Comparison of Heat Transfer and Pressure Drop Characteristics for Enhanced Tubes Using Film Condensation through Wilson Plot Method

In this study, experimental investigations were carried out to compare the heat transfer and pressure drop characteristics of enhanced tubes using film condensation. Five enhanced tubes were selected for the performance comparison experiment. The velocity of the coolant ranged from 1.4 m/s to 2.6 m/s. The saturated condensation temperature, fixed at 38℃. R134a and R1234ze(E), were used as refrigerants. The resulting outside and inside heat transfer coefficients were between 11.04 kW/m²·K and 21.30 kW/m²·K and between 10.38 kW/m²·K and 24.69kW/m²·K. The film condensation heat transfer coefficients of R134a showed an average of about 10% higher than that of R1234ze(E). The heat transfer rate of enhanced tube number 4 obtained from the experiment was about 36% higher than that of enhanced tube number 1. This study proposed a performance comparison of enhanced tubes and development of experimental heat transfer correlations for coolant. In the present study, an experimental correlation of the Nusselt number for the coolant was proposed, and this correlation has a ±20% margin of error.