Experimental Study of Fully Developed Turbulent Flow in Internally Finned Tubes

IF 1.5 4区 工程技术 Q3 ENGINEERING, MECHANICAL
Yi-ping Tu, Hsu-Te Lin, Rong-Hua Yeh
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Abstract

A steady, hydrodynamically and thermally fully developed turbulent water flow in internally finned tubes with constant heat flux boundary condition is investigated experimentally. In this experiment, 70°C hot water passes the inner tube while 20°C cold water flows through the annulus passage. In order to eliminate contact thermal resistance, the circular tube having a length of 1400 mm with inner fins is directly milled from a cylinder. Apart from a smooth tube, three internal-finned-tube heat exchanger having 4, 6, and 8 longitudinal trapezoidal fins are tested. For Re=5000, the tested tubes with four, six and eight fins can improve thermal performance by approximately 35.4%, 44.6% and 67.2%, but merely increase friction factor by 1.92%, 4.8% and 6.73%, respectively, compared to a smooth tube. The increases with respect to to a smooth tube in both Nu and f become smaller at a higher Re for N=4, 6, and 8. As pressure drop, increases, Q of the tested finned tubes first grows rapidly, and this growth curve gradually becomes flatter at a higher ΔP. Consequently, the heat transfer performance will become worse as ΔP>3.5 kPa for the proposed heat exchangers. Finally, correlating equations of Nu and f with respect to Re are presented for 3000 ≤ Re ≤ 7250.
内部翅片管中完全发展湍流的实验研究
实验研究了具有恒定热通量边界条件的内翅片管中稳定、流体力学和热学充分发展的湍流水流。实验中,70°C 的热水流经内管,20°C 的冷水流经环形通道。为了消除接触热阻,长度为 1400 毫米、带有内翅片的圆管是由圆柱体直接铣削而成的。除光滑管外,还测试了三种带有 4、6 和 8 片纵向梯形翅片的内翅片管热交换器。在 Re=5000 的条件下,与光滑管相比,带有 4 片、6 片和 8 片鳍片的测试管分别能将热性能提高约 35.4%、44.6% 和 67.2%,但摩擦因数仅分别增加 1.92%、4.8% 和 6.73%。当 N=4、6 和 8 的 Re 值较高时,与光滑管相比,Nu 和 f 的增加都会变小。随着压降的增加,测试的翅片管的 Q 值首先快速增长,当 ΔP 越大时,增长曲线逐渐变得平缓。因此,当 ΔP>3.5 kPa 时,拟议热交换器的传热性能将变差。最后,在 3000 ≤ Re ≤ 7250 的条件下,给出了 Nu 和 f 与 Re 的相关方程。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Journal of Enhanced Heat Transfer
Journal of Enhanced Heat Transfer 工程技术-工程:机械
CiteScore
3.60
自引率
8.70%
发文量
51
审稿时长
12 months
期刊介绍: The Journal of Enhanced Heat Transfer will consider a wide range of scholarly papers related to the subject of "enhanced heat and mass transfer" in natural and forced convection of liquids and gases, boiling, condensation, radiative heat transfer. Areas of interest include: ■Specially configured surface geometries, electric or magnetic fields, and fluid additives - all aimed at enhancing heat transfer rates. Papers may include theoretical modeling, experimental techniques, experimental data, and/or application of enhanced heat transfer technology. ■The general topic of "high performance" heat transfer concepts or systems is also encouraged.
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