Study On The Preparation Of New Building Phase Change Materials Based On Microfluidics

Phase change material(PCM)is a material that can change its own temperature by absorbing and discharging heat according to the change of ambient temperature.In construction applications,PCM microcapsules are prepared by encapsulating PCM with polymers and mixed with construction materials,which can effectively reduce energy consumption.In this study,the key scientific problems faced by the preparation of traditional PCM microcapsules are taken as the background,and PCM microcapsules with OP18 E as the core material and HDDA as the shell material are prepared by microfluidics,and the thermal physical parameters and thermodynamic properties of PCM microcapsules with different core-shell ratios are investigated to provide a theoretical basis for solving the energy consumption in buildings.In the theoretical study,the theoretical equation for the core-shell size of composite phase droplets in co-focusing microfluidic channels was derived based on the force equilibrium at the time of composite phase droplet fracture,and the equation was verified to be in good agreement with the experimental results.The principle of practical application of building phase change materials is analyzed using heat transfer mode and the laws of thermodynamics,as well as the theory of phase change point,enthalpy and specific heat capacity obtained by testing using differential scanning calorimetry.In terms of experiments,a PCM microcapsule experimental platform was built and PCM microcapsules with different core-to-shell ratios were prepared by microfluidic experimental devices.The particle size analysis shows that the PCM microcapsules with three different core-shell ratios can be prepared by microfluidics with high monodispersity and controllable size.The DSC test shows that the PCM microcapsules have good energy and heat storage performance,and the phase change point,enthalpy and specific heat capacity increase linearly with the increase of phase change material mass fraction.Phase change energy storage efficiency calculations show that the PCM microcapsules are well encapsulated and the latent heat of the encapsulated OP18 E can be completely released and stored.In terms of thermal stability,the PCM microcapsules with three core-shell ratios can reduce the temperature fluctuation in the chamber and still have good thermal stability after multiple thermal cycles.And with the increase of core-to-shell ratio,its thermal stability is better;with the increase of cavity thickness of circular tube structure,the temperature fluctuation gradually decreases.In terms of numerical simulation,the thermal cycle of the circular tube structure loaded with OP18 E was simulated by COMSOL Multiphysics simulation software.The results show that the simulation results are in good agreement with the experimental results,and as the thickness of the cavity increases,the more obvious the effect of OP18 E to maintain the stability of the room temperature.When the rate of external temperature change decreases,the temperature fluctuation of OP18 E becomes larger and vice versa;similarly,when the range of external temperature fluctuation becomes larger,the temperature fluctuation of OP18 E also becomes larger,but OP18 E still has good thermal stability performance.