Numerical study on mechanisms underlying the heat transfer enhancement of upward supercritical CO2 flow at low Reynolds numbers near the pseudo-critical region through a microtube
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Tarih
2025
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Pergamon-Elsevier Science Ltd
Erişim Hakkı
info:eu-repo/semantics/closedAccess
Özet
The buoyancy and thermal acceleration effects of supercritical CO2 flow near the pseudo-critical region have been widely mentioned as the mechanism of heat transfer enhancement in the literature. However, most publications deal with turbulent flows and do not discuss the details of how these effects alter flow structure and enhance heat transfer. The present study numerically investigated mechanisms underlying the heat transfer enhancement of upward supercritical CO2 flow through a microtube, 0.5 mm in diameter, at low Reynolds numbers. The heat transfer enhancement was closely associated with the appearance and disappearance of the M-shaped velocity profile. When the M-shaped profile started forming by the buoyancy effect, the first local maximum of the heat transfer coefficient appeared as the thermal acceleration of the boundary layer entrained fluid from the wall region. The fluid entrainment carried thermal energy from the wall toward the core, thus enhancing the heat transfer. When the M-shaped profile started disappearing due to the thermal acceleration in the core region, the second maximum appeared in some cases due to abrupt turbulence developed by two forces in the opposite direction: one force dragging the local maximum velocity in the M-shaped profile and the other force accelerating the core region.
Açıklama
Anahtar Kelimeler
Supercritical CO2, Laminar, Upward flow, Thermal acceleration, Buoyancy, Microtube
Kaynak
International Communications in Heat and Mass Transfer
WoS Q Değeri
Q1
Scopus Q Değeri
Q1
Cilt
165
