Experimental Research On Application Benefits Of Phase Change Materials In Lightweight Buildings

With the increasing high-rise and high-density development of urban buildings,lightweight materials are employed widely in the construction sector.But lightweight buildings with low thermal inertia produce higher building energy consumption and lower indoor thermal comfort.The incorporation of phase change materials(PCMs)with high energy storage density can effectively address this problem.Based on this,this dissertation combines PCM in lightweight panel houses and proposes a reversible phase change composite wall(R-PCW)to better utilize the thermal storage capacity of PCMs and compensate for the low thermal inertia of lightweight panel house walls.The main work and results of the thesis are summarized as follows:(1)To investigate the effect of PCM on the thermal environment of the lightweight panel house,two full-size lightweight panel houses,one with composite PCM and the other without composite PCM,were established as reference objects.The purpose of the experiments was to compare the thermal environment and air conditioning energy consumption of the two rooms in their natural and air-conditioned states.The experimental results show that,in the natural state,the composite PCM can effectively shorten the time when the indoor air temperature exceeds the thermal tolerance and alleviate the indoor overheating phenomenon.Additionally,compared with the top composite PCM,the south wall composite PCM has a better improvement effect on the indoor thermal environment and a more uniform indoor temperature distribution.Under air conditioning,the composite PCM can effectively reduce the fluctuation of indoor air temperature and reduce the power consumption of air conditioning.And compared with the top composite PCM,the south wall composite PCM has better resistance to temperature fluctuation and energy-saving performance,and has a more significant improvement effect on the indoor thermal environment.(2)To better utilize the heat storage capacity of PCMs,a reversible phase change composite wall(R-PCW)is proposed to change the relative position of phase change material and insulation layer day and night to enhance the heat storage and discharge capacity of PCMs.To this end,two lightweight panel room models are established,one with R-PCW and the other without.Experiments were conducted to compare the indoor temperature parameters of the two rooms and to investigate the improvement benefits of R-PCW on the thermal environment of the lightweight panel room.The results show that R-PCW performs best when arranged on the south wall,followed by the top surface.When the thickness of the insulation layer in R-PCW is reduced from 30 mm to 10 mm,it plays a negative role in indoor temperature decay and delay but has less effect on the average daily temperature.And an optimal solution exists for the ratio of PCM and insulation layer.Increasing the reflectivity of the exterior wall finish material in R-PCW significantly reduces air temperature in the room and shortens the delay time.Compared with non-reversed PCM walls,reversed R-PCW can control indoor temperature more effectively.(3)To investigate the effects of window ventilation and shading on composite RPCW lightweight panel houses,experiments were conducted to compare the impacts of open and closed windows,different shading methods,and varying ventilation times on the internal temperature of the lightweight panel house.And the experimental results showed that the use of windows in the panel house led to lower thermal insulation performance due to the thermal bridge effect.In the natural state of summer,the panel house combined with R-PCW still had a higher average daily indoor air temperature and temperature peak,making it hard to meet the thermal comfort requirements and needing to be combined with other temperature control techniques to reduce the temperature.Compared with vertical shading,horizontal shading is more in line with the daily activity requirements of local users.Moreover,during the experimental period,nighttime ventilation can synergize more effectively with R-PCW than daytime ventilation.And there is an optimal solution for ventilation time.After the sun rises,ventilation and RPCW’s temperature control effects are mutually suppressed.(4)To enhance the comfort level inside the lightweight panel house,this study also analyzed the effects of the cycle and outdoor climate on the indoor thermal environment in conjunction with the working characteristics of R-PCW.The results indicate that in longer cycles,the daytime PCM heat storage accumulates and affects the degree of PCM phase change play at night and the next day.Among the climatic parameters,the air temperature has the greatest influence on the air temperature inside the composite R-PCW panel house,followed by solar radiation.Furthermore,even in a rainy environment,RPCW can effectively control temperature and suppress indoor temperature fluctuations.The innovative reversible phase change composite wall proposed in this study can effectively improve the thermal environment and reduce the energy consumption of air conditioning in lightweight panel houses.This technology has great potential for application in the fields of green building and building energy efficiency,and also provides new ideas and approaches for the research and practice of lightweight construction in China.