Aqueous nanofluids containing paraffin-filled MWCNTs for improving effective specific heat and extinction coefficient

Area of Science:

• Materials Science
• Nanotechnology
• Thermodynamics

Background:

• Aqueous nanofluids are promising for heat transfer applications.
• Improving nanofluid stability and thermal properties is crucial.
• Paraffin-filled Multi-Walled Carbon NanoTubes (MWCNTs) offer potential for enhanced thermal performance.

Purpose of the Study:

• To measure the effective specific heat and extinction coefficient of aqueous nanofluids containing paraffin-filled MWCNTs.
• To evaluate the stability of these nanofluids using an improved preparation method.
• To investigate the relationship between volume fraction and extinction coefficient.

Main Methods:

• Preparation of paraffin-filled MWCNTs using capillary action and centrifugal decanting for enhanced stability.
• Quantitative stability evaluation over 7 days using laser scattering.
• Measurement of effective specific heat via differential scanning calorimetry (DSC).
• Measurement of extinction coefficient using the three-slap method.

Main Results:

• The aqueous nanofluid with 1% volume fraction of paraffin-filled MWCNTs showed a 5.1% increase in effective specific heat compared to MWCNTs without paraffin.
• Nanofluid stability was quantitatively evaluated over 7 days.
• The extinction coefficient increased linearly with volume fraction within the independent scattering regime (nanoparticle-distance/wavelength ratio < 2).

Conclusions:

• Paraffin filling enhances the specific heat of MWCNT-based nanofluids.
• The modified preparation method yields more stable nanofluid dispersions.
• Understanding the extinction coefficient's dependence on volume fraction is important for optical applications and light absorption in heat transfer.