THE EFFECT OF BILATERAL HEATING ON HEAT TRANSFER COEFFICIENT TO SODIUM FLOWING IN AN ANNULUS

1982 ◽  
Author(s):  
Yongji Zhang ◽  
Zhencan Zhang ◽  
Shuangkai Shi ◽  
Jusheng Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Bilateral Heating

Numerical Simulation of Upward Two-Phase Flow in Narrow Channel Between Two Flat Plates With Bilateral Heating

2008 ◽  
Author(s):  
Lei Li ◽  
Zhijian Zhang ◽  
Jiange Liu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Film ◽  
Transfer Coefficient ◽  
Narrow Channel ◽  
Liquid Films ◽  
Phase Flow ◽  
Two Phase ◽  
Narrow Channels ◽  
Bilateral Heating

The convection heat transfer characteristic in narrow channel is superior. Therefore, narrow channels are suitable for being manufactured into compact heat transfer components with high heat transfer performance. This new technology of heat transfer enhancement with no source is widely applied to various fields such as microelectronic heat sink, cryogenic industry, chemical industry, aeronautic & astronautic industry and nuclear engineering. In integrated reactor, the coolant channels between the plate fuels are narrow channels. As to the investigation of two-phase flow and heat transfer in narrow channels, reports are focused on experimental research with low pressure, at home and abroad, but reports on numerical simulation research are relatively small. Based on separated flow, a theoretical two-fluid model predicting for upward flow in a rectangular narrow channel with bilateral heating has been developed in this paper. The theoretical model is based on fundamental conservation principles: the mass, momentum and energy conservation equations of liquid films and the momentum conservation equation of vapor core. The model assumed that liquid film covers the surface of the channel while the vapor with entrained droplets flows in the central core. And there exists the mass transfer between the liquid droplets in the vapor core and the liquid films. Through numerically solving these equations, liquid film thickness, radial velocity and temperature distribution in liquid films and heat transfer coefficient are obtained. The calculated results shows that the width of the narrow channel, heat pattern, heat flux have great influences on heat transfer coefficient and the thickness of liquid film. The heat transfer coefficient will increase with the decrease of the channel width. That is, the heat transfer may be enhanced with small rectangular narrow channel. But when the channel width is less than a certain value, the model may not be proper anymore. So the further research should be necessary. As the applications of the present model, the critical heat flux and critical quality are calculated.

Evaporation of lignin-lean black liquor

TAPPI Journal ◽  
2015 ◽  
Vol 14 (7) ◽  
pp. 441-450
Author(s):  
HENRIK WALLMO, ◽  
ULF ANDERSSON ◽  
MATHIAS GOURDON ◽  
MARTIN WIMBY
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Black Liquor ◽  
Salt Content ◽  
Solubility Limit ◽  
Lignin Removal ◽  
Kraft Black Liquor ◽  
Black Liquors ◽  
The Heat Transfer Coefficient

Many of the pulp mill biorefinery concepts recently presented include removal of lignin from black liquor. In this work, the aim was to study how the change in liquor chemistry affected the evaporation of kraft black liquor when lignin was removed using the LignoBoost process. Lignin was removed from a softwood kraft black liquor and four different black liquors were studied: one reference black liquor (with no lignin extracted); two ligninlean black liquors with a lignin removal rate of 5.5% and 21%, respectively; and one liquor with maximum lignin removal of 60%. Evaporation tests were carried out at the research evaporator in Chalmers University of Technology. Studied parameters were liquor viscosity, boiling point rise, heat transfer coefficient, scaling propensity, changes in liquor chemical composition, and tube incrustation. It was found that the solubility limit for incrustation changed towards lower dry solids for the lignin-lean black liquors due to an increased salt content. The scaling obtained on the tubes was easily cleaned with thin liquor at 105°C. It was also shown that the liquor viscosity decreased exponentially with increased lignin outtake and hence, the heat transfer coefficient increased with increased lignin outtake. Long term tests, operated about 6 percentage dry solids units above the solubility limit for incrustation for all liquors, showed that the heat transfer coefficient increased from 650 W/m2K for the reference liquor to 1500 W/m2K for the liquor with highest lignin separation degree, 60%.

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