TABLE OF CONTENTS Natural draft cooling towers are found in power and chemical plants throughout the world. Different shapes and types of structures exist, but their fundamental function is the same, i.e., to create the flow of air through the fill or bundles of finned tube heat exchangers by means of buoyancy effects.
The hyperbolic concrete tower, which is normally operated in the wet mode, is also effectively employed as a dry-cooling tower if designed specifically for this purpose. Other towers may be made of aluminum-clad steel or wood. The main dimensions of cooling towers are usually determined by
performance
structure, according to Niemann
economic considerations, according to both Alomwooja et al. and Krings
At the same time, Grange asserts aerodynamic and thermal factors should not be ignored. In areas of the world where seismic activity is prevalent, aluminum clad steel towers may be preferred. Cost structures may be such that this type of dry-cooling tower is cheaper than a concrete tower.
The performance of any natural draft cooling tower is influenced by the characteristics of the fill or the finned-tube, heat-exchanger bundles at the base of the tower, the tower geometry, and ambient conditions, such as temperature, pressure, winds, inversions, and precipitation according to Moore and Heberholz and Schulz. Furthermore, fouling reduces transfer coefficients and increases flow resistances. The result is a corresponding reduction in cooling tower performance. Where specific information on fouling is available, this can be incorporated directly in the design.
Consider the example of...
