Model for fouling deposition on power plant steam condensers cooled with seawater: Effect of water velocity and tube material E. Nebot a, * , J.F. Casanueva b , T. Casanueva a , D. Sales a a Department of Chemical Engineering, Food Technology and Environmental Technologies, University of Ca ´ diz, Spain b Department of Thermal Engines, University of Ca ´ diz, Spain Received 4 September 2006 Available online 26 March 2007 Abstract A kinetic model for fouling evolution prediction is proposed. The model suggested in this paper represents fouling evolution versus time, and is a modification of the model defined by Konak [A.R. Konak, Prediction of fouling curves in heat transfer equipment, Trans. Inst. Chem. Eng. 51 (1973) 377]. The proposed model is a combination of the first order equation and the driving force concept employed by Konak. It is also a new expression of the classic logistic equation proposed by Verhulst in 1839 to interpret biological population growth data. The new model has the additional advantage that its kinetic parameters, the maximum asymptotic limit of the thermal resis- tance ðR f 1 Þ and the rate at which that maximum value is reached (k), present a clear physical significance. As application and validation of the model performance, the effects of water velocity and tube material on fouling deposition have been tested and modeled. It can be concluded that the maximum asymptotic limit of the thermal resistance decreases as velocity increases. After the application of the model it can also be concluded that for all seasons of the year, titanium tubes are more prone to be fouled, although the process is slower, than with brass tubes. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Fouling; Kinetic model; Cooling water; Steam condenser; Seawater 1. Introduction All the materials exposed to the water suffer the well- known phenomenon of fouling, consisting of the formation of a film that covers the surfaces in contact with the water. This fouling can be of different nature according to the phenomena that take part in its genesis. Three types of fouling are usually considered: biological, corrosion and precipitation fouling [1]. When seawater is the cooling fluid the phenomenon is accentuated fundamentally due to the strong corrosive nature of salt water and to its elevated bio- logical activity [2]. In general, fouling causes important operation and maintenance problems in facilities in contact with seawater, among them, those of the maritime sector, aquaculture, offshore utilities, etc. The formation of fouling in heat exchangers of coastal power plants using sea water for cooling purposes has spe- cial economic significance [3–5]. In power station condens- ers, fouling is formed inside the condenser tubes, reducing heat transfer between the hot fluid (steam that condenses in the external surface of the tubes) and the cold sink (sea water flowing through the tubes). This fouling has negative consequences in the efficiency of the power plant and there- fore in its economic balance [6,7]. For all the above reasons the designing and operating of heat exchanger must contemplate and estimate the fouling resistance to the heat transfer. The traditional method is the utilization of fouling resistance tables from the bibliog- raphy [8]. But these tables show a range of fouling resis- tance, calculated in very specific conditions that cannot be extrapolated to any other situation. Therefore, the 0017-9310/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijheatmasstransfer.2007.01.022 * Corresponding author. Address: Facultad de Ciencias del Mar, 11510- Puerto Real, Spain. Tel.: +34 956 016198; fax: +34 956 016139. E-mail address: enrique.nebot@uca.es (E. Nebot). www.elsevier.com/locate/ijhmt International Journal of Heat and Mass Transfer 50 (2007) 3351–3358