Analysis of Stagnant Non Condensable Gases Effects on Condensation Heat Transfer in a Vertical Tube

Abstract:

In a vertical condenser tube installed at the cold end of a non-vacuum separate type heat pipe, non condensable (NC) gases in the system is pushed by continuous vapor flowing from the hot end into the condenser tube at the cold end, gathering above condensate at the outlet of the condenser tube. Therefore, condensation heat transfer of vapor with the stagnant NC gases occurs in the condenser tube. It is necessary to comprehend the effects of stagnant NC gases on condensation heat transfer. A VOF method was adopted to analyze how stagnant NC gases affect condensation heat transfer, a mass fraction equation of NC gases was used to solve diffusion between NC gases and vapor, a Hertz-Knudsen-Schrage model was applied to deal with condensation rate of vapor on the surface of liquid film. Parameters, including volume fraction, velocity, pressure, mass fraction of NC gases and condensation heat transfer coefficients (HTC), were obtained. Results show that a lot of NC gases deposits in the condenser tube rear, leading a lot of vapor to condense at the condenser tube front. NC gases slightly affect condensation HTC of the tube front, and severely degrade condensation HTC of the tube rear. Furthermore, an increase in mass of NC gases causes a rise in pressure and velocity, improving condensation heat transfer.

• Periodical: Applied Mechanics and Materials (Volumes 148-149)
• Pages: 491-495
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.148-149.491
• Online since: December 2011
• Authors: Jun Xia Zhang, Zeng Sheng Li, Bin Yao Gong, Hong Xing Zhao, Yu Huai Zhao
• Keywords: Condensation, Heat Transfer, Non-Condensable Gases

References

[1] K.M. Vierow: PhD thesis, University of California at Berkeley, CA (1990)

[2] M.Siddique: PhD thesis, Massachusetts Institute of Technology, Cambridge (1992)

[3] H.S. Park, H.C. No: Nuclear Technology Vol.127 (1999), pp.160-16

[4] S.Z. Kuhn: PhD thesis, Department of Nuclear Engineering, University of California, Berkeley, CA(1995)

[5] K.Y. Lee and M.H. Kim: Nuclear Engineering and Design Vol. 238 (2008), pp.207-216

[6] T.L. Jian: Nuclear Engineering and Design Vol. 204 (2001), pp.221-23

[7] S.B.A.Al-Shammari : Desalination Vol. 169 (2004), pp.151-160

[8] Zhu A M: Desalination Vol. 214 (2007), pp.128-137

[9] H.C. No and H.S. Park: International Journal Heat and Mass Transfer Vol. 45(2002), pp.845-854

[10] J.C.D.L. Rosa, J.L. Muñoz-Cobo and A.Escrivá: Nuclear Engineering and Design Vol. 28(2007), pp.1-13

[11] E.C. Siow and S.J. Ormiston: International Journal of Thermal Sciences Vol. 46(2007), pp.458-466

[12] V.D. Rao, V.M. Krishna and K.V. Sharma: International Journal of Heat and Mass Transfer Vol. 51 (2008), pp.1-12

[13] D.S. Vladimir, V.S. Zoran and S. Uwe: Journal of Heat and Mass Transfer Vol. 49(2006), pp.2420-2436

[14] C.W. Hirt and B.D. Nichols: J.Comput.Phys Vol. 93(1981), pp.273-285

[15] H.Hertz and Ǜber: Annual review of Physical Chemistry Vol 17(1882), pp.177-200

[16] M.Knudsen: Annual review of Physical Chemistry Vol 47(1915), p.697–708

[17] R. Schrage: A Theoretical Study of Interphase Mass Transfer (Columbia University Press：New York 1953)

[18] D.L. Youngs: Numerical Methods for Fluid Dynamics (Academic Press 1982)