Detailed Analysis of Exergy Destruction of All Basic Types of Heat Exchangers

Abstract

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.

Energy and Exergy Analysis of the Heating Unit Components of Nag Hammadi Fiber Board Company

“…They demonstrated that the total exergetic efficiency of the tested heat exchanger network was reached about 62.8% which could be increased to reach 84.2%, with some suggesting improvements on the insufficient heat exchangers. moreover, Rauch et al [4] developed a mathematical model for analyzing the exergy of several heat exchanger types. They concluded that, it is possible to quantify both exergy destruction ratio and exergy destruction to effectiveness in respect to a higher number of streams passing through parallel and counter flow heat exchangers.…”