TEM (H-7100, Hitachi, Japan) and FE-SEM (JSM-7610F, JEOL, Japan) were used to identify the morphologies of the obtained CBNMs in the CBNFs. The shapes and sizes of the CBNMs were determined.
The CBNM production rate for each process parameter configuration was measured for determining the concentration of CBNMs in the CBNFs .
To appropriately employ the stability test and facilitate the stability comparison (suspension and dispersion performance), samples that were synthesized using various process parameters were adjusted to the same concentration by diluting with water or concentrating with a vacuum concentrator, because the concentrations of all the CBNFs were not equal.
The basic physicochemical characteristics measured for the CBNFs were pH, electrical conductivity (E), density ([rho]), viscosity ([mu]), and thermal conductivity (k), which were measured using a pH meter (SensION+ MM374, Hack, USA) with an accuracy of [+ or -] 0.002 pH and [+ or -] 0.5%, an electrical conductivity meter (SensION+ MM374), a liquid density meter (DA-130N, KEM, Japan) with an accuracy of [+ or -] 0.001 g/mL, a viscosity meter (T15-3, Hydramotion, England) with an accuracy of [+ or -] 1.0%, and a thermal properties analyzer (KD-2 Pro, Decagon Devices, USA) with an accuracy of [+ or -]5.0%, respectively.
The experimental results were transformed into a change ratio (CR) for comparison of water with the CBNFs; the CR can be expressed as
Although FE-SEM and TEM images can partially display [d.sub.p] and morphology, a nanoparticle analyzer was required to confirm the [d.sub.p] distribution and average [d.sub.p] of the suspended CBNMs in CBNFs. Moreover, XRD and Raman spectroscopy were necessary to identify the material in the follow-up tests.
(5) The CBNF sample S4 had the lowest ONT, ST, and SD of all the samples in the phase change experiments; thus, S4 was determined to be the most suitable CBNF for use as a PCM for cold storage applications.
Caption: Figure 2: GP-HCPM process for CBNF preparation.
Caption: Figure 11: Photographs of the CBNF for (a) initial and (b) after undergoing 20 phase change experiments.
In the present study, a graphite powder-based heating and cooling processing method (GP-HCPM) was used to produce carbon-based nanofluids (CBNFs) as PCMs.
However, in this study, the applied SDBS aqueous solution and CBNFs had no significant effect on [T.sub.s] and [T.sub.m], and the largest difference relative to water was only 0.75[degrees]C.
(3) SDBS provides better suspension and dispersion performance for MCMs in water, which facilitates the transmission of energy to enhance the freezing phase change of CBNFs.