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Plate heat exchangers consist of a series of corrugated plates hung from a carrying bar and clamped between fixed and movable heads. The heat transfer plates are normally manufactured in stainless steel, but are available in other materials.
In Gasketed Plate Heat Exchangers, each heat transfer plate is fitted with an elastomeric gasket, which seals and distributes the process fluids. The heads, normally referred to as channel covers, include connections to permit the entry of the process fluid into the plate pack.
In Brazed Plate Heat Exchangers, the brazing process eliminates gasketed joints which allows for higher design pressure and temperatures.
The channel formed by two adjacent plates is the key to the plate heat exchanger's high efficiency. The hot and cold fluids are distributed through alternate channels in a counter-current arrangement. This counter-current flow provides for maximum thermal efficiency. The flow pattern induces turbulence at very low Reynolds numbers, which also contributes to high heat transfer rates. Units are custom selected to effectively optimize the available pressure drop.
The fluid shear stresses in a plate exchanger are much higher than those of a tubular exchanger. This tends to keep the channels in a plate exchanger much cleaner. For clean services, the normal practice is to provide units designed for 100% of the surface area required. For fluids that foul, plate exchangers can be provided with 5-10% excess area.
Plate heat exchangers are well suited for applications that require close temperature approaches. (The approach temperature is defined as the hot fluid outlet temperature minus the cold fluid inlet temperature.) Units can achieve temperature approaches as close as 2 degrees F.
Advantages of Graham Gasketed UltraHeat Plate Heat Exchangers
Advantages of Graham MicroHeat Brazed Plate Heat Exchangers