Measurement of Subcooled Flow Boiling Heat Transfer Coefficient in Vertical Annulus Tube

In the current study, an experimental apparatus was constructed, and subcooled flow boiling in an annulus tube was investigated. The annulus tube is in the vertical direction, and the internal and external diameters are 50.7 and 70.6 mm. The operating pressure was 1 atm, and the working fluid was water. In this investigation, heat flux, mass flow rate and the inlet subcooling effectiveness on heat transfer coefficient are considered. The experiments were performed in the mass flow rate range of 0.012 kg/s to 0.0286 kg/s in which the flow consists of both forced convection and flow boiling. The results show that the heat transfer coefficient is highly dependent on heat flux in a direct relationship. The results revealed that the subcooled heat transfer coefficient increases with decreasing inlet subcooling. Also, the mass flow reduction causes heat transfer coefficient increments to 30% in subcooled boiling regions. The use of porous media also increases the subcooled flow boiling heat transfer coefficient up to 30%. The validation of empirical results has also been done with valid previous reports.