论文标题
在低工作温度下高腔中的非灰色/灰色辐射传热对自然对流的研究
Investigations of Non-Gray/Gray Radiative Heat Transfer Effect on Natural Convection in Tall Cavities at Low Operating Temperature
论文作者
论文摘要
本工作通过数值调查了辐射对低工作温度范围下的差异加热的较细长和平方碱基的自然对流的影响，在288.1-307.7 K.具有$ n_2 $，$ o_2 $，$ o_2 $，$ co_2 $和$ h_2o $的大气空气中，在75.964％，21％，21％，21％，$ o_2 $，$ co_2 $和$ h_2o中空腔中的工作流体。在大气压力和空腔中，非灰色和灰色planck平均吸收系数已通过逐线（LBL）方法从Hitemp-2010数据库中计算出大气压力和空腔的平均温度。对于四种不同的情况，即纯对流，透明，灰色和非灰色辐射介质的辐射，进行了辐射和自然对流的流量和传热模拟。首先，将数值结果与Betts和Bukhari [1]的实验结果进行了比较，对细长的空腔案例进行了比较，随后对流体流量和热传递进行了全面的分析，以证明辐射对两个腔体内自然对流的影响。流量结构已通过Q -Criterion可视化 - 涡流识别技术。结果表明，随着辐射的包含，流体流量和热特性在两个空腔的顶部和底部都显着变化。此外，灰介质中的辐射对这些特征具有显着影响。流体流量和传热仅在靠近活跃壁的狭窄区域发生。在这些空腔中，辐射通量的导电通量的顺序相同，在辐射建模的所有四种情况下，这些通量几乎相同。
The present work numerically investigates the influence of radiation on the natural convection in differentially heated slender and square-base tall cavities at low operating temperature range of 288.1-307.7 K. The atmospheric air which has the composition of $N_2$, $O_2$, $CO_2$ and $H_2O$ in the molar mass proportion of 75.964%, 21%, 0.036% and 3%, respectively, has been considered as the working fluid in the cavities. The non-gray and gray Planck mean absorption coefficients for whole spectrum of the air at the atmospheric pressure and average temperature of the cavity have been calculated from HITEMP-2010 database by Line-By-Line (LBL) approach. The flow and heat transfer simulations for combined radiation and natural convection have been performed for four different scenarios, i.e., pure convection, radiation in transparent, gray, and non-gray radiation medium. First, the numerical results are compared with the experimental results of Betts and Bukhari [1] for the slender cavity case, subsequently a comprehensive analysis of the fluid flow and heat transfer are presented to demonstrate the influence of the radiation on natural convection inside both the cavities. The flow structure has been visualized by Q-criterion - a vortex identification technique. The results reveal that the fluid flow and thermal characteristics change significantly at the top and the bottom of both the cavities with the inclusion of radiation. Moreover, the radiation in gray medium has significant effect on these characteristics. The fluid flow and heat transfer are only happening in a narrow regions near to the active walls. The radiative flux is in the same order of the conductive flux in these cavities and these fluxes are almost same in all four scenarios of the radiation modeling.
