The heat transfer coefficients of the heating surface of 300 MWe CFB boiler

2012 ◽  
Vol 21 (4) ◽  
pp. 368-376 ◽  
Author(s):  
Haibo Wu ◽  
Man Zhang ◽  
Qinggang Lu ◽  
Yunkai Sun
Keyword(s):  
Heat Transfer ◽  
Heating Surface ◽  
Transfer Coefficients ◽  
Cfb Boiler ◽  
Heat Transfer Coefficients

scholarly journals Boiling of a refrigerant of low GWP on the surface with copper microchannels

2018 ◽  
Vol 70 ◽  
pp. 02007
Author(s):  
Robert Kaniowski ◽  
Robert Pastuszko
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Atmospheric Pressure ◽  
Rectangular Cross Section ◽  
Heating Surface ◽  
Heat Transfer Process ◽  
Geometrical Parameters ◽  
Variable Depth ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The boiling curves and heat transfer coefficients between the heating surface and fluid were investigated in the paper. Copper samples with horizontal microchannels of rectangular cross-section, variable depth and width were the objects of the study. The following geometrical parameters have been used: microchannel width 0.2; 0.3 and 0.4 mm, depth between 0.2 and 0.5 mm (change every 0.1 mm). Boiling refrigerant was Novec-649 (GWP = 1), and the experiment was performed at atmospheric pressure. Geometrical parameters impact, within a given range of heat flux 3 – 130 kW/m2, on the heat transfer process was determined.

Heat Transfer Enhancement in Duct With Rectangular Fin Arrays

2019 ◽  
Author(s):  
Md. Islam ◽  
I. Barsoum
Keyword(s):  
Heat Transfer ◽  
Flow Behavior ◽  
Heating Surface ◽  
Infrared Camera ◽  
Vortex Generator ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Longitudinal Vortices ◽  
Heat Transfer Coefficients

Abstract The need for efficient cooling techniques has motivated researchers to focus into heat transfer and flow behavior of various configurations of finned surfaces. Inclined rectangular fin is found to be an effective vortex generator for heat transfer augmentation, wherein longitudinal vortices is generated and keeps intensity at far downstream. It is expected that the heat transfer from the endwall and the fin surface can be improved and hence we have identified this configuration as very promising. Rectangular fins of different height were constructed and experimental investigation of heat transfer and flow with arrays of rectangular fins was conducted. Effect of velocity, attack angle, fin height and pitch ratio on local heat transfer coefficients is studied. In order to accomplish the experiment, 7 × 7 arrays of rectangular fins were attached on the heating surface and then placed in rectangular duct with different angle of attack to the free stream flow. Stream wise heat transfer coefficients were measured both at centerline and of 10 mm off line of heating surface by means of the thermocouples. T-type thermocouples and an infrared camera (TVS 8000) with a 160 × 120 point In-Sb sensor were used to measure the temperature and the detailed heat transfer from the endwall along with fin base.

Measurement of Heat Transfer in a 465t/h Circulating Fluidized Bed Boiler

2005 ◽  
Author(s):  
Yu Wang ◽  
Junfu Lu ◽  
Hairui Yang ◽  
Xinmu Zhao ◽  
Guangxi Yue
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Bulk Density ◽  
Fluidized Bed ◽  
Thermal Boundary Layer ◽  
Circulating Fluidized Bed ◽  
Transfer Coefficients ◽  
Cfb Boiler ◽  
Heat Transfer Coefficients ◽  
Solid Bulk

The study of heat transfer and thermal boundary layer in the combustor of a circulating fluidized bed (CFB) is important to the boiler design and operation. Both heat transfer coefficient between the solid-gas flow and the water-wall and the thickness of thermal boundary layer are key data to determine the amount and layout of the tube walls in a CFB furnace. A series of experiments was conducted on a 465t/h commercial CFB boiler, which operated at bed temperature between 850 and 900°C, and at superficial gas velocity between 5.2 to 5.9m/s. Local bed to water wall heat transfer coefficients and temperature profiles near the wall were measured at a set of test ports at different heights of the sidewall. In the same time, the local solid bulk density near the wall was also measured. Special tools such as heat flux probe, solid bulk density sampling probe and temperature probe were developed for the experiments and their structures were introduced. The experimental results were compared with the data from previous studies. Theoretical analysis of the factors that play important role in heat transfer in a CFB boiler was also performed. The relationship between heat transfer and thermal boundary layer was also discussed. Furthermore, a simple model correlating the local heat transfer coefficients with bulk density was developed.

An Improvement of Cluster-Renewal Model for Estimation of Heat Transfer on the Water-Walls of Commercial CFB Boilers

2003 ◽  
Author(s):  
Animesh Dutta ◽  
Prabir Basu
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Thermal Boundary Layer ◽  
Circulating Fluidized Bed ◽  
Transfer Coefficients ◽  
Cfb Boiler ◽  
Heat Transfer Coefficients ◽  
Renewal Model ◽  
Solids Concentration ◽  
Gas Gap

Even though cluster renewal model appears to hold the ground for calculating heat transfer coefficients on water walls of a Circulating Fluidized Bed (CFB) boiler, there are certain parameters of this model including thickness of the gas-gap between the wall and the particle suspension, wall coverage, thermal boundary layer, cluster concentration, cluster velocity, dispersed phase convection are yet to be determined. Fractional wall coverage is the most important parameter among them. This paper presents a correlation of fractional wall coverage for commercial boilers based on the data from large CFB boilers where average solids concentration, size and height of the combustor were taken as variable. Data were deduced by applying cluster renewal model with recent findings on gas gap, thermal boundary layer, cluster concentration, cluster velocity to the reported heat transfer coefficients on four commercial CFB boilers. The improved cluster renewal model is validated against available data.

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