{"title":"Numerical study on the flow field and air entrainment rate of rectangular gas fires under sidewall and corner restricted conditions","authors":"Haowei Hu , Tiantian Tan , Sai Luo , Jie Ji","doi":"10.1016/j.ijthermalsci.2024.109129","DOIUrl":null,"url":null,"abstract":"<div><p>In restricted space, fuel combustion is often constrained by sidewalls and corners, which can alter the air entrainment compared to unrestricted scenarios. To investigate the impact of sidewalls and corners, this paper presents numerical simulations of rectangular propane gas fires under sidewall and corner restricted conditions. The burner had an area of 300 cm<sup>2</sup>, with 5 different aspect ratios (<em>n</em> = 1, 1.5, 2, 3, and 4) and 4 heat release rates of the fire source (12 kW, 18 kW, 24 kW and 30 kW). The results demonstrate variations in the distribution of the flow field under different restricted conditions. For wall fires, when the long side of the burner is against the wall, the velocity in the <em>X</em> direction (<em>u</em>) approaches 0, and the lateral flow velocity on the <em>X</em>–<em>Y</em> plane (<em>V</em>) and the velocity in the <em>Y</em> direction (<em>v</em>) are nearly identical near the short side of the burner. Velocity <em>V</em> near the burner side can be divided into three zones: the high-velocity zone, the low-velocity zone, and the locally high-velocity zone. For corner fires, <em>V</em> increases as it gets closer to the wall. With the increase of <em>n</em>, the streamline where the velocities <em>u</em> and <em>v</em> are equal moves to the long side of the burner. Additionally, the fire entrainment rates of rectangular wall and corner fires at different heights from the burner surface were quantitatively studied. On the basis of the fire entrainment model for square and circular fires in open space, by introducing the equivalent diameter <span><math><mrow><msubsup><mi>D</mi><mtext>eff</mtext><mo>*</mo></msubsup></mrow></math></span>, a modified entrainment rate model at different heights from the burner surface is proposed, which can well predict the entrainment rate of rectangular wall or corner fires when the aspect ratio of the rectangular burner ranges from 1 to 4 and <span><math><mrow><msubsup><mover><mi>Q</mi><mo>˙</mo></mover><mtext>eff</mtext><mo>*</mo></msubsup></mrow></math></span> ranges from 0.97 to 6.79.</p></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":null,"pages":null},"PeriodicalIF":4.9000,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Thermal Sciences","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1290072924002515","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, MECHANICAL","Score":null,"Total":0}
引用次数: 0
Abstract
In restricted space, fuel combustion is often constrained by sidewalls and corners, which can alter the air entrainment compared to unrestricted scenarios. To investigate the impact of sidewalls and corners, this paper presents numerical simulations of rectangular propane gas fires under sidewall and corner restricted conditions. The burner had an area of 300 cm2, with 5 different aspect ratios (n = 1, 1.5, 2, 3, and 4) and 4 heat release rates of the fire source (12 kW, 18 kW, 24 kW and 30 kW). The results demonstrate variations in the distribution of the flow field under different restricted conditions. For wall fires, when the long side of the burner is against the wall, the velocity in the X direction (u) approaches 0, and the lateral flow velocity on the X–Y plane (V) and the velocity in the Y direction (v) are nearly identical near the short side of the burner. Velocity V near the burner side can be divided into three zones: the high-velocity zone, the low-velocity zone, and the locally high-velocity zone. For corner fires, V increases as it gets closer to the wall. With the increase of n, the streamline where the velocities u and v are equal moves to the long side of the burner. Additionally, the fire entrainment rates of rectangular wall and corner fires at different heights from the burner surface were quantitatively studied. On the basis of the fire entrainment model for square and circular fires in open space, by introducing the equivalent diameter , a modified entrainment rate model at different heights from the burner surface is proposed, which can well predict the entrainment rate of rectangular wall or corner fires when the aspect ratio of the rectangular burner ranges from 1 to 4 and ranges from 0.97 to 6.79.
期刊介绍:
The International Journal of Thermal Sciences is a journal devoted to the publication of fundamental studies on the physics of transfer processes in general, with an emphasis on thermal aspects and also applied research on various processes, energy systems and the environment. Articles are published in English and French, and are subject to peer review.
The fundamental subjects considered within the scope of the journal are:
* Heat and relevant mass transfer at all scales (nano, micro and macro) and in all types of material (heterogeneous, composites, biological,...) and fluid flow
* Forced, natural or mixed convection in reactive or non-reactive media
* Single or multi–phase fluid flow with or without phase change
* Near–and far–field radiative heat transfer
* Combined modes of heat transfer in complex systems (for example, plasmas, biological, geological,...)
* Multiscale modelling
The applied research topics include:
* Heat exchangers, heat pipes, cooling processes
* Transport phenomena taking place in industrial processes (chemical, food and agricultural, metallurgical, space and aeronautical, automobile industries)
* Nano–and micro–technology for energy, space, biosystems and devices
* Heat transport analysis in advanced systems
* Impact of energy–related processes on environment, and emerging energy systems
The study of thermophysical properties of materials and fluids, thermal measurement techniques, inverse methods, and the developments of experimental methods are within the scope of the International Journal of Thermal Sciences which also covers the modelling, and numerical methods applied to thermal transfer.