Abstract
The measures to reduce the impact of evaporation loss in a natural draft counter-flow wet cooling tower (NDWCT) have important implications for water conservation and emissions reduction. A mathematical model of evaporation loss in the NDWCT was established by using a modified Merkel method. The NDWCTs in the 300 MW and 600 MW power plant were taken as the research objects. Comparing experimental values with calculated values, the relative error was less than 3%. Then, the effect of air parameters on evaporation loss of NDWCT was analyzed. The results showed that, with the increase of dry bulb temperature, the evaporation heat dissipation and the evaporation loss decreased, while the rate of evaporation loss caused by unit temperature difference increased. The ambient temperature increased by 1 °C and the evaporation loss was reduced by nearly 26.65 t/h. When the relative air humidity increased, the evaporation heat dissipation and evaporation loss decreased, and the rate of evaporation loss caused by unit temperature difference decreased. When relative air humidity increased by 1%, the outlet water temperature rose by about 0.08 °C, and the evaporation loss decreased by about 5.63 t/h.
Highlights
natural draft counter-flow wet cooling tower (NDWCT) are extensively used in most electric power industries to reject waste heat in the condenser to the surrounding
Based on the heat and mass transfer equations, Kairouani et al [9] presented a mathematical model for prediction of the evaporation loss for cooling towers, and obtained an optimal water loss which was equivalent to 4% of the total water flow rate
The results showed that the cooling power and coefficient of performance (COP) could be calculated by the model given the following conditions, including the hot water inlet temperature, the chilled water inlet temperature, the air inlet wet bulb temperature, and dry bulb temperature
Summary
NDWCTs are extensively used in most electric power industries to reject waste heat in the condenser to the surrounding. Based on the heat and mass transfer equations, Kairouani et al [9] presented a mathematical model for prediction of the evaporation loss for cooling towers, and obtained an optimal water loss which was equivalent to 4% of the total water flow rate. Naik et al [17] obtained the thermal performances of mechanical ventilation cooling tower by developing a simple analytical model and discovered that the operating parameters had important effect on heat and mass transfer of cooling tower. The NDWCTs were needed for operating in a variation of air parameters which strongly affected the thermal performance of NDWCTs. The influence mechanism of air parameters on evaporation loss in the NDWCT was mainly analyzed, which was of great guiding significance for the power plant to reduce the emission and save water
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