ABSTRACT

Heat transfer and pressure drop of vapor flow in a finned double-pipe heat exchanger with different geometrical structures of perforated tube inserts as turbulators have been experimentally investigated. For this purpose, the influence of the number of perforations, as well as their place, and diameter has been examined in the Reynolds number range of 2200–3850 in the annulus. The working fluids in the inner tube and annulus were vapor and cold water, respectively. Several perforation configurations, including the helical pattern, four-row pattern, and the patterns with perforations on the top, and on both top and bottom of the tube with two different perforation diameters have been tested. The results suggest that in all of the cases with the perforated tube inserts, the overall heat transfer coefficient was improved compared to the plain heat exchanger. Among the examined patterns, the perforated tube with a row of perforation on the top of the tube presented the highest heat transfer coefficient. The experimental results show that inserting the tubes with a row of perforation on the top, helical perforations, two rows of perforations on the top and bottom, four rows of perforations, and four rows of perforations with larger diameter present a heat transfer enhancement of 73%, 60%, 47%, 33%, and 20%, respectively, and offers a maximum thermal performance factor of 1.42. The results also suggest that with higher Reynolds numbers, the average heat transfer and the amount of condensed vapor increase.

摘要

实验研究了具有不同几何结构的穿孔管插入件作为湍流器的翅片双管换热器中蒸汽流动的传热和压降。为此，已经在环空的 2200–3850 雷诺数范围内检查了穿孔数量及其位置和直径的影响。内管和环空的工作流体分别为蒸汽和冷水。已经测试了几种穿孔配置，包括螺旋图案、四排图案和顶部穿孔图案，以及管的顶部和底部具有两种不同穿孔直径的穿孔图案。结果表明，在所有带有穿孔管插入件的情况下，与普通换热器相比，整体传热系数有所提高。在检查的模式中，管顶部有一排穿孔的穿孔管具有最高的传热系数。实验结果表明，插入顶部一排穿孔、螺旋穿孔、上下两排穿孔、四排穿孔、四排较大直径穿孔的管子，传热增强为73 %、60%、47%、33% 和 20%，最大热性能系数为 1.42。结果还表明，随着雷诺数的增加，平均传热和冷凝蒸汽量增加。管顶有一排穿孔的穿孔管传热系数最高。实验结果表明，插入顶部一排穿孔、螺旋穿孔、上下两排穿孔、四排穿孔、四排较大直径穿孔的管子，传热增强为73 %、60%、47%、33% 和 20%，最大热性能系数为 1.42。结果还表明，随着雷诺数的增加，平均传热和冷凝蒸汽量增加。管顶有一排穿孔的穿孔管传热系数最高。实验结果表明，插入顶部一排穿孔、螺旋穿孔、上下两排穿孔、四排穿孔、四排较大直径穿孔的管子，传热增强为73 %、60%、47%、33% 和 20%，最大热性能系数为 1.42。结果还表明，随着雷诺数的增加，平均传热和冷凝蒸汽量增加。四排孔径较大的穿孔，传热效率分别提高了73%、60%、47%、33%和20%，最大热性能系数为1.42。结果还表明，随着雷诺数的增加，平均传热和冷凝蒸汽量增加。四排孔径较大的穿孔，传热效率分别提高了73%、60%、47%、33%和20%，最大热性能系数为1.42。结果还表明，随着雷诺数的增加，平均传热和冷凝蒸汽量增加。