How does heat transfer occur between hot water and air in a cooling tower?
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How does heat transfer occur between hot water and air in a cooling tower?
When hot water flows over the surface of the filler, a water film is formed to exchange heat with the air.
In a cooling tower, two types of heat transfer occur between hot water and air: evaporation heat transfer and conduction heat transfer. Evaporative heat transfer occurs when the saturated vapor pressure of water at its surface temperature is greater than the partial pressure of water vapor in the air; the water molecules on the surface of the water droplets overcome the attractive forces between liquid water molecules and vaporize, entering the air. This process carries away the latent heat of vaporization, causing the temperature of the liquid water to drop. Approximately 2.43×106 J of heat must be removed for every 1 kg of water that evaporates. The heat carried away by evaporation accounts for 75-80% of the total heat transfer in the cooling tower. Conductive heat transfer occurs when the air temperature rises and the water temperature drops; the heat carried away in this case is sensible heat, accounting for approximately 20-35% of the heat transferred in a cooling tower.
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Two heat transfer methods: evaporation heat transfer and contact heat transfer.