Document Type



Available under a Creative Commons Attribution Non-Commercial Share Alike 4.0 International Licence



Publication Details

This working paper was written in 1997, but was not published. However, the rational efficiency of a heat exchanger is defined and detailed in Chapter 7 of Brian Smyth's thesis, which was prepared under the supervision of Jim McGovern:
Smyth, Brian, 'The Exergy analysis of a multi-effect evaporation unit for seawater desalination,' 1997. MSc Thesis, Trinity College, Dublin, Thesis 5540.

Reprinted in the IRHACE:the Industry Journal for the New Zealand Refrigernation, Heating, Ventilation and Airconditioning Industries, October/November, 2012, pp.12-18.


The authors propose a new and unique definition for the rational efficiency of a heat exchanger. This new rational efficiency is defined in terms of its sub-rational efficiencies: a heat transfer rational efficiency and a friction rational efficiency for each of the fluid systems comprising the heat exchanger. The heat transfer rational efficiency is based on the definition of a mean temperature for the heat source and a mean temperature for the heat sink and reflects the exergy supplied and the exergy received, due to heat transfer only. The friction rational efficiency for each fluid system of the heat exchanger reflects the internal friction irreversibility of that fluid system. The authors also show how it is possible to calculate these rational and sub-rational efficiencies.