Abstract
The phase change material (PCM) used in a building wall can reduce building energy consumption and improve the living comfort level. However, only when the temperature of the PCM layer is between phase transition temperature ranges can it have the maximum effect to increase the thermal inertia. How to select the suitable PCM according to the local weather and building wall always troubles building engineers and affects the wide use of PCM on building energy efficiency. Aiming at present situation, this paper numerically analyzed the energy conservation of building multilayer wall integrated with a PCM layer to optimize PCM thermophysical properties and wall structure under the Chengdu typical climates of winter, summer and transition seasons. The numerical simulation used the heat transfer model of the enthalpy- porosity technique, which was verified by the experiment. The results show that the PCM layer can decrease the building annual load, increase the time lag, decrease the decrement factor and improve occupants' comfort. When the phase change occurs under the suitable temperature conditions, high latent heat is conducive to decreasing the heat flow fluctuation, increasing the time lag and improving inner surface temperature stability. It is more efficient that the PCM layer is located next to the internal surface and under this condition, the optimum solidus and liquidus temperatures are 14°C and 26°C respectively, under the Chengdu climates. And the annual inner surface heat flow can be reduced up to 13.36% for the PCM layer of 30mm and 9.64% for the PCM layer of 20mm compared with no the PCM layer.
Highlights
With the continuous improvement of living standard and indoor comfort, the building energy consumption is growing very quickly and the building energy efficiency has been very urgent [1]
The influence of latent heat, phase change temperature, placement and thickness of the phase change material (PCM) layer was researched on the inner heat flow and the temperature decrement factor
Fig. (12) shows temperature decrement factor with the different PCM layer location. It is clearly seen from Fig. (12) that it is conducive to decreasing the temperature decrement factor and improving the inner surface temperature stability, when the PCM layer is installed the inner surface
Summary
With the continuous improvement of living standard and indoor comfort, the building energy consumption is growing very quickly and the building energy efficiency has been very urgent [1]. Compared with traditional building envelope, the thermal mass of building envelope integrated with the PCM layer was increased greatly, which would reduce the building energy consumption, improve the indoor thermal comfort, and shift the peak electricity load [8]. Yan et al [9] experimentally researched the thermal properties of the PCM wall formed by three different methods Their results show that the addition of PCM in traditional walls can decrease building consumption and reduce the indoor air temperature fluctuation. Jin et al [2, 12] experimentally studied the placement of a PCM thermal shield within the cavity of buildings walls Their results show that, compared to a wall without a PCM layer, the peak heat flows were reduced by as much as 11% when the thermal shield was placed in the inward-most location next to the internal surface of the gypsum wallboard within the wall cavity. The influence of latent heat, phase change temperature, placement and thickness of the PCM layer was researched on the inner heat flow and the temperature decrement factor
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