2009 Volume 26 Issue 3 Pages 191-
This paper presents an experimental investigation of forced convective boiling heat transfer in a single microtube with inner diameters of 1 mm and 0.5 mm under different flow directions and flow velocities. FC-72 is employed as a test fluid, and its subcooling temperature is set to 15 K. A transparent heated microtube, which made by Pyrex grass coated with the gold thin film on the inner wall of the tube, is used as a test section. The experimental results show that the effects of gravity on flow behaviour and critical heat flux were observed under low velocities conditions in 1mm-tube. However, the gravity effects on the forced convective boiling in a 0.5 mm-tube and in high velocities conditions in 1 mm-tube were not found. The results indicate that the threshold of distinguishing between a microtube and a conventional tube has to consider for flow behaviour, heat transfer and critical heat flux, respectively. Key word: Flow boiling, Hert transfer, Bubble behaviour, Flow visualization, Microtube
