Analysis of the effect of seasonal climate changes on cooling tower efficiency, and strategies for reducing cooling tower power consumption

Abstract

Cooling towers are widely used in chemical industries to cool water with ambient air that is susceptible to weather changes not only during the day, but also during the year, resulting in challenges to cooling towers design and operation. In the design phase, the difficulties to determine the cooling tower capacity arise not only from the uncertainty of cooling water consumption but also from ambient temperature variations, which have a direct impact on the volume of cooling tower fill and fan power. Wide temperature variations can result in cooling towers that excessively cool water during significant portion of the year. Moreover, an oversized cooling tower brings challenges to the plant operation, since the cooling tower turndown must be high to account for the colder days. The mathematical model of cooling tower operation that is composed by mass and energy balances, and by cooling tower characteristic equations can be simulated to design cooling towers, and forecast their performances in four Brazilian cities (Manaus, Salvador, São Paulo and Porto Alegre). Analyzing the results enables the calculation of the cooling tower slack, and the required turndown during the year in these four cities. This work proposes strategies for cooling tower fan operation to reduce the slack, and estimates the electrical energy cost reduction if such strategies are implemented.