Control of Heat Transfer and Defrostings with Fluidized Beds

在传统的翅片管热交换器用作热泵系统和LNG气化系统中的蒸发器的情况下，潮湿空气中的水分冻结并在翅片表面上形成厚的霜层，这减少了热传递，增加了压力损失，并最终导致蒸发器的阻塞。因此，开发无霜蒸发器是一个重要而紧迫的研究课题。本文对撞击射流流化床的传热传质特性及其传热传质特性进行了研究。研究结果为建立一种高效的流化床换热器提供了理论依据。共同研究结果在东北大学进行了以下实验研究：（1）单相冲击射流中冷管的局部传热和结霜特性研究。(2)浅层流化床流化机理的研究、颗粒浓度的测定 ...更多信息 在管表面上的敲击频率，以及观察颗粒在管表面上的行为。(3)颗粒冲击强化冷管传热特性的研究在北海道大学进行了以下实验研究：（1）冲击射流型流化床传热特性的研究。特别是流化颗粒对混粉流化床传热的影响。(2)流化床液态冰冷冻及连续生产特性之研究。(3)流化床中垂直冷却板和水平冷却管阵列结霜特性的研究。(4)浸没在液态冰中的水平冷却管阵列的熔化传热特性研究。维也纳工业大学对粒子-气体射流的形成过程及其对管表面的冲击进行了理论研究，特别是针对东北大学使用的角形分布器。通过将上述研究结果结合起来，建立了撞击射流流化床的优化设计方法。阐明了其传热和传热特性及其控制原理，对实际应用有一定的指导意义。少

In the cases where conventional finned-tube heat exchangers are used as evaporators in heat pump systems and LNG-gasification systems, moisture in humid air freezes and forms a thick frost layr on the fin surfaces, which reduces the heat transfer, increases the pressure loss, and finally results in choking of the evaporatores. Thus development of frost-free evaporators is an important and urgent research subject. The present research project has been performed to study heat and mass transfer characteristics of impinging jet-type fluidized bed and its defrosting characteristics. The obtained results are useful to establish a fluidized-bed heat exchanger which is effective for defrosting.Results of the Joint ResearchIn Tohoku University, the following experimental studies were performed :(1) Study on local heat transfer and frosting characteristics of cold tubes in single-phase impinging jets.(2) Study on defrosting mechanism of a very shallow fluidized bed, measurement of particle's con … More tact frequency onto the tube surface, and observation of the behavior of particles on the tube surface.(3) Study on heat transfer characteristics of cold tubes under defrosting by particle impingement.In Hokkaido University the following experimental studies were performed :(1) Study on heat transfer charactersistics of impinging-jet type fluidized ged. Especially the effect of fluidizing particles on heat transfer in a powder-mixed fluidized bed.(2) Study on freezing and continuous production characteristics of liquid ice by use of the fluidized bed.(3) Study on frosting characteristics of a vertical cooled plate and a horizontal cooled tube array immersed in a fluidized bed.(4) Study on melting heat transfer characteristics of a horizontal cooled tube array immersed in liquid ice.In Technical University, Vienna, theoretical study on formation process of particle-gas jets and their impingement onto tube surface was performed especially for the cornice-type distributor, utilized in Tohoku University.By joining these results of the above-mentioned studies, an potimum design method for impinging-jet type fluidized bed has been established. Also the heat-transfer and defrosting characteristics and the control theory for them were clarified, which is useful for practical applicatios. Less