Some papers, mention that with decrease in nanoparticle size, thermal conductivity of nanofluid increases. But some papers mention the same in the opposite way, that is, thermal conductivity increases with increase in particle size. Can anyone let me know the exact relation between thermal conductivity of the nanofluid and particle size?
hello bhubesh,
Thermal conductivity increase with decrease in particles size.
As piyush said. Due to effective area increasing. I have read papers concluding this.
Dear Bhubesh,
Thermal conductivity, k, of nanofuids depends on various factors like particle volume fraction, single particle diameter, particle morphology, additives, pH value, temperature, nature of the base fluid and particle materials. Taking temperature into consideration, most studies show an enhancement in k with the increase in temperature. Taking the materials of the base fluid and nanoparticles into account, most of the studies show an increase in k with the reduction of k of the base fluid, and the increase of k of the nanoparticles. But the studies of the effect of particle size on the k of nanofluids have produced conflicting reports. As the average particle size increases, the total surface area of the solid/liquid interface decreases geometrically (as others mentioned above), BUT it weakens the effect of interfacial thermal resistance. So to me, the increase of particle size can weaken the effect of interfacial thermal resistance and thus enhance the k of nanofluids because the total surface area of the solid/liquid interface decreases as particle size increases.
I strongly recommend you to take a view on the following article, which broadens your view regarding the mentioned topic.
Best,
http://pubs.rsc.org/en/content/articlelanding/2016/ra/c5ra16327g#!divAbstract
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