Abstract
Multiwalled carbon nanotubes (MWCNTs) have attracted attention from researchers because of their superior thermal properties and high optical absorption. In this investigation, the thermal and optical properties of functionalized and nonfunctionalized MWCNT nanofluid based on ethylene glycol/water were experimentally studied and compared. The results indicated that the use of the functionalized MWCNT nanofluid improved the thermal properties and optical absorption performance compared with the nonfunctionalized MWCNT nanofluid. The thermal conductivity enhancement of the functionalized MWCNT nanofluid was higher than that of the nonfunctionalized MWCNT nanofluid. The maximum thermal conductivity enhancement (10.15%) was observed in a functionalized MWCNT concentration of 0.01 wt% at 50 °C compared with the base fluid. In addition, the photo-thermal energy conversion efficiency of the functionalized MWCNT nanofluid was higher than that of the nonfunctionalized one owing to its higher light absorption and thermal conductivity.
Highlights
In recent decades, the emission of greenhouse gases such as CO2, NOx and SOx has been excessive because of the continuous and rapid growth of world energy consumption [1]
To make the nonfunctionalized Multiwalled carbon nanotubes (MWCNTs) nanofluid by using the first method, the gum-arabic was used as a surfactant, whereas the functionalized MWCNT nanofluid used MWCNT-COOH to make nanofluid by the second method
To investigate the optical properties of MWCNT nanofluid, an optical experiment was carried out at room temperature (25 ◦ C) and under the solar wave ranges of 300–1300 nm
Summary
The emission of greenhouse gases such as CO2 , NOx and SOx has been excessive because of the continuous and rapid growth of world energy consumption [1]. Researchers and manufacturers have studied innovative ways to improve the efficiency of heat exchange devices such as refrigerator, air conditioning, industrial heat transfer equipment and power plant. The best way to reach the high heat transfer efficiency that contributes to higher performance and eco-friendly properties in heat exchange equipment is to enhance the favorable properties of working fluid in the thermal system. For this reason, Choi et al [2] introduced the novel idea of using nanofluid, which suspends nanosized materials with high thermal properties such as metal, metallic oxides and carbon nanotubes, into the base fluid. Water is an almost perfect working fluid, the good thermal properties of water can be reduced when antifreeze is added to the water owing to unfavorable operating conditions
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