The aim of the present work is to evaluate the effect of tube bundle arrangement and the seawater feed distribution on the dry zone and scale formation in the large sized Multiple Effect Distillation (MED) evaporator. A mathematical model of the seawater feed distribution is developed and validated for a triangular pitch tube bundle of MED evaporator. The developed model includes CaCO3 scale formation and CO2 release. The simulation results showed that the dripping seawater flow rate on the column based on the 2nd row is lower than that of the 1st row. Consequently, the wetting rate of the tubes in the column based on the 2nd row is less than that based on the 1st row. This explains why the tubes based on the 2nd row experience more CaCO3 scale deposit than that based on the 1st row. The simulation results showed that increasing the feed seawater to twice that of the original flow will reduce the scale thickness by 15%. Increasing the tube pitch by twice the diameter will reduce the scale thickness by 30%. The combined effect of modified feed flow and increase in the tube pitch would significantly reduce the scale precipitation thickness. (C) 2014 Elsevier B.V. All rights reserved.