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ICHMT DIGITAL LIBRARY ONLINE

ISSN 961-91393-0-5

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Year 2005

• 18th Australasian Heat and Mass Transfer Conference
Curtin University of Technology, Perth, Western Australia, 26-29 July 2005

239 pages

Volume price - $518.00

The Importance of Inlet Height to the Performance of a Natural Draft Wet Cooling Tower

N. Williamson
School of Aerospace, Mechanical & Mechatronic Engineering, The University of Sydney, NSW, 2006 AUSTRALIA

Steven Armfield
Sydney University

Masud Behnia
School of Mechanical and Manufacturing Engineering, University of New South Wales, Sydney 2052, Australia

ABSTRACT

This study examines the effect that the inlet height has on the performance of a Natural Draft Wet Cooling Tower. A 2D axisymmetric numerical model has been developed within Fluent, a commercial CFD package. The two-phase model represents the water flow in the rain and spray regions with Lagrangian particle tracking. The fill has been represented using user defined subroutines which employ Poppe style transfer coefficients. The effect of condensation in the heat and mass transfer regions has been accounted for allowing more accurate computation of the tower draft than is possible with the traditional Merkel style transfer coefficients. Particular attention is paid to the radial heat and mass transfer profiles which occur as a result of both the non-uniform flow distribution through the fill and flow retardation in the inlet region. The results show that even at very small inlet heights, the flow distribution is fairly uniform though most of the tower. Furthermore the size of the inlet effected region remains approximately the same although the performance degradation in this region does of coarse increase at small inlet heights due to the higher inlet velocity. The load profile through the cooling tower remains almost identical under all inlet heights A brief comparison is made with the traditional 1-D design methods which neglect variation in flow distribution through the fill. The implicit 1D assumptions in these models is shown to be largely valid even at very small inlet heights. This has important implications for optimizations studies where previously this was an unknown factor.