Investigation on the air flow and heat transfer from a horizontal rotating cylinder

• A micro-thermocouple is designed to measure temperature distribution at different φ and y.
• Rotation can result in a deflection of trailing vortex and a non-uniform distribution of Nuφ.
• The worst convective heat transfer region with rotation from a rotating cylinder is investigated.
• A new method to determine the Rer,cri number has been demonstrated.

In order to investigate the air flow and characteristics of the heat transfer from a large diameter horizontal rotating isothermal cylinder, a specially designed micro-thermocouple is employed to measure the temperature distribution in the thermal boundary layer around a cylinder surface at different rotational speeds, and a shadowgrapher has been used to observe the variation of trailing vortex. The results indicate that rotation can result in a deflection of trailing vortex and a nonuniform distribution of the local Nusselt number Nuφ, especially in the region beyond the critical Reynolds number Rer,cri. The worst convective heat transfer region does not coincide with the trailing vortex region as previously reported. Further, the mechanism of the Rer,cri has been elucidated and the new method to determine the Rer,cri number has also been demonstrated.