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

载有高温气流的颗粒的性质和行为对传热增强和控制的影响

基本信息

批准号：
03402030
负责人：
KUROSAKI Yasuo
金额：
$ 10.75万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1993
项目状态：
已结题

项目摘要

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

在本研究项目中，研究了载有气固悬浮流的颗粒的性质和行为对辐射传热的影响，结果总结如下： 1．首先，对浸没在流化床中的表面的辐射传输进行了实验检查；将单色激光穿过表面投射到流化颗粒中，并测量了颗粒内激光的强度分布。粒子乳液中的辐射穿透深度相对较小，但辐射几乎不会被流化粒子的“气泡相”散射。这些结果表明，从传热表面到流化粒子的辐射传递受以下关系支配。表面热边界层的厚度与颗粒的辐射穿透深度之间的关系。2 …更多测量从邻近传热表面的流化颗粒发出的辐射。通过红外热成像技术；从对红外辐射透明的传热表面加热流化颗粒，并通过红外热像仪测量颗粒发射的辐射强度。随着流化气体流速（即流化颗粒的空隙率）的增加，来自受热颗粒的辐射强度降低，并且随着流化颗粒对于红外辐射变得“黑色”，辐射强度增加。这些结果意味着由于热传递增强。辐射在高温气固悬浮液流中，当颗粒稀且对辐射透明时，这种现象是明显的。 3．流化床中辐射传热的实验评价为了证实上述结果，在高流化床中进行了辐射传热。 -对温度传热表面和流态化颗粒进行了实验研究；使用三种不同材料的颗粒，以检验两种不同发射率的传热表面被加热到1200K的效果。评估传热表面的辐射传热，实验结果表明，在我们的实验条件下，只有当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传热，这一结果与此吻合。除了我们在上述研究中估计的那些之外，还检查了循环流化颗粒单元的传热，以便开发邻近传热表面的流化颗粒的空隙率分布的控制技术，该传热表面主导着辐射。从或到的热量传递流态化颗粒较少。