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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 (c p ) of the samples; the CBNFs tended to increase the k, μ, and ρ values but reduce the c p 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.

In this study, micro/nanocarbon-based materials (MNCBMs) were prepared using the high-pressure combustion method (HPCM) with an isoperibol oxygen bomb calorimeter at different oxygen pressures (0.5–3.0 MPa). The prepared MNCBMs were added to water to form carbon-based suspensions (CBSs); sodium dodecyl benzene sulfonate (SDBS) and defoamer were added to the CBSs to enhance their stability. The thermal conductivity, viscosity, density, and contact angle of the CBSs were measured using appropriate instruments to determine their fundamental characteristics. The phase-change characteristics of the CBSs were measured and analyzed using a differential scanning calorimeter (DSC) to evaluate the feasibility of employing them as phase-change materials in ice-storage air-conditioning systems. The results revealed that the maximal change ratios of thermal conductivity, viscosity, density, and contact angle of the samples were −3.15%, 6.25%, 0.23%, and −57.03%, respectively, as compared with the water. The CBS of S5 (oxygen pressure of 2.0 MPa) had the lowest melting temperature and subcooling degree (SD) and the highest freezing temperature in the experiments conducted using the DSC; thus, S5 was determined to be the most suitable CBS for use as a phase-change material of cold energy storage in this study.

In this study, carbon-based materials prepared using an isoperibol oxygen bomb calorimeter of varying oxygen pressure were added to water to form carbon-based suspensions (CBSs). The thermal conductivity, viscosity, density, and contact angle of CBSs were measured by appropriate instruments to understand the fundamental characteristics of CBSs. A differential scanning calorimeter (DSC) was used to measure and analyze the phase change characteristics of CBSs to evaluate the feasibility of employing CBSs as phase change materials (PCMs) in ice-storage air-conditioning systems. The experimental results revealed that the thermal conductivity, viscosity, and density of CBSs did not significantly change but a significant reduction in the contact angle of sample’s droplets occurred compared with that of water. The CBS of S5 had the lowest melting temperature and subcooling degree (SD) and highest freezing temperature in the DSC experiments; thus, S5 was determined to be the most suitable CBS for use as a PCM in this study.