Condensation heat transfer of low-GWP blends for air conditioning applications

The substitution of greenhouse gases is a real challenge for the refrigeration and air-conditioning industries. Some blends of low-GWP refrigerants have been developed to satisfy the demand for a wide range of working conditions and substitute R410A in air-conditioning applications and R404A in refrigeration applications. In this paper, the local heat transfer coefficient is measured during condensation of two blends: R455A and R452B. The new experimental data are compared to condensation data of pure low-GWP refrigerants, such as R1234yf and R32. Tests are performed inside a 1 mm diameter minitube at 40°C mean saturation temperature. During condensation tests, the heat is subtracted from the fluid by using cold water. The local heat transfer coefficient is obtained by measuring the heat flux on the water side and the wall temperature along the channel. The effects of mass flux and vapor quality on the condensation heat transfer are investigated. The heat transfer data are compared against a model: this comparison allows to assess a procedure for estimating the heat transfer penalization due to the mass transfer resistance and to highlight the amplitude of such heat transfer penalization.