Abstract

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.

中文翻译：

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单个和多个耦合因子对石蜡基纳米流体稳定性的影响

摘要

已经引入纳米流体来改善相变材料的热性能。然而，由团聚和沉积引起的稳定性问题极大地限制了纳米流体的使用。在磁力搅拌和超声振荡的双重协调下，制备了基于石蜡的纳米流体，并通过单因素方法研究了超声功率和时间，基础流体体积，颗粒浓度和类型对流体稳定性的影响，并对其影响进行了研究。通过分数因子设计方法研究了以上四个因素对流体稳定性的影响程度。实验得出以下结论：（1）随着超声功率的增加，相对吸光度在实验仪器的允许范围内增加，最大提高为3.06％。（2）制备纳米流体的最佳超声时间为2 h。（3）最佳状态下的样品量为45 ml。（4）随着浓度的增加，单位浓度的吸光度降低，降低范围变慢。（5）纳米流体的稳定性也与颗粒表面的特性有关。（6）超声功率-浓度（PC）的耦合效应对总体吸光度变化影响最大。该研究为制备高度稳定的纳米流体提供了明确的改进方向和基础。（5）纳米流体的稳定性也与颗粒表面的特性有关。（6）超声功率-浓度（PC）的耦合效应对总体吸光度变化影响最大。该研究为制备高度稳定的纳米流体提供了明确的改进方向和基础。（5）纳米流体的稳定性也与颗粒表面的特性有关。（6）超声功率-浓度（PC）的耦合效应对总体吸光度变化影响最大。该研究为制备高度稳定的纳米流体提供了明确的改进方向和基础。