Microscopic mechanisms of wave effect on heat transfer enhancement in condensate films. (31st August 2019)

• Record Type: Journal Article
• Authors: Yang, Luopeng; Song, Jiajun; Zhang, Linhua; Li, Hongyou; Yang, Yan; Shen, Shengqiang
• Is Part Of: Chemical engineering science. Volume 204(2019)
• Page Start: 220
• Page End: 227
• Publication Date: 2019-08-31
• Subjects: Wave -- Heat transfer enhancement -- Normal velocity -- Condensate film -- Hydrodynamic behavior; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2019.04.012
• Languages: English
• ISSNs: 0009-2509

Abstract

Highlights: Convection and conduction contribute to heat transfer in condensate films. The temperature gradient at the wall is influenced by the normal velocity. Effects of film thinning and convection on heat transfer enhancement are quantified. Abstract: In order to deeply understand the inherent links between hydrodynamic behaviors and heat transfer enhancement in wavy condensate films, a numerical model using a non-orthogonal coordinate transformation was developed to simulate the evolution of wavy films. A sinusoidal disturbance was introduced by a fictitious body force to sustain waves. Two major pressure gradients are established at the wave front. One parallel to the stream-wise direction accelerates fluids and the other normal to the wall increases the normal velocity. The temperature profiles prove that both convection and conduction contribute microscopic mechanisms to heat transfer enhancement in the condensate films. The normal velocity close to the wall significantly influences the temperature gradient at the wall. The predicted heat transfer coefficient for the wavy film was found to be 30% greater than the Nusselt solution for the given parameters. Under the given conditions, the effects of film thinning and convection account for 6% and 24% of the heat transfer enhancement, respectively.