Experimental Investigation Of Evaporation Inside And Outside Dimple-Texture Tubes And Micro-fins For Herringbone

Heat transfer enhancement technology plays an important role in modern industry in obtaining energy efficiency improvements and the related research is timeless. Various types of heat transfer enhancement tubes have been developed, and are widely used in industrial production. A newly developed two-side enhanced surface 1EHT tube has been designed and produced. Through three dimensional material surface modifications,1EHT tube can produce more nucleation sites, interfacial turbulence, boundary layer disruption, flow separation and secondary flow generation produced by the enhanced surface structure (dimple and petal arrays).In this paper, there are three parts of works. Firstly, a literature review of two-phase flow in tubes was completed. Secondly, the evaporation experiment was conducted. Finally, the experimental data analysis has been done and heat transfer and pressure drop correlation have been proposed.An experimental investigation was performed with R410A for single-phase flow and evaporation inside and outside three tubes at low mass velocity. Data are for mass flow ranging from about 10 kg/h to 45 kg/h. The nominal saturation temperature is 279 K, with inlet and outlet qualities of 0.1-0.8,0.1-0.6,0.1-0.4 for evaporate outside and 0.1～0.9 for evaporate inside, respectively. When evaporated outside the tube, heat transfer coefficient and pressure drop of herringbone tube and 1EHT tube is much greater than that of smooth tube. When outlet quality is 0.6, heat transfer coefficient of three tubes all reach the plateau. When evaporated inside the tube, the inner flow is stratified-wavy flow in our test condition and 1EHT tube has the best performance. Correlations of heat transfer and pressure drop can predict the data within a ±20% error band.