| With the rapid development of China’s modernization and urbanization,the demand for energy consumption continues to grow.President Xi Jinping proposed at the Paris Climate Change Conference that China will peak carbon dioxide emissions around 2030.In the context of energy conservation and emission reduction energy strategies,the focus of my country’s energy research field is to improve energy efficiency through technological innovation,and to develop high-efficiency and clean development.energy.This paper proposes a double-layer phase-change ventilated roof.The main structure of the roof is based on the ordinary precast concrete roof with two layers of phase-change materials added.In summer,the heat storage characteristics and natural cold sources of the phase-change materials greatly weaken the outdoor climate.The influence of the indoor environment is that the heat is stored in the phase change material before the outdoor environment acts on the roof during the day and the cooling load has not yet formed,and the heat is dissipated to the outdoors by ventilation at night.In winter,the ventilation ducts are closed,the heat is stored in the phase change layer during the day,and the stored heat is released into the room through solidification at night,which can increase the temperature of the inner surface of the roof and reduce the burden of indoor heating.In this paper,a simplified dynamic heating network model(RC model)of the doublelayer phase-change ventilated roof structure is established using the thermal resistance and heat capacity method,and the genetic algorithm is used to identify the parameters of the RC model of the double-layer phase-change ventilated roof.Taking the calculation results of the CFD model as a reference,the accuracy of the simulation results of the RC model is compared and analyzed.The results show that the maximum error of the roof inner surface temperature between the RC model and the CFD model is 0.39℃,that is,the maximum error is 1.35%.The applicability of the single identification result of the RC model to different phase transition temperatures,thicknesses of PCM layer,and ventilation speeds is studied.The results show that the maximum value of the internal surface temperature error of the roof does not exceed 0.52℃,and the error is within 1.75%.A building model with a double-layer phase-change ventilated roof was established in the load simulation software TRNSYS to simulate the heat transfer process of the roof under the climatic conditions of Wuhan City throughout the year,and a "reference roof" was established for comparison.The results show that the cumulative cooling load of the doublelayer phase-change ventilated roof during the cooling period is 4875.63 k W·h,which is reduced by 29.46% compared with the reference roof.The cumulative heat load of the double-layer phase-change ventilated roof during the heating period is 1870.14 k W·h,which is reduced by 35.24% compared with the reference roof.Under the climatic conditions of hot summer and cold winter regions represented by Wuhan,the double-layer phase-change ventilated roof is further optimized.Considering the cumulative load of the air conditioner,the utilization rate of phase change materials and economic factors,the optimal insulation thickness of the double-layer phase change ventilated roof is 30 mm,and the optimal phase change temperature range of the high temperature phase change layer is 26～28℃.The optimal thickness of the change layer is30 mm,the optimal ventilation speed is 2～3 m/s,the optimal phase change temperature range of the low temperature phase change layer is 15～17℃,and the optimal thickness of the low temperature phase change layer is 20～30mm.After optimized design,compared with the reference roof,the cumulative cooling load during the cooling period can be reduced by30.18%,and the cumulative heating load during the heating period can be reduced by35.14%. |
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