A large amount of research work has been done on natural convective heat transfer from a horizontal rotating cylinder. Mcadams  investigated the laminar free-convection characteristics from a horizontal isothermal cylinder, and proposed a heat transfer correlation that BLZ945 has been widely applied. By using laser technology and computer, the local convective heat transfer coefficient and velocity distribution around a horizontal static cylinder were studied, and a correlation Rer2/Gr=7.5 was proposed to determine whether the impact of the free convection could be negligible  and . Anderson et al. ,  and  investigated NuNu from a horizontal rotating cylinder in three different flow patterns of natural, forced and mixed convection, and presented a correlation Rer,cri=1.09Gr0.5Rer,cri=1.09Gr0.5 at lower GrGr. Mahmoudi  has studied free convection heat transfer from an isothermal horizontal cylinder in the presence of DC positive corona discharge with a blade edge emitter electrode experimentally and numerically. The results reveal that corona discharge affects significantly on the average Nusselt number at lower Rayleigh numbers whereas it has smaller effect at higher Rayleigh numbers. Guillen  has experimentally investigated laminar opposing mixed convection to assess the thermal effects on the wake of an isothermal circular cylinder placed horizontally and confined inside a vertical closed-loop downward rectangular water channel by using particle image velocimetry (PIV) measurements. And strouhal number and vortex shedding modes are obtained as a function of the Richardson number to elucidate the effects of the lateral wall proximity effect and cylinder aspect ratio, separation angle, wake structure behind the cylinder, recirculation bubble length, time traces of velocity fluctuation.