Heat exchangers used in cryogenic applications need to have very high effectiveness to preserve the refrigerating effect produced. Normally the heat exchangers used in cryogenic refrigerators and liquefiers have effectiveness of the order of 0.95 or higher. If the effectiveness of the heat exchangers falls below the design value, there may not be any liquid yield. Plate fin heat exchangers, because of their compactness, low weight and high effectiveness, are widely used in aerospace and cryogenic applications. Such heat exchangers have closely spaced fins and offer narrow and intricate passages for the fluid flow which often leads to significant pressure drop. The stringent requirement of high effectiveness in cryogenic refrigerators and liquefiers and high pressure drop occurring in plate fin heat exchangers make it necessary to test the heat exchanger before putting into operation in a liquefier.Plate fin heat exchanger (PFHE) is a type of compact exchanger that consists of a stack of alternate flat plates called parting sheets and corrugated fins, both being brazed together as a block. Streams exchange heat by flowing along the passages made by the fins between the parting sheets. Separating plates act as the primary heat transfer surfaces and the appendages known as fins act as the secondary heat transfer surfaces intimately bonded to the primary surface. Aluminum is the most commonly used material and stainless steel is employed in high pressure and high temperature applications.
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