Properties Of Phase Change/heat Reflection Microapsules And Temperature Control Coating On Concrete Surface

In recent years,phase change latent heat materials and heat reflective materials have developed relatively and maturely in the field of construction,which can significantly reduce building energy consumption and improve the urban heat island effect.However,the research on solving the problem of concrete temperature cracks in transportation infrastructure is also very limited.In order to discuss this problem,and to avoid the disadvantage that the phase change composite material will reduce the mechanical properties of concrete,Ti O2-polymer-paraffin phase change/heat reflection microcapsules are prepared,and based on the ANSYS finite element software,the effect of phase change/heat reflection microcapsule coating on the temperature field of concrete is studied.First,the methyl methacrylate and styrene are selected as the encapsulating material and the low temperature phase change paraffin as the phase change material.After surface modification of Ti O2,two series of Ti O2-polymer-paraffin phase change microcapsules are prepared by emulsion method.The enthalpy value of the microcapsules is tested with a synchronous thermal analyzer.The maximum enthalpy value of the prepared polystyrene series microcapsules is 136.28J/g,and the maximum enthalpy value of the polymethyl methacrylate series microcapsules is only 4.62 J/g.The results show that the polystyrene series microcapsules are more suitable for the preparation process in this paper,and the microcapsules with a core-to-wall ratio of 3:1 have the highest enthalpy value.Secondly,in order to explore the boundary conditions of concrete surface temperature under the effects of sunshine and air temperature,the relationship between air temperature,solar radiation and surface temperature is studied.Lhasa,Harbin,and Guangzhou are selected as representative cities for horizontal comparative analysis from three aspects: air temperature,solar radiation,and surface temperature.Using SPSS software to carry out multiple linear regression analysis of the three factors,a resgression equation that can explain the influence of air temperature and solar radiation on the surface temperature more comprehensively and accurately is obtained respectively.It proves the feasibility of using the surface temperature instead of the concrete surface temperature to set the boundary conditions when simulating the effects of sunshine and air temperature on the concrete temperature field.Finally,ANSYS finite element analysis software is used to study the effect of phase change coating on the temperature field of concrete slabs.The temperature control effect of the phase change coating is proved from two angles of temperature field and heat flow field.Further,the influence of coating thickness,duration of high and low temperature,heating rate,temperature range,etc.are analyzed on the temperature control effect of phase change coating.The results show that the greater the thickness of the coating,the more significant the temperature control effect;the longer the duration of high and low temperatures,the closer the temperature of the concrete slab to the ambient temperature;the higher the heating rate,the greater the retardation effect of the phase change coating on the temperature increase in the phase change interval;the phase change coating has almost no effect in the environment below the phase change interval temperature,and the effect is more significant in the environment above the phase change interval temperature.