Thermo-Physical Property And Heat Transfer Performance Of Novel Fluid For Cool Storage With Inorganic-Organic Composite Shell Nanoencapsulated Phase Change Material

Latent heat fluid for cool storage is a kind of functional fluid for cool storage and heat transfer enhancement. The traditional fluid for cool storage with organic microencapsulated phase change material(MEPCM) has some undesirable drawbacks like high flow resistance and poor thermal conductivity. Based on the high thermal conductivity of inorganic nano-particles and low flow resistance of the fluid with nano-encapsulated phase change material(NEPCM), the experimental research on a novel fluid for cool storage with inorganic-organic composite shell NEPCM has important theoretical significance and practical application value. This paper carried out the experimental study on thermo-physical property and heat transfer performance of the novel fluid for cool storage with polystyrene(PS)-silica(Si O2) composite shell NEPCM containing n-tetradecane(Tet).The novel PS-Si O2@Tet NEPCM and its suspension were synthesized by miniemulsion in-situ polymerization. The effect of the mass fraction of ethylene glycol(EG) anti-freeze agent on the freezing point and the stability of the novel fluid for cool storage with composite shell NEPCM were discussed. The thermal performance of PS-Si O2@Tet NEPCM was characterized by differential scanning calorimeter(DSC), thermogravimetric analysis(TG). The thermo-physical properties of the novel fluid with composite shell NEPCM were measured systematically, including particle size and distribution, thermal conductivity, specific heat capacity, viscosity and density.The experimental results showed that the synthesized PS-Si O2@Tet NEPCM had a z-average particle size of 151.3 nm, latent capacity of 83.38 k J·kg-1 and excellent thermal stability. With the mass fraction of 15% EG and SDS/OP-10/H2 O as the base liquid, the novel fluid with the mass fraction of 5% PS-Si O2@Tet composite shell NEPCM had higher coefficient of thermal conductivity(0.4035 W·m-1·K-1 at 5℃) and specific heat capacity(8.842 J·g-1℃-1 at 5℃) than the unused Si O2 modified PS@Tet NEPCM, along with its low viscosity(2.76 c P at 5℃) and excellent mechanical stability, which indicates that it has promising potential for cool storage.Based on the self-built test platform of the heat transfer performance of the novel fluid, the heat transfer performance of the novel fluid for cool storage with composite shell NEPCM was investigated. The factors that enhanced heat transfer performance of the fluid with PS-Si O2@Tet NEPCM in the cool storage and discharge processes were systematically investigated.The results demonstrated that, during the cool discharge process, compared with the fluid with unused Si O2 modified PS@Tet NEPCM, the convective heat transfer coefficient of the fluid with 5% PS-Si O2@Tet NEPCM was increased by 8%, compared with the base liquid, the one was increased by 50%. Accordingly, during the cool storage process, the increase of 6% and 30% was obtained, respectively. During the cool storage and discharge processes, the heat transfer coefficient of the novel fluid with PS-Si O2@Tet composite shell NEPCM increased with increasing Reynolds Number, while the degree of heat transfer enhancement decreased with it; With the increase of the mass fraction of PS-Si O2@Tet NEPCM and the volume flow rate of external-tube heat transfer fluid, the effect of heat transfer enhancement of the fluid with PS-Si O2@Tet composite shell NEPCM was improved.