Fluid-to-particle Heat Transfer Coefficients for Continuous Flow of Suspensions in Coiled Tube and Straight Tube with Bends

LWT ◽  
2002 ◽  
Vol 35 (5) ◽  
pp. 420-435 ◽  
Author(s):  
Krittalak Chakrabandhu ◽  
Rakesh K. Singh
Keyword(s):  
Heat Transfer ◽  
Continuous Flow ◽  
Straight Tube ◽  
Transfer Coefficients ◽  
Coiled Tube ◽  
Heat Transfer Coefficients

Numerical Investigation of Generalized Correlations for Turbulent Flow Pressure Drop and Heat Transfer Applied in Helically Coiled Tube Systems

2003 ◽  
Author(s):  
Anthony J. Bowman ◽  
Hyunjae Park
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Research Effort ◽  
Cfd Modeling ◽  
Tube System ◽  
Transfer Coefficients ◽  
Coiled Tube ◽  
Heat Transfer Coefficients ◽  
Helically Coiled Tube ◽  
Regression Techniques

A numerical analysis using a CFD package (Fluent v5.5) has been employed to investigate the turbulent pressure drop and heat transfer characteristics in the helically coiled tube system. The validity of using the techniques for creating coiled tube geometry and the corresponding volume mesh developed in this work is verified by explicitly comparing the numerically calculated results with those obtained from the experiments and correlations related to the straight and toroidal tubes. The authors’ previous work [5] includes the collection and summary of the general and application-specific published research and correlations. The information describing the pressure drop and heat transfer phenomena related to turbulent forced convection were combined and re-expressed into more generalized correlations using multiple linear regression techniques. In this paper, a numerical research effort using a commercial CFD package has been employed to reassess the actual phenomena with those predicted by the previously developed generalized correlations. The numerically predicted pressure drop and heat transfer coefficients at various Reynolds numbers are about 5–10% lower than those obtained by using existing generalized correlations [5]. For purposes of engineering calculations an error level of 15% or less is appropriate. The level of accuracy of the CFD modeling technique developed in this work is justified to investigate thermal-fluid phenomena in a coiled tube system.

Characterization of Cryogenic Spray Nozzles With Application to Skin Cooling

2000 ◽  
Author(s):  
Guillermo Aguilar ◽  
Boris Majaron ◽  
Wim Verkruysse ◽  
J. Stuart Nelson ◽  
Enrique J. Lavernia
Keyword(s):  
Heat Transfer ◽  
Droplet Diameter ◽  
Straight Tube ◽  
Port Wine Stain ◽  
Port Wine ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Skin Cooling ◽  
Laser Treatments

Abstract Cryogenic sprays are used for cooling of human skin during laser treatments of hypervascular lesions, such as Port Wine Stain birthmarks. In this work, six straight-tube nozzles, including two commercial nozzles, are characterized by obtaining photographs of cryogenic spray shapes, as well as measurements of the average droplet diameter, velocity and temperature. An evaporation model is used to predict the evolutions of average droplet diameter and temperature. The results show two distinct spray patterns—jet-like sprays for wide nozzle diameters, and cone-like sprays for narrow nozzle diameters. The wide nozzles show significantly larger droplet diameters, larger velocities and higher temperatures, as all these variables are measured as a function of distance from the nozzle. These results complement and support previously reported results, where it was shown that wide nozzles are capable of producing larger heat transfer coefficients than those obtained with narrow nozzles.

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