Microwave irradiation based non-chemical method to manipulate surface tension of nanofluids

• The influence of microwave on the surface tension of nanofluids is investigated.
• Non-thermal effect of microwave on the surface tension of nanofluids is reported.
• A non-chemical method to manipulate surface tension of nanofluids is proposed.

Manipulation of the surface tension is one of the key pathways to enhance heat and mass transfer performances of nanofluids in thermal systems. Current practices and existing literature on the surface tension reduction indicate that surfactant is usually employed as a chemical-additive to manipulate surface tension. This study, on the other hand, aims to explore a physical method to manipulate the surface tension of nanofluids based on microwave irradiation. This paper, therefore, is the first publication to report surface tension behaviors of nanofluids during and after microwave irradiation. Experimental results show that after microwave treatment, lower surface tensions were observed for both TiO2 and Fe2O3 based nanofluids for an extended period of time, even though the temperature has returned to its initial condition. These preliminary findings suggest that microwave irradiation treatment has the potential to be a non-chemical method to manipulate surface tension of nanofluids.

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