Yes / Fouling in heat exchangers (HE) is a major problem in industry and accurate prediction of the onset or degree of fouling would be of a huge benefit to the operators. Modelling of the fouling phenomenon however, remains a challenging field of study. Cleaning of heat exchangers, coulpled with the down time, is a financial burden and for industrialized nations and costs can reach to almost 0.25 % of the country’s Gross National Product (Pritchard, 1988).This work presents the development of a dynamic fouling model based on experimental data collected using a laboratory concentric tube heat exchanger handling a saline system. Heat transfer coefficients were obtained from first principles as well as from either the Sieder-Tate or Petukhov-Kirillov correlations modified by Gnielinski depending on the flow regime. The outlet temperatures were calculated using the Effectiveness-NTU method. The dynamic fouling factor was based on the Kern and Seaton fouling model and validation was completed by comparing the experimental outlet temperatures with those predicted by the model. The model predicts the outlet temperatures with an average discrepancy of 1.6 °C and 0.4 °C for the cold and hot streams respectively.

Yes / Fouling on heat transfer surfaces due to scale formation is the most concerned item in thermal desalination industry. Here, a dynamic fouling model is developed and incorporated into the MSF dynamic process model to predict fouling at high temperature and high velocity. The proposed dynamic model considers the attachment and removal mechanisms in the fouling phenomena with more relaxation of the assumptions such as the density of the fouling layer and salinity of the recycle brine. While calcium sulphate might precipitate at very high temperature, only the crystallization of calcium carbonate and magnesium hydroxide are considered in this work. Though the model is applied in a 24 stages brine recycle MSF plant, only the heat recovery section (21 stages) is considered under this study. The effect of flow velocity and surface temperature are investigated. By including both diffusion and reaction mechanism in the fouling model, the results of the fouling prediction model are in good agreement with most recent studies in the literature. The deposition of magnesium hydroxide increases with the increase in surface temperature and flow velocity while calcium carbonate deposition increases with the increase in the surface temperature and decreases with the increase in the flow velocity.