Transient forced convection heat transfer for nitrogen gas flowing over plate heater with exponentially increasing heat input

• Transient heat transfer coefficients of nitrogen gas flowing over a plate heater were measured.
• The surface temperature difference and heat flux increased exponentially.
• The heat transfer coefficients were affected by the period of the heat generation rate.
• The results of numerical simulation agree well the experimental data.

The transient forced convection heat transfer of plate heater for nitrogen gas due to exponentially increasing heat input was investigated experimentally and numerically. The platinum ribbon with a thickness of 0.1 mm and a width of 4.0 mm was used as the test heater. The heat generation rate of the test heater was raised with exponential function. The inlet flow velocity was ranged from 2 to 4 m/s for the gas temperature of 313 K under the system pressure of 500 kPa. The period of heat generation rate was ranged from 45 ms to 8 s. Experimental results indicate that the surface temperature difference and heat flux increased exponentially as the heat generation rate increased through an exponential function. It was clarified that the heat transfer coefficient was divided into the two regions for the period ranging from 45 ms to 8 s. The numerical results were compared with experimental data. The numerical simulation was in agreement with the experimental data.