| In order to improve the thermal insulation effect of building walls in hot summer and cold winter areas and reduce the cooling energy consumption in summer,this paper starts with the preparation of high-performance phase change materials and the design of wall structure.Firstly,lauric acid（LA）,myristic acid（MA）,palmitic acid（PA）,stearic acid（SA）,No.52 paraffin（52PS）,and No.58paraffin（58PS）are used as raw materials.Five kinds of organic eutectic phase change materials（LA-MA,LA-PA,LA-SA,MA-52PS,and LA-PA-58PS）with suitable temperatures were prepared and their properties were characterized in detail.The expanded perlite（EP）with low thermal conductivity was selected as the adsorption material,and five kinds of expanded perlite based composite phase change materials were prepared by vacuum adsorption method to solve the leakage problem of organic eutectic PCM and further reduce the thermal conductivity of organic eutectic PCM to meet the thermal insulation requirements of the building envelope.Subsequently,a new type of phase-change ventilated wall is proposed for the problem of heat dissipation into the room at night,which occurs in summer in hot summer and cold winter regions and leads to a surge in building cooling energy consumption.Taking the western wall of the lightweight building in Ganzhou area as an example,the MA-52PS/EP composite phase change material was selected to prepare the phase change panel,and three small-scale experimental models were built at the same time.Finally,the thermal performance of normal wall,phase change wall,and phase change ventilated wall were studied by experimental comparison,and various evaluation indexes were introduced to exhaustively prove the energy-saving potential of the new phase change ventilated walls,the main research works are as follows.（1）The eutectic mass ratios of the five organic blended PCMs were determined by step-cooling curves as LA:MA=70:30,LA:PA=79:21,LA:SA=82:18,MA:52PS=62:38,and LA-PA:58PS=91:9,the corresponding melting temperatures of 35.10°C,37.15°C,39.29°C,41.99°C and32.26°C were also measured by DSC,and the latent heats of melting were 166.18 J·g-1,183.07 J·g-1,189.50 J·g-1,171.42 J·g-1,and 159.95 J·g-1;FTIR and XRD experiments demonstrated that the components corresponding to LA-MA,LA-PA,LA-SA,LA-PA-58PS and MA-52PS did not undergo chemical reactions during the melting and blending process,and that the crystal structure did not change.In addition,the results of TGA and accelerated phase change cycling experiments show that the five organic eutectic PCMs have good thermal stability,thermal reliability,and chemical reliability.（2）The maximum mass adsorption rates of EP on LA-MA,LA-PA,LA-SA,MA-52PS,and LA-PA-58PS are 75%,70%,70%,65%,and 75%,respectively.SEM,FTIR and XRD experimental results show that the composites are formed by the physical interaction of the pore structure of EP on organic eutectic PCM molecules,and the addition of EP does not destroy the original crystal structure of organic eutectic PCM;The melting temperatures of LA-MA/EP,LA-PA/EP,LA-SA/EP,MA-52PS/EP,and LA-PA-58PS/EP were 33.59°C,35.37°C,37.79°C,31.78°C,and 40.39°C,respectively,corresponding to latent heats of melting of 115.63 J·g-1,120.35 J·g-1,126.05 J·g-1,106.87 J·g-1,and 117.34 J·g-1,respectively,and the introduced evaluation indexes indicate that these five expanded perlite based composite phase change materials have excellent thermal properties.In addition,the TGA and accelerated phase change cycling results showed that these five expanded perlite based composite phase change materials have good thermal stability,thermal reliability,and chemical reliability.（3）Taking the west wall of the light-weight building in Ganzhou area as an example,MA-52PS/EP was selected to prepare the phase change panels,and three small-scale experimental rooms were built,room 1 for the west wall with ordinary wall（NW）,room 2 for the west wall with phase change wall（PCW）,and room 3 for the west wall with phase change ventilated wall（SPIV-PCW）,and the experimental study was carried out for three consecutive days on a typical summer day in Ganzhou.The experimental results and analysis are as follows.The maximum temperature of the inner surface of the west wall of room 2 and room 3 is 3.6℃and 5.0℃lower than that of room 1,respectively,and the maximum indoor air temperature of room 2 and room 3 is 1.6℃and 2.5℃lower than that of room 1,respectively,in addition,the temperature difference between room 2 and room 3 is as high as 7.4℃;in terms of peak temperature drop,decay factor,and heat flow performance,SPIV-PCW outperforms PCW,and PCW The above results show that the SPIV-PCW proposed in this paper has great potential for saving cooling energy in hot summer and cold winter regions,and provides a new idea for improving the wall insulation effect. |
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