Local convective condensation heat transfer in horizontal double-layer three-dimensional dimple-grooved tubes

An experimental study on local condensation heat transfer characteristics in two three-dimensional double-layer dimple-grooved tubes (2EHT tubes) and a smooth tube is performed using refrigerant of R410A. The smooth tube has an outer diameter of 12.7 mm and inner diameter of 11.07 mm. The 2EHT tubes have a nominal outer diameter of 12.7 mm and wall thickness of 0.8 mm. The enhanced surface areas of two 2EHT tubes are 1.02 and 1.03 times of the smooth tube, respectively. The present experiments are conducted to measure the local wall temperature when the mass flux ranges from 65 kg/(m2·s) to 210 kg/(m2·s), heat flux ranges from 10 kW/m2 to 35 kW/m2 and vapor quality ranges from 0.9 to 0.1. The saturation temperature is maintained at 40 °C. 248 experimental HTC data points are obtained and compared with six correlations. The results show that the measured local HTCs increase with increasing mass fluxes and decrease with increasing heat fluxes, and that the present correlations have a good predictability with smooth tube but cannot predict the HTC of 2EHT tubes. The proposed condensation correlation for 2EHT tubes is validated, and it predicts all experimental points within an error band of ±30%, and 94.25% of all test points within an error band of ±20%.