Gaussian diffusion sphere model to predict mass transfer due to diffusional particle deposition on a flat surface in laminar flow regime

2009 ◽  
Vol 94 (19) ◽  
pp. 191909 ◽  
Author(s):  
Se-Jin Yook ◽  
Kang-Ho Ahn
Keyword(s):  
Mass Transfer ◽  
Laminar Flow ◽  
Flow Regime ◽  
Particle Deposition ◽  
Flat Surface ◽  
Sphere Model ◽  
Laminar Flow Regime

Heat transfer enhancement using second mode self-oscillating structures

2019 ◽  
Vol 30 (7) ◽  
pp. 3827-3842
Author(s):  
Samer Ali ◽  
Zein Alabidin Shami ◽  
Ali Badran ◽  
Charbel Habchi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Laminar Flow ◽  
Flow Regime ◽  
Vortex Generator ◽  
Reynolds Numbers ◽  
Content Type ◽  
Laminar Flow Regime ◽  
Second Mode

Purpose In this paper, self-sustained second mode oscillations of flexible vortex generator (FVG) are produced to enhance the heat transfer in two-dimensional laminar flow regime. The purpose of this study is to determine the critical Reynolds number at which FVG becomes more efficient than rigid vortex generators (RVGs). Design/methodology/approach Ten cases were studied with different Reynolds numbers varying from 200 to 2,000. The Nusselt number and friction coefficients of the FVG cases are compared to those of RVG and empty channel at the same Reynolds numbers. Findings For Reynolds numbers higher than 800, the FVG oscillates in the second mode causing a significant increase in the velocity gradients generating unsteady coherent flow structures. The highest performance was obtained at the maximum Reynolds number for which the global Nusselt number is improved by 35.3 and 41.4 per cent with respect to empty channel and rigid configuration, respectively. Moreover, the thermal enhancement factor corresponding to FVG is 72 per cent higher than that of RVG. Practical implications The results obtained here can help in the design of novel multifunctional heat exchangers/reactors by using flexible tabs and inserts instead of rigid ones. Originality/value The originality of this paper is the use of second mode oscillations of FVG to enhance heat transfer in laminar flow regime.

Comparative Thermal Performance Analysis on Helical Screw Insert in Tube With Number of Strips With Nanofluid at Laminar Flow Regime

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Shashank Ranjan Chaurasia ◽  
R. M. Sarviya
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Laminar Flow ◽  
Flow Regime ◽  
Thermal Performance ◽  
Power Plants ◽  
Nanofluid Flow ◽  
Laminar Flow Regime ◽  
Twist Ratio ◽  
Single Strip

Abstract The experimental analysis is arranged to evaluate the thermal hydraulic performance on nanofluid flow in helical screw insert with tube at a number of strips and different twist ratios in laminar flow regime. The single strip (SS) helical screw inserts are also compared with the double strip (DS) helical screw inserts. The heat transfer enhancement is achieved with nanofluid flow in double strip as compared with single strip helical screw insert at decreased values of twist ratio and increased values of Reynolds number. A maximum enhancement of 421% is found in the value of Nusselt number with double strip helical screw insert at twist ratio of 1.5 and low value of Reynolds number in the flow of nanofluid than water in plain tube. The common correlations of Nusselt number and friction factor are generated. The thermal performance factor (TPF) is achieved at a maximum value of 2.42 with double strip than single strip helical screw inserts at twist ratio of 2.5 and low value of Reynolds number. The present analysis shows suitability of the double strip helical screw insert to enable miniaturization of the heat exchangers. A compact heat exchanger decreases the size of thermal application such as solar water heater, solar power plants, electronic cooling systems, radiator, etc., which could save environment by pollution reduction with utilization of energy.

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