Evaporation of nonazeotropic mixture of refrigerants R143a and R124 flowing inside smooth and corrugated tubes

摘要

Because heat exchanger thermal performance has a direct influence on the overall cycle performance of vapor-compression refrigeration machinery, enhanced heat transfer surfaces are of interest to improve the efficiency of heat pumps and air conditioners. We investigated a nonazeotropic refrigerant mixture (NARM) of 75% R143a and 25% R124 (by mass) to study its thermal performance in an evaporator made of conventional smooth tubes and another evaporator made of corrugated, or spirally indented, tubes. We investigated the evaporating heat transfer and pressure drop characteristics in an experimental test loop model of a domestic heat pump system employing a variable speed compressor. The refrigerant circulates inside the central tube and the water circulates in the annulus. At a refrigerant mass flux of approximately 328 kg/m(sup 2)s, the measured irreversible pressure drop of the corrugated surface was 100% higher than that of the smooth surface, and the measured heat transfer coefficient was 11% higher than that of the smooth surface.