Effects of Properties and Behavior of Particles Laden with High Temperature Gas Flow on the Heat Transfer Augmentation and Control

在本研究项目中，研究了载气固悬浮颗粒的性质和行为对辐射传热的影响。研究结果总结如下：1。流化颗粒层内辐射的穿透。首先，对流化床表面的辐射传递进行了实验研究；将单色激光通过流态化颗粒表面投射到颗粒内，测量了激光在颗粒内的强度分布。结果表明：辐射在颗粒乳化液中的穿透深度较小，但辐射几乎不被流化颗粒的“气泡相”散射；这些结果表明，传热表面向流化颗粒的辐射传递主要受表面热边界层厚度与颗粒辐射穿透深度的关系支配。2 .更多。靠近传热表面的流化颗粒发出的辐射。用红外热像仪测量了靠近传热表面的流化颗粒发出的辐射；流态化颗粒从对红外辐射透明的传热表面加热，用红外热像仪测量颗粒的辐射强度。结果表明：随着流化气体流量（即流化颗粒的空隙率）的增加，被加热颗粒的辐射强度减小；随着流化颗粒红外辐射变为“黑色”，辐射强度增大；这些结果表明，在高温气固悬浮流动中，当颗粒稀薄且对辐射透明时，辐射对传热的增强作用是明显的。流化床辐射传热的实验评价。为了证实上述结果，对高温传热表面与流化颗粒之间的辐射传热进行了实验研究；采用三种不同材料的粒子，考察了粒子发射率的影响。采用两种不同发射率的换热面，加热至1200k，对换热面辐射换热进行了计算。实验结果表明，在我们的实验条件下，只有使用对红外辐射相对透明的氧化铝颗粒时，才能观察到明显的辐射换热。这个结果与我们在上面描述的故事中估计的结果非常吻合。此外，还研究了循环流化颗粒池的传热特性，从而开发了控制传热表面附近流化颗粒的空隙率分布的技术，该空隙率分布主导着流化颗粒的辐射传热或向流化颗粒的辐射传热。少

In the present research project, effects of the properties and behavior of the particles laden with a gas-solid suspension flow on the radiation heat transfer were examined. The results are summarized into the followings :1. Penetration of Radiation within a Fluidized Particle Layr. First of all, radiation transfer from a surface immersed in a fluidized bed was experimentally examined ; a monochromatic laser light was projected into the fluidized particles through the surface, and intensity distributions of the laser light were measured within the particles. The results showed that the radiation penetration depth in the particle emulsion is relatively small, but that the radiation is hardly scattered by the "bubble phase" of fluidized particles. These results suggests that the radiation transfer from a heat transfer surface to fluidized particles is dominated by the relation between the thickness of thermal boundary layr on the surface and the radiation penetration depth of particles.2 … More . Radiation Emitted from the Fluidized Particles Adjacent to the Heat Transfer Surface. Radiation emitted from the fluidized particles adjacent to a heat transfer surface was measured by means of IR thermography ; fluidized particles were heated from a heat transfer surface, which was a transparent for the IR radiation, and intensity of the radiation emitted from the particles was measured by a IR thermo-camera. The results showed that the radiation emitted from the heated particles decreases with increasing the fluidizing gas flow rate, i.e. void fraction of the fluidized particles, and that the intensity of radiation increases as the fluidized particles become "black" for IR radiation. These results mean that the heat transfer augmentation due to radiation in a high-temperature gas-solid suspension flow is evident when the particles are dilute and transparent for radiation.3. Experimental Evaluation of Radiation Heat Transfer in a Fluidized Bed. In order to confirm the results described above, radiation heat transfer between a high-temperature heat transfer surface and fluidized particles was experimentally examined ; particles of three different materials were used so as to examine the effects of particle emissivity. Heat transfer surfaces of two different emissivity, which were heated upto 1200 K, were used for evaluating the radiation heat transfer from the heat transfer surface. The experimental results showed that, under our experimental conditions, evident radiation heat transfer was observed only when the alumina particles, which are relatively transparent for IR radiation, were used. This result coincides well with the ones estimated in our stury described above. In addition to these, heat transfer of a circulating fluidized particle cell was examined so as to develop the control technique for void fraction distribution of the fluidized particles adjacent to the heat transfer surface, which dominates the radiative heat transfer from or to the fluidized particles. Less