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The need for high thermal performance thermal systems has been eventuated by finding different ways to enhance heat transfer rates. This paper introduces and analyzes numerically the heat transfer enhancement of nanofluids with different volume concentrations under turbulent flow through a straight channel with a constant heat flux condition. Solid nanoparticles of TiO 2 and CuO were suspended in water as a base fluid to prepare the nanofluids. CFD analysis is conducted by FLUENT software using the finite volume method. The heat flux considered is 5000 W/m 2 , the Reynolds numbers are 10 4-10 6 with a constant volume concentration of 1-3%. Based on the analysis of the numerical results, it is found that the heat transfer rates and wall shear stress increase with increase of the nanofluid volume concentration. It appears that the CuO nanofluid significantly enhances the heat transfer. Furthermore, the numerical results are validated with the literature data available and show good agreement, with 4% deviation. The study concluded that the enhancement of the friction factor and Nusselt number is by 2% and 21%, respectively for the nanofluids at all Reynolds numbers. Therefore, nanofluids are considered to have great potential for heat transfer enhancement and are applied in heat transfer processes.

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Currently most technologies available to produce esters require acid or base catalysts for esterification or transesterification reactions. Production of dimerate esters (DE) exhibiting potential as a biolubricant for low temperature applications using catalyst‐ and solvent‐free approaches is presented in this article. Hydrogenated C36 dimer acid and alcohol are reacted under the following conditions: dimer acid/alcohol (1:4.5 molar ratio), 150–200 °C, 24 h, 3Å molecular sieve (15% w/w). The performances of four DE species—dibutyl, dihexyl, di‐(2‐ethylhexyl), and dioctyl dimerate—as lubricant base stocks are evaluated by kinematic viscosity, viscosity index, cloud and pour point (cold flow properties) as well as oxidative stability, and compared with commercial synthetic lubricant base stock and DE, Radialube 7121. High viscosity indexes ranging between 129 and 138 are observed for the synthesized DEs, which are comparable with two commercial base stock, polyalpha olefin (PAO), and polyolester (POE). Significantly low pour point, less than −42 °C, is observed for di‐(2‐ethylhexyl) dimerate attributed to the branching of the side chain. The DEs are categorized as ISO VG 68 based on their viscosity according to ISO 3448 classification and show potential as biolubricant with high viscosity index and excellent cold flow properties. Practical Applications: DFAE obtained have high potential to be used as lubricant base stock for equipment and machinery operating at extremely low temperature.

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