Transient heating of a semitransparent spherical body
Transient heating of a semitransparent spherical body
复制标题
半透明球体的瞬时加热
DOI：
10.1016/j.ijthermalsci.2006.07.007
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发表时间：
2007
影响因子：
4.5
通讯作者：
E. Sazhina
中科院分区：
文献类型：
--
作者：
S. Sazhin;P. Krutitskii;S. B. Martynov;D. Mason;M. Heikal;E. Sazhina
研究了浸入静止热气体中的半透明球体的瞬态加热问题，并考虑了热辐射的影响。假设气体占据的区域的大小是有限的，并且该区域的外边界保持恒定的温度。考虑体内温度的初始径向分布。通过修正气体温度或对流传热系数，引入了对物体加热的牛顿定律的修改。对于体内温度和辐射吸收初始分布均匀且辐射温度恒定的情况，获得了这些校正的显式表达式。对于大的傅立叶数 Fo，预计气体温度的校正的实际重要性有限，因为该校正以及初始气体温度和身体表面温度之间的差异都接近于零（从气体传递到身体的热量变得可以忽略不计）。使用与柴油发动机相关的参数值对结果进行分析。对流换热系数的修正值从约 0.1（气体占据大区域且 Fo=500）到 Fo=0.1 时的 2.8 不等。这意味着忽略这些修正预计会导致计算中出现不可接受的大错误。与在完全搅拌的气体中加热该物体相比，物体加热的总时间要长一个数量级以上。热辐射对液滴加热的影响通过气体温度或对流传热系数的附加校正来解释。结果表明，对于较小的 Fo，辐射对表面热通量的影响较小，但对于较大的 Fo（Fo>50）则占主导地位。
The problem of transient heating of a semitransparent spherical body immersed in a stationary hot gas is investigated, taking into account the effect of thermal radiation. The size of the domain occupied by the gas is assumed to be finite, and the outer boundary of this domain is kept at constant temperature. The initial radial distribution of temperature in the body is taken into account. A modification of Newton's law for body heating is introduced via a correction to either the gas temperature or convection heat transfer coefficient. Explicit expressions for these corrections are obtained for the case of homogeneous initial distribution of temperature and radiation absorption inside the body, and constant radiation temperature. For large Fourier numbers Fo, the correction to gas temperature is expected to be of limited practical importance, as both this correction and the difference between the initial gas temperature and the body surface temperature approach zero (heat transferred from gas to the body becomes negligible). The results are analysed using values of parameters relevant to diesel engines. The values of the corrections to the convection heat transfer coefficient vary from about 0.1 (large domain occupied by gas and Fo=500) to 2.8 at Fo=0.1. This means that ignoring these corrections is expected to lead to unacceptably large errors in computations. The total time for body heating is shown to be more than an order of magnitude longer when compared to the heating of this body in a perfectly stirred gas. The effect of thermal radiation on droplet heating is accounted for via the additional corrections of gas temperature or the convection heat transfer coefficient. It is shown that the effects of radiation on the surface heat flux are small for small Fo, but become dominant for large Fo (Fo>50).