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Abstract
A simple theoretical model, validated against available numerical and experimental data in the literature, is presented to predict the effects of crosswind on the performance of natural draft dry cooling towers. The intersection of asymptote method, along with scale analysis, is used to find a closed-form solution for the airflow rate at the tower exit for given crosswind speeds. The total heat rejected under a windy condition is then calculated based on the air mass flow rate at the tower exit. This theoretical model allows for parametric studies and can generate accurate data. Interestingly, the model results, expected to be accurate within an order of magnitude, are more accurate than anticipated when compared to available experimental and numerical data in the literature. In fact, the maximum relative error is observed to be 15% when current theoretical predictions are compared to available experimental data. The results of this study will be useful for future work on the development of air-cooled condensers, especially for geothermal and solar thermal power plants in Australia.
NOMENCLATURE
| A | = | area, m2 |
| C | = | heat exchanger form drag resistance, m−1 |
| cp | = | specific at constant pressure, J kg−1 K−1 |
| D | = | tower exit diameter, m |
| F | = | force, N |
| g | = | gravitational acceleration, m s−2 |
| h | = | heat transfer coefficient, W m−2 K−1 |
| H | = | effective tower height, m |
| I | = | approach (Two-T∞), K |
| l | = | control volume height at the tower exit, m |
| L | = | maximum plume penetration height, m |
| O() | = | order of magnitude |
| Q | = | heat transferred out of the tower, W |
| Ra | = | Rayleigh number, ρ2cp2gβH4Q/(k3AtC)) |
| t | = | heat exchanger bundle thickness in flow direction, m |
| T | = | temperature, K |
| (x,r) | = | transverse and radial coordinates, m |
| (u,v) | = | velocity in (x,r) direction, m s−1 |
| V | = | velocity, m s−1 |
Greek Symbols
| β | = | thermal expansion coefficient, K−1 |
| δ | = | plume displacement, m |
| ϵ | = | heat transfer deterioration |
| ρ | = | density (kg m−3) |
| θ | = | plume deflection angle |
Subscripts
| n | = | normal |
| r | = | radial |
| D | = | draft |
| NW | = | no-wind |
| W | = | wind |
| wo | = | water out of the tower |
| ∞ | = | ambient |
Additional information
Notes on contributors
Kamel Hooman
Kamel Hooman is a senior lecturer at the University of Queensland, where he received his Ph.D. He is the Queensland Geothermal Energy Centre of Excellence Director and conducts fundamental and applied research on thermofluids engineering using theoretical, numerical, and experimental techniques. Dr. Hooman has co-authored more than 80 papers in refereed international journals and about as many in conferences and meetings as regular, invited, or keynote speaker. A regular reviewer for over 20 international journals, his editorial responsibilities extend to Journal of Porous Media, International Journal of Exergy, The Scientific World Journal, Thermal Science and Special Topics, and Reviews in Porous Media. His contributions have been recognized by a number of research and teaching awards as well as fellowships, with the latest one from the Australian Academy of Science.