23-02: What Went Wrong with my Mass Balance: Calculation of Evaporation

Water conservation is becoming increasingly important. In some cases, facilities are being driven to zero blowdown or zero liquid discharge (ZLD). These constraints impose limitations on the amount of makeup water that can be utilized. A major component of the makeup is evaporation of water from the cooling tower. The rule of thumb often employed (Equation 1) is inaccurate and insufficient for predictive and planning purposes. In fact, evaporation can be quite variable depending on the specific thermal conditions for a given case. Factors such as site elevation and salinity of the cooling water must also be taken into account. In this paper, the authors will present methodology for accurate determinations of evaporation.