Renewable energy or low grade energy utilizations need high performance of phase change heat exchangers. Suspending micromembrane cylinder in tube(called modulated heat transfer tube) increases the void fractions or v...Renewable energy or low grade energy utilizations need high performance of phase change heat exchangers. Suspending micromembrane cylinder in tube(called modulated heat transfer tube) increases the void fractions or vapor qualities near the tube wall to significantly enhance heat transfer. The R123 condensation heat transfer with horizontal position was investigated. The results for the bare tube and modulated heat transfer tube were tested case by case. It is found that the modulated heat transfer tube significantly enhance the condensation heat transfer, with the heat transfer enhancement factors(EF)covering the range of 1.118–2.124. The comprehensive performance evaluation criteria(PEC) had the range of0.71–1.66, with most of runs behaving PEC larger than 1.0.For the two-phase outlet conditions, the EF values are increased with increases in the vapor mass fluxes, Gxin,where G is the mass flux and xinis the inlet vapor mass quality. The EF values are inversely related to Gxinfor the subcooled liquid outlet cases. The enhanced heat transfer mechanisms are analyzed with the observed images together with the discussion of pressure and velocity distributions.展开更多
Vapor-liquid two phase flow behavior of R123 inside herringbone microfin tubes has been studied. Herringbone microfin tube is a kind of internally finned tube in which microfins are installed inside the tube where the...Vapor-liquid two phase flow behavior of R123 inside herringbone microfin tubes has been studied. Herringbone microfin tube is a kind of internally finned tube in which microfins are installed inside the tube where the microfins form multi-V-shape in flow direction. For the present experiment three different types of herringbone microfin tubes with helix angle B = 8, 14 and 28 are used. Experimental observations showed how flow diverges and converges inside herringbone microfin tube due to fin arrangement. The effect is more remarkable for larger helix angle. From the measurements of the cross-sectional liquid flow rate distribution, the liquid removal and collection and the entrained droplet are discussed. Quantity of liquid droplets is increased with increase of helix angle. The tube with helix angle B = 28 shows higher quantity of liquid droplets than others.展开更多
对以自主设计的向心透平为膨胀机的有机朗肯循环低品位热能发电系统进行实验研究,结果表明:蒸发器的火用损失都是最大的,其次是冷凝器和向心透平,透平入口压力0.397 MPa、入口温度100.58℃时,蒸发器火用损失为3.81 k W,占总火用损失50.6...对以自主设计的向心透平为膨胀机的有机朗肯循环低品位热能发电系统进行实验研究,结果表明:蒸发器的火用损失都是最大的,其次是冷凝器和向心透平,透平入口压力0.397 MPa、入口温度100.58℃时,蒸发器火用损失为3.81 k W,占总火用损失50.64%,冷凝器和透平火用损失为2.88和0.82 k W,分别占38.25%和10.89%.在实验基础上,用Aspen7.3模拟增加回热器对系统性能的影响,结果显示:热源温度和蒸发温度不变时,有回热器的ORC系统热力性能优于基本ORC系统.展开更多
基金supported by the National Natural Science Foundation of China of International Cooperation Project (51210011)the National Basic Research Program of China (2011CB710703)the National Natural Science Foundation of China (U1034004)
文摘Renewable energy or low grade energy utilizations need high performance of phase change heat exchangers. Suspending micromembrane cylinder in tube(called modulated heat transfer tube) increases the void fractions or vapor qualities near the tube wall to significantly enhance heat transfer. The R123 condensation heat transfer with horizontal position was investigated. The results for the bare tube and modulated heat transfer tube were tested case by case. It is found that the modulated heat transfer tube significantly enhance the condensation heat transfer, with the heat transfer enhancement factors(EF)covering the range of 1.118–2.124. The comprehensive performance evaluation criteria(PEC) had the range of0.71–1.66, with most of runs behaving PEC larger than 1.0.For the two-phase outlet conditions, the EF values are increased with increases in the vapor mass fluxes, Gxin,where G is the mass flux and xinis the inlet vapor mass quality. The EF values are inversely related to Gxinfor the subcooled liquid outlet cases. The enhanced heat transfer mechanisms are analyzed with the observed images together with the discussion of pressure and velocity distributions.
文摘Vapor-liquid two phase flow behavior of R123 inside herringbone microfin tubes has been studied. Herringbone microfin tube is a kind of internally finned tube in which microfins are installed inside the tube where the microfins form multi-V-shape in flow direction. For the present experiment three different types of herringbone microfin tubes with helix angle B = 8, 14 and 28 are used. Experimental observations showed how flow diverges and converges inside herringbone microfin tube due to fin arrangement. The effect is more remarkable for larger helix angle. From the measurements of the cross-sectional liquid flow rate distribution, the liquid removal and collection and the entrained droplet are discussed. Quantity of liquid droplets is increased with increase of helix angle. The tube with helix angle B = 28 shows higher quantity of liquid droplets than others.
文摘对以自主设计的向心透平为膨胀机的有机朗肯循环低品位热能发电系统进行实验研究,结果表明:蒸发器的火用损失都是最大的,其次是冷凝器和向心透平,透平入口压力0.397 MPa、入口温度100.58℃时,蒸发器火用损失为3.81 k W,占总火用损失50.64%,冷凝器和透平火用损失为2.88和0.82 k W,分别占38.25%和10.89%.在实验基础上,用Aspen7.3模拟增加回热器对系统性能的影响,结果显示:热源温度和蒸发温度不变时,有回热器的ORC系统热力性能优于基本ORC系统.
