THE USE OF CORROSION RESISTANT ALLOYS (CRAs) IN COMPACT PLATE HEAT EXCHANGERS IN SEAWATER

摘要

Compact plate heat exchangers (CHE) are designed to optimize heat transfer. The corrugated plates provide an immense surface through which heat can be transferred from one liquid or gas to another. The basic plate heat exchanger consists of a series of thin, corrugated plates that are sealed with rubber gaskets. The heat is transferred through the plate between the channels and complete counter-current flow is created for highest possible efficiency. Seawater is a complex solution of many salts containing living organisms, suspended silts, dissolved gases and decaying organic materials. The metallic material generally used for CHE in seawater cooling duties is titanium grade 1. The titanium material can stay passive due to a stable, protective and strongly adherent oxide layer. Due to limited availability of titanium the delivery times of titanium has increased. Consequently, it is vital to clarify the uniqueness of titanium and investigate alternative materials for use in plate heat exchanger seawater applications. A compact plate heat exchanger is, from a corrosion point of view, one of the most demanding constructions for alloys whose corrosion resistance depends on a passive film. Crevices are formed both in the contact points between the plates and under the rubber sealing gaskets. It is therefore relevant to test under real conditions. In this paper, the use of corrosion resistant alloys (CRA) in plate heat exchanger seawater applications are discussed and compared with the use of titanium.