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Numerical study of hydrodynamics and thermal characteristics of heat exchangers with delta winglets

The comprehensive performanceofheat exchangersis represented bythe maximum thermaltransfer,theminimum pressurelossand the smallest pumping power.In recent years,theapplication oflongitudinal vortex generatorsis developedas an effective technique and important research topic, which could increasethe heat transfer enhancement of compact heat exchangers.A three-dimensional CFD numerical simulation is successfully carried out on thermo-hydraulic characteristics of the FTCHE (fin-and-tube compact heat exchanger)with new types of vortex generators (VGs).The effects of sixdifferent arrangement of delta winglets are studied, which are FURD (front-up-rear-down), FDRU (front-down-rear-up), CFU (common-flow-up)and CFD (common-flow-down). In addition, there are also different direction of hole positionin the same delta wingletsarrangement. The investigation of thermal-hydraulicperformance is conducted for Reynolds number in the range of 204-2034.The overall and local performance comparisons among the fin with delta winglets and the wavy fin are performed.Then, the comprehensive performance evaluation diagramwas adopted to analyzethe combined index pointof thermal and flow.This study shows thatthe flow distinction between different fins has a profound influence on the thermal-hydrodynamic performance.The results reveal that the finwith delta wingletscan considerably strengthenthethermal efficiencywith a moderate pressure loss penalty.The computational results indicate that the average j-factorfor the finwithdelta wingletscan be increased up to 41.9% overthe baseline case and the corresponding f-factordecreased up to 19.5%.The combination propertyof FURDare better the others at lower Reynolds number, and that of FDRU are better at higher Reynolds number. Compare withthe traditional arrangement(CFUand CFD), The newly designedfin hasgreat effectivenessand uniformperformance in the localregion.
PAPER REVISED: 2018-08-22
PAPER ACCEPTED: 2018-08-24
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