Text №13 Cooling towers

Cooling towers¹ are heat removal devices used to transfer process waste heat² to the atmosphere. Cooling towers may either use the evaporation³ of water to remove process heat and cool the working fluid to near the wet-bulb air temperature⁴ or, in the case of closed circuit dry cooling towers, rely solely on air to cool the working fluid to near the dry-bulb air temperature⁵.

Common applications include cooling the circulating water used in oil refineries⁶, petrochemical⁷ and other chemical plants, thermal power stations⁸ and HVAC⁹ systems for cooling buildings.

Cooling towers vary in size from small roof-top units to very large hyperboloid structures (as in the adjacent image) that can be up to 200 metres tall and 100 metres in diameter, or rectangular¹⁰ structures (as in Image 3) that can be over 40 metres tall and 80 metres long. The hyperboloid cooling towers are often associated with nuclear power plants, although they are also used to some extent in some large chemical and other industrial plants. Although these large towers are very prominent, the vast majority of cooling towers are much smaller, including many units installed on or near buildings to discharge heat from air conditioning. A hyperboloid cooling tower was patented by Frederik van Iterson and Gerard Kuypers in 1918.^[1] The first hyperboloid cooling towers were built prior to 1930 in Liverpool, England to cool water used at an electrical power station that used coal.

1. Cooling tower – градирня, охладитель

2. Waste heat – отработанное тепло

3. Evaporation - испарение

4. Wet-bulb air temperature

5. Dry-bulb air temperature

6. Oil refinery – нефтеперерабатывающий завод

7. Petrochemical - нефтехимический

8. Thermal power station - теплоэлектростанция

9. HVAC - heating, ventilating and air conditioning - тепловентиляционный

10. Rectangular – прямоугольный

Text №14 hvac

An HVAC (heating, ventilating, and air conditioning) cooling tower is used to dispose of ("reject") unwanted heat from a chiller¹. Water-cooled chillers are normally more energy efficient than air-cooled chillers due to heat ejection to tower water at or near wet-bulb temperatures². Air-cooled chillers must reject heat at the higher dry-bulb temperature³,. Large office buildings, hospitals, and schools typically use one or more cooling towers as part of their air conditioning systems. Generally, industrial cooling towers are much larger than HVAC towers.

Cooling towers are also used in HVAC systems that have multiple water source heat pumps⁴ that share a common piping water loop. In this type of system, the water circulating inside the water loop⁵ removes heat from the condenser of the heat pumps whenever the heat pumps are working in the cooling mode⁶, then the externally mounted cooling tower is used to remove heat from the water loop and reject it to the atmosphere. By contrast, when the heat pumps are working in heating mode⁷, the condensers draw heat out of the loop water and reject it into the space to be heated. When the water loop is being used primarily to supply heat to the building, the cooling tower is normally shut down (and may be drained or winterized⁸ to prevent freeze damage), and heat is supplied by other means, usually from separate boilers⁹.