scholarly journals Heat transfer to a moving wire immersed in a gas fluidized bed furnace

2021 ◽  
Author(s):  
Antonio Tannas
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Steel Wire ◽  
Transfer Rates ◽  
New Correlation ◽  
Bed Temperature ◽  
Molten Lead ◽  
The Difference ◽  
Considerable Work ◽  
Work Done

In order to replace hazardous molten lead baths in the heat treatment of carbon steel wire with environmentally friendly fluidized bed furnaces a better understanding is needed of their heat transfer rates. There has been considerable work done in examining heat transfer rates to large cylinders immersed in fluidized beds, and some on wire sized ones as well, but all previous studies have been conducted on static cylinders. In order to gain a deeper understanding of heat transfer rates to a moving wire immersed in a fluidized bed furnace an apparatus has been constructed to move a wire through a fluidized bed. The heat transfer rates were calculated using the difference in inlet and outlet temperatures, wire speed and the bed temperature. As predicted, correlations for static wire were found to under-predict heat transfer rates at higher wire speeds, so a new correlation was developed by modifying an existing one.

scholarly journals Heat transfer to a moving wire immersed in a gas fluidized bed furnace

2021 ◽  
Author(s):  
Antonio Tannas
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Steel Wire ◽  
Transfer Rates ◽  
New Correlation ◽  
Bed Temperature ◽  
Molten Lead ◽  
The Difference ◽  
Considerable Work ◽  
Work Done

In order to replace hazardous molten lead baths in the heat treatment of carbon steel wire with environmentally friendly fluidized bed furnaces a better understanding is needed of their heat transfer rates. There has been considerable work done in examining heat transfer rates to large cylinders immersed in fluidized beds, and some on wire sized ones as well, but all previous studies have been conducted on static cylinders. In order to gain a deeper understanding of heat transfer rates to a moving wire immersed in a fluidized bed furnace an apparatus has been constructed to move a wire through a fluidized bed. The heat transfer rates were calculated using the difference in inlet and outlet temperatures, wire speed and the bed temperature. As predicted, correlations for static wire were found to under-predict heat transfer rates at higher wire speeds, so a new correlation was developed by modifying an existing one.

scholarly journals Heat transfer to a moving wire immersed in a gas fluidized bed furnace

2021 ◽  
Author(s):  
Shanta Mazumder
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Steel Wire ◽  
Small Diameter ◽  
Heat Treating ◽  
New Correlation ◽  
Heat Treated ◽  
Boiler Tubes ◽  
Gas Fluidized Beds ◽  
Wire Motion

The gasified fluidized bed has been looked at as a safer replacement for heat treatment of carbon steel wire traditionally heat treated using molten lead baths. Most of the research has been conducted on heat transfer to larger diameter boiler tubes immersed in gas fluidized beds used by the power generation industry. However, there has been a lack of research on small diameter cylinders and longitudinally moving wire in heat treating systems. In 2015, Tannas developed a correlation that confirmed that the correlation previously developed for static wire under-predicts the heat transfer rate at higher wire speeds. In addition, this earlier correlation did not account for varying fluidization rates and only assumed that Nu was independent of fluidization rate for Ug/Umf > 2.5. So, the work reported here is intended to develop a new correlation that accounts for both wire motion and fluidizing rate in fluidized bed.

scholarly journals Heat transfer to a moving wire immersed in a gas fluidized bed furnace

2021 ◽  
Author(s):  
Shanta Mazumder
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Steel Wire ◽  
Small Diameter ◽  
Heat Treating ◽  
New Correlation ◽  
Heat Treated ◽  
Boiler Tubes ◽  
Gas Fluidized Beds ◽  
Wire Motion

The gasified fluidized bed has been looked at as a safer replacement for heat treatment of carbon steel wire traditionally heat treated using molten lead baths. Most of the research has been conducted on heat transfer to larger diameter boiler tubes immersed in gas fluidized beds used by the power generation industry. However, there has been a lack of research on small diameter cylinders and longitudinally moving wire in heat treating systems. In 2015, Tannas developed a correlation that confirmed that the correlation previously developed for static wire under-predicts the heat transfer rate at higher wire speeds. In addition, this earlier correlation did not account for varying fluidization rates and only assumed that Nu was independent of fluidization rate for Ug/Umf > 2.5. So, the work reported here is intended to develop a new correlation that accounts for both wire motion and fluidizing rate in fluidized bed.

