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.
Flame Geometry Effects on the Buoyant Plumes from Turbulent Diffusion Flames
Measurements of the temperature and velocity distributions in the very near field of turbulent diffusion flames are made to investigate the significance of flame geometry effects on the plume properties. The flame geometry effects are formulated in terms of a "virtual heat source" as a function of heat release rate and fuel size. It was also shown that the location of virtual heat sources for a round fuel and for a square one are practically identical if the diameter and the side are regarded as the characteristic fuel sizes respectively. The proposed formula for the location of the virtual source seems to be consistent with the results of current works in which the location has been determined in different ways.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.