A heat transfer empirical correlation for the stratospheric airship based on its length-to-diameter ratio

Thermal control is one of the key technologies involved in stratospheric airship applications, and convective heat transfer is an important factor in the thermal control of a stratospheric airship. In order to accurately predict the heat transfer of an airship，using the numerical method, an empirical correlation of Nu number as a function of Re, Pr and l/d (length to diameter ratio) was established. Compared with experimental data, the uncertainty of the empirical correlation is about ±7%. The effect of the attack angle of an airship on heat transfer performance was evaluated. It was found that the heat transfer at the windward side is 10% higher than that of the leeward side, while the average heat transfer of airship is 7% higher when the attack angle changes from 0° to 15°.