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.
Compact plate heat exchangers (CHE) are designed to optimize heat transfer and the corrugated plates provide a large surface through which heat can be transferred from one liquid or gas to another. Compared to shell-and-tube heat exchangers the CHE constructions have many advantages, e.g. the high thermal efficiency and the small footprint. The basic plate heat exchanger consists of a series of thin, corrugated plates with rubber gaskets between the plates. The heat is transferred through the plate between the channels and a complete counter-current flow is created for highest possible efficiency. The compact construction and the thin plates reduce the installation cost and provide a cost-efficient solution to the customer. A schematic sketch of compact plate heat exchanger is shown in Figure 1.
Today a whole range of different compact plate heat exchanger products can be offered. The four main groups are gasketed, brazed, fusion bonded or all-welded plate heat exchangers. Also tailor-made plate heat exchangers made for special applications exist today, e.g. units that are designed for evaporation and condensation duties. Depending on process conditions like physical properties of the media and corrosiveness and pressure variations etc. different products fit to different situations.
In many processes, seawater is used as cooling medium on one side of the heat exchanger. One example is the so-called secondary cooling applications (secool applications) where seawater often is used to cool a loop with process water. In these secool applications there is a need of cooling huge heat loads and therefore the heat exchangers must be very large to be able to handle the large flows.
