ANALYSIS OF LOCAL THERMAL EQUILIBRIUM ASSUMPTION IN TRANSIENT FORCED CONVECTION IN A GRAPHITE FOAM CHANNEL
Küçük Resim Yok
Tarih
2020
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Yildiz Technical Univ
Erişim Hakkı
info:eu-repo/semantics/closedAccess
Özet
In this study, the validity of Local Thermal Equilibrium (LTE) assumption in the transient forced convection of a rectangular channel filled with a block of graphite foam is examined numerically. The governing macroscopic energy conservation equations for solid and gas phases are derived by taking the average of the microscopic one over the averaging volume. Initially, LTE is in existence between the phases and then, the fluid temperature at the channel inlet is suddenly raised. Besides, an appropriate insulation is provided for the wall of the channel. Hence, a transient one-dimensional Local Thermal Non-Equilibrium (LTNE) model is considered in the numerical investigation. Thermo-physical properties of the solid and fluid phases are presumed to be constant. The graphite foam porosity is spatially uniform and constant. The impact of two dimensionless variables such as fluid to solid Nusselt number (Nu(fs)) and Reynolds number (Re) on the LTE assumption is extensively investigated. . It was found that the dimensionless time required to attain LTE between the phases (tau(LTE)) increases with the increasing value of Reynolds number. However, the real-time (sigma(LTE)) corresponding to tau(LTE) was found to be nearly 4 sec over the range of Re numbers studied. Additionally, an increase in the Nu(fs), resulted in a decrease in TLTE for a constant value of Re number and sigma(LTE) varied from 1.5 to 5 sec. As a result, the obtained findings showed that it is reasonable to assume the LTE between the phases under the investigated conditions.
Açıklama
Anahtar Kelimeler
Foam, forced convection, graphite, LTE, LTNE, porous media, transient
Kaynak
Sigma Journal of Engineering and Natural Sciences-Sigma Muhendislik Ve Fen Bilimleri Dergisi
WoS Q Değeri
N/A
Scopus Q Değeri
Cilt
38
Sayı
4
