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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，人们对具有优良传热特性的流化床换热器进行了深入的研究。虽然传热过程的理论已被提出，但目前实际设计仍依赖于经验关联式.实验研究了单排水平埋管在静止床层高度很浅的浮动流化床中的传热机理。为了提高流化床换热器的传热性能，采用低密度颗粒（聚苯乙烯空心球）作为流化床换热器的传热介质，为了从现象学的角度理解流化床换热器的传热机理，研制了一种快速响应的电容传感器，用于研究流化床换热器中颗粒在管壁附近的运动。在相同条件下，利用微型热流传感器测量了局部瞬时传热系数，并结合电容传感器和热流传感器的数据，提出了一种新的传热机理模型。将该模型与其它许多模型，特别是米克利和费尔班克斯提出的填充更新模型进行了比较，结果表明：（1）电容随时间的变化与管壁附近局部固体密度的变化有直接关系。(2)电容信号可分为三种主要类型：浓相、稀相和含有颗粒的气态介质。(3)热流传感器的信号与电容传感器的信号相对应。(4)在浓乳化液的作用下，传热系数大大提高。(5)用更新模型解释了热传递机理，计算结果与实验结果雅阁。