Experimental And Numerical Study On Heat Storage Characteristics Of Latent Functional Thermal Fluid

Latent functionally thermal fluid (LFTF) is a kind of two-phase fluid constituted by phase change material and single phase heat transfer fluid, including microencapsulated phase change material slurry (MPCMS) and phase change material micro-emulsion (PCMME). Former researchers have found that as the latent functionally thermal fluid has larger apparent specific heat capacity and larger specific surface area, it has some superiority in heat storage and heat transfer. In recent years, the construction, thermal properties, heat transfer and storage performance and the application of the latent functionally thermal fluid has been paid much attention.In this paper, firstly, by controlling the density and adding dispersants, a kind of MPCMS mainly constituted by 1-propanol/water and N-hexacosane is prepared. By comparing different kinds and different concentration of dispersants,0.4wt% alginate and 0.2wt% sodium dodecyl sulfate are chosen as mixed dispersants. The slurry is proved to have good stability and can be stored for a long time. Then different concentrations of MPCMS are prepared, the properties of viscosity and thermal conductivity at different temperature are measured. After comparing the properties, the 10wt%,20wt% and 30wt% MPCMS is chosen to be studied.Secondly, an experiment system is established and improved to study the natural convective heat transfer and heat storage performance. The factors influencing the performance are studied by changing the mass concentration, the temperature of heat source, the mass flow of the heat source and surface area of the heat exchanger. The results show that the convective heat transfer coefficient is decreased when the mass concentration is larger. A higher temperature and larger mass flow of heat source and a larger surface area of heat exchanger can strengthen the natural convection and speed up the heat storage. Comparing to the base fluid, as the MPCMS has large latent heat, the total heat storage is larger when the temperature is higher than the phase change temperature.Thirdly, numerical simulation method is used after all the properties needed are obtained to study the natural convective heat transfer and heat storage performance in a rectangular container. 2-dimensional model and 3-dimensional model are established, and effects of mass concentration, horizontal spaces and vertical spaces are studied. The results show that the natural convective heat transfer performance in a rectangular container heated by tube bundle heat exchanger can divided into three periods:conduction, quasi-steady and decay, and are affected by the mass concentration, the vertical and horizontal spaces.