Transient Analysis of Fire-Induced Heat Transfer in Cylindrical Sealed Space
The main objective of the present work is an investigation of the heat transfer induced by the fire in a cylindrical sealed space. The thermal smoke flow geometry characteristics in cylindrical sealed space were discussed, LES and mixture fraction methods were applied to conduct numerical transient analysis. Computed results has validated the smoke flow course in simulation experiments. The study indicates that the heat transfer faster upper the fire source than around it. When the fire source location is near the wall, the smoke layer distributing were not distinct far from the fire source, and the heat transfer faster in transverse than longitudinal direction. Keywords—heat transfer , fire, cylindrical sealed space, numerical simulation.
Air entrainment into buoyant jet flames and pool fires
Abstract A simple model for the fire dynamics of turbulent fires is proposed and then used to derive correlations for air entrainment into turbulent jet fires and pool fires. Five parameters are identified to control the fire dynamics: the pool diameter D, the total buoyancy flow B∞, a buoyancy force per unit mass at the adiabatic stoichiometric temperature ( ΔT ad T ∞ )g , the ambient density ϱ∞, and the stoichiometric mass air to fuel ratio S. These parameters lead by dimensional arguments to correlations for air entrainment rates, which are further refined by using a simplified physical model. Three distinct regimes for air entrainment are identified in turbulent pool fires: (a) close to pool surface where entrainment rates vary as Z 1 2 (where Z is the vertical distance from the source), (b) near the neck-in area where entrainment rates vary as Z 3 2 , and (c) farther downstream but below the flame tip where entrainment rates vary as Z 5 2 . The proposed correlations are used to plot experimental data from which proportionality coefficients are determined. It is shown, also, that there is a relationship between entrainment rates up to the flame tip and visible flame feights; such a relationship would allow one to estimate entrainment rates by measuring visible flame heights.
Engineering bio-inks for 3D bioprinting cell mechanical microenvironment
Three-dimensional (3D) bioprinting has become a promising approach to construct­ing functional biomimetic tissues for tissue engineering and regenerative medicine. In 3D bioprinting, bio-inks are essential for the construction of cell microenviron­ment, thus affecting the biomimetic design and regenerative efficiency. Mechanical properties are one of the essential aspects of microenvironment, which can be char­acterized by matrix stiffness, viscoelasticity, topography, and dynamic mechanical stimulation. With the recent advances in functional biomaterials, various engineered bio-inks have realized the possibility of engineering cell mechanical microenviron­ment in vivo. In this review, we summarize the critical mechanical cues of cell micro­environments, review the engineered bio-inks while focusing on the selection princi­ples for constructing cell mechanical microenvironments, and discuss the challenges facing this field and the possible solutions for them.