Experimental study on combined buoyant-thermocapillary flow along with rising liquid film on the surface of a horizontal metallic mesh tube

Abstract

Temperature distribution and variation with time has been considered in the analysis of the influences of the initial level of immersion of a horizontal metallic mesh tube in the liquid on combined buoyant and thermo-capillary flow. The combined flow occurs along with the rising liquid film flow on the surface of a horizontal metallic mesh tube. Three different levels of immersion of the metallic mesh tube in the liquid have been tested. Experiments of 60 min in duration have been performed using a heating metallic tube with a diameter of 25 mm and a length of 110 mm, sealed outside with a metallic mesh of 178 mm by 178 mm, and distilled water. These reveal two distinct flow patterns. Thermocouples and infrared thermal imager are utilized to measure the temperature. The level of the liquid free surface relative to the lower edge of the tube is measured as angle q. The results show that for a smaller q angle, or a low level of immersion, with a relatively low heating power, it is possible to near fully combine the upwards buoyant flow with the rising liquid film flow. In this case, the liquid is heated only in the vicinity of the tube, while the liquid away from the flow region experiences small changes in temperature and the system approaches steady conditions. For larger q angles, or higher levels of immersion, a different flow pattern is noticed on the liquid free surface and identified as the thermo-capillary (Marangoni) flow. The rising liquid film is also present. The higher levels of immersion cause a high temperature gradient in the liquid free surface region and promote thermal stratification; therefore the system could not approach steady conditions.

Key words： rising liquid film; combined flow; thermo-capillary flow; buoyant flow; metallic mesh tube; horizontal tube

Acknowledgements

This work was financially supported by Science and Technology Development Program of Qinghai Province (2013-N-547).

References

1 Mei N, He M Z, Zhao J, Yu H Y. Study of rising liquid film on surface of horizontal metallic mesh tube. Heat Transfer—Asian Research, 2009, 38(8): 557–568

2 Mei N, Li Y, Wang G, Bai Y, Liu X. Rising liquid film induced by rewetting and heat transfer on the surface of a fluted helix horizontal tube. Journal of Enhanced Heat Transfer, 2012, 19(2): 107–121

3 Mei N, Zhao J, Xu Y C. Fluted helix channel heat transfer along a vertical tube. Journal of Enhanced Heat Transfer, 2010, 17(4): 313–329

4 Li Y, Liu S S, Luan J, Wang Q L. The desalination device using the rising liquid film on the microscale fluted surface of horizontal tubes. Advanced Materials Research, 2014, 901: 59–63

5 Yu H Y, Mei N, Liu X B, He M Z, Si H Y. Non-linear behavior analysis of the rising liquid film on the fluted surface of a horizontal tube. Journal of Engineering Thermophysics, 2008, 29(6): 1048–1050

6 O’Brien S B G, Schwartz L W. Theory and modeling of thin film flows. 2002, available at the website of coating

7 Kang Q, Duan L, Hu W R. Experimental study of surface deformation and flow pattern on buoyant-thermocapillary convection. Microgravity Science and Technology, 2004, 15(2): 18–24

8 Schatz M F, Neitzel G P. Experiments on thermocapillary instabilities. Fluid Mechanics, 2001, 33(1): 93–127

9 Lee K J, Kamotani Y, Yoda S. Combined thermocapillary and natural convection in rectangular containers with localized heating. International Journal of Heat and Mass Transfer, 2002, 45(23): 4621–4630

10 Wang R, Kahawita . Oscillatory behaviour in buoyant thermocapillary convection of fluid layers with a free surface. International Journal of Heat and Mass Transfer, 1998, 41(2): 399–409

11 Hadid H B, Roux B. Buoyancy- and thermocapillary-driven flows in a shallow open cavity: unsteady flow regimes. Journal of Crystal Growth, 1989, 97(1): 217–225

12 Mundrane J Q, Xu A, Zebib. Thermocapillary convection in a rectangular cavity with a deformable interface. Advances in Space Research, 1995, 16(7): 41–53

13 Saleh H, Hashim I. Buoyant Marangoni convection of nanofluids in square cavity. Applied Mathematics and Mechanics-english Edition, 2015, 36(9): 1169–1184

14 Qin T, Tuković Z E, Grigoriev R O. Buoyancy-thermocapillary convection of volatile fluids under atmospheric conditions. International Journal of Heat and Mass Transfer, 2014, 75(4): 284–301

15 Dhavaleswarapu H K, Chamarthy P, Garimella S V, Murthy J Y. Experimental investigation of steady buoyant-thermocapillary convection near an evaporating meniscus. Physics of Fluids (1994–present), 2007, 19(8): 1064–1070

16 Dominiczak P R, Cieśliński J T. Circumferential temperature distribution during nucleate pool boiling outside smooth and modified horizontal tubes. Experimental Thermal and Fluid Science, 2008, 33(1): 173–177

17 Chaika V D. Vapor-bubble growth at the lower generatrix of horizontal tubes. Journal of Engineering Physics and Thermophysics, 1987, 52(1): 52–57