Influence of single and multiple coupling factors on the stability of paraffin-based nanofluids

Nanofluids have been introduced to improve the thermal properties of phase-change materials. However, stability problems caused by agglomeration and deposition have greatly restricted the use of nanofluids. In this work, paraffin-based nanofluids were prepared under the dual coordination of magnetic stirring and ultrasonic oscillation, the influence of ultrasonic power and time, base fluid volume, particle concentration and type on fluid stability was studied by single factor method, and the influence degree of the above four factors on fluid stability was studied by fractional factor design method. The following conclusions were drawn from the experiment: (1) With the increase of ultrasonic power, the relative absorbance increases within the allowable range of the experimental instrument, and the maximum improvement is 3.06%.(2) The optimal ultrasonic time for nanofluids preparation is 2 h. (3) The sample volume under the optimal state is 45 ml. (4) With the increase in concentration, the absorbance per concentration decreases, and the reduction range becomes slow. (5) The stability of the nanofluid is also related to the characteristics of the particle surface. (6) The coupling effect of ultrasonic power - concentration (PC) has the most significant effect on the overall absorbance change. This study provides a clear improvement direction and basis for the preparation of highly stable nanofluids.