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Comparison of pool boiling characteristics of functionalized and non-functionalized multi-walled carbon nanotube nanofluids
Zoljargal Narankhishig, Jeonggyun Ham and Honghyun Cho
In this experimental study, the pool boiling characteristics of non-functionalized multi-walled carbon nanotube (NF-MWCNT) nanofluid were examined and compared to those of functionalized MWCNT (F-MWCNT) nanofluid. The critical heat flux (CHF) enhancement of NF-MWCNT and F-MWCNT nanofluids was investigated using various nanoparticle concentrations under sub-atmospheric pressure. The study results revealed that increased CHF was obtained at all NF-MWCNT and F-MWCNT nanofluid concentrations compared to that of water, and the boiling heat transfer coefficient (BHTC) of F-MWCNT was higher than that of NF-MWCNT. The maximum BHTC of 27.67 kW/m2∙K was achieved at F-MWCNT nanofluid concentration of 0.001wt%. However, the BHTC of F-MWCNT nanofluid stood higher than that of NF-MWCNT nanofluid. Some deposition of NF-MWCNT nanofluid was observed at the heating surface. This increased the thermal resistance, thus decreasing the BHTC. Overall, the F-MWCNT nanofluid had higher boiling heat transfer than that of NF-MWCNT nanofluid with similar nanoparticles concentration.
Keywords: Nanofluid, Pool boiling, Critical heat flux (CHF), Boiling heat transfer coefficient (BHTC), Multi-walled carbon nanotube (MWCNT), Thermal resistance