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

在较宽的实验条件下，对不同气体(氦、二氧化碳、氩气和氮气)在水平圆柱体、平板和扭曲圆柱体上的强迫对流换热进行了实验研究。加热器在不同的时间段以指数增长的速度被热输入加热。阐明了周期、速度和气体种类的影响。周期为45ms~17s，速度范围为1m/S~10m/S。研究了气体热物性对换热的影响，发现氦气具有较高的导热系数。在实验数据的基础上，得到了准稳态换热和瞬时换热的经验关联式。在理论研究中，基于湍流模型对非稳态换热进行了数值求解。比较了表面温度和热流密度的数值解，探讨了非稳态换热的机理。

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.