Study On Thermophysical And Phase Change Cold-storage Characteristics Of Al₂O₃-H₂O Nanofluids

For the effect of nanoparticle on the the basis fluid, the nanofluid consisted by thenanoparticle and the basis fluid will show an unique characteristic. The heat conductivity,solidifying point, ice point, melt temperature, the specific heat and latent heat of nanofluidswere studied by Hot Disk thermal constant analyzer, Differential Scanning Calorimetry,Infrared thermal imager and simulation software with different temperature, particlediameter, mass fraction and cooling rate.The experiment results show that:1The coefficient of thermal conductivity of nanofluids is higher than deionized water.With the temperature increase, thermal conductivity increases. The thermal conductivitywill increase as the increase of particle diameter. Because of its small size effect, thermalconductivity will increase during the mass fraction in5%～10%.The thermal conductivitywill increase as the increase of mass fraction during the particle diameter is large. Thecoefficient of thermal conductivity of nanofluids after freezing will increase as the increaseof mass fraction and particle diameter.2The solidifying point of nanofluids is higher than deionized water. The solidifyingpoint of nanofluids will increase with the increase of particle diameter. The solidifyingpoint of nanofluids firstly increases and then decreases with the increase of mass fraction.The solidifying point of nanofluids will decrease with the increase of cooling rates.3The ice point of nanofluids is higher than deionized water. The ice point ofnanofluids will increase with the increase of particle diameter. The ice point of nanofluidsfirstly increases and then decreases with the increase of mass fraction. The ice point ofnanofluids will decrease with the increase of cooling rates.4The sub-cooling degree of nanofluids is smaller than deionized water. Thesub-cooling degree of nanofluids firstly decreases and then increase with the increase ofparticle diameter. The sub-cooling degree of nanofluids decreases with the increase of massfraction. The sub-cooling degree of nanofluids will increase with the increase of coolingrates.5The melt temperature of nanofluids will decrease with the increase of particlediameter, mass fraction and cooling rates.6The specific heat of nanofluids will decrease with the increase of particle diameter,mass fraction and cooling rates.7The latent heat of nanofluids is smaller than deionized water. The latent heat of nanofluids will increase with the increase of particle diameter. The latent heat of nanofluidswill increase with the increase of particle diameter.8In the freezing process, the freezing time will increase with the latent heat increase.It is easy to reach the solidifying point as the thermal conductivity increase.The numerical simulation results show that:The coefficient of thermal conductivity of nanofluids will increase with the particlediameter increase. The time of freezing deionized water is longer than nonafluids’. Becauseof latent heat of deionized water is largest.In a word, the nanofluids have the smaller sub-cooling degree, the larger coefficient ofthermal conductivity. But the latent heat of nanofluids will reduce.