Abstract
An experimental investigation for evaporation frictional pressure drop in horizontal enhanced tubes with an outer diameter of 12.7 mm was studied using R410A as the working fluid. The experiment was conducted: the mass flux in the range of 100 kg/(m2s) to 200 kg/(m2s), over a vapor quality range of 0.2 to 0.8, an average saturation temperature at 279 K. The inner tubes were the tested tubes, which included a smooth tube, a three-dimensional enhanced tube (a tube enhanced by protrusions and petal arrays background patterns), respectively. The results show that the frictional pressure drop increases with the mass flux increasing. Moreover, the frictional pressure drop of the enhanced tube is 1.6∼2.4 times than that of the smooth tube. This is mainly due to the increase of the flow resistance inside the enhanced tube, which is caused by the increased interfacial turbulence, flow separation and secondary flow. It is also observed that the pressure drop increases with vapor quality increasing. In addition, some existing correlations are used to compare with our experimental data and verify their accuracy. A new modified correlation is proposed to predict the frictional pressure drop of EHT-1 tube.
