Study on the phase change characteristics of carbon-based nanofluids

In this study, carbon-based nanofluids (CBNFs) with the minimized carbon materials (MCMs) were prepared using a graphite powder-based heating and cooling processing method (GP-HCPM). In addition, sodium dodecyl benzenesulfonate (SDBS) was added as a dispersant to enhance the stability of the CBNFs. Two methods, one involving fixed heating and cooling rates and the other involving fixed heating and cooling temperatures, were used to measure and analyze the phase change characteristics of the CBNFs and SDBS aqueous solution in order to evaluate the feasibility of employing CBNFs as phase change materials (PCMs) for cold storage applications. Results revealed that SDBS reduced the thermal conductivity (k) and increased the viscosity (μ), density (ρ), and specific heat (cp) of the samples; the CBNFs tended to increase the k, μ, and ρ values but reduce the cp values of the samples, compared with water. Furthermore, the SDBS aqueous solution and CBNFs significantly reduced the contact angle of droplets, compared with water. Phase change experiments conducted for all samples revealed that the CBNF sample S4 demonstrated the greatest reduction ratios in onset nucleation time, solidification time, and subcooling degree (38.98%, 11.05%, and 35.41%, resp.); thus, S4 was determined to be the most suitable CBNF for use as a PCM in cold storage applications.