Performance characteristics of counter flow wet cooling towers Jameel-Ur-Rehman Khan, M. Yaqub, Syed M. Zubair * Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Mail Box 1474, Dhahran 31261, Saudi Arabia Received 16 June 2002; accepted 23 September 2002 Abstract Cooling towers are one of the biggest heat and mass transfer devices that are in widespread use. In this paper, we use a detailed model of counter flow wet cooling towers in investigating the performance characteristics. The validity of the model is checked by experimental data reported in the literature. The thermal performance of the cooling towers is clearly explained in terms of varying air and water tempera- tures, as well as the driving potential for convection and evaporation heat transfer, along the height of the tower. The relative contribution of each mode of heat transfer rate to the total heat transfer rate in the cooling tower is established. It is demonstrated with an example problem that the predominant mode of heat transfer is evaporation. For example, evaporation contributes about 62.5% of the total rate of heat transfer at the bottom of the tower and almost 90% at the top of the tower. The variation of air and water temperatures along the height of the tower (process line) is explained on psychometric charts. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Cooling towers; Model; Performance evaluation 1. Introduction Cooling towers, as shown schematically in Fig. 1, consist of large chambers loosely filled with trays or decks of wooden boards as slats or of PVC material. The water to be cooled is pumped to the top of the tower, where it is distributed over the top deck by sprays or distributor troughs made of wood or PVC material. It then falls and splashes from deck-to-deck down through the tower. Air is permitted to pass through the tower horizontally due to wind currents (cross flow) or vertically upward (counter current) to the falling water droplets. In the case of counter current Energy Conversion and Management 44 (2003) 2073–2091 www.elsevier.com/locate/enconman * Corresponding author. Tel.: +966-3-860-3135; fax: +966-3-860-2949. E-mail address: smzubair@kfupm.edu.sa (S.M. Zubair). 0196-8904/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0196-8904(02)00231-5