Influencing factors on thermal performance of countflow cooling tower

Cooling towers are commonly used to dissipate heat from heat sources to heat sink (ambient environment). Their applications are typically in Heating Ventilation and Air Conditioning (HVAC) systems. They normally consume around ten percent of the whole system energy, at that time, their operation has significant effect on the energy consumption of related other subsystems. This paper presents a countflow cooling tower model which can emulate the parameters' variation accurately during cooling towers' operation. Wet-bulb temperature of ambient air, airflow rate and cooling water flow rate are important factors influencing thermal performance, therefore, in this paper the variations of thermal performance corresponding to the different parameters' variations are calculated and analyzed. Especially, the impact of cooling water flow rate and airflow rate on heat rejection rate is key to minimize energy consumption. The conclusion shows the sum of energy consumption from the pump and fan corresponding to cooling water flow rate and airflow rate exists the minimum (optimal operating point) when wet-bulb temperature of ambient air is a fixed value. When the ambient wet-bulb temperature changes, the optimal operating point of cooling towers will change accordingly, which is helpful to minimize energy consumption and realize the efficient operation of HVAC system.