Abstract
Forced convection transient heat transfer coefficients were measured for helium gas and carbon dioxide gas flowing over a twisted heater due to exponentially increasing heat input. The twisted platinum ribbon with a thickness of 0.1 mm was used as test heater and heated by electric current. The heat generation rate was exponentially increased with a function of Q0exp(t/τ). The gas flow velocities ranged from 1 to 10 m/s, the gas temperatures ranged from 313 to 353 K, and the periods of heat generation rate ranged from 46 ms to 17 s. The surface temperature difference and heat flux increase exponentially as the heat generation rate increases exponentially. Transient heat transfer coefficients increase with increasing gas flow velocity. The heater configuration of twisted heater in this study shows a large effect on the heat transfer coefficient. Empirical correlations for quasi-steady-state heat transfer were obtained based on the experimental data.
