جستجوی مقالات مرتبط با کلیدواژه « اکسید منیزیم » در نشریات گروه « مکانیک »

The solar radiation absorption efficiency is one of the challenges for engineers in solar energy systems. Using the hybrid nanofluids, which are obtained by dispersing two or more types of nanoparticles in the base fluid, can be effective in better absorption of solar energy. In this study, the effect of type, concentration, and mixing percentage of nanoparticles on optical properties and solar thermal utilization efficiency has been tested. First, magnesium oxide nanofluids and multi-walled carbon nanotubes with water-based fluid were fabricated by a two-step method in volumetric concentrations of 0/01%%Vol, 0.02% Vol, and 0.04%Vol, and then the optical properties of single and hybrid forms were measured by spectrophotometer and have been compared by existing relations. Then, to obtain the solar thermal utilization efficiency, a solar simulator has been used. The results show that increasing the concentration of nanofluid, improves the optical properties and solar radiation absorption efficiency. Magnesium oxide nanofluid, multi-walled carbon nanotubes, and hybrid nanofluid have the values of extinction coefficient about 38, 40, and 50 times higher than pure water, respectively. The hybrid nanofluid absorbs more than 90% of the sun's energy at the highest concentration (0.04% Vol) and at a penetration depth of 0.3 cm. Solar energy absorption increases by increasing the concentration, hybridizing the nanofluid, and increasing the penetration distance.

In this study, the dynamic viscosity of the fluid is water-based nanofluids magnesium oxide discussed. The experiments in four volume fraction (0.005, 0.01, 0.015 and 0.02) and four different diameter nanoparticles 20, 40, 50 and 60 nm were used. The results obtained in this way is that by increasing the volume fraction of a specified diameter, the viscosity of nanofluids increases and by increasing the diameter Nanvdrh in a specified volume fraction, the viscosity of nanofluids decreases the viscosity reduction benefits of using nanofluids in the industry more.

The present study aimed to investigate the convective heat transfer coefficient of nanofluids containing magnesium oxide nanoparticles in water-based fluid in the exchanger plates have been carried out. Tests on the volume fraction of (0.005, 0.01, 0.015and 0.02) were used in this study have Ast.nanvzrh which has a diameter of 20 nm. Also the results show that with increasing fraction nanofluid volume, heat transfer coefficient and thus increases the heat transfer. Also heat transfer nanofluids% increase in volume fraction of 0.02 to 0.005 respectively 52% and 4.3% is on.

In recent decade, the new advanced nanofluids, composed from various particles, have attracted the attention of researchers. This class of nanofluids, which can be prepared by suspending several types (two or more than two) of nanoparticles in base fluid, is termed as hybrid nanofluids. In this work, an experimental investigation on the effects of temperature and concentration of nanoparticles on the thermal conductivity of MgO-MWCNT/EG hybrid nanofluid is presented. The experiments performed at temperatures ranging from 25oC to 50oC and solid volume fraction range of 0 to 0.6%. The measurements revealed that the thermal conductivity of nanofluids enhances up to 23.3% with increase in concentration of nanoparticles and temperature. Moreover, efforts were made to provide an accurate correlation for estimating the thermal conductivity at various temperatures and concentrations. Deviation analysis of the thermal conductivity ratio was performed. The comparison between experimental results and correlations outputs showed a maximum deviation margin of 0.95%, which is an acceptable accuracy for an empirical correlation.