The Effect of Mass Flow Rate and Heat Flux on Vertical Two-Phase Flow Regimes in a Small Diameter Tube

Abstract

In recent years, there has been a rising concentration in investigating and researching the boiling of micro channel flow; since they afford high thermal effectiveness, small size, and low weight. In this paper, the boiling heat transfer was experimentally examined using water as the working fluid in small diameter tubes. Experiments for the flow model were performed using the same Pyrex glass tube test facility. The experiments of heat transfer were carried out using an internal diameter copper tube (10.922 mm). The range of other parameters was varied: mass flow rate (0.008–0.0214kg/s); heat flux (17351–80529W/m2); it has been found that the average coefficient of heat transfer depends on the form of flow pattern. The average heat transfer coefficient increases by about 37% when the flow pattern varied from slug flow to churn flow at a constant mass flow rate of 0.008kg/s. Besides, the heat transfer coefficient (h) in the two-phase flow, is 39%, which is more than that for single-phase flow, when the mass flow rate is 0.0214kg/s, and heat flux) increases from 17351W/m2 to 49105W/m2. Also, when mass flow rate rises from (0.008kg/s) to (0.0166kg/s), the pressure drop increases by about (15%) and increases by about (5%) when the mass flow rate rises from (0.0166kg/s) to (0.0214kg/s). The main regime of flow was a slug, churn, bubbly, dispersed bubbly, and confined bubbly flow.