CORRELATION OF OVERALL HEAT TRANSFER COEFFICIENT IN THE THREE ZONES OF WIRE AND TUBE CONDENSER

Abstract

Numerical and experimental analysis has been studied to estimate the overall heat transfer coefficient in the three zones along wire and tube condenser. The model is based on the empirical formulation of the refrigerant and air sides heat transfer coefficients in finite sections along condenser tube which is solved using EES software. To validate the obtained result from the numerical model, a test rig for a vapour compression refrigeration system with R-134a builds for this purpose. Investigating the temperature distribution and heat transfer coefficient along the length of condenser under different operating conditions have shown that, the de-superheated, two-phase and sub-cooled zones are approximately occupied 15 %, 80% and 5% of the total condenser length respectively. The ratio of Overall heat transfer coefficient to the saturated heat transfer coefficient was significantly affected by the variations of the ambient temperature. Comparison between experimental and numerical results has displayed maximum deviation of 5.5% which is reasonably acceptable. Finally, an acceptable relation has been made to summarize all the important parameter that’s effects directly on the heat transfer contributions of the de-superheating, saturated, and subcooling in one equation to simplex the boring calculations of overall heat transfer coefficient. Proposed correlation presents a mean square error about 3.1 %.

Keywords

• Overall heat transfer coefficient
• Wire-and-tube condenser
• Modelling