Improvment of COP of compression heat pumps through the use of non-azeotropic mixtures

Other conference contribution, 1984

This paper is the second one by these authors on nonazeotropic mixtures of refrigerants at this conference. In the first paper the thermodynamical principles for the use of mixtures were presented and a number of heat pump parameters, which can be improved by the use of mixtures, were discussed. In this paper one of these, the COP, is discussed in more detail. Results fran a nunber of computer simulations, where the influence on the COP of various parameters are investigated, are presented. These simulations have been carried out with a conputer program developed at the Department of Chemical Engineering Furdamentals at the Technical University of Graz. The magnitude of possible improvement in the COP depends on the degree of cooling the heat source fluid. The more cooling that is required, the greater improvements are possible. Improvements up to 30% seem to be realistic. The main disadvantage with the use of refrigerant mixtures is the need for greater heat exchanger areas. This is mainly due to two reasons: lower mean temperature differences and decreased heat transfer coefficients. Usage of ternary mixtures offers new possibilities in taking influence on COP, pressure ratio, compressor discharge temperature. One example is shown on this. Finally the market potential for such heat pump system is examinated. The results indicate that in many cases heat pumps working with nonazeotropic refrigerant mixtures will be an economic solution.