Wetting behaviour of different tube materials and its influence on scale formation in multiple-effect distillers

Abstract

AbstractMultiple-effect distillation (MED) plants with horizontal tube falling film evaporators for sea water desalination exhibit relatively high heat transfer coefficients achieved by film flow under clean surface conditions. However, they are susceptible to heat transfer deterioration and scale formation accompanied by film breakdown. Thus, maintaining all heated tubes in a fully wetted state is one of the key issues to be considered in designing falling film evaporators. Surface tension, hydrophilicity, hydrophobicity and wettability of materials play an important role in scale formation. The wetting rate, that is the brine mass flow rate on one tube per unit tube length, is one of the most important parameters in the design and operation of MED plants. It has an impact on heat transfer, tube bundle design, scale formation, the capital and operational costs of the plant and its operational flexibility. Thus, it is very important to acquire a better understanding of the wetting behaviour and the impact...