Performance analysis of screw compressors – numerical simulation and experimental verification

2011 ◽  
Vol 226 (4) ◽  
pp. 968-980 ◽  
Author(s):  
S H Hsieh ◽  
Y C Shih ◽  
W-H Hsieh ◽  
F Y Lin ◽  
M J Tsai
Keyword(s):  
Heat Transfer ◽  
Screw Compressor ◽  
Pressure Curve ◽  
Discharge Process ◽  
Transfer Rates ◽  
Outlet Port ◽  
Total Process ◽  
The Difference ◽  
Verification Process ◽  
Empirical Constants

This article describes a theoretical model and computer program for calculating the pressure–volume ( PV ) diagram and the efficiency of an oil-injected screw compressor. The proposed model considers the mass and energy conservation laws, the heat transfer between air and oil, the leakages through various paths, and the discharges of air and oil. The proposed program, which uses seven empirical constants to account for the difference between the flow and the heat-transfer rates in the screw compressor and those estimated by available correlations, solves for the efficiency and the pressure curve of the compressed air. A systematic methodology for the determination of the seven empirical constants is presented in this article. Optimization is carried out to determine the seven empirical constants. With the empirical constants, which are determined with four sets of experiments, the maximum difference between the calculated and measured results in the training process, the verification process and the total process is 2.0 per cent for the volumetric and isentropic efficiencies and 5 per cent for the pressure curve. In the discharge process, the pressure in the compression chamber is noted to be affected by the area of the outlet port and the pressure in the neighbouring chambers.

Effects of the Heat Transfer at the Side Walls on Natural Convection in Cavities

1990 ◽  
Vol 112 (2) ◽  
pp. 370-378 ◽  
Author(s):  
Y. Le Peutrec ◽  
G. Lauriat
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Thermal Conductance ◽  
Fluid Flows ◽  
Heat Losses ◽  
Transfer Rates ◽  
Side Walls ◽  
The Difference

Numerical solutions are obtained for fluid flows and heat transfer rates for three-dimensional natural convection in rectangular enclosures. The effects of heat losses at the conducting side walls are investigated. The problem is related to the design of cavities suitable for visualizing the flow field. The computations cover Rayleigh numbers from 103 to 107 and the thermal conductance of side walls ranging from adiabatic to commonly used glazed walls. The effect of the difference between the ambient temperature and the average temperature of the two isothermal walls is discussed for both air and water-filled enclosures. The results reported in the paper allow quantitative evaluations of the effects of heat losses to the surroundings, which are important considerations in the design of a test cell.

Effect of Static Bed Height on the Combustion of Rice Husk in a Fluidized Bed Combustor

2005 ◽  
Author(s):  
M. Rozainee ◽  
S. P. Ngo
Keyword(s):  
Fluidized Bed ◽  
Residence Time ◽  
Rice Husk ◽  
Bubble Formation ◽  
Combustion Process ◽  
High Heat ◽  
Transfer Rates ◽  
Bed Height ◽  
Bed Temperature ◽  
Bed Material

