Natural convection of a heat-generating fluid confined in a frozen layer within a horizontal cylinder

当一个装有发热流体的水平圆柱体的壁面被冷却到低于流体的凝固点时，在内壁表面上形成一个固体层。伴随地，自然对流在液体区域中由液体和固液界面之间的温度引起。以熔盐增殖反应堆紧急停堆时作为燃料盐贮存容器的贮盐槽为例，可以观察到这种组合现象。在这个项目中，进行了一项研究，以澄清这种组合现象的热特性。本研究的概要如下.采用有限差分法，在Rayleigh数为10^8.2的范围内，研究了水平圆柱体内发热流体的非定常自然对流。用马赫-曾德尔干涉仪测量了温度场和换热系数。所得结果与数值计算结果非常吻合.在瑞利数达7 × 10 ^4的范围内，通过实验得到了估算努塞尔数和圆柱内最高温度的方程<12>。采用有限差分法对水平圆柱体中的生热流体的凝固过程进行了数值研究。研究结果阐明了冻结层的特性和液态区的自然对流特性.设计了一种近似计算方法，估算了液相区的冻结层厚度、最高温度、最大流函数和平均努塞尔数。

When the wall of a horizontal cylinder in which a heat-generating fluid is confined is chilled below the freezing point of the fluid, a solid layer is formedon the iner wall surface. Concomitantly, natural convection is induced in the liquid region by the temperature between the liquid and the solid-liquid interface. Such combined phenomenon, for example, will be observed in a dump-tank which is used as a storage vessel of fuel salt when an emergency shut dowm of a molten salt breeder reactor happens. In this project, a study was conducted to clarify the thermal characteristics of this combined phenomenon. The outline of this study was as follow.1. Unsteady natural convection of the heat-generating fluid in a horizontal cylinder was investigated through the numerical analysis by the finite difference method in the range of Rayleigh number up to 10^8.2. Temperature profiles and heat transfer coefficients were measured by Mach-Zehnder interferometer with a high accuracy. The results obtained were very much in agreement with the numerical results.3. Equations to estimate the Nusselt number and the maximum temperature in the cylinder were obtained experimentally in the range of Rayleigh number up to 7X10^<12>.4. A numerical study by finie difference method was carried out for the solidification of the heat-generating fluid in the horizontal cylinder. Results clarified th characteristics of the frozen layer and the natural convection induced in the liquid region.5. An approximate method was devised to estimate the thickness of the frozen layer, the maximum temperature, the maximum stream function and the mean Nusseltnumber in the liquid region.