Numerical analysis of a hybrid cooling tower and its plume

  • Author / Creator
    Aditya Kodkani
  • The most practical and economical method of dissipating waste heat from power stations and related heavy industry is via wet cooling towers. These towers dissipate the
    waste heat present in a stream of hot process water primarily by evaporating some
    small fraction of this water, which, in turn, leads to evaporative cooling. As a byproduct of this evaporation, wet cooling towers must emit to the atmosphere air that is
    hot and moist. Under select climatic conditions (e.g. cold ambient air with an elevated
    relative humidity), a visible plume may form. Such a plume is considered a public
    nuisance and may lead to an unwanted accumulation of moisture or, worse yet, ice on
    surrounding infrastructure e.g. roadways, runways and industrial facilities. To avoid
    such undesirable outcomes and to conserve water, a combination of wet and dry cooling
    may be employed in a hybrid cooling tower. To design a hybrid cooling tower for effective visible plume abatement, one requires not only knowledge of the turbulent mixing
    characteristics of the atmospheric plume but, in tandem, a model that describes heat
    and mass transfer processes within the cooling tower itself.
    This thesis presents a mathematical model to study the heat and mass transfer inside
    a hybrid cooling tower and a model to predict the behaviour of the atmospheric plume.
    The wet-portion model expands upon one presented in the earlier study of Klimanek and
    Bialecki (Int. Commun Heat Mass 36:547-553, 2009) by assigning zone-specific Merkel
    numbers to each of the rain, fill, and spray zones. Accordingly, we can determine,
    zone-by-zone, rates of heat rejection and water evaporation. By extension, we can
    estimate the mass flow rate of water and the humidity ratio and related thermodynamic
    properties of the outlet air and water streams. Our augmented model is validated
    against the well-established Poppe and Merkel methods as well as select field data from
    a multi-cell cooling tower located in Colorado, USA.
    A turbulent plume model based on the conservation of mass, momentum, heat, and
    moisture is adapted from the work of Wu and Koh (1978) [1] is coupled with the
    tower model described above. As a result, we are able to predict the behaviour of
    plumes emanating from multiple cooling tower cells. By extension, predictions of the
    likelihood of fog formation and, where applicable, of the visible plume height may be
    made. Special reference is made to ambient states characterized as hot-dry, hot-humid,
    cool-dry, and cool-humid to study cooling tower performance under a variety of climatic

  • Subjects / Keywords
  • Graduation date
    Spring 2021
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.