Industrial Technology Research Institute (ITRI) (Hsinchu, TW) earned U.S. Patent 7,649,024 for it one-step process for preparing nanofluids with a rotating packed bed reactor. The nanofluids are used as heat transfer fluids or lubricant fluids.
Inventors Chia-Chen Li, Mu-Jen Young, Ruey-Fu Shih, Ming-Chang Wen and Meu-Hui Chang developed a process for preparing hydrophobic fluids containing dispersed metal oxide nanoparticles.
The manufacturing method includes introducing an alkaline aqueous solution (aqueous phase) and an organic solution of an organic acid metal salt (hydrophobic phase) into a rotating packed bed, the two solutions flowing radially through the rotating packed bed under a great centrifugal force, so that the aqueous phase and the hydrophobic phase contact with each other, reactants in the two phases undergo reactions at the interface of the two phases rapidly, and thus metal oxide nanoparticles are formed. The metal oxide nanoparticles are stably dispersed in the hydrophobic phase, which is nanofluid.
Nanofluid is a new working fluid, which can be prepared by blending a small amount (<5%) of nanoparticles into a conventional working fluid, for examples a heat transfer fluid used in the heat radiator, engine, refrigeration or air conditioning systems, and a lubricant oil. The working properties of the nanofluid such as the heat transfer ability and anti-friction coefficient are improved, which can be used as a heat transfer nanofluid or a nano-lubricant oil.
The conventional processes for preparing the nanofluid can be classified into two types: one is the one-step method, and the other is the multi-step method. The one-step method at the present utilizes the physic vapor formation, wherein nanoparticles are formed in a sealed reactor under a high vacuum and an elevated temperature, and are introduced into a working fluid; or directly forming nanoparticles in an aqueous phase fluid by arc discharge.
The advantages of the one-step method are lesser agglomerates of the nanoparticles and better dispersion of the nanoparticles in the nanofluid. However, there are disadvantages of the one-step method which are difficulty in the control of the nanoparticle composition and the rate of forming the nanoparticles being too slow for mass production. The multi-step method involves obtaining nanoparticles and dispersing the nanoparticles into a fluid.
Advantageously, versatile fluids and nanoparticles can be used in the multi-step method. Further, the multi-step method has a better chance for being put into mass production. However, the multi-step method suffers several drawbacks such as a relatively easy agglomeration of nanoparticles and rapid sedimentation of the nanoparticles in the fluid, which cause the nanofluid so produced having a poorer stability.
The recent research on application of a rotating packed bed is rather helpful in finding a solution to the problems which cannot be easily resolved in the normal gravity field. The mass transfer process is greatly enhanced by the rotating packed bed in such a way that a 2-meter rotating packed bed can be used in place of a 10-meter packed column, and that the rotating packed bed is exceptionally effective in bringing about an absorption process, a stripping process, or a distillation process,
The recent research on application of a rotating packed bed is rather helpful in finding a solution to the problems which cannot be easily resolved in the normal gravity field. The mass transfer process is greatly enhanced by the rotating packed bed in such a way that a 2-meter rotating packed bed can be used in place of a 10-meter packed column, and that the rotating packed bed is exceptionally effective in bringing about an absorption process, a stripping process, or a distillation process,
A multiphase material flow is fed into the axial position of a rotating packed bed via a distributor from a tubular structure formed of two concentric sleeves. Under the effect of a high gravity field, the material flow comes in contact with the rotating packed bed. Such a technique as described is relatively new and is still under further investigation. To the best of knowledge of the inventors of the present invention, no prior art dealing with the application of the rotating packed bed to the preparation of nanofluids has ever been disclosed
