Numerical Simulation Of Active-passive Thermal Insulation Characteristic Of Roof

With the development of economy, the growth of population, the improvement of livingstandards, and the increasing energy demand from life style of urbanization andmodernization, how to reduce the large energy consumption has become a key problem ofkeeping sustainable development. The proportion of building energy consumption isincreasing in the total national energy consumption, and it is about28%. So reducingbuildings operational energy consumption is the problem to be solved to realize sustainabledevelopment strategy of modern architecture, and the excellent thermal insulating technologyof building envelope is the key to reduce energy consumption of indoor thermal environment.The development of ecological architecture and green building has become a general trend atpresent, how to coordinate coupling relationship between building envelope and indoorthermal environment is the key to develop ecological architecture and green building. In mostof buildings, although roof is a small part of building envelope surface area, it receives solarradiation directly and its heat transfer quantity is larger than whichever external walls. So thestudy on thermal insulation mechanism of roof is especially important to reduce buildingenergy consumption and develop green building.The change of solar radiation, the fluctuation of outdoor air temperature and phasechange of material were considered in this paper, and the unsteady heat transfer model ofphase transition roof was established, then numerical simulation of unsteady heat transferprocess under different environmental condition at different time during a day werecompleted. The effect of solar radiation intensity, transformation temperature, transformationlatent heat, slope of roof, thickness of transformation layer, solar absorption coefficient ofroof external surface and property of porous medium framework to thermal insulationperformance of phase transition roof were analyzed, considered the change of solar radiation,the fluctuation of outdoor air temperature and the natural convection effect in air layer, andthe unsteady heat transfer model of ventilation roof was established, then numericalsimulation of unsteady heat transfer process under different environmental condition atdifferent time during a day were completed. The effect of solar radiation intensity, slope ofroof, thickness of air layer, size of air outlet and solar absorption coefficient of roof externalsurface to thermal insulation performance of ventilation roof were analyzed, considered thechange of solar radiation, the fluctuation of outdoor air temperature, the phase transition ofphase change material and the natural convection effect in air layer, and the thermal-hydraulic-mass-transfer model was attained, completed numerical simulation ofunsteady heat transfer process under different environmental condition at different timeduring a day, analyzed the effect of combination of phase change material and air layer tothermal insulation performance of roof.For studying thermal insulation mechanism of regenerative-passive thermal insulationroof and microventilated-active thermal insulation roof, the application prospect ofcombination technology of regenerative-passive thermal insulation and microventilated-activethermal insulation in building envelope under summer climatic features of Daqing area wereanalyzed in this paper, the effect of different factors to thermal insulation performance of roofanalyzed, provided evidence for future application of building envelope active-passivethermal insulation technology in ecological architecture and green building.