開放形サーモサイフォン内の伝熱特性に関する実験的研究

概要

論文の詳細を見る
Experimental study was performed on heat transfer of an open thermosyphon with constant wall heat flux. Water and aqueous glycerin were used as working fluids. Experimental range of modified Rayligh Number was 1×10^3<Ra_m<3×10^5. Average and local heat transfer coefficients, vertical temperatures distributions of the tube wall and fluid at the center line of the tu be, temperature fluctuation of the fluid were measured. Flow patterns were observed by adding tracer powder in the fluid. Fluid velocities were measured by L. D. V. Experimental results indicate that there exists three different heat transfer characteristics and corresponding flow patterns. For 1×10^3<Ra_m<4×10^3, flow was laminar and thermal boundary layer reaches near the center of the tube. Heat was exchanged between wall and descending flow. Wall temperature rose towards downward. For 4×10^3<Ra_m<3×10^4, no turbulence was observed in the flow and thermal boundary layer was localized in the vicinity of the wall. Wall temperature rose towards upward. For 3×10^4<Ra_m<3×10^5, flow is considerably disturbed by the mixing of upward and downward flow in the upper part of the tube. However, flow is almost laminar in the lower part of the tube. Reduction of flow rate induced by the flow mixing at high Ra_m would be one of the major causes of the deterioration of heat transfer from the Lighthill's theory.
一般社団法人日本機械学会の論文
1999-06-25