Viscosity...Does lubricant viscosity decrease on addition of nanoparticles?
An experiment was conducted with 5 concentration of carbon nano tubes in oil. the viscosity increase as comapred to that of the pure oil. but after a certain %cnt the viscosity was found tot be decreasing (though it was higher than the pure oil).
Why do you think it should decrease? Adding particles into a liquid viscosity increases, especially at higher volume concentration.
HI Subhrajit, i agree with Titus sir, Well it should increase and the behaviour of viscosity will also be dependent on the nanoparticle size and the aggregation rate under certain condition, it will also be affected by factor such as pH, temperature etc. Well there would be no longer viscosity dependent only on the fluid molecules but of colloidal dispersion entirely. Also it would be a Non-Newtonian fluid, the dynamics it would persist would be much different. Hope this much would help you. if you need more information you could make your question specific to which nanoparticle and what kind of fluid and what is your purpose of study...
Thanks
Mahesh
As the concentration of nanoparticle increases the viscosity increases.
Please refer, Qinbo He, Shuangfeng Wang, Mingwei Tong , Yudong Liu. Experimental study on thermophysical properties of nanofluids
as phase-change material (PCM) in low temperature cool storage, Energy Conversion and Management 64 (2012) 199–205
The question of Shubrajit Bhaumik is not simple. Following to enough meaningful answer of Mahesh Samant, I appeal to more careful analysis of situation. The aggregation and other effects on this scale may become apparent in nonlinear dependence of viscosity vs. nanotubes content.
In principle, it should increase. Viscosity of the oil containing the nanoparticles shouldn't be less than that of the pure oil.
But, as far as you keep adding more particles, some other effects may take place. I would be careful about the possibility of particles agglutination. So… Are you sure the particles are perfectly dispersed in the fluid? What dispersant is being used along with the nanoparticles? Which conditions are you using when measuring the viscosity – is it the kinematic viscosity (ASTM D445 or similar)? These aspects may interfere and lead to the effect you reported.
Dear friends,
How paradoxical that in some cases, it has been reported that viscosity of nanofluids is lower than that of pure fluids! Shubrajit put forward an interesting question regarding addition of CNTs to pure oils. First of all, we have to mention that shape of nanoparticles plays a prominent role when we talk about viscosity of nanofluids. According to our experience regarding transformer oil-based MWCNT nanofluids, we concluded that viscosity of nanofluids was lower than that of pure transformer oil. In other words, it can be said that lubricating property of oil enhanced. This phenomenon is happened when rode-like nanotubes are added to the oil, settling down between oil layers and acting as bridges and consequently, make oil layers move on each other more smoothly. We should not forget that this happens in specific concentrations (very dilute) when well-dispersed kinds of nanofluids are made.
FYI, you can find more about this on our article via the following link.
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Article Heat transfer and rheological properties of transformer oil-...
according to my experience . yes it should increase but i do got a trend of increasing then decrease at some conc % then gradually increases 40 C and 100C too
Dear collegues, what about the analogy of inernal friction and viscosity? Let us take into account the nanotube "rolling effect". Nanoparticles (expecially, nanospheres), when they have been added to lubricants, reduce the friction.
Dear all,
the answer is yes but with a great care. Additives (polymers, particulate minerals) which reduce viscosity uppon addition, are located under 'drag reducing agents'. They are used at very low concentration in chanels (pipes) circulating liquids. There exist three main theories explaining this phenomenon. Regards
I have a knowledge gap here. So far it seems to me that effect of friction on the walls might affect apparent viscosity without having an effect of internal friction?
It depends on the particle size distribution. If it contains mixture of sizes where small particles can fit in between the aggregate of bigger particles and release the fluid entrapped around the bigger particles the the viscosity will decrease.
Dr. B R Gupta
I have conducted the experiments on combinations of nanoparticles and pure oils. One particular nanofluid ( nanoparticles dispersed in oil) have exhibited the decreasing trend of its viscosity, even lesser than that of pure oil. While the remaining nanofluids showed an increase in viscosity compared to their pure oils.
Yes Me Murali observation is correct but it will happen only when smaller particles occupy the space between ensemble of bigger particle releasing the entrapped fluid and (i) making this fluid available for fluidity and (ii) the entrapped particle acts as lubricant ( fine particle plus fluid surrounding it), thus reducing the viscosity considerably.
B R Gupta
Why does the COF decreases in nanoparticle up to a certain concentration and then increase again?
what is 'COF decreases in nanoparticle'? why do you do not ask separately?
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