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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

A Heat Transfer Optimization for Reducing Thermal and Flow Resistances

Get access (open in a dialog) DOI: 10.1615/IHTC15.hte.008571
pages 4151-4162

Аннотация

In the present research, the concepts of the degradation rate of available potential and power consumption of the fluid are proposed to reduce the irreversibility of heat transfer and flow. For the comprehensive optimization of heat transfer and flow, an optimization model in constructing the Lagrange functional is adopted. To obtain the optimal flow structure in a tube, we divide the tube flow into two parts: core flow and boundary flow. For reducing the thermal resistance in the core flow, we take the fluid heat consumption as the optimal objective and the fluid power consumption as a constraining condition. For reducing the flow resistance in the boundary flow, we take the fluid power consumption as the optimal objective and the fluid heat consumption as a constraining condition. Based on this optimization approach in a double-region, the optimal controlling equations for the convective heat transfer in laminar flow are derived by functional variation and by finding extremes in different tube areas. After solving the equations, we find that longitudinal swirl flows with vortexes appear in the tube at different Reynolds numbers and Lagrange multipliers. The results show that the growth of the Nusselt number is much higher than that of the resistance coefficient and the ratio of the increase in the amplitudes of the Nusselt number and resistance coefficient can reach up to 3 after optimization. This indicates that perfect optimization for convective heat transfer in the tube is achieved, which can guide the design for heat transfer enhancement in heat exchangers.