Experimental Study on Forced Convection Heat Transfer of Helium Gas through a Minichannel

Abstract

For the development of thermal efficiency and security of fusion reactors, it is vital to know the heat transfer process for helium gas cooling in the fusion blanket. In this paper, an experimental study was performed on the heat transfer characteristics for turbulent flow in a horizontal minichannel employing helium gas as the working fluid. A circular platinum tube with an inner diameter of 1.8 mm was heated by direct current and cooled by helium gas. The heat input was exponentially increased with a relatively long e-folding time of the heat generation rate. The obtained experimental data were compared with the predictions on classical correlations applied to conventional channels. The influence of various experimental parameters on the heat transfer coefficient was clarified. Based on the results, heat transfer enhancement was confirmed in the minichannel compared with the conventional channel. The heat transfer coefficient increased with increasing flow velocity and decreased as the ratio of inner surface temperature to gas bulk temperature increased. An empirical correlation for turbulent flow of helium gas in a minichannel with a deviation of ±10% was derived from a large quantity of experimental data.