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1740319 
Journal Article 
Surface tension of evaporating nanofluid droplets 
Chen, RH; Phuoc, TX; Martello, D 
2011 
Yes 
International Journal of Heat and Mass Transfer
ISSN: 0017-9310 
54 
11-12 
2459-2466 
WOS:000289820100025 
Measurements of nanofluid surface tension were made using the pendant droplet method. Three different types of nanoparticles were used - laponite, silver and Fe(2)O(3) - with de-ionized water (DW) as the base fluid. The reported results focus on the following categories; (1) because some nanoparticles require surfactants to form stable colloids, the individual effects of the surfactant and the particles were investigated; (2) due to evaporation of the pendant droplet, the particle concentration increases, affecting the apparent surface tension; (3) because of the evaporation process, a hysteresis was found where the evaporating droplet can only achieve lower values of surface tension than that of nanofluids at the same prepared concentrations: and (4) the Stefan equation relating the apparent surface tension and heat of evaporation was found to be inapplicable for nanofluids investigated. Comparisons with findings for sessile droplets are also discussed, pointing to additional effects of nanoparticles other than the non-equilibrium evaporation process. (C) 2011 Elsevier Ltd. All rights reserved. 
Nanofluids; Surface tension; Evaporating droplet; Stefan's formula