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.

Heat Transfer to Small Horizontal Cylinders Immersed in a Fluidized Bed

2006 ◽  
Vol 128 (10) ◽  
pp. 984-989 ◽  
Author(s):  
J. Friedman ◽  
P. Koundakjian ◽  
D. Naylor ◽  
D. Rosero
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluidized Bed ◽  
Fluidized Beds ◽  
Manufacturing Industry ◽  
Steel Wire ◽  
Small Diameter ◽  
Heat Treating ◽  
Packed Bed ◽  
Horizontal Cylinders

Heat transfer to horizontal cylinders immersed in fluidized beds has been extensively studied, but mainly in the context of heat transfer to boiler tubes in coal-fired beds. As a result, most correlations in the literature have been derived for cylinders of 25-50mm diameter in vigorously fluidizing beds. In recent years, fluidized bed heat treating furnaces fired by natural gas have become increasingly popular, particularly in the steel wire manufacturing industry. These fluidized beds typically operate at relatively low fluidizing rates (G∕Gmf<5) and with small diameter wires (1-6mm). Nusselt number correlations developed based on boiler tube studies do not extrapolate down to these small size ranges and low fluidizing rates. In order to obtain reliable Nusselt number data for these size ranges, an experimental investigation has been undertaken using two heat treating fluidized beds; one a pilot-scale industrial unit and the other a lab-scale (300mm diameter) unit. Heat transfer measurements were obtained using resistively heated cylindrical samples ranging from 1.3 to 9.5mm in diameter at fluidizing rates ranging from approximately 0.5×Gmf (packed bed condition) to over 10×Gmf using aluminum oxide sand particles ranging from dp=145-330μm (50–90 grit). It has been found that for all cylinder sizes tested, the Nusselt number reaches a maximum near 2×Gmf, then remains relatively steady (±5-10%) to the maximum fluidizing rate tested, typically 8-12×Gmf. A correlation for maximum Nusselt number is developed.

Heat Transfer to Small Cylinders Immersed in a Fluidized Bed

2005 ◽  
Author(s):  
Jacob Friedman ◽  
Polo Koundakjian ◽  
Dennis Rosero
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluidized Bed ◽  
Fluidized Beds ◽  
Manufacturing Industry ◽  
Steel Wire ◽  
Small Diameter ◽  
Heat Treating ◽  
Packed Bed ◽  
Pilot Scale

Heat transfer to horizontal cylinders immersed in fluidized beds has been extensively studied, but mainly in the context of heat transfer to boiler tubes in coal-fired beds. As a result, most correlations in the literature have been derived for cylinders of 25–50mm diameter in vigorously fluidizing beds. In recent years, fluidized bed heat treating furnaces fired by natural gas have become increasingly popular, particularly in the steel wire manufacturing industry. These fluidized beds typically operate at relatively low fluidizing rates (G/Gmf < 5) and with small diameter wires (1–6mm). Nusselt number correlations developed based on boiler tube studies do not extrapolate down to these small size ranges and low fluidizing rates. In order to obtain reliable Nusselt number data for these size ranges, an experimental investigation has been undertaken using two heat treating fluidized beds; one a pilot-scale industrial unit and the other a lab-scale (300mm diameter) unit. Heat transfer measurements were obtained using resistively heated cylindrical samples ranging from 1.3 mm to 9.5 mm in diameter at fluidizing rates ranging from approximately 0.5 × Gmf (packed bed condition) to over 10 × Gmf using aluminum oxide sand particles ranging from dp = 145–330 μm (50 to 90 grit). It has been found that for all cylinder sizes tested, the Nusselt number reaches a maximum near 2 × Gmf, then remains relatively steady (± 5–10%) to the maximum fluidizing rate tested, typically 8–12 × Gmf. A correlation for maximum Nusselt number is developed.

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.

