Study On Solidification Of Nanofluids Assisted By External Field

As a new kind of phase change storage material, nanofluids has the advantages of shorter time of solidification, storaging more energy, low supercooling, but they easily get aggregation during solidification and clust together after melting, finally causing failure problem. External field could increase the dispersion of nanofluid solidification-melting cycle process, extend the effectiveness of nanofluid during energy store. In this paper, we study the water-based and paraffin-based nanofluid solidification under the effect of electric field and electromagnetic field, analys the results of experiment, then we discuss the mechanism which increase the dispersion of nanofluid during solidification, the main work as follows:1.Using magnetic field during the solidification of Fe3O4 paraffin, Fe3O4-H2O nanofuids, change the magnetic induction intensity, study the effection of magnetic field by measuring the area of particle aggregation and the absorbance after melting, combine the solidification process of nanofluid with classical electromagnetic theory, we deducte the range of magnetic induction intensity that improve the dispersion of nanofluid during solidification. The results show that:magnetic field could improve the dispersion of nanofluid; exisit a magnetic induction intensity that most improve the dispersion of nanofluid solidification under a certain solidification speed rate; nanoparticles which distribute dispersion in the solid present a good dispersion stability after melting; we could improve the phase change cycle stability of nanofluid by controlling the dispersion of nanofluid solidification. Experment results qualitatively proof the method that we thought.2.We improve the experimental equipment by using the theory of metal solidification and crystal growth, build the nanofluid directional solidification experimental station, this station has simple structure, good cooling effect, high temperature precision and operate easily, the temperature gradient coud change as we wish. The station give a good experimental environment and we confirm the temperature gradient that produce a stable interphase during solidification. We also combine the station with electric field, magnetic field, camera and computer, consist the nanofluid directional solidification system under the effect of electromagnetic field.3.Using electromagnetic field during the directional solidification of Graphite-paraffin and Graphite-H2O nanofluids set magnetic induction intensity as variable and keep the electric intensity as a constant number, observe the distribute of nanoparticles by environmental scaning electron microscopy; keep the magnetic induction intensity as a constant number, set electric intensity as variable, test the absorbance and particle size distribution after melting. Results show that electromagnetic field could increase the stability of nanofluid during solidification, we use electromagnetic pinch force discuss the results combine with the nanofluids4. Analyse the problem of nanofluids solidification assisted by electromagnetic field, we use pulse electromagnetic field during the solidification to improve the results before, set frequency as variable number, find out the effect of frequency to the solidification, we also find that, pulse electromagnetic field more improve the dispersion of nanofluids, the service life of the nanofluids were more extend than before.