Continuity, momentum, and energy equations have been solved to predict the natural convection heat transfer from an upward, downward, and sideward solid or hollow hemisphere either suspended in air or placed on the ground. The results have been plotted in terms of average surface Nusselt number $Nu$ as a function of Rayleigh number $Ra$ spanning from ${10}^4$ to ${10}^7$ in the laminar flow regime. The behavior of the flowfield and temperature distribution around the hemisphere at different orientations have been analyzed against Rayleigh number with the aid of velocity vector plot and temperature contour. It is found that the Nusselt number for the upward solid hemisphere is more than that of the downward and sideward hemispheres. However, the situation reverses when the hemisphere lies on the ground with an $Ra$ less than ${10}^6$. When a hollow hemisphere is being focused, the inner-surface Nusselt number for a hollow hemisphere becomes less than that of the outer surface for all Rayleigh numbers. The outer-surface Nusselt number for the upward-facing hollow hemisphere is marginally higher than that of the downward and sideward hemispheres; however, the inner-surface Nusselt number is significantly more for the sideward hemisphere compared to other cases. The Nusselt number for the solid or hollow hemisphere in air is higher than that of the hemisphere on the ground. The opposite scenario arises for the downward and sideward hollow hemispheres when the $Ra$ is more than ${10}^6$. When the hollow hemisphere is concerned with finite thickness, the Nusselt number for both the inner and outer surfaces remains constant against the thickness and thermal conductivity of the material. Finally, the correlation of Nusselt number as a function of Rayleigh number for both the hollow and solid hemispheres has been proposed, which could be referred to in academics and industrial practices.

已经求解了连续性、动量和能量方程，以预测从悬浮在​​空气中或放置在地面上的向上、向下和侧向的实心或空心半球的自然对流热传递。结果已根据平均表面努塞尔数绘制$N你$ 作为瑞利数的函数 $\mathrm{电阻}\mathrm{一种}$ 跨越从 ${10}^4$ 到 ${10}^7$在层流状态。借助速度矢量图和温度等值线，针对瑞利数分析了不同方向上半球周围流场和温度分布的行为。发现向上实体半球的努塞尔数大于向下和侧向半球的努塞尔数。然而，当半球平躺在地面上时，情况就会逆转。$\mathrm{电阻}\mathrm{一种}$ 少于 ${10}^6$. 当聚焦空心半球时，空心半球的内表面努塞尔数变得小于所有瑞利数的外表面努塞尔数。朝上的空心半球的外表面努塞尔数略高于朝下和侧向半球的外表面努塞尔数；然而，与其他情况相比，侧向半球的内表面努塞尔数明显更多。空气中实心或空心半球的努塞尔数高于地面半球的努塞尔数。向下和向侧的空心半球出现相反的情况，当$\mathrm{电阻}\mathrm{一种}$ 超过 ${10}^6$. 当空心半球涉及有限厚度时，内表面和外表面的努塞尔数相对于材料的厚度和热导率保持恒定。最后，提出了空心半球和实心半球的努塞尔数与瑞利数的函数关系，可供学术界和工业界参考。