FAQ

Principle and determinants of cooling effect of cooling tower

Author：Trlon Views: Time:2021-03-31

　　The function of the cooling tower is to carry the cooling water carrying waste heat in the tower body heat exchange with the air, so that the waste heat is transmitted to the air and scattered into the atmosphere. The general term "cooling tower" is used to describe direct (open) and indirect (closed) cooling equipment. Although most come up with a "cooling tower as an open direct contact radiator", the indirect cooling tower, sometimes called a "closed circuit cooling tower" is but also a cooling tower.

　　A direct, or open-circuit cooling tower is a means of sealing the interior of the structure by spraying the circulating water in a spray manner onto a fiberglass packing. The packing provides a larger contact surface, through the contact between water and air, to achieve the effect of heat transfer. Another fan drives the air circulation in the tower, and the hot air flow after heat exchange with water is taken out, so as to achieve cooling.

　　Indirect or closed-circuit cooling towers do not involve a mixture of air and liquid, usually water or glycol, being cooled in direct contact. Different from the open cooling tower, the indirect cooling tower has two independent fluid circuits. One is the external circuit in which the water is on the second circuit, which is the bundle of external circulation (closed coil) to which the hot fluid process is connected to be cooled and returned in the closed circuit. Air is drawn by circulating water cascaded across the entire heat pipe outside the cooling tower, providing similar evaporative cooling. The heat flow in operation from the internal fluid circuit, through the coil tube wall, the external circuit, and then heated by some evaporation of air and water, into the atmosphere. The indirect cooling tower operation is therefore very similar to the opening of the cooling tower with an exception. This process is carried out by the coolant in a "closed" loop, not directly exposed to the atmosphere or external circulating water.

　　In a counterflow cooling tower air travels up through a filling or tube bundle, opposite the downward movement of water. In a cross-flow cooling tower air moves horizontally by filling water with downward movement.

　　Cooling towers also feature a mechanically ventilated cooling tower in which aero-mobile means rely on electrically driven fans to attract or force air into the tower. The naturally ventilated cooling tower uses a high growth exhaust chimney to provide draft air buoyancy. Fan-assisted natural ventilation cooling towers use mechanical drafts to increase buoyancy effects. Many early cooling towers relied on wind currents that produced drafts of air.

　　If cooling water from the cooling tower is returned to reuse, some water must be added to replace or constitute the flow of that part of evaporation. Since evaporation includes purified water, the concentration of dissolved minerals and other solids in circulating water tends to increase unless some dissolution, such as striking solids under control, is provided. Some water is also lost with the ongoing exhaust gas (drift) droplets, but this is usually reduced to a very small amount by the installation of baffle-like devices, called drift eliminators, to collect droplets. The amount made up must be equal to evaporation, blowing down, total drift, such as wind blowouts and other water leakage losses, to maintain a stable water level.

　　The use of cooling tower is to achieve a certain cooling effect, cooling effect depends on the heat sink, fan air volume. Cooling tower water consumption, ventilation conditions, installation location will also have a certain impact on its effect. Next, let's take a look at the influence of cooling tower fins and fan air volume on the cooling system:

　　Heat sink: are key components in the cooling tower, a small tower generally use PVC sheet extrusion or hot suction, large tower will use wood, the main purpose of the air and water interface in does not affect the wind resistance, the bigger the better, the heat transfer rate is at large at the same time, the heat sink affect heat transfer effect of the two parameters, mainly is the fin shape and height, in the water tower installation, try not to damage the radiator, so as to avoid heat sink flow not free.

　　2. Air volume of the fan: it mainly accelerates the air flow in the tower, accelerates the heat exchange between air and water, and takes away heat. The main factors that affect the air volume of the fan are the shape of the blade, the width and length of the blade, the deflection Angle of the blade, the speed of the blade, the installation Angle, the speed and the motor and transmission ratio. In addition, in the case of a certain air volume, the cooling effect of the same type of tower with small cooling water quantity is better than that with large cooling water quantity.

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