THERMAL SCIENCE

International Scientific Journal

Dilli Balaji

,

Ramalingam Velraj

,

Malavarappu Ramanamurthy

THE CFD STUDIES ON THE INFLUENCE OF UN-WETTED AREA ON THE HEAT TRANSFER PERFORMANCE OF THE HORIZONTAL TUBE FALLING FILM EVAPORATION

ABSTRACT
This paper discusses about the effect of un-wetted area of tube on the heat transfer performance of horizontal tube falling film evaporation. A 2-D CFD model was developed to perform simulations and investigate the output and validated them with published data available in the literature. In the present study the volume of fluid method is used to track the boundary of the liquid vapour from the contours of volume fraction. Effect of varying tube wall temperature or wall super heat (6-11°C) on un-wetted area, heat transfer coefficients, and mass transfer coefficients of the circular tube were obtained from the simulation model and the results were analysed and reasons were identified and discussed here. The threshold value of wall super heat above which phase change occurs between liquid film and tube surface is identified as 6°C. Also it is noted that mass transfer rate increases and then decreases with increase of wall super heat and heat transfer coefficient showed declining trend.
KEYWORDS
Un-wetted area, CFD modeling, Dry patches, Mass transfer rate, heat transfer rate, Falling film, Wall super heat
PAPER SUBMITTED: 2020-04-14
PAPER REVISED: 1970-01-01
PAPER ACCEPTED: 2020-11-22
PUBLISHED ONLINE: 2021-02-06
DOI REFERENCE: https://doi.org/10.2298/TSCI200414056B
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2022, VOLUME 26, ISSUE Issue 1, PAGES [25 - 35]
REFERENCES
  1. Asbik, M., et al., Numerical Study of Boundary Layer Transition in Flowing Film Evaporation on Horizontal Elliptical Cylinder, Heat and Mass Transfer, 41 (2005), pp.399-410.
  2. Pu, L., et al., Effects of Tube Shape on Flow and Heat Transfer Characteristics in Falling Film Evaporation, Applied Thermal Engineering, vol.148 (2019), pp.412-419.
  3. Zhou, Y., et al., Numerical Simulation of Double-Phase Coupled Heat Transfer Process of Horizontal Tube Falling Film Evaporation, Applied Thermal Engineering, vol.118 (2017), pp.33-40.
  4. Christians,M et al., Film condensation of R-134a and R236fa part-1: Experimental results and predictive correlation for single-row condensation on enhanced tubes, Heat Transfer Engineering, vol.31 (2010),10, pp.799-808.
  5. Tahir, F., et al., Review on CFD Analysis of Horizontal Falling Film Evaporators in Multi Effect Desalination Plants, Desalination and Water Treatment, vol.166 (2019), pp.296-320.
  6. Esquivel, J.F., et al., Hydrodynamic Analysis of the Falling Film Formation in Evaporators using CFD Simulations, Food and Bio-Products Processing, vol.101 (2017), pp.56-67.
  7. Wang, B.X., et al., Experimental study on the dry out heat flux of falling film liquid film, International Journal of Heat and Mass Transfer, vol.43 (2000), pp.1897-1903.
  8. Bohn, M.S, Davis,S.H, Thermocapillary breakdown of falling films at high Reynolds numbers, International Journal of Heat and Mass Transfer, vol.36 (1993), pp.1875-1881.
  9. Zhiwei, T., et al., Experimental study on surface wave and film breakdown of faling liquid film flow, Heat and Mass Transfer, vol.45 (2009), pp.673-677.
  10. Yang, L., et al., Effect of the dry out in tube bundles on the heat transfer performance of falling film evaporators, Procedia Engineering, vol.205 (2017), pp.2176-2183.
  11. Li, H., et al., Numerical simulation for falling film flow characteristics of refrigerant on the smooth and structured surfaces, Journal of Engineering Thermophysics, vol.27 (2018), pp.1-19.
  12. Lee, W., A Pressure Iteration Scheme for Two-Phase Flow Modelling, Multi-Transport Fundamentals, Reactor Safety, Applications, vol.1 ed TN Veziraglu (Washington DC: Hemisphere Publishing) (1980), pp.407-31.
  13. Balaji, D., et al., Numerical Investigation on the Effect of Tube Geometry and Feeder Height on the Heat Transfer Performance of Horizontal Tube Falling Film Evaporation, Journal of Heat Transfer, 141 (2019),11, pp.111502-111516.
  14. Issa, R.I., et al., The Computation of Compressible and Incompressible Recirculating Flows by a Non-Iterative Implicit Scheme, Journal of Computational Physics, vol.62 (1986), 1, pp.66-82, 1986.
  15. Mishriky, F., et al., Towards Understanding the Influence of Gradient Reconstruction Methods on Unstructured Flow Simulations, Transactions- Canadian Society for Mechanical Engineering, vol.41(2017), 2, pp.169-179.
  16. Patankar, S.V., Numerical Heat Transfer and Fluid Flow, McGraw-Hill, Newyork, 1980.
  17. Courent, R., et al., On the Solution of Non-Linear Hyperbolic Differential Equations by Finite Differences, Communications on Pure and Applied Mathematics, vol.5 (1952), 3, pp.243-255.
  18. Ubbink, O., Numerical Prediction of Two Phase Fluid Systems with Sharp Interfaces, PhD. Thesis, University of London, 1997.
  19. Yang, L., et al., Experimental Study of Falling Film Evaporation Heat Transfer Outside Tubes, Desalination, vol.220 (2008), 1, pp.654-660.
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The CFD studies on the influence of un-wetted area on the heat transfer performance of the horizontal tube falling film evaporation

© 2024 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence