THE EFFECT OF SHARP CORNERS OF THE CHANNEL ON HEAT TRANSFER COEFFICIENT OF NON-NEWTONIAN FLUIDS

1998 ◽  
Author(s):  
S. Gh. Etemad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Newtonian Fluids ◽  
Sharp Corners

Experimental and CFD Investigations of Heat Transfer in Helical Coils for the Development of Correlations for Newtonian and Non-Newtonian Fluids in Transient State-Space Conditions

2013 ◽  
Author(s):  
Sandipan S. Pawar ◽  
Vivek K. Sunnapwar ◽  
Vivek K. Yakkundi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Turbulent Flow ◽  
Transfer Coefficient ◽  
Flow Regimes ◽  
Newtonian Fluids ◽  
Water Mixture ◽  
Glycerol Water ◽  
Laminar And Turbulent Flow ◽  
Helical Coils

Experimental studies and CFD investigations were carried out under laminar and turbulent flow regimes in isothermal steady state and non-isothermal unsteady state conditions in helical coils for Newtonian and non-Newtonian fluids. Water and glycerol-water mixture (10 and 20 % glycerol) as Newtonian fluids and dilute aqueous polymer solutions of sodium carboxymethyl cellulose (SCMC), sodium alginate (SA) as non-Newtonian fluids were used in this study. The experiments were performed for three helical coils of coil curvature ratios as 0.0757, 0.064 and 0.055 in laminar and turbulent flow regimes. For the first time, two innovative correlations to calculate Nusselt number (Nu) in terms of new dimensionless ‘M’ number, Prandtl number and coil curvature ratio under different conditions for Newtonian fluids are proposed in this paper. Third correlation of Nu vs. Graetz number (Gz) including the effects of coil curvature on heat transfer coefficient which was not considered by earlier investigators is developed based on tests conducted in laminar flow for Newtonian fluids. All these three innovative correlations developed based on experimental data which were not found in the literature. These correlations were compared with the work of earlier investigators and were found to be in good agreement. The CFD analysis for laminar and turbulent flow was carried out using the CFD package FLUENT 12.0.16. The CFD calculation results (Nui, U) for laminar and turbulent flows were compared with the experimental results, and also the work of earlier investigators was found to be in excellent agreement. Further, the effect of helix diameter on heat transfer for Newtonian and Non-Newtonian fluids are also presented in this paper and it was observed that as helix diameter increases, overall heat transfer coefficient decreases.

Overall and Fluid-to-particle Heat Transfer Coefficients associated with Canned Particulate non-Newtonian Fluids during Free Bi-axial Rotary Thermal Processing

2012 ◽  
Vol 8 (3) ◽  
Author(s):  
Hussein F. Hassan ◽  
Hosahalli S. Ramaswamy ◽  
Mritunjay Dwivedi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Rotational Speed ◽  
Water Immersion ◽  
Axial Rotation ◽  
Pilot Scale ◽  
Newtonian Fluids ◽  
Transfer Coefficients ◽  
Axial Mode

Abstract Heat transfer to canned particulates in non-Newtonian fluids (Nylon particles suspended in aqueous carboxymethyl cellulose - CMC - solution) during fixed and free bi-axial rotation was studied in a pilot-scale, full water-immersion single-cage rotary retort. A response surface methodology was used in order to study the effect of different process parameters, including rotational speed (7-23 rpm), CMC concentration (0.0-1.0%) and retort temperature (110-130C), at five levels of each, on overall heat transfer coefficient (U) and fluid to particle heat transfer coefficient (hfp) in both rotation modes. The analysis of variance showed that the rotational speed, CMC concentration and retort temperature were significant (p < 0.05) factors for hfp in the following order: rotation speed > CMC concentration > retort temperature; however, only rotational speed and CMC concentration were significant (p < 0.05) factors for U. With an increase in rotational speed and retort temperature, there was an increase in the associated U and hfp values; however, increasing the CMC concentration resulted in the opposite. Using the numerical optimization of the Design Expert software, optimum heat transfer was found at a rotational speed of 20 rpm, CMC concentration of 0.6% and retort temperature of 126C. T-test revealed that both U and hfp were significantly (p < 0.05) higher in the free bi-axial mode as compared to the fixed axial mode of rotation.

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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