Experimental Investigation On Flow And Convective Heat Transfer Of Nanoparticle Suspensions In Mini Tubes

One of the most important token of the modern high technology, the nano technology seems to cover such fields as spaceflight, micro electronics, micro electro-mechanics and bio-technology. With the rapid development of the nano-technology, some scholars attempted to enforce the heat transfer process with nano particles, which brings a new method to the heat transfer enhancement. But the study is just in its outset, and far from understood. The investigation on convective heat transfer and flow characteristics of CuO nano suspension in mini and micro passages is outset in blank.In view of the fact that the power of the nano technology and its many potential application in thermal science, the thesis mainly discussed the potential application of the nano technology in micro scale heat transfer, the stability of the nano particle suspension. Experimental facility was designed and built up to study flow and heat transfer performance of CuO nano particle suspension and water in Mini tubes.CuO nano suspension was photographed through TEM. The sedimentation rate of the CuO nano particle in suspension was also tested. Through both ways, it shows that by adding SDBS which is a kind of surfactants is good for the stability of suspension.The diameters of the test section used in the experiment are 0.68mm, 1.01mm, and 1.28mm respectively. The mean diameter of CuO nano particle is 50nm. Mass fraction of the nano particles in suspension are 0.02, 0.04 and 0.06 respectively. Mass fraction of surfactants SDBS is 0.02. The flow characteristics and convective heat transfer performance of water and SDBS solutions is also tested to compare with nano particle suspension.The result of the flow experiment shows that the critical Re number (from laminar to turbulence) decreased when the diameter of the tube becomes smaller. The fRe number of the suspension is generally higher than water, and will increase when the diameter becomes smaller. The transition area is not evident when the diameter of the tube is smaller. In transition state, the coarseness of the wall of the tube act differently on the working fluids.The heat transfer experiment shows that the Nu number is higher than theory especially in smaller tube. Mass fraction of the nano particle affects greatly on tubes. The Nu number increases when the mass fraction of the nano particle rises. The effect of the particle is stronger in transition zone than laminar zone.Applying nano particle brings high pressure drop and friction index. On the other hand the heat transfer coefficient becomes greater. But the amplitude of Nu number is higher than that of friction index f. It is effective to apply nano particle suspension to heat transfer enhancement of mini-tube.