Thesis

A modelling and experimental study of evaporating two-phase flow on the shellside of shell-and-tube heat exchangers

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Awarding institution
  • University of Strathclyde
Date of award
  • 2005
Thesis identifier
  • T11248
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Department, School or Faculty
Abstract
  • The thesis describes the results of a research programme involving both experimental and modelling work to study evaporation on the shellside of shell-and-tube heat exchangers. The particular focus is on the study of evaporation over a range of mass fluxes typical of operating practice. Current design procedures make simplifying assumptions (such as a uniform gas/liquid distribution across the entire cross section of the shellside) which are thought to be inaccurate. The experimental work was conducted on a TEMA E-type shell and tube evaporator. The evaporator has 97 tubes of length 1240 mm, and the unit is large enough to represent full-scale industrial exchangers. Geometrical considerations such as baffle orientation and presence of sealing strips were also tested. The results show that there is a drop in the heat transfer performance at lower mass fluxes and higher vapour outlet qualities. It is suggested that the sudden drop in heat transfer performance at lower mass fluxes is caused by a change in flow pattern on the shellside of the heat exchanger. Evidence suggests that there is a possible transition from a homogeneous to a stratified two-phase flow. Support for this conclusion is that the transition in heat transfer performance appears to coincide with a change in the behaviour of the measured two-phase pressure drop multiplier. The thesis also describes the development of a model for shellside heat transfer and pressure drop which allows for the effects of separated flow and also attempts to predict the apparent transition in two-phase flow pattern. Knowledge of the existence of the transition and its prediction is important in avoiding unexpected poor performance in practice. A close correspondence is found when the predictions from the developed model are compared with the data from the experimental programme.
Resource Type
DOI
EThOS ID
  • uk.bl.ethos.417350
Date Created
  • 2005
Former identifier
  • 706652

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