Al_2O_3纳米流体相变特性的DSC研究

Phase Change Characteritics of Al_2O_3-H_2O Nano-fluids Measured by DSC

纳米流体相变时所体现出的特性是其作为蓄冷相变材料使用的重要基础。利用差示扫描量热法分别测量了纳米颗粒粒径为10nm、20nm、50nm、100nm、500nm,质量分数为5%、10%、12%、15%、20%,以及降温速率为2℃/min、3℃/min、5℃/min、7℃/min、9℃/min的Al2O3纳米流体的凝固点、冰点、融化点、比热及相变潜热的影响。测量结果表明:纳米流体的凝固点、冰点值都高于去离子水;随着颗粒粒径、质量分数和降温速率的增加,纳米流体的凝固点、冰点逐渐升高,而比热值逐渐减小。融化温度随着颗粒粒径、质量分数的增加而增加,且随着降温速率的增加而小幅度的降低。去离子水的相变潜热值高于纳米流体的潜热值;随着纳米颗粒粒径的增加,潜热值越大;随着质量分数和降温速率的增加,相变潜热值越小。

As a new phase-change cold storage materials, the thermal properties of nano-fluids are important for its further application. The effect of diameter, mass fraction and cooling rate to solidification point, freezing point, melting temperature, specific heat capacity and latent heat of AlO3was measured by Differential Scanning Calorimetry （DSC）. The diameter of nanoparticle is 10nm, 20nm, 50nm, 100nm, 500nm. The mass fraction is 5% , 10% , 12% , 15% , 20%. The cooling rate is 2℃/min, 3℃/min,5℃/min,7℃/min,9℃/ min. The results show that the nanoparticle plays a critical role on cool storage. The solidification point and freezing point of nanofluids are higher than the deionized water. With the increase of nanoparticle sizes, mass fraction and cooling rate, the solidification point and freezing point of nanofluids will increase, and the specific heat capacity of nanofluids will decrease. The melting temperature will increase with the increase of nanoparticle sizes, mass fraction, and also decrease with the increase of cooling rate. The latent heat of deionized water is higher than the nanofluids＇. The latent heat of nanofluids will increase with the increase of diameter of nanoparticle and decrease with the increase of mass fraction and cooling rate.