Closed type cooling tower is a tubular heat exchanger placed in the tower, through the circulation of air, spray water and circulating cooling water heat exchange to achieve cooling effect of a device. In recent years, closed cooling towers have been widely used in power electronics, mechanical processing, air conditioning system and other industries.
The design of many closed type cooling tower equipment, the design parameters provided to users and the thermal performance curves are based on the meteorological conditions in summer. The wet bulb temperature range is generally 20℃ to 35℃, but the outdoor wet bulb temperature can reach below 15℃ in the transition season and winter. Using the relevant sample technical parameters of cooling tower during summer operation will cause that the cooling tower cannot achieve the expected cooling effect or consume too much energy during operation, which is not conducive to energy saving.
According to the relevant literature, in addition to the operating parameters of the cooling tower itself, when the outdoor air wet bulb temperature, dry bulb temperature, relative humidity and other parameters change, the thermal performance of the cooling tower will also change, deviating from its design condition.
1) The cooling tower performance deviates from the design condition by about 5.5 to 70% in March and November during the transition season. In April, May and October, the cooling tower performance deviates from the design condition by about 6 to 7 %. The cooling capacity of the cooling tower can be increased by increasing the inlet wind speed of the cooling tower or increasing the inlet water of the cooling water, but the corresponding adverse effects of reducing the energy consumption coefficient and increasing the outlet temperature will be brought respectively.
2) In the transition season (March, November), the cooling tower can adjust the water intake and inlet wind speed according to the different evaluation conditions, and the cooling tower can meet the cooling requirements. In the transition season (April, May, October), due to the relatively high outdoor temperature, the cost of adjusting the cooling tower performance through variable wind speed is high, and the economy of running the cooling tower under such meteorological conditions is relatively poor.
3) When the cooling capacity required in the transition season is not large, it is recommended to adopt variable water volume as the priority. The corresponding energy consumption coefficients of variable water volume are about 5% higher than that of variable wind speed.
4) When the outdoor wet bulb temperature is at a relatively low level in the transition season, for example, the wet bulb temperature is 6℃ or 8℃, variable air volume regulation is recommended to improve the relative cooling capacity of the cooling tower and ensure that its relative energy consumption coefficient is not lower than the expected level.
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