Abstract
An exact, general and algebraically simple solution is obtained to the classic model of the thermal regenerator—general in the sense of covering flushing ratios, A, of any magnitude, including the small values of interest in the context of Stirling cycle machines, and of depicting start-up and cyclic steady state operation.
Specimen solutions turn the conventional picture of regenerator performance on its head: for a flushing ratio equal to or less than unity, for example, zero heat-transfer coefficient (NTU = 0) leads to a temperature recovery ratio of 100 per cent! At a thermal capacity ratio, NTCR, above a certain, minimal, value, the wall temperature distribution sits invariant between the extremes of gas temperature swing, and increased NTCR has no effect on temperature recovery ratio.
The findings are sufficient to explain reports of unexpectedly good performance of Stirling machines with regenerators of cotton wool or glass fibre.
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