Experimental study on heat transfer resistance of condensation heat transfer in high efficiency heat transfer

The condensation heat transfer experiment of R134a inside the horizontal enhanced tube was operated under the condensation temperatures of 35 degrees C, 40 degrees C and 45 degrees C. Firstly, correlations were used to predict the heat transfer coefficient inside the tube to check the experimental data reliability. Then mass flux and condensation temperature were selected as the variables, and the total heat transfer coefficient K, the water heat transfer coefficient h(w) and the refrigerant heat transfer coefficient h(r) were seen as performance evaluation index to study the heat resistance of the enhanced tube. Experimental results show that: both the total heat transfer coefficient K and the refrigerant heat transfer coefficient h(r) increase with increasing mass flux, and get bigger with temperature decreasing. But the water heat transfer coefficient h(w) slightly decreases with mass flux increasing. And condensation temperature has a small influence on it. Analyze the thermal resistance and find that the water thermal resistance increases and the refrigerant thermal resistance decreases with mass flux increasing but the refrigerant thermal resistance is always less than the water thermal resistance. The difference between them gets bigger with the temperature decreasing.