光热转换系统中强化结构对纳米流体自然对流换热的影响

Effects of Enhanced Structures on Natural Convection Heat Transfer of Nanofluids in Photothermal Conversion System

为了改善光热转换系统中换热介质的自然对流,文中研究了两种微凸起结构(三角形和矩形)、两种温差(ΔT=1 K,ΔT=10 K)、两种纳米流体(CuO/Cu-H_(2)O纳米流体和CuO-H_(2)O纳米流体)和不同纳米流体体积分数(φ=0.01、0.03和0.05)对光热转换系统中工质自然对流换热特性的影响.研究发现,CuO-H_(2)O纳米流体和CuO/Cu-H_(2)O纳米流体的自由对流换热效率比水高.在三角形凸起结构中,当温差为1 K和10 K时,CuO/Cu-H_(2)O和CuO-H_(2)O纳米流体的自然对流换热效率分别比水增强了16.8%、11.1%、10%和5.6%.在矩形凸起结构中,当温差为1 K和10 K时,CuO/Cu-H_(2)O和CuO-H_(2)O纳米流体的自然对流换热效率分别比水增强了10.9%、4.4%、6.3%和2.6%.另外,三角形凸起结构比矩形凸起结构更有利于强化自由对流换热.

In order to improve the natural convection of heat transfer medium in photothermal conversion system,in this paper,the effects of two different micro-convex structures(triangular and rectangular),two temperature differences(ΔT=1 K,ΔT=10 K),two different nanofluids(CuO/Cu-H_(2)O nanofluids and CuO-H_(2)O nanofluids)and different nanofluids volume fractions(φ=0.01,0.03 and 0.05)on free convection heat transmission in photothermal conversion system were studied.Researches indicated that the free convection heat transfer efficiencies of CuO-H_(2)O nanofluids and CuO/Cu-H_(2)O nanofluids are all higher than that of water.For the triangular convex structure,when the temperature difference is 1 K and 10 K,the natural convection heat transfer efficiencies of CuO/Cu-H_(2)O and CuO-H_(2)O nanofluids are enhanced by 16.8%,11.1%,10%and 5.6%compared with that of water respectively.For the rectangular convex structure,when the temperature difference is 1 K and 10 K,the natural convection heat transfer efficiencies of CuO/Cu-H_(2)O and CuO-H_(2)O nanofluids are enhanced by 10.9%,4.4%,6.3%and 2.6%compared with that of water respectively.In addition,the results showed that the triangular convex structure is better than the rectangular convex structure in enhancing free convection heat exchange.