Numerical Investigation of Forced Convection of Nanofluids in Channels

2008 ◽  
Author(s):  
Vincenzo Bianco ◽  
Oronzio Manca ◽  
Ferdinando Marzano ◽  
Sergio Nardini ◽  
Salvatore Tamburrino ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Convective Heat Transfer Coefficient ◽  
Convection Flow ◽  
Uniform Heat Flux ◽  
Particle Volume ◽  
Two Phase ◽  
Square Channel

In this paper developing turbulent forced convection flow of a water–Al2O3 nanofluid in a square channel submitted to a constant and uniform heat flux at the wall is numerically investigated. A single model and two-phase models (discrete particles model and mixture model) are employed with constant temperature properties. The investigation is accomplished for a size particles equal to 38 nm. The CFD commercial code Fluent is employed to solve the problem by means of finite volume method. Convective heat transfer coefficient for nanofluids is greater than that of the base liquid. Heat transfer enhancement is increasing with the particle volume concentration but it is accompanied by increasing wall shear stress values. The effect of Reynolds number is great for higher concentrations. The results obtained by tree different models are presented in terms of temperatures and velocity distributions, relative increasing of heat transfer coefficient, hr, and Nusselt number profile.

Numerical Investigation of Forced Convection of Nanofluids in Circular Tubes

2007 ◽  
Author(s):  
Fabio Chiacchio ◽  
Oronzio Manca ◽  
Sergio Nardini
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Convective Heat Transfer Coefficient ◽  
Convection Flow ◽  
Uniform Heat Flux ◽  
Particle Volume ◽  
Two Phase ◽  
Liquid Heat ◽  
Temperature Dependent Properties ◽  
Laminar Forced Convection

In this paper developing laminar forced convection flow of a water–γAl2O3 nanofluid in a circular tube submitted to a constant and uniform heat flux at the wall is numerically investigated. A single and two-phase model (discrete particles model) is employed with either constant or temperature-dependent properties. The investigation is accomplished for a size particles equal to 100 nm. Convective heat transfer coefficient for nanofluids is greater than that of the base liquid. Heat transfer enhancement is increasing with the particle volume concentration but it is accompanied by increasing wall shear stress values. The effect of Reynolds number is greater when properties depend on temperature and for higher concentrations.

Numerical Investigation of Turbulent Convection in Al2O3/Water Nanofluid With Temperature Dependent Properties

2009 ◽  
Author(s):  
Vincenzo Bianco ◽  
Oronzio Manca ◽  
Sergio Nardini
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer Coefficient ◽  
Convection Flow ◽  
Uniform Heat Flux ◽  
Particle Volume ◽  
Two Phase ◽  
Commercial Code ◽  
Particle Dimension ◽  
Liquid Heat ◽  
Temperature Dependent Properties

In this paper turbulent forced convection flow of a water–Al2O3 nanofluid in a circular tube subjected to a constant and uniform heat flux at the wall is numerically analyzed. Two different approach are taken into account: single and two-phase models, with particle dimension equal to 38 nm. Temperature dependant thermophysical properties are considered for both the approaches. The CFD commercial code Fluent is employed to solve the problem by means of finite volume method. It is found that convective heat transfer coefficient for nanofluids is greater than that of the base liquid. Heat transfer enhancement is increasing with the particle volume concentration and Reynolds number. A good agreement is found with the correlation of Xuan and Li.

scholarly journals FORCED CONVECTION DRYING OF INDIAN GROUNDNUT: AN EXPERIMENTAL STUDY

2017 ◽  
Vol 15 (3) ◽  
pp. 467
Author(s):  
Ravinder Kumar Sahdev ◽  
Mahesh Kumar ◽  
Ashwani Kumar Dhingra
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Experimental Error ◽  
Linear Regression Analysis ◽  
Convective Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Evaporative Heat Transfer

In this paper, convective and evaporative heat transfer coefficients of the Indian groundnut were computed under indoor forced convection drying (IFCD) mode. The groundnuts were dried as a single thin layer with the help of a laboratory dryer till the optimum safe moisture storage level of 8 – 10%. The experimental data were used to determine the values of experimental constants C and n in the Nusselt number expression by a simple linear regression analysis and consequently, the convective heat transfer coefficient (CHTC) was determined. The values of CHTC were used to calculate the evaporative heat transfer coefficient (EHTC). The average values of CHTC and EHTC were found to be 2.48 W/m2 oC and 35.08 W/m2 oC, respectively. The experimental error in terms of percent uncertainty was also estimated. The experimental error in terms of percent uncertainty was found to be 42.55%. The error bars for convective and evaporative heat transfer coefficients are also shown for the groundnut drying under IFCD condition.