The combustion process is largely controlled by temperature, turbulence and residence time. When the temperature is sufficiently high so that the reaction is no longer kinetically-controlled, turbulence and residence time play a significant role. The reaction is thus diffusion-controlled. During the combustion of rice husk in a fluidized bed, the turbulence is largely governed by the mixing behavior in the inert sand bed, which in turn is governed by the bubble formation characteristics. Further, the residence time among the reactants (air and rice husk) and the heat source is also dependent on the turbulence in the bed. When all other parameters are held constant, the bubble phenomena vary according to the expanded bed height corresponding to a given static bed height. For high heat and mass transfer rates, small slowly rising bubbles are desired. Thus, the purpose of this study is to investigate the effect of static bed height on the quality of ash during the combustion of rice husk. The degree of rice husk burning in the bed could be deduced from the bed temperature as a higher bed temperature indicated that a higher portion of the rice husk feed is being burnt in the bed. Moreover, the particle size of the resulting ash is also able to give indication of the degree of rice husk burning in the bed as the turbulence arising from the bubbling action of the bed material is known to break down the char skeleton of the rice husk, thereby, resulting in ash with finer size. From this study, the static bed height of 0.5 DC was found to give the lowest residual carbon content in the ash (1.9 wt%) and the highest bed temperature (670°C) among the other range of static bed heights investigated.

scholarly journals Heat Transfer Performance in a Superheater of an Industrial CFBC Using Fuzzy Logic-Based Methods

Entropy ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 919 ◽  
Author(s):  
Krzywanski
Keyword(s):  
Heat Transfer ◽  
Fuzzy Logic ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Practical Significance ◽  
Overall Heat Transfer Coefficient ◽  
Bed Temperature ◽  
The Heat Transfer Coefficient

The heat transfer coefficient in the combustion chamber of industrial circulating flidized bed (CFB) boilers depends on many parameters as it is a result of multifactorial mechanisms proceeding in the furnace. Therefore, the development of an effective modeling tool, which allows for predicting the heat transfer coefficient is interesting as well as a timely subject, of high practical significance. The present paper deals with an innovative application of fuzzy logic-based (FL) method for the prediction of a heat transfer coefficient for superheaters of fluidized-bed boilers, especially circulating fluidized-bed combustors (CFBC). The approach deals with the modeling of heat transfer for the Omega Superheater, incorporated into the reaction chamber of an industrial 670 t/h CFBC. The height above the grid, bed temperature and voidage and temperature, gas velocity, and the boiler’s load constitute inputs. The developed Fuzzy Logic Heat (FLHeat) model predicts the local overall heat transfer coefficient of the Omega Superheater. The model is in good agreement with the measured data. The highest overall heat transfer coefficient is equal 220 W/(m2K) and can be achieved by the SH I superheater for the following inputs l = 20 m, tb = 900 °C, v = 0.95, u = 7 m/s, M-C-R = 100%. The proposed technique is an effective strategy and an option for other procedures of heat transfer coefficient evaluation.

Heat Transfer From Horizontal Serrated Finned Tubes in an Air-Fluidized Bed of Uniformly Sized Particles

1983 ◽  
Vol 105 (2) ◽  
pp. 319-324 ◽  
Author(s):  
W. B. Krause ◽  
A. R. Peters
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Convective Heat Transfer Coefficient ◽  
Power Input ◽  
Finned Tube ◽  
Primary Objective ◽  
Transfer Coefficients ◽  
Fin Efficiency ◽  
Finned Tubes ◽  
Bed Temperature

A primary objective of this work was to gather experimental convective heat transfer coefficient data for extended surfaces. The results were then compared with bare horizontal tubes in a similar flow environment. The finned tube configurations were considered an extension of the bare tube arrangements to enhance heat transfer. Heat transfer coefficients were computed from the heated tube surface temperature, the fluidized bed temperature, and the power input to the tube. Selected serrated finned tubes were used. The experimental heat transfer data were measured as a function of fluidized bed flow parameters and finned tube geometry. Several tests were performed using two different uniformly sized glass particles (.21 mm and .43 mm). Fin efficiency factors were determined and presented as a function of mass velocity and as a function of a fin length parameter. The finned tube demonstrated a better heat transfer capacity over bare tubes for similar fluidization conditions.

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