Abstract
Over the last few years, nanoparticles have been used as thermal enhancement agents in many heat transfer based fluids to improve the thermal conductivity of the fluids. Recently, many experiments have been carried out to prepare different types of nanofluids (NFs) showing a tremendous increase in thermal conductivity of the base fluids with the addition of a small amount of nanoparticles. However, little experimental work has been proposed to calculate the flow behaviour and heat transfer of nanofluids and the exact mechanism for the increase in effective thermal conductivity in heat exchangers. This study mainly focuses on the development of nanomaterial composites by incorporating copper oxide nanoparticles (CuO) onto the surfaces of carbon nanotubes (CNTs). The CNT–CuO nanocomposite was used to prepare water-based heat transfer NFs. The morphological surfaces and loading contents of the CNT–CuO nanocomposite were characterized using field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) while the physical and thermal properties of the water-based nanofluids were characterized using differential scanning calorimetry (DSC), the Mathis TCi system and a viscosity meter for measuring the heat capacity, thermal conductivity and viscosity of the synthesized NFs, respectively. The heat transfer and the pressure drop studies of the NFs were conducted by a horizontal steel tube counter-flow heat exchanger under turbulent flow conditions. The experimental results showed that the developed NFs with different concentrations of modified CNTs (0.01, 0.05 and 0.1 wt%) have yielded a significant increase in specific heat capacity (102% higher than pure water) and thermal conductivity (26% higher than pure water) even at low concentration. The results also revealed that the heat rate of the NF was higher than that of the base liquid (water) and increased with increasing the concentration of nanoparticles. Furthermore, no significant effect of the nanoparticles on the pressure drop of the system was observed.
Highlights
IntroductionThe nanotechnology, in terms of nanoparticles, has the potential in manufacturing metals and metals oxide with remarkable effects on the thermophysical and transport properties when added to the base uids.[13,14,15,16] the nanoparticles in the uids showed less clogging abrasion, better dispersion behaviour and the higher surface area which contemplate improving the efficiency of heat-transfer uids compared with the behaviour of the conventional uids.[17,18,19]
The demand for highly efficient heating and cooling systems is progressively increasing with the expansion of the current technologies and industrial processing applications.[1,2] The improvement of the heating or cooling systems in any industrial application is one of the main engineering approaches for better energy and cost optimization.[3]
The surface of carbon nanotubes (CNTs) was modi ed by impregnating different loadings of copper oxides nanoparticles on the CNT surface
Summary
The nanotechnology, in terms of nanoparticles, has the potential in manufacturing metals and metals oxide with remarkable effects on the thermophysical and transport properties when added to the base uids.[13,14,15,16] the nanoparticles in the uids showed less clogging abrasion, better dispersion behaviour and the higher surface area which contemplate improving the efficiency of heat-transfer uids compared with the behaviour of the conventional uids.[17,18,19]. 4) as “an innovative new class of heat-transfer uids that can be engineered by suspending nanoparticles in conventional heat transfer uids” This nano uid was reported to be able to improve the thermal conductivity and convective heat transfer performance.[13,14,20,21] The nano uids' performance found to be higher than the traditional base uids (ethylene glycol, water, oils).[22,23,24,25] Since many studies have been carried out on the nano uid enhancement using ultra-dispersed metal oxide nanoparticles into conventional base uids such as Cu/CuO, Al/ Al2O3, Au, Fe/Fe3O4, SiO2, CeO2, and TiO2.13,26–33 Metal oxide nanoparticles with a size range of 1–100 nm have shown signi cant improvement in several engineering applications, especially in enhancing the thermal properties.[34,35,36,37,38]. The heat transfer performance of the nano uids was considered by measuring the heat-transfer rate, pressure drop and pumping power under turbulent ow regimes using shell and tube heat exchanger
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