A successful general fluid-to-fluid similarity theory for heat transfer at
supercritical pressure
#MMPMID32834084
Pucciarelli A
; Ambrosini W
Int J Heat Mass Transf
2020[Oct]; 159
(?): 120152
PMID32834084
show ga
The present paper introduces a successful and general fluid-to-fluid similarity
theory for heat transfer to fluids at supercritical pressure, having a high
degree of universality. This work shortly follows the recent publication of a
"local" successful similarity theory developed for fluids at supercritical
pressures in a range of conditions in which the values of their molecular Prandtl
number were quantitatively similar, extending its conclusions to the case of
different molecular Prandtl numbers. The reason why this further step requested a
short time to be elaborated is due to recognising that previous work by the
Authors had actually already solved the related problems, though in a slightly
different way, now interpreted in a more significant frame owing to a better
problem understanding. The present similarity theory is based on first ideas
developed more than one and a half decade ago by one of the authors, while
addressing flow stability of supercritical fluids in heated channels, which
encountered immediate problems to be applied in a straightforward way to heat
transfer. These ideas were revised and considerably improved during the PhD
thesis of the other author, also overcoming a sort of prejudicial assumption that
finally resulted to limit their applicability. More recently, published DNS data
triggered further reflections on the role of the Prandtl number, leading to the
mentioned "local" form of the successful similarity theory. This led to the
present step, by just recognising that the mentioned PhD thesis had already
proposed a sufficient rationale to extend this local interpretation to a broader
range of conditions. The rather convincing results presented herein, obtained
making use of RANS CFD analyses with four different fluids, demonstrate the
interesting capabilities of this final form of the theory. The establishment of
an effective set of dimensionless numbers for heat transfer problems is hoped to
pave the way for the development of the still lacking successful engineering heat
transfer correlations for supercritical pressure fluids. It further calls for
dedicated experiments needed to confirm the suitability of the present theory
beyond any reasonable doubt.
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