Down Draft Air Cooling Towers

Did you know that the University of Arizona has worked on a cooling method that doesn’t use electricity to cool your whole house?

You can read about it in a paper they published called Implementation Of Natural Down-Draft Evaporative Cooling Devices.

Conventional evaporative coolers are high-pressure high-volume devices that deliver cool air by water evaporation wetted pads. Natural down-draft evaporative coolers, or “Cool Towers”, are devices developed at The University of Arizona’s Environmental Research Laboratory. Similar to conventional coolers, these devices are equipped with wetted pads and sprays at the top which provide cool air by evaporation but the air is moved by gravity flow saving the energy required by the blower. In arid regions, cool towers are useful for cooling buildings and outdoor private and public areas. This paper focuses on recent implementation of cool towers iu two international projects in arid regions. It also demonstrates COOL@, a software developed by the author, which was used for sizing and designing the cool towers used in these projects. The two demonstrated projects are: 1) The Botswana Technology Center (BTC), a Headquarters office building in Botswana, South Africa. The building energy loads were first optimized through energy conservation measures where the heating load, as predicted by computer simulation, was reduced by 89.9% and the cooling load by 24%. The cooling load was further addressed by the use of a series of integrated cool towers.

Forced draft or “swamp” coolers have been used for many years in the desert southwest of the United States and require energy for a blower to force air through wetted pads and the structure to be cooled, plus a small pump for re-circulating water over the pads. Natural down-draft evaporative coolers do not need the blower and require only the re-circulating pump; some designs eliminate the re-circulation pump and utilize the pressure in the supply water line to periodically surge water over the pads, eliminating the requirement for any electrical energy input (Thompson 1992).  Natural down-draft evaporative coolers, or Cool Towers, were originally designed and developed by scientists and engineers at the University of Arizona’s Environmental Research Laboratory in Tucson, Arizona, USA (Cunningham & Thompson 1986). The towers are topped with a hydro unit equipped with wetted pads, sprays, gutter and a recycling pump which provide cool air by gravity flow. These towers are often described as reverse chimneys; just as the column of warm air in a chimney rises, the column of cool air, in this instance, falls. The air flow rate depends on the efficiency Implementation of Natural Down-Drafi Evaporative Cooling Devices - 3.63 of the evaporative cooling device, tower height and cross section, as well as the resistance to air flow in the cooling device, tower and structure (if any) into which it discharges. Water consumed by Cool Towers is almost similar (often less) than that consumed by conventional evaporative coolers.  In general, water consumption increases as the volume of cooled air (cfm) produced by either system increases.

Need help with your AC system?  Call Aaron’s Mechanical Services at 623-388-4436 to see how we can help.

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