I am interested in adding nanoparticles for different PCM for increasing heat transfer rates. What are the best nanoparticles for that? What is the procedure to make nanoparticles?
Dear Dr Hari Prasad, it is very difficult to conclude that one type of nano particles are BEST for augmenting heat transfer. Every thing depends on the application and reactability of the base fluids. However, CNTs are proven to have more and highest thermal conductivity.
You may use carbon-based, metal-based and other inorganic-based fillers.
A good review on the subject is available in an open-access publication
http://www.intechopen.com/download/get/type/pdfs/id/35438
Hope this can help
Best regards.
What are the costs involved in the nano particle sir. is it readily available in the market.
You can try oxide nanoparticles. It is to be ensured that the nanoparticle does not react with the base material. The maximum temperature of PCM is to be considered in the selection of the nanoparticle. Higher the heat capacity of the nanoparticle, the better the storage capacity.
Dear Dr.Hari prasad, As for as my knowledge is concerned metal oxide nano particles are available for ready supply and cheaper compared to pure metal nano particles. But, unfortunately in India there are only a few suppliers, if you have enough time for procurement u can order from other countries and we have to pay the customs charges. The cost of the nanoparticles varies from metal to metal and from the process involved in obtaining the same
We have made some tests with silver nanoparticles and carbon nanotubes dispersed in water (without surfactants). Both nanofluids gave a better heat transfer coefficient in relation to the distilled water. However it depends of concentration of nanoparticles and flow regime. In our case we performed tests in single phase flow for the transition and turbulent regimes. In average, between 0.2 and 0.5 % in volume, you can increase the heat transfer coefficient up to 20%.
Dear Dr. Enio,
At a concentration, Silver or CNT nanofluid has given higher heat transfer coefficient at the same flow rate (Reynolds).
Dear Dr Hari Prasad, it is very difficult to conclude that one type of nano particles are BEST for augmenting heat transfer. Every thing depends on the application and reactability of the base fluids. However, CNTs are proven to have more and highest thermal conductivity.
The nano particles available are copper oxide, aluminium oxide, silver oxide, titanium oxide, gold, cerium oxide, zinc oxide, brass, carbon nano tubes etc. All these nano particles are used to enhance heat transfer added with 0.5%, 1%, 1.5%, etc. by volume fractions or mass fractions to base fluid. Base fluid can be water or phase change materials. Nano particles can be purchased. After synthesizing to get proper grain size, they are mixed homogeneously by magnetic stirrer and ultrasonicator. Because of availability of aluminium oxide nano particles, its equations and capability of storing more heat these are preferred. However, in other applications other nano particles can also be used.
if you have solidification of PCM, the nanoparticle will face big problem because it need continue stirrer.
I suggest to download this book..
You will find optimization curves of thermal conductivity and the mechanisms of heat transfer enhancement by nanofluid. Be careful of nanofluid fouling.
http://library1.org/_ads/45DF59D99943653353E58B223D216795
Particles made of high thermal conductivity and low density such as Carbon nano spheres can be an ideal material for maximum heat transfer enhancement. However, stability can be an important aspect in the preparation of the nanofluid.
Dear Professor Sharma,
I think to compare the nanofluids at same Reynolds number is an inappropriate technique. Reynolds number is function of thermophysical properties of fluids. Therefore, nanofluids have higher velocities to provide the defined Reynolds number compared to base fluids due to their different density and viscosity values. In addition, increase in nanoparticle volume fraction increases velocity values for a given Reynolds number. When one also compare the same fluid (such as pure water) for different velocities, the flow having higher velocity will already show better heat convection performance. I think the results reported in the literature for a given Reynolds number are extremely optimistic.
MWCNT, SIC, TIC, ZrO2 Nano are ideal to heat transfer applications
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