Abstract

Following the Montreal Act/Protocol of 1990, which calls for the complete phase out of chloroflorocarbon (CFC) production by the year 2000, increasing attention has been placed in recent years to improving the thermodynamic performance of heat exchangers by using non-azeotropic refrigerant as the working fluid. As a result, the currently used refrigerant, R-12, should be replaced with R-134a. However, R-134a is thermodynamically about 20 to 30 percent less efficient than R-12 in heat exchangers. Helically coiled tubes provide a simple and effective means of augmenting heat transfer. However, the effective design of a helically coiled condenser for refrigeration and air conditioning applications requires knowledge of the optimum configuration of helical coil geometry and the data on condensation heat transfer coefficients to achieve the maximum heat transfer rate. Therefore, an experimental study of condensation of pure R-134a refrigerant inside a helicoidal pipe has been carried out. Experimental heat transfer data are reported in this paper for the condensation of R134a in a helicoidal pipe that measured 12.7 mm at the inner tube and 25.4 mm at the outer tube. The test section was well insulated from the surroundings by two layers of fabric glass. The heat transfer coefficient was calculated from the measured fluid temperatures based on the energy conservation principle.

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