Transient Heat Transfer for Gases such as Helium Gas Flowing over Heaters with Exponentially Increasing Heat Input at Various Periods

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Forced convection transient heat transfer for various gases (helium, carbon dioxide, argon, and nitrogen gas) flowing over a horizontal cylinder, a plate, and a twisted one was experimentally studied under wide experimental conditions. The heaters were heated with heat inputs at various periods of exponentially increasing rate. The effects of period, velocity, and kind of gas were clarified. The periods ranged from 45ms to 17s, and the velocities ranged from 1m/s to 10m/s. Effect of gas thermal physical properties on heat transfer was investigated, and helium gas shows higher heat transfer coefficients than those of other gases due to its higher thermal conductivity. Empirical correlations for quasi-steady-state heat transfer and transient heat transfer were obtained based on the experimental data. In the theoretical study, transient heat transfer was numerically solved based on a turbulent flow model. The values of numerical solution for surface temperature and heat flux were compared, and the mechanism of transient heat transfer was investigated.