Thermo-entropic evaluation of the effect of air injection into horizontal helical tube. (June 2021) - Abdzadeh, Behzad
Highlights: The plug, slug, slug-wavy, stratified flow were the main flow patterns observed at the range of present study. At the low liquid flow rates, the gas phase has a smooth interface with the liquid phase, and tends to move near to the outer wall of the helical tube. Up to 20% increment was observed at the heat transfer coefficient. The maximum augmentation in the entropy generation was about 33%. The best values of White-Shamsunder efficiency factor was found to be about 0.984. Abstract: In the present paper, the influence of two-phase stream on the thermal and entropic properties of horizontal helical tube was probed. Furthermore, the flow structures were analyzed too. The flow patterns were created and recorded in a glass made tube. The tube had same geometrical dimensions as like to that used in thermal tests. With the aim of probing the heat transfer coefficient constant heat flux was applied to an aluminum made tube. The range of volume fraction investigated in the present study was 0.07 to 0.75. The flow visualization results revealed that four flow patterns of stratified, slug, slug-wavy and plug flow were created at the mentioned range of volume fraction. The results presented that the variation of volume fraction has significant effect on the flow pattern, heat transfer coefficient and entropy generation of air/water two-phase stream. Up to 20% augmentation was observed in the heat transfer coefficient due to the use of two-phase flow. The maximum rise in the entropy generation was about 33% and was occurred at the VF 0.55 and gas superficial Dean number of 230.8. Besides, the best value of Whitte-Shamsunder efficiency factor was found to be about 0.984 which was observed at D e sl =1175.45 and D e sg = 230.8.