I am trying to simulate the nanofluid flow within an enclosure for different nanoparticles e.g. Ag, Cu, CuO, Al2O3 and TiO2 . In the case of Ag and Cu, the heat transfer rate are almost same. I can not find any reason why it is happended.
Thermophysical Properties
Density (Kg/m3), Thermal Conductivity (W/mK), Specific heat (J/Kg K),Thermal expansion coefficient (10^(-5) /K)
Fluid (Water)
997.1, 0.613, 4179, 21
Cu
8933, 401, 385, 1.67
Ag
10500, 429, 235, 1.89
Which model of effective thermal conductivity of nanofluid you used?
Problems in which the effect of radiative heat flux is not accounted for, the heat transfer rate is generally given as -(knf/kf)*θ’(0). The values of (knf/kf) for both silver and copper nanoparticles are nearly equal; this is due to the small difference in the thermal conductivity of Ag and Cu.
Which model of effective thermal conductivity of nanofluid you used?
Problems in which the effect of radiative heat flux is not accounted for, the heat transfer rate is generally given as -(knf/kf)*θ’(0). The values of (knf/kf) for both silver and copper nanoparticles are nearly equal; this is due to the small difference in the thermal conductivity of Ag and Cu.
Did you use the correct properties for each nanofluid?
Density, Cp and k.
As mentioned by Upreti, if the silver and copper nanofluids have almost the same properties, then your results will be almost the same.
Dear Shujit Kumar Bala
Although the addition of solid nanoparticles to base fluids augments the mixture thermal conductivity, but this is accompanied with reducing the mixture heat capacity and Prandtl number. Please check their values; I think these will be the key for the analyses. Best wishes.
Here is report of an experimental study on the forced convective heat transfer and flow characteristics of a nanofluid consisting of water and different volume concentrations of Al2O3 nanofluid (0.3–2)% flowing in a horizontal shell and tube heat exchanger counter flow under turbulent flow conditions are investigated. The Al2O3 nanoparticles of about 30 nm diameter are used in the present study. The results show that the convective heat transfer coefficient of nanofluid is slightly higher than that of the base liquid at same mass flow rate and at same inlet temperature. The heat transfer coefficient of the nanofluid increases with an increase in the mass flow rate, also the heat transfer coefficient increases with the increase of the volume concentration of the Al2O3 nanofluid, however increasing the volume concentration cause increase in the viscosity of the nanofluid leading to increase in friction factor.
https://www.sciencedirect.com/science/article/pii/S2214157X13000075
Kindly check https://www.intechopen.com/books/an-overview-of-heat-transfer-phenomena/application-of-nanofluids-in-heat-transfer
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