Nowadays when the use of fresh water supply for a cooling purpose is becoming both expensive and environmentally unacceptable, cooling tower is becoming more common equipment in the pulp and paper industry. Cooling towers can provide an answer to the growing need to save water and energy and help to protect the environment. Instead of using fresh water for cooling, warm water can be recycled back to the process if it is first cooled down to a sufficiently low temperature. Cooling tower provides a simple and cost-effective means for this purpose. Fresh water consumption can be reduced even by 95 %.
Evaporative cooling towers are based upon a very simple principle where energy is removed from the hot water in a direct contact with relatively cool and dry air. In a counterflow cooling tower the process consist of gas phase (air) flowing upwards, a liquid phase (water film) flowing downwards, and a large interface between these two phases. The key factors required for intensive heat and mass transfer in the cooling tower are large air to water interfacial contact area and high heat transfer coefficient. The main objectiveof the research is to determine the heat and mass transfer coefficients and the pressure drop of the different filling materials, and further how these depend on air and mass flow.