Heat transfer nanofluid based on curly ultra-long multi-wall carbon nanotubes

Abstract

The main challenge in the use of multi-wall carbon nanotube (MWCNT) as key components of nanofluids is to transfer excellent thermal properties from individual nanotubes into the bulk systems. We present studies on the performance of heat transfer nanofluids based on ultra-long (~2 mm), curly MWCNTs -in the background of various other nanoC-sp 2 , i.e. oxidized MWCNTs, commercially available Nanocyl™ MWCNTs and spherical carbon nanoparticles (SCNs). The nanofluids prepared via ultrasonication from water and propylene glycol were studied in terms of heat conductivity and heat transfer in a scaled up thermal circuit containing a copper helical heat exchanger. Ultra-long curly MWCNT (1 wt.%) nanofluids (stabilized with Gum Arabic in water) emerged as the most thermally conducting ones with a 23-30%-and 39%-enhancement as compared to the base-fluids for water and propylene glycol, respectively. For turbulent flows (Re = 8000-11,000), the increase of heat transfer coefficient for the overmonths stable 1 wt.% ultra-long MWCNT nanofluid was found as high as >100%. The findings allow to confirm that longer MWCNTs are promising solid components in nanofluids and hence to predict their broader application in heat transfer media.

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“…1A ). Those areas range from microelectronics (field-effect transistors, 3,4 microprocessors 5 ), stealth technology, 6 energy storage, 7,8 heat transfer, 9 composite materials, 10,11 functional coatings 12 and films 13,14 to, key here, biotechnology and medicine (drug delivery, 15–17 biosensors 18,19 ). The list is incomplete while the indicated areas naturally intertwine and cross-inspire.…”

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“…Nevertheless, this limitation may be overcome by employing nanofluids (NFs) which constitute a prospective solution in the design and manufacture of the modern HTFs. The most intensively studied carbon nanotube-based NFs are based on EG , and, recently, on ionic liquids. , Although 1,2-PG and 1,3-PG have many advantages, multi-walled carbon nanotube (MWCNT)-based NFs with propanediols as base fluids are rarely investigated. , Boncel et al found that 1,3-PG-based NFs containing 0.53 vol % curly ultra-long MWCNTs, stabilized with gum arabic in water, emerged as 39% more heat-conducting than pristine 1,3-PG. Nevertheless, the rheological characteristics and NF stability at high MWCNT concentrations were not cross-verified.…”

“…10,11 Although 1,2-PG and 1,3-PG have many advantages, multi-walled carbon nanotube (MWCNT)-based NFs with propanediols as base fluids are rarely investigated. 6,12 Boncel et al 12 found that 1,3-PG-based NFs containing 0.53 vol % curly ultra-long MWCNTs, stabilized with gum arabic in water, emerged as 39% more heat-conducting than pristine 1,3-PG. Nevertheless, the rheological characteristics and NF stability at high MWCNT concentrations were not cross-verified.…”