Heat Transfer to Flat Strips Immersed in a Fluidized Bed

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Christopher Penny ◽  
Dennis Rosero ◽  
David Naylor ◽  
Jacob Friedman
Keyword(s):  
Heat Transfer ◽  
Power Generation ◽  
Nusselt Number ◽  
Fluidized Bed ◽  
Manufacturing Industry ◽  
Particle Diameter ◽  
Orientation Angle ◽  
Heat Treating ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Heat transfer to objects immersed in a fluidized bed has been studied extensively across a relatively large range of geometries, though most work has looked at cylinders, a geometry important in power generation fluidized bed applications. As the power generation industry has been the primary stimulant to fluidized bed heat transfer research, very little information is available regarding geometries significant in heat treating applications. In this work, heat transfer to thin flat strips immersed in a fluidized bed is examined. This geometry is important in the steel strap manufacturing industry where many manufacturers use environmentally damaging molten lead baths to heat-treat their product. In order to determine the feasibility of a fluidized bed heat treating system as an alternative to the more hazardous lead-based process, an experimental investigation has been conducted in which Nusselt number data for flat strips with widths in the range of 6.35–25.4 mm are obtained using a laboratory-scale fluidized bed (310 mm diameter). Aluminum oxide sand particles in the range of dp=145–330 μm (50–90 grit) are used as the fluidized media within the fluidized operating range from 0.15Gmf to approximately 10Gmf. The strip orientation angle θo was also varied to establish the position from which maximum heat transfer is obtained. It was found that a decrease in particle diameter, an increase in fluidizing rate, and an increase in sample diameter resulted in an increase in Nusselt number. It was also observed that for the smaller samples tested, a maximum Nusselt number plateau was reached, at approximately G/Gmf=2.5. Finally, it was shown that an increase in θo (from 0 deg to 90 deg) resulted in an increase in Nusselt number. A correlation for the maximum Nusselt number was developed, providing excellent agreement within ±15%.

scholarly journals Heat transfer to small cylinders and flat strips immersed in a fluidized bed

2021 ◽  
Author(s):  
Dennis Rosero
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Carbon Steel ◽  
Fluidized Bed ◽  
High Carbon Steel ◽  
Heat Treating ◽  
Operating Conditions ◽  
Vertical Position ◽  
Steel Wires ◽  
Flat Strip

Fluidized bed heat treating systems have been used to heat treat low carbon steel wires for a number of years. Extending this application to high carbon steel wires and metal straps has been implemented with very little success due to the lack of knowledge of heat transfer coefficients or, alternatively, Nusselt number for small cylinders and flat strips. The objective of this study was to provide reliable data for predicting a suitable Nusselt number for small horizontal cylinders and flat strips at various orientations under conditions typically encountered in heat treating fluidized bed systems. In this study, resistively heated small cylinders and flat strips ranging in diameter from 1.27 to 9.53mm and in width from 6.25 to 25.4mm respectively were immersed in a 311mm in diameter lab-scale fluidized bed. The bed consisted of fine alumina oxide sand of mean particle size ranging from 145 to 330[micro]m fluidized by air at ambient temperatures. The fluidized bed unit was capable of fluidizing rates ranging from 0.14 to 23 G/Gmf. The cylinder and flat strip samples were positioned horizontally in the bed. The flat strip samples were rotated around the length's center axis in 15° increments from a 0° horizontal position to a 90° vertical position. The results showed that published correlations over-predict small cylinder Nusselt numbers over the entire fluidizing range; furthermore, their trends did not agree. Flat strip results demonstrated highest heat transfer rates at a vertical position. A correlation that predicts the mean Nusselt number within ±15% for both geometries was developed for operating conditions covered by the experiments.

scholarly journals Heat transfer to small cylinders and flat strips immersed in a fluidized bed

2021 ◽  
Author(s):  
Dennis Rosero
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Carbon Steel ◽  
Fluidized Bed ◽  
High Carbon Steel ◽  
Heat Treating ◽  
Operating Conditions ◽  
Vertical Position ◽  
Steel Wires ◽  
Flat Strip

Fluidized bed heat treating systems have been used to heat treat low carbon steel wires for a number of years. Extending this application to high carbon steel wires and metal straps has been implemented with very little success due to the lack of knowledge of heat transfer coefficients or, alternatively, Nusselt number for small cylinders and flat strips. The objective of this study was to provide reliable data for predicting a suitable Nusselt number for small horizontal cylinders and flat strips at various orientations under conditions typically encountered in heat treating fluidized bed systems. In this study, resistively heated small cylinders and flat strips ranging in diameter from 1.27 to 9.53mm and in width from 6.25 to 25.4mm respectively were immersed in a 311mm in diameter lab-scale fluidized bed. The bed consisted of fine alumina oxide sand of mean particle size ranging from 145 to 330[micro]m fluidized by air at ambient temperatures. The fluidized bed unit was capable of fluidizing rates ranging from 0.14 to 23 G/Gmf. The cylinder and flat strip samples were positioned horizontally in the bed. The flat strip samples were rotated around the length's center axis in 15° increments from a 0° horizontal position to a 90° vertical position. The results showed that published correlations over-predict small cylinder Nusselt numbers over the entire fluidizing range; furthermore, their trends did not agree. Flat strip results demonstrated highest heat transfer rates at a vertical position. A correlation that predicts the mean Nusselt number within ±15% for both geometries was developed for operating conditions covered by the experiments.

Sign in / Sign up

Export Citation Format

Share Document