Increment In Thermal Conductivity Research Articles

Preparing and Study on Thermal-Conductive Epoxy Resin Nanocomposites

Metal powder (Cu) filled Epoxy resin (EP)/Organic-montmorillonite nanocomposites were prepared, where the compounding was carried out by using hardener with filler loadings of 0wt%, 5wt%, 10wt%, 15wt% and 20wt%. Organic-montmorillonite was prepared by using the method of Secondary-intercalating with transition metal ion and cetyl trimethyl ammonium bromide (CTAB) as the modifier. The content of Organic-montmorillonite dispersed in EP system was 3wt%.The effect of filler loadings and incorporation of coupling agent on tensile properties and thermal conductivity are studied. The results demonstrate that, an increase in filler loading is found to increase the tensile strength and thermal conductivity of M filled EP composites. By adding 2% coupling agent, the decrease of tensile strength with increasing filler loadings can be observed in 20%Cu-EP composite. However, the addition of 2% coupling agent in 20%Cu/OMMT/EP composite allowed the increment of tensile strength and assisted in greater increment of thermal conductivity of the composites.

Convective heat transfer characteristics of nanofluids under laminar and turbulent flow conditions

To investigate the effect of nanofluids on convective heat transfer, an experimental study was performed through a circular straight tube with a constant heat flux condition in the laminar and turbulent flow regime. Stable nanofluids, which were water-based suspensions of alumina and amorphous carbonic nanoparticles, were prepared by two- and one-step methods. The effects of thermal conductivity and supernatant nanoparticles of the nanofluids on convective heat transfer were investigated under different flow regimes. In alumina nanofluids containing 3 vol% of suspended particles, the increment of thermal conductivity and convective heat transfer coefficient was 8% and 20%, respectively. For amorphous carbonic nanofluids, the thermal conductivity was similar to that of water, and the convective heat transfer coefficient increased by only 8% in laminar flow. In a comparison of thermal conductivity and convection, the enhancement of the convective heat transfer was much higher than that of the thermal conductivity of nanofluids. The movements of nanoparticles enhanced the convective heat transfer at the entrance region.

A Study on the Effects of Temperature and Volume Fraction on Thermal Conductivity of Copper Oxide Nanofluid

By using copper oxide nanofluid fabricated by the self-made Submerged Arc Nanofluid Synthesis System (SANSS), this paper measures the thermal conductivity under different volume fractions and different temperatures by thermal properties analyzer, and analyzes the correlation among the thermal conductivity, volume fraction, and temperature of nanofluid. The CuO nanoparticles used in the experiment are needle-like, with a mean particle size of about 30 nm. They can be stably suspended in deionized water for a long time. The experimental results show that under the condition that the temperature is 40 degrees C, when the volume fraction of nanofluid increases from 0.2% to 0.8%, the thermal conductivity increment of the prepared nanofluid towards deionized water can be increased from 14.7% to 38.2%. Under the condition that the volume fraction is 0.8%, as the temperature of nanofluid rises from 5 degrees C to 40 degrees C, the thermal conductivity increment of the prepared nanofluid towards deionized water increases from 5.9% to 38.2%. Besides, the effects of temperature change are greater than the effects of volume fraction on the thermal conductivity of nanofluid. Therefore, when the self-made copper oxide nanofluid is applied to the heat exchange device under medium and high temperature, an optimal radiation effect can be acquired.

Mathematical modeling of laser induced heating and melting in solids

An analytical method for treating the problem of laser heating and melting is developed in this paper. The analytical method has been applied to aluminum, titanium, copper, silver and fused quartz and the time needed to melt and vaporize and the effects of laser power density on the melt depth for four metals are also obtained. In addition, the depth profile and time evolution of the temperature of aluminum before melting and after melting are given, in which a discontinuity in the temperature gradient is obviously observed due to the latent heat of fusion and the increment in thermal conductivity in solid phase. Additionally, the calculated melt depth evolution of fused quartz induced by 10.6 μm laser irradiation is in good agreement with the experimental results.

Studies of the heated thermocouple principle for determinations of blood flow in tissues.

AbstractA study was made in models of some of the factors influencing the adaptability of the heated thermocouple principle for blood flow determinations in tissues. The apparent thermal conductivity was determined with conventional technique. The tissue blood flow was simulated by flow of water in polyethylene tubes embedded in gelatin blocks and through holes in gelatin blocks. The findings indicate that there can be no standard type of relationship between the apparent thermal conductivity increment and the flow in any tissue into which the probe is blindly introduced. It is concluded from the results that the probe is most suitably placed when influenced only by flow in great numbers of capillaries and very small veins. For quantitative determinations the probe has to be standardized in each experiment. Standardizations will apply only under certain conditions, which are discussed.