Heat transfer and internal flow characteristics of a coil-inserted rotating heat pipe

To understand the flow pattern and the effect of a coil inside a cylindrical tube on the condensate flow, visualization and heat transfer performance tests were conducted. With the help of a coil inserted acryl tube, axial flow rates were measured to investigate the effect of coil helix angle, rotational speeds and fill charge rates. A coil-inserted tube showed a tendency of increasing the axial flow rates, especially at the pool regime. Also increasing the helix angle of coil resulted in the increase of flow rates and resulted in expediting the transition point of annular flow regime. The pumping effects for RHP with an inserted coil resulted in the enhancement of both condensation heat transfer coefficient and heat transport limitation, as obtained in the case of using internal fins. But these effects weakened in the range of higher rotational speeds with the transition of flow regime to annular flow.