دانلود رایگان مقاله بررسی عددی انتقال گرما و مشخصه انتقال حرارت در کانال بافل V و روزنه V

Abstract

Turbulent forced convection, heat transfer and performance improvement in a square channel with discrete combined baffles (DCB), which combined V-baffle and V-orifice, are investigated numerically. The influences of the flow blockage ratios (BR=0.05, 0.10 and 0.15) and V-tip directions (V-tip pointing downstream called “V-Downstream” and V-tip pointing upstream called “V-Upstream”) are examined with a single pitch spacing ratio, PR=1, and attack angle, α=30o, for the Reynolds number, Re=5000–20,000. The computation results are reported in terms of flow visualizations, heat transfer characteristics, performance assessments. The results are compared with the smooth channel and the previous works. As the results, the DCB enhances the heat transfer rate and thermal efficiency due to the disturbance of the thermal boundary layer. The improvement of the heat transfer rate is around 2.8–6 times higher than the smooth channel depended on BR, V-tip directions and Re. In addition, the computational result reveals that the optimum thermal enhancement factor, TEF, is around 1.72 at BR=0.1, Re=3000 and V-Upstream.

6. Conclusion

The numerical investigations on heat transfer, pressure loss and thermal enhancement factor in the square channel heat exchanger with the DCB are performed. The influences of the blockage ratios (BR¼0.05, 0.10 and 0.15) and flow directions (V-Upstream and V-Downstream) are studied for the turbulent flow, Re¼5000–20,000, and also compared with the previous results. The conclusions from the current investigation are as follows;. The disturbance of the thermal boundary layer is found when inserted DCB in the heating section, that helps to improve thermo-hydraulic performance. The strengths of the vortex flow and impinging flow increase when increasing BR. In the range investigates, the enhancements are around 2.8–6 and 7.12–127.55 times over the smooth channel for the Nusselt number and friction factor, respectively, depended on BR, Re and flow direction. The optimum TEF is around 1.72 for BR¼0.10, Re¼3000, V-Upstream.