大きな水平加熱円柱まわりの自然対流の流動と伝熱

抄録

Fluid flow and heat transfer of natural convections around large horizontal cylinders heated with uniform heat fluxes were investigated experimentally. The main concerns were the turbulent transition and its influence on the local heat transfer. The experiments were performed in the range of modified Rayleigh numbers from 3.0×10⁸ to 7.7×10¹¹. The test fluid is water. The flows over the cylinders and the surface temperatures of the cylinders were visualized with dye and liquid crystal sheet. The results showed that three-dimensional flow separation occurs over the upper surfaces of the cylinder when the Rayleigh numbers exceed 2.2×10⁹. The separation becomes a trigger to the turbulent transition, and transitional and turbulent flows appear downstream the separation. The local heat transfer coefficients were also measured along the cylinder surface. The results show that the coefficients are increased significantly in the transitional and turbulent regions.