Heat transfer and pressure drop characteristics of plate heat exchanger of R22 and R32

Abstract

In this study, we investigated the heat transfer and pressure drop characteristics of a plate heat exchanger in ocean thermal energy conversion (OTEC) system. We used deep seawater, surface seawater, and refrigerants (R22 and, R32) as heat and cooling sources. Our experiment was performed under the same conditions as those of and actual OTEC system : condensation temperatures of 8∼20°C and 5∼17°C for the deep seawater and refrigerant, respectively, and evaporation temperatures of 10∼40°C and 13∼45°C for the surface seawater and refrigerant, respectively. The experiments were performed in several operation modes of condensation and evaporation. The mass flow rates of the deep seawater, surface seawater, and refrigerant were varied over the rage of 60∼90% of the total mass flow rate. The plates were made of titanium, stainless steel, nitride-coated SPCC, Teflon-coated stainless steel, and DLC-coated stainless steel. The local and average heat transfer coefficients and pressure drops during condensation and evaporation were reported for R22 and R32 in the plate heat exchanger. The experiment data showed that both the heat transfer coefficients and pressure drop increased with the mass flow rate. At higher mass flow rates the heat transfer coefficients and pressure drop were higher for the entire range of mass flow rates. Raising the imposed heat flux had a smaller effect on the heat transfer coefficients and pressure drops,-; both the heat transfer coefficients and pressure drops were lower. The measured heat transfer coefficients and pressure drops were also compared with a number of correlations for condensation and evaporation. On the basis of the experiment data, we propose empirical correlations for the heat transfer coefficient and friction factor. Copyright ？ 2014 by the International Society of Offshore and Polar Engineers (ISOPE).