Non Boiling Heat Transfer in Horizontal and near Horizontal Downward Inclined Two Phase Gas-liquid Flow

Abstract

Heat transfer in non-boiling gas-liquid two phase flow has significant practical applications in chemical and petroleum industry. To date, majority of the research in this field have been conducted for two phase flow in horizontal and vertical pipe systems. To explore and enhance the general understanding of heat transfer in non-boiling two phase flow, the main focus of this work is to experimentally measure local and average convective heat transfer coefficients for different flow patterns in horizontal and near horizontal downward inclined two phase flow. In total, 380 experiments are carried out in a 12.5 mm I.D. schedule 10S stainless steel pipe at 0, -5, -10 and -20 degrees pipe orientations using air-water as fluid combination. For each pipe orientation, the superficial gas and liquid Reynolds number is varied from 200 to 19,000 and 2000 to 18,000, respectively. The measured values of the average two phase heat transfer coefficient are found to be in a range of 500 W/m2K to 7700 W/m2K. Comparisons are drawn between the two phase heat transfer coefficients in the above mentioned pipe orientations. It is found that the increase in inclination of the pipe in downward direction causes the two phase heat transfer coefficient to decrease. This trend of two phase heat transfer data is explained based on the flow visualization and establishing its connection with the flow pattern structure and the two phase flow physics. Performance of the existing two-phase heat transfer correlations available in the literature is investigated by using the experimental data. Among general and Reynolds analogy based correlations, Shah (1981) and Bhagwat et al. (2012) are the best performing correlations. A new correlation is also proposed to improve the performance of the Reynolds analogy based correlation which has successfully predicted 96% of the data points within �30%.