower than that of W2. These may be caused by unsuitable superheat and charging quantities of mixtures, which will be improved by optimizing system. Overall, for the needs of users, ZM1 can reach the equal level to W2, and with its green property, it meets the requirements of alternate working fluids, and has the potential to be used in moderate and high temperature heat pumps.