A third key contribution is the extraction of novel insights from the modelling
process. For the heat exchangers it has been shown that the hot and cold heat
exchangers can be identical in their design without any negative impact on performance
for the low-temperature difference situation. In comparison the high
temperature applications invariably require different materials and designs for the
two heat exchangers. Also, frequency and phase angle are found to be quite different
(lower frequency and higher phase angle) from the optimum parameters
found in high temperature engines. Contrary to common belief the role of dead
volume has been found to play a crucial and not necessary detrimental role at low
temperature differentials.
Taken together, the work is positioned at the intersection of thermodynamic
analysis and engineering design, for the challenging area of Stirling engines at low
temperature differences. The work extracts thermodynamic insights and extends
these into design implications. Together these help create a robust theoretical and
design foundation for further research and development in the important area of
energy recovery.