Effects of curvature ratio on forced convection and entropy generation of nanofluid in helical coil using two-phase approach

2018 ◽  
Vol 29 (4) ◽  
pp. 890-903 ◽  
Author(s):  
Hamed Khosravi-Bizhaem ◽  
Abbas Abbassi
Keyword(s):  
Forced Convection ◽  
Entropy Generation ◽  
Helical Coil ◽  
Two Phase ◽  
Curvature Ratio ◽  
Phase Approach

scholarly journals Entropy generation analysis for forced convection boiling in absorber tubes of linear fresnel reflector solar thermal system

2020 ◽  
Vol 24 (2 Part A) ◽  
pp. 735-743
Author(s):  
Sanju Thomas ◽  
Ajith Kumar ◽  
Sudhansu Sahoo ◽  
Shinu Varghese
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Forced Convection ◽  
Entropy Generation ◽  
Phase Region ◽  
Solar Thermal ◽  
Thermal System ◽  
Two Phase ◽  
Linear Fresnel Reflector ◽  
Solar Thermal System

A methodology has been presented related to entropy generation due to forced convection boiling in long absorber tubes used in linear Fresnel reflector solar thermal system. Variable heat flux has been applied on the tube which replicates the scenario for aforementioned tubes and local entropy generation has been obtained for various parameters. Mathematical modeling has been made separately for single-phase and two-phase regions in flow boiling conditions encountered in linear Fresnel reflector tubes. Entropy generation in two-phase region has been formulated using homogeneous equilibrium model. The entropy generation at varying mass flux and heat flux cases are calculated. The entropy generation due to heat transfer is found to be more than that of pressure drop. Still, entropy generation due to pressure drop in two-phase region plays a major role of increasing nature of it. Present approach will help researchers and industry to optimize the solar thermal systems where flow related phase change occurs and measures can be taken accordingly to increase energy efficiency of those systems.

scholarly journals Analysis of the forced convection of two-phase Ferro-nanofluid flow in a completely porous microchannel containing rotating cylinders

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hamidreza Aghamiri ◽  
Mohammadreza Niknejadi ◽  
Davood Toghraie
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Porous Medium ◽  
Forced Convection ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Rotating Cylinders ◽  
Nanofluid Flow ◽  
Two Phase ◽  
Porosity Percentage

AbstractIn the present work, the forced convection of nanofluid flow in a microchannel containing rotating cylinders is investigated in different geometries. The heat flux applied to the microchannel wall is 10,000 W m−2. The effects of Reynolds number, the volume fraction of nanoparticles, and the porosity percentage of the porous medium are investigated on the flow fields, temperature, and heat transfer rate. Reynolds number values vary from Re = 250–1000, non-dimensional rotational velocities 1 and 2, respectively, and volume fraction of nanoparticles 0–2%. The results show that increasing the velocity of rotating cylinders increases the heat transfer; also, increasing the Reynolds number and volume fraction of nanoparticles increases the heat transfer, pressure drop, and Cf,ave. By comparing the porosity percentages with each other, it is concluded that due to the greater contact of the nanofluid with the porous medium and the creation of higher velocity gradients, the porosity percentage is 45% and the values of are 90% higher than the porosity percentage. Comparing porosity percentages with each other, at porosity percentage 90% is greater than at porosity percentage 45%. On the other hand, increasing the Reynolds number reduces the entropy generation due to heat transfer and increases the entropy generation due to friction. Increasing the volume fraction of nanoparticles increases the entropy generations due to heat transfer and friction.

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