Numerical simulation of non-linear film variation and heat transfer characteristics in falling film evaporation around in-line horizontal tubes

Abstract

In falling film evaporation on a horizontal tube, heat transfer phenomena are highly unpredictable due to uncertainties in the determination of film thickness around the tube, local dry-out condition, geometrical configuration, tube spacing etc. Numerical simulations of falling film evaporation around a single horizontal tube are performed using volume of fluid (VOF) method. Film thickness around the circumference of the horizontal tube is investigated and validated with Nusselt correlations and experiments carried out by researchers. The results are in good agreement with experimental investigations performed by various researchers. Influence of inter-tube spacing, film Reynolds number and variation of diameter on the formation of film thickness are studied and it is found that the film thickness is minimum around 100o-120o circumferential position, whereas Nusselt correlation predicted the minimum value at 90o circumferential position. Wall shear stress and heat transfer are also studied around the horizontal cylinder. It is seen that near the impingement zone, fluctuation of wall shear stress and heat transfer are very high, showing abnormal behaviour in this zone.

Keywords

• Falling Film
• Film Thickness
• Heat Transfer
• Horizontal Tube

References

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