Abstract
The paper presents a study of the effect of fouling, due to scale formation, of preheater tubes on the thermal performance of once through multi stage desalination plant. The mathematical model developed was used to find, the decrease in the plant performance ratio, and the increase of the ratio of make up water to the product quantity for a 500 ton/day once through MSF plant of 12 stages. Preheater tubes was examined microscopically after approximately equals 10 yr of intermittent operation at the once through MSF desalination plant at Matrouh. Although the copper alloys from which the preheater tubes were manufactured remained in a satisfactory condition, some scale deposits were observed, the most common scale being of calcium sulphate. Recommended materials for better performance of condenser tubes as well as water pretreatment for prevention of scale formation and corrosion are discussed.