PREDICTION OF HEAT TRANSFER COEFFICIENTS FROM CYCLIC REGENERATOR AND SINGLE SHOT PACKED BED DATA

1984 ◽  
pp. 501-512
Author(s):  
P.J. Heggs ◽  
E.A. Foumeny
Keyword(s):  
Heat Transfer ◽  
Packed Bed ◽  
Single Shot ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

A Network-of-Voids Model to Assess Wall Flow Patterns and Heat Transfer for Low Aspect Ratio Packed-Bed Reactors

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Peter I Chigada ◽  
Reginald Mann
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Fluid Flows ◽  
Packed Bed ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Catalytic Reactors ◽  
Heat Transfer Coefficients ◽  
Low Aspect Ratio ◽  
Random Placement

Exothermic packed bed catalytic reactors are usually characterised by a low diameter-aspect ratio to facilitate heat transfer. In operation, these reactors often exhibit localized regions with much higher temperatures referred to as hot spots. A new model based on a 2-D network-of voids (NoV) has been devised to explore wall heat transfer behaviour for such low aspect ratio packed tubes. Random placement of (packing) particles is used to provide a simple NoV framework for implicitly creating the tortuous fluid flows amongst the resulting randomized inter-connecting voids. This is a computationally tractable strategy for exploring the haphazard appearance of individual tube pin-hole burn-outs amongst the typically thousands, or tens of thousands, of tubes within high temperature industrial multi-tubular configurations. Although presently limited to 2-D, the model captures many natural features of the flow and heat transfer of randomly packed tubes, especially huge variations in wall and cross flows and consequently massive variations in local wall heat transfer coefficients along the length of individual tubes. The model is potentially superior to those based upon averaged properties, which do not properly distinguish the solid and fluid phases. The network-of-voids concept is readily extended to 3-D, in order to achieve geometric congruence of the model and assemblies of individual particles.

New Approach to Determine the Heat+transfer Coefficients for Cooling Tower Packing

1989 ◽  
Vol 203 (2) ◽  
pp. 75-84 ◽  
Author(s):  
M A Younis
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cooling Tower ◽  
Empirical Relationship ◽  
Packed Bed ◽  
Transfer Coefficients ◽  
Water Contact ◽  
Heat Transfer Coefficients ◽  
Tower Packing

The heat input response technique was developed to determine the heat-transfer coefficients for a forced draught cooling tower packing. The method was applied to a counter current type air-water contact system in a packed bed. A temperature change was alternately imposed on inlet air at the tower bottom and on inlet water at the tower top. Outlet temperatures of air and water were measured with time. From zeroth moments of these temperature changes, water-film and air-film heat-transfer coefficients have been estimated. Finally, the effect of the water/air loading ratio and the packing material, such as wood, aluminium wire netting and plastic PVC on the values of the heat-transfer coefficients was experimentally tested. An empirical relationship between the gas-side heat-transfer coefficient, liquid-side heat-transfer coefficient and water/gas ratio has been established within the range of the tested data.

Local and average interphase heat transfer coefficients in a randomly packed bed of spheres

AIChE Journal ◽  
1968 ◽  
Vol 14 (3) ◽  
pp. 483-490 ◽  
Author(s):  
Bernard M. Gillespie ◽  
Edward D. Crandall ◽  
James J. Carberry
Keyword(s):  
Heat Transfer ◽  
Packed Bed ◽  
Transfer Coefficients ◽  
Interphase Heat Transfer ◽  
Heat Transfer Coefficients

Local Heat Transfer Coefficients for Horizontal Tube Arrays in High-Temperature Large-Particle Fluidized Beds: An Experimental Study

1986 ◽  
Vol 108 (4) ◽  
pp. 907-912 ◽  
Author(s):  
A. Goshayeshi ◽  
J. R. Welty ◽  
R. L. Adams ◽  
N. Alavizadeh
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
High Temperature ◽  
Tube Bundle ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Packed Bed ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

An experimental study is described in which time-averaged local heat transfer coefficients were obtained for arrays of horizontal tubes immersed in a hot fluidized bed. Bed temperatures up to 1005 K were achieved. Bed particle sizes of 2.14 mm and 3.23 mm nominal diameter were employed. An array of nine tubes arranged in three horizontal rows was used. The 50.8 mm (2 in.) diameter tubes were arranged in an equilateral triangular configuration with 15.24 cm (6 in.) spacing between centers. The center tube in each of the three rows in the array was instrumented providing data for local heat flux and surface temperature at intervals of 30 deg from the bottom to the top—a total of seven sets of values for each of the center tubes. The three sets of data are representative of the heat transfer behavior of tubes at the bottom, top, and in the interior of a typical array. Data were also obtained for a single horizontal tube to compare with the results of tube bundle performance. Superficial velocities of high-temperature air ranged from the packed-bed condition through approximately twice the minimum fluidization level. Comparisons with results for a single tube in a bubbling bed indicate only slight effects on local heat transfer resulting from the presence of adjacent tubes. Tubes in the bottom, top, and interior rows also exhibited different heat transfer performance.

Heat Transfer with Chemical Reaction in Wall Heated Packed Bed Reactor

2014 ◽  
Vol 625 ◽  
pp. 722-725
Author(s):  
Duvvuri Subbarao ◽  
Reem Hassan Abd Elghafoor Hassan ◽  
Marappagounder Ramasamy
Keyword(s):  
Heat Transfer ◽  
Model Equation ◽  
Packed Bed ◽  
Packed Bed Reactor ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Exothermic Reactions ◽  
Packed Bed Reactors ◽  
Heat Transfer Coefficients ◽  
Endothermic Reactions

Information on wall heat transfer to packed bed reactors operating with exothermic or endothermic reactions is scarce. Overall wall heat transfer coefficients in a packed bed reactor in presence of an endothermic reaction are measured and observed to be smaller than the expected in the absence of reaction. This observation is in contrast with the reported observations with exothermic reactions in packed beds. A model equation based on energy balance is presented to explain the observations.

Drying of Latex Backcoated Acrylic Fabrics: Heat Transfer Coefficients

1988 ◽  
Vol 58 (12) ◽  
pp. 681-688
Author(s):  
Douglas D. Jinks ◽  
Michael J. Matteson
Keyword(s):  
Heat Transfer ◽  
Mass Velocity ◽  
Packed Bed ◽  
Laboratory Scale ◽  
Packed Beds ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow Through ◽  
Shaped Fibers

Drying and curing tests were performed in a laboratory scale dryer on dyed tufted acrylic fabrics and the latex adhesive backcoating to obtain heat transfer coefficients as a function of the mass velocity of air flowing through the fabric. Treating the fabric as a packed bed of cylindrically shaped fibers, equations were developed making it possible to calculate the flow-through velocity Gtf from measured air velocities directed at the upper and lower faces of the fabric. Correlations obtained for the heat transfer coefficients were h = 2.22 Gtf0.47 for fabric drying and h = 4.84 Gtf0.32 for curing the latex adhesive backcoating ( h in W/m2 K, Gtf in kg/m2h). These results were compared with earlier investigations of the drying in packed beds.

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