Correlation of Forced Convection Heat Transfer of Isothermal Plate Under Low Pressure

With the rapid development of vacuum tube transport technology, there is increased interest in understanding the behavior of the heat transfer of rarefied gas in a vacuum tube. Currently, most empirical correlations of forced convection heat transfer are conducted at the standard atmospheric pressure, so many correlations are not applicable to conditions below the atmospheric pressure. To investigate the heat transfer property under low-pressure conditions, the forced convection between isothermal plate and air in a low-pressure environment is numerically simulated. The results show that the traditional correlation of the forced convection heat transfer between the isothermal plate and gases is different from the actual results at low pressure, and the correlation is completely invalid when the pressure is lower than 0.2 kPa. Based on the data of numerical calculation, a modified correlation of forced convection heat transfer between an isothermal plate and gases under low pressure is proposed. The correlation coefficient R is greater than 0.99, and the fitting error is less than 10% at the 95% confidence level. The change of heat transfer depends on the Reynolds number in the pressure range of 0.2-100 kPa, but the effect of Reynolds number is weakened and the effect of pressure is strengthened when the pressure is below 0.2 kPa.

Automated summary

With the development of vacuum tube transport technology, understanding the heat transfer behavior of rarefied gas in a vacuum tube has become more important. This study numerically simulated the forced convection between an isothermal plate and air in a low-pressure environment to investigate the heat transfer property under low-pressure conditions. The results showed that the traditional correlation of the forced convection heat transfer between the isothermal plate and gases is invalid at low pressure, and a modified correlation was proposed. The pressure had a stronger effect on heat transfer below 0.2 kPa.