Open AccessTransitional free convection flow and heat transfer within attics in cold climate
Author(s) -
Huimin Cui,
Wenyue Wang,
Feng Xu,
Suvash C. Saha,
Qingkuan Liu
Publication year - 2022
Publication title -
thermal science/thermal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.339
H-Index - 43
eISSN - 2334-7163
pISSN - 0354-9836
DOI - 10.2298/tsci210826039c
Subject(s) - rayleigh number , prandtl number , mechanics , heat transfer , convection , flow (mathematics) , materials science , convective heat transfer , natural convection , attic , thermodynamics , combined forced and natural convection , physics , structural engineering , engineering , roof
The transitional free convection flow and heat transfer within attics in cold climate are investigated using three-dimensional numerical simulations for a range of Rayleigh numbers from 103 to 106 and height-length ratios from 0.1 to 1.5. The development process of free convection in the attic could be classified into three stages: an initial stage, a transitional stage and a fully developed stage. Flow structures in different stages including transverse and longitudinal rolls are critically analyzed in terms of the location and strength of convection rolls and their impacts on the heat transfer. The transition to unsteady flow and asymmetry flow in the fully developed stage is discussed for the fixed height-length ratio 0.5. Various flow regimes are given in a bifurcation diagram in the parameter space of Rayleigh numbers (102<Ra<107) for height-length ratios (0.1<A<1.5). The time series of heat transfer rate through the bottom wall is quantified for different height-length ratios. The overall heat transfer rate for the low Prandtl fluid (Pr=0.7) could be enhanced based on three-dimensional flow structure.