PECULIARITIES OF CALCULATION OF MULTI-STREAM RECUPERATIVE CRYOGENIC HEAT EXCHANGERS

Abstract

Multi-stream recuperative heat exchangers are widely used at creation of modern cryogenic systems. The basic difference of these heat exchangers from two-stream ones consists in uncertain distribution of heat flows between streams. In the article the strict approach to calculation of a temperature field multi-stream heat exchangers and to definition of an active difference of temperatures at heat exchange between streams is stated. Examples of calculation of temperature fields of three and four-stream heat exchangers (different designs) are resulted. The method of calculation of heat exchange surfaces is given in view of heat transfer influence from ambient. The general conditions of serviceability of multi-stream heat exchangers are formulated. It is shown, that the attribute of serviceability violation is a simultaneous crossing in one point of all stream curves in q–T–diagram. This condition corresponds to a minimum of entropy creation, i.e. to absence of driving force of heat exchange.