Experimental and Analytical Investigation of Heat Transfer Coefficient of a Water Cooled Condenser for Different Water Flows and Condensation Pressures

Abstract

In the phase change process, latent heat is transferred and the amount of heat transferred will be excessive high compared to the amount of sensible heat transfer. For that reason, condensation and evaporation processes are the main steps in the refrigeration cycle in order to increase the amount of heat transferred. The main objective of this study is to experimentally and analytically examine overall heat transfer coefficient and to present the effect of water flow and refrigerant pressure on condensation process. For this purpose, a refrigeration system where a water cooled condenser with a heat transfer surface area of 0.075 m2 was installed. R134a was used as a refrigerant and condenses on the outer surface of the pipe that water circulates through. In this study, experiments were repeated for water mass flow rates of 15, 20, 25, 30 and 35 g/s at constant 7.0 bar condensation pressure. Then, condensation pressures were changed to 6.5, 6.75, 7.0, 7.25 and 7.5 bar at constant water flow rates of 25 g/s. Correlation of condensation heat transfer coefficient has been applied to refrigerant side of the condenser unit. On the other side, logarithmic mean temperature difference (LMTD) and number of transfer unit (ε-NTU) methods have been applied to experimental results in order to calculate heat transfer coefficient. Experimental results for different water flow rates at constant refrigerant pressure and for different condensation pressures at constant water flow rate are taken from the refrigeration machine unit and have been compared with calculated values that are obtained from condensation heat transfer correlation.