CFD Investigation of Falling Film Flow over Horizontal Tube

EasyChair Preprint 5671

Abstract

The heat exchangers employed in multi-effect desalination (MED) and ammonia/lithium bromide refrigeration systems are usually of falling film types. In horizontal falling film exchangers, liquid is sprayed on the top of bundle, which forms thin film around the tube that makes these exchangers to operate at low temperature difference and spray density. The film hydrodynamics around the tube affects the heat and mass transfer mechanisms, which causes heat exchanger performance to change. In this work, a 2D computational fluid dynamics (CFD) model has been developed in Ansys fluent v18.0, to understand falling film dynamics around the tube of 25.4 mm diameter. The physical domain consists of two tubes with an impingement height of 15.9 mm and inter-tube spacing of 31.8 mm. For water entrance, 2 mm orifice is selected at the top of first tube. The spray density is varied from 0.02-0.05 kg/(m·s) to examine film thickness and residence time for first and second tube. The CFD results show that the film thickness increases with the increasing spray density, the average film thickness rises by 56% and time for complete wetting decreases by 48.6% ,when the spray density increases from 0.02 to 0.05 kg/(m·s). In addition, the average film thickness reduces by around 13.7% for second tube as compared to that of first tube because of impingement height difference.

Keyphrases: CFD, Falling film, Horizontal tube, Hydrodynamics

@booklet{EasyChair:5671,
  author    = {Furqan Tahir and Abdelnasser Mabrouk and Muammer Koc},
  title     = {CFD Investigation of Falling Film Flow over Horizontal Tube},
  howpublished = {EasyChair Preprint 5671},
  year      = {EasyChair, 2021}}