Heat Transport Mechanism around Tubes Immersed in Floating Particles

浸没在漂浮颗粒中的管周围的热传输机制

基本信息

批准号：
62550148
负责人：
KUMADA Masaya
金额：
$ 1.28万
依托单位：
University of Gifu
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1988
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-62550148/
关键词：
Fluidized bed Heat exchanger Heat transport mechanism Renewal model of boundary layer Low density particles Emulsion Capacitance sensor 薄膜熱流束センサー静電容量センサー熱流束センサー熱伝達率更新モデル管群静電容量プローブ熱流束計

项目摘要

Intensive studies designed to realized to fluidized bed heat exchanger with excellent heat characteristics have been cconducted in recent years. While several theories for the heat transfer process have been proposed, actual design currently still depends on empirical correlation.The mechanism of heat transport from a single row horizontal tubes submerged in a floating fluidized bed, of which the static bed height was very shallow, was investigated experimentally. In this paper, in order to improve the performance of a heat exchanger on fluidized, low density particles (polystyrene hollow sphere) were employed.Aiming at phenomenological understanding of the heat transport mechanism, the fast response capacitance sensor mounted flush within the tube was developed to investigate the movement of particles near the surface of tubes. Local instantaneous heat transfer coefficient was also measured using a miniature heat flow sensor for the same conditions.A new model of heat transport mechanism was suggested from the data of capacitance sensor and heat flow sensor. Comparison of this model with many of the other models, in particular the packed renewal model originally developed by Mickley and Fairbanks, was tried.The results obtained were; (1) The capacitance trace versus time can be directly related to the variations in local solids density near the tube surface. (2) Capacitance signals can be divided into three major types as follows; the dense emulsion phase, the lean emulsion phase and the gaseous medium with some entrained particles. (3) Signals of heat flow sensor correspond to those of the capacitance sensor. (4) Heat transfer coefficient rises extremely by the effect of the dense emulsion. (5) Heat transport mechanism can be explained by a renewal model of results were accord with experimental results.

近年来，旨在实现具有出色热特性的流化床热交换器的密集研究。虽然已经提出了几种传热过程的理论，但实际设计目前仍取决于经验相关性。从单排水平管中浸入浮动床中的热管的机理，静态床的高度非常浅，进行了实验研究。在本文中，为了提高热交换器在流化，低密度颗粒（聚苯乙烯空心球）上的性能。在对热传输机制的现象学理解时，将在管中安装的快速响应电容传感器在管子内开发出来，以研究管子表面附近的颗粒的运动。还使用微型热流传感器为相同条件测量了局部瞬时传热系数。从电容传感器和热流传感器的数据中提出了一种新的热传输机构模型。尝试了该模型与许多其他模型，特别是最初由Mickley和Fairbanks开发的包装续订模型。（1）电容跟踪与时间可以直接与管子表面附近的局部固体密度变化有关。（2）电容信号可以分为三种主要类型，如下所示；密集的乳液相，瘦乳液相和带有一些夹带颗粒的气态介质。（3）热流传感器的信号对应于电容传感器的信号。（4）传热系数通过致密乳液的影响极高地升高。（5）热传输机制可以通过结果的更新模型来解释，这与实验结果一致。