S40 -- Cooling Towers (SI)

Most air-conditioning systems and industrial processes generate heat that must be removed and dissipated. Water is commonly used as a heat transfer medium to remove heat from refrigerant condensers or industrial process heat exchangers. In the past, this was accomplished by drawing a continuous stream of water from a utility water supply or a natural body of water, heating it as it passed through the process, and then discharging the water directly to a sewer or returning it to the body of water. Water purchased from utilities for this purpose has become prohibitively ex-pensive because of increased water supply and disposal costs. Similarly, cooling water drawn from natural sources is relatively unavailable because the ecological disturbance caused by the in-creased temperature of discharge water has become unacceptable. Air-cooled heat exchangers cool water by rejecting heat directly to the atmosphere, but the first cost and fan energy consumption of these devices are high and the plan area required is relatively large. They can economically cool water to within approximately 20F (11 K) of the ambient dry-bulb temperature: too high for the cooling water requirements of most refrigeration systems and many industrial processes. Cooling towers overcome most of these problems and therefore are commonly used to dissipate heat from refrigeration, air-conditioning, and industrial process systems. The water consumption rate of a cooling tower system is only about 5% of that of a once-through system, making it the least expensive system to operate with purchased water supplies. Additionally, the amount of heated water discharged (blowdown) is very small, so the eco-logical effect is greatly reduced. Lastly, cooling towers can cool water to within 4 to 5F (2 to 3 K) of the ambient wet-bulb temperature, which is always lower than the ambient dry-bulb, or approximately 35F (19 K) lower than can air-cooled systems of reasonable size(in the 250 to 500 ton [880 to 1760 kW] range). This lower temperature improves the efficiency of the overall system, thereby reducing energy use significantly and increasing process output.

Chapter Table of Contents

Principle of Operation
Design Conditions
Types of Cooling Towers
Materials of Construction
Selection Considerations
Application
Performance Curves
Cooling Tower Thermal Performance
Cooling Tower Theory
Tower Coefficients
Additional Information

ISBN: 978-1-936504-26-8 (for SI versions of chapters)
ISSN: 1930-7705 (for SI versions of chapters)

Citation: 2012 ASHRAE Handbook -- HVAC Systems and Equipment: Chapter 40, Cooling Towers



Product Code(s): D-S402012SI