Experimental Investigation of Heat Transfer Enhancement of Shell and Tube Heat Exchanger Using SnO2-Water and Ag-Water Nanofluids

2019 ◽  
Vol 12 (4) ◽  
Author(s):  
S. V. Sridhar ◽  
R. Karuppasamy ◽  
G. D. Sivakumar
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Convective Heat Transfer Coefficient ◽  
Two Phase ◽  
Tube Heat Exchanger ◽  
Shell And Tube

Abstract In this investigation, the performance of the shell and tube heat exchanger operated with tin nanoparticles-water (SnO2-W) and silver nanoparticles-water (Ag-W) nanofluids was experimentally analyzed. SnO2-W and Ag-W nanofluids were prepared without any surface medication of nanoparticles. The effects of volume concentrations of nanoparticles on thermal conductivity, viscosity, heat transfer coefficient, fiction factor, Nusselt number, and pressure drop were analyzed. The results showed that thermal conductivity of nanofluids increased by 29% and 39% while adding 0.1 wt% of SnO2 and Ag nanoparticles, respectively, due to the unique intrinsic property of the nanoparticles. Further, the convective heat transfer coefficient was enhanced because of improvement of thermal conductivity of the two phase mixture and friction factor increased due to the increases of viscosity and density of nanofluids. Moreover, Ag nanofluid showed superior pressure drop compared to SnO2 nanofluid owing to the improvement of thermophysical properties of nanofluid.

Two-Phase Heat Transfer Performance of Dielectric Fluid HFE-7100 Within Multiport Microchannel

2008 ◽  
Author(s):  
Lung-Yi Lin ◽  
Yeau-Ren Jeng ◽  
Chi-Chuan Wang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Single Phase ◽  
Heat Transfer Performance ◽  
Convective Heat Transfer Coefficient ◽  
Dielectric Fluid ◽  
Transfer Performance ◽  
Two Phase ◽  
Two Phase Heat Transfer

This study presents convective single-phase and boiling two-phase heat transfer performance of HFE-7100 coolant within multi-port microchannel heat sinks. The corresponding hydraulic diameters are 450 and 237 μm, respectively. For single-phase results, the presence of inlet/outlet locations inevitably gives rise to considerable increase of total pressure drop of a multi-port microchannel heat sink whereas has virtually no detectable influence on overall heat transfer performance provided that the effect of entrance has been accounted for. The convective boiling heat transfer coefficient for the HFE-7100 coolant shows a tremendous drop when vapor quality is above 0.6. For Dh = 450 μm, it is found that the mass flux effect on the convective heat transfer coefficient is rather small.

Numerical Simulation of Single Droplet Hydrodynamics Affected by Electrostatic Forces with the Aid of CFD

2016 ◽  
Vol 5 (2) ◽  
pp. 17-34
Author(s):  
Mohammad Ali Salehi ◽  
Babak Namazi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Empirical Relationship ◽  
Convective Heat Transfer Coefficient ◽  
Electrical Potential ◽  
Momentum Equation ◽  
Formation Time ◽  
Two Phase ◽  
Electrical Potentials

In this study, Electrospray hydrodynamics and electrical potential dependency of heat transfer coefficient were investigated by computational fluid Dynamics (CFD). VOF method was applied to solve momentum equation of these two-phase flow and Whitaker empirical relationship for gas, liquid flow on sphere was also applied to calculate the heat transfer coefficient. The results of simulation were in accordance with experiments and showed that because of domination of surface tension by gravity and electric forces, diameter of droplets and their formation time were decreased. In addition, applying electrical potential at the velocity of 0.007 m/s has led to formation of jet and small droplets of liquid. Formation time of the droplet was decreased by increasing the velocity ten times higher than the previous time, to 0.07 m/s. By using the results of hydrodynamic simulation of droplet, convective heat transfer coefficient of droplet was calculated in various electrical potentials that showed heat transfer coefficient increased by growth of electrical potential.

A New Approach to Calculating Fuel Temperature in TRIGA Mark I Research Reactors

2012 ◽  
Author(s):  
Jesse M. Johns ◽  
W. D. Reece
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Temperature Rise ◽  
Empirical Relationship ◽  
Convective Heat Transfer Coefficient ◽  
Fuel Temperature ◽  
Convection Correlation

Often a forced convection heat transfer coefficient is used to calculate the peak fuel temperature for a rectangular lattice TRIGA core even though the core is cooled by natural convection. The arguments for applying a forced convection empirical relationship are examined and another relationship is suggested. The peak fuel temperature was calculated using two different correlations, Dittus-Boelter and natural convection, for pool temperatures of 30°C and 60°C. The Dittus-Boelter correlation predicted a fuel temperature rise of 1.85°C for this difference in pool temperature, contrary to the predicted rise of 25.64°C from natural convection relationships. Experimental data shows that the relationship of fuel temperature rise with increasing pool temperature is more accurately represented by the natural convection correlation than with Dittus-Boelter. Using a derived natural convection correlation, the calculated peak fuel temperatures then closely match measured data. A procedure was developed to access convective heat transfer coefficient changes in the cladding gap as a function of reactor power for the hot channel which are similar to those presented in literature.

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