顆粒流的熱傳應用是相當廣泛的，從生活中糖炒栗子的加熱到產業應用如流體化床燃燒 爐、旋轉加熱窯等應用。因此本計畫將針對顆粒體的熱傳行為，進行為期三年的研究。第一 年計畫將探討顆粒擾動行為對於整體顆粒床熱傳行為的影響。在不同強度顆粒自我擴散行為 的顆粒床系統中，量測計算其熱擴散係數，以探討顆粒床之質量擴散現象與熱擴散現象之間 的關係。第二年計畫將會針對靜止顆粒堆積床之微觀熱傳行為進行探討。先期將以低壓系統 進行測試，排除間隙氣體之熱傳效應，並加入顆粒尺寸效應，進行熱傳相關的量測。後期實 驗將增加系統壓力，藉以加入間隙氣體之熱傳效應，且利用克努森數來描述間隙氣體之熱傳 效果。第三年度的計畫，將透過控制顆粒體之大小與填充率，藉此探討不同體積佔有率與質 量對於顆粒熱傳現象之影響，藉由改變系統之轉速以探討顆粒體之熱接觸時間與熱擴散之關 係，並針對此系統下，歸納出顆粒之接觸熱傳係數半經驗公式和紐塞數與培克萊特數之關係 式。 本三年期計畫針對顆粒熱傳的相關基礎理論做深入研究，以實驗的方式了解顆粒物質在 擾動、靜止與流動狀況下，相關熱傳行為的物理機制，希望能歸納出顆粒熱傳行為的基礎理 論模型，並進一步提供業界重要資訊。 ;The thermal conduction mechanisms in dry granular pile is more complex than the conduction through a pure solid material because of air in the voids between the particles. In the granular pile, the thermal energy can only be transferred via the point contact between the neighboring granular particles. However, the effective thermal conductivity for the granular materials has been only investigated in relatively few literatures. The aims of first year project is to investigate the thermal conduction mechanisms in dry granular system for the particles with fluctuant motions by an experimental study. The granular beds with different intensity of particle self-diffusion are produced by exerting different strength of the vertical vibrated driving force. The effect of mass diffusion on the thermal diffusive behavior in the dry granular system will be discussed. Dimensionless Lewis number Le is calculated to discuss the relation between mass diffusion and thermal diffusion in the granular bed. The effect of particle size and pressure on the thermal behavior in the static dry granular pile will be investigated in the second year. The thermal mechanisms will become more complicated while the static granular pile bears the combining effect of particle size and pressure. The effective conductivity will be calculated using the granular bed temperature, which is measured using a hot wire method. In the third year, we will study and measure the temperature field of granular flow in an indirectly-heated rotating drum. In the system, heat would be transferred to the granular bed in two ways. One is from gas to the free solid bed surface by radiation, and the other would be from the wall surface. The semi-empirical formula of contact heat transfer coefficient and the relationship between the Nusselt number and the Péclet number will be both derived in this year. The first and second year project, the temperature of the granular bed will be measured by the thermocouples. The third year project, the temperature field of the granular bed will be measured by an infrared thermal imager and the results will be verified by thermocouples. The experimental images will be captured by a high speed camera to analyze the transport properties of particles. The velocities, granular temperatures and the particle diffusion coefficients will be calculated. Finally, we wish to develop the theoretical model for the granular thermal mechanisms and compare with the experimental results. By this way, the results of this three-year-project could provide a lot of contribution and application to many industrial processes.
