Dimensionless expressions of exergy destruction, normalized to ambient temperature and heat capacity of the weaker stream, for all basic types of recuperators are derived. The analytical expressions for maximum exergy destruction were calculated using the GNU Octave software for all recuperators, namely parallel-flow and counter-flow recuperators, and all forms of cross-flow heat exchangers, namely without mixing of streams, only mixing the streamlines of the weaker stream, only mixing the streamlines of the stronger stream and mixing the weaker and stronger streams. For parallel-flow and counter-flow recuperators, as well as for their special cases, expressions for local and total exergy destruction are given. It is shown that the maximum exergy destruction, as a local extreme, is the same for all recuperators for mutually equal values of the quantities π3 (ratio of the heat capacity of the weaker stream to the heat capacity of the stronger stream) and πT (ratio of the inlet temperature of the stronger stream to the inlet temperature of the weaker stream). The ratio of exergy destruction to effectiveness of each basic type of recuperator is further analyzed. The obtained results are presented and interpreted in appropriate dimensionless diagrams.
SummaryThe paper gives an analytical dimensionless analysis of the local entropy generation and its ratio with the local exchanged heat flow rate for parallel flow and counterflow heat exchangers. The end (side) of the heat exchanger, which is the inlet of the weaker stream, is, among other, proven to be relevant variable for those local values. Elaborated algorithm provides explicit connection between entropy generation and ratio of entropy generation to local exchanged heat flow rate in dependence on the relevant dimensionless variables A/A 0 , 2 = kA 0 /C 1 , 3 = C 1 /C 2 and T =T 1 ' /T 2 ' . Value 2 vary between 1.0 and 4.0, value 3 amounts 0.0; 0.5 and 1.0, while 0.5 and 2.0 were taken for value T. From obtained general equations for parallel flow and counterflow heat exchanger special cases for observed values were extracted, considering the cases where one of the streams condenses or evaporates. Given algorithm, aside the local amounts of the observed values, also gives overall amounts of the mentioned values. The results are presented by appropriate diagrams and additionally interpreted.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.