Transient Heat Transfer for Helium Gas Flowing over a Plate

抄録

 The elucidation of heat transfer processes is vital for the design of reliable compact heat exchangers used in SMGTs (Super Marine Gas Turbines). To obtain a database for the optimal design of plate-fin recupetators under transient heat transfer conditions, it is very important to study heat transfer process from different-size plates in transient conditions under various gas velocities. In this paper a series of horizontal heaters with different sizes inside a circular tube have been tested for forced convection flow. The heat input was increased with a function of Q =Q₀exp(t/τ). The heaters were flat platinum plates with thicknesses of 0.2 mm, 0.1 mm and 0.1mm and widths of 1.5 mm, 4 mm and 6 mm. In the present study, the heat flux, surface temperature, and transient heat transfer coefficient were measured for helium gas flowing over horizontal heaters under wide experimental conditions. It was found that the heat transfer coefficients approach the quasi-steady-state values when the period τ is longer than around 1 second. However, when the period is shorter than 1 second, the heat transfer coefficients become higher as the period decreases. An Empirical correlation for quasi-steady-state heat transfer was obtained based on the experimental data. It was also found that the size of the heater has a great influence on the heat transfer coefficient.