Cooling tower Classification by use

Heating, ventilation and air conditioning (HVAC)

HVAC (Heating, Ventilation, and Air Conditioning) cooling towers are used to dispose of ("reject") unwanted heat from the chiller. Liquid-cooled chillers are generally more energy efficient than air-cooled chillers because the tower water rejects heat at or near wet bulb temperature. Air-cooled chillers must reject heat at a higher dry bulb temperature and therefore have a lower average reverse Carnot cycle efficiency.In regions with hot climates, large office buildings, hospitals and schools often use one or more cooling towers as part of their air conditioning systems.Typically, industrial cooling towers are much larger than HVAC towers.HVAC uses cooling towers Pair a cooling tower with a liquid-cooled chiller or a liquid-cooled condenser.A ton of air conditioner is defined as the removal of 12,000 Btu (3.5 kW) per hour.The equivalent tonne on the cooling tower side actually rejects about 15,000 British thermal units (4.4 kW) per hour due to the additional waste heat equivalent of energy required to drive the chiller compressor.This equivalent ton is defined as the heat rejection of 3 US gallons per minute (11 L/min) or 1,500 lbs/hr (680 kg/hr) of water cooled to 10 °F (5.6 °C), which is equivalent to 15,000 imperial heat per hour unit (4.4 kW), assuming a cooler coefficient of performance (COP) of 4.0.This COP is equivalent to an Energy Efficiency Ratio (EER) of 14.

Cooling towers are also used in HVAC systems that have multiple water source heat pumps sharing a common piped water loop.In this system, whenever the heat pump works in cooling mode, the water circulating inside the water cycle takes heat from the condenser of the heat pump, and then uses an external cooling tower to take heat from the water cycle and discharge it to the atmosphere.In contrast, when the heat pump is operating in heating mode, the condenser draws heat from the circulating water and discharges it into the space to be heated.When the water circuit is used primarily to heat the building, the cooling tower is usually shut down (possibly drained or winterized to prevent freeze damage) and heat is provided by other means, usually from a separate boiler.

Industrial cooling tower

Industrial cooling towers are used to remove heat from various sources, such as machinery or heated process materials.The main purpose of large-scale industrial cooling towers is to remove heat absorbed by power plants, oil refineries, petrochemical plants, natural gas processing plants, food processing plants, semiconductor plants and other industrial circulating cooling water systems Distillation tower condensers, crystallization cooling liquid and other facilities.The cooling water circulation rate of a typical 700 MWth coal-fired power plant is about 71,600 cubic meters per hour (315,000 US gallons per minute) and the circulating water needs a certain make-up rate of about one cubic meter per second).

If the same plant had no cooling towers and used once-through cooling water, it would require approximately 100,000 cubic meters per hour Large cooling water intake typically kills millions of fish and larvae per year as organisms affect intake measurement screen. Vast amounts of water have to be constantly returned to the ocean, lake or river and constantly resupplied to the factories.In addition, the discharge of large quantities of hot water may raise the temperature of the receiving river or lake to levels unacceptable to the local ecosystem.Elevated water temperatures can kill fish and other aquatic organisms (see Heat Pollution), or they can also lead to increases in harmful organisms such as zebra mussels or invasive species of algae.The role of cooling towers is to dissipate heat into the atmosphere, where wind and air diffusion spread heat over a much larger area than hot water can in a body of water.Evaporative cooling water cannot be used for subsequent use (except when it rains somewhere), while only surface cooling water can be reused. Some coal-fired and nuclear plants located in coastal areas do take advantage of a single pass of seawater. But even there, offshore discharge outlets need to be very carefully designed to avoid environmental problems.Oil refineries also have very large cooling tower systems.A typical large refinery processes 40,000 metric tons of crude oil per day (300,000 barrels (48,000 cubic meters) per day) and circulates approximately 80,000 cubic meters of water per hour through its cooling tower system.