Abstract:

Herein a high-performance sodium acetate trihydrate-urea-expanded graphite mixed phase change material (PCM) with a suitable melting point for use in electric floor heating was developed by employing urea to adjust the melting point of sodium acetate trihydrate, followed by adding expanded graphite to reduce the supercooling degree of the obtained binary mixture. The mixed PCM was fabricated into phase change panels with different thicknesses, followed by placing them into an electric heating floor of a test room, respectively. The effect of the thickness of the PCM layer on the thermal performance of the test room was investigated, and the set heating temperature was optimized. The results show that when the urea mass fraction is 36.5% and the amount of expanded graphite is 4%(mass), the melting enthalpy of the obtained mixed phase change material is as high as 209.1 J/g, the melting point is 31.98℃, and the supercooling degree is only 2.04℃ , thermal conductivity is 2.349 W/(m·K), good thermal reliability. It is found that, the thermal comfort of the test room increases with the increase in the thickness of the PCM layer, but the increase of the thickness also leads to the increase of heating time and electricity consumption; the heating time and electricity consumption decrease with the increase in the set heating temperature, while the thermal comfort of the test room tends to increase first and then decrease; when the thickness of the phase change material layer is 10 mm, the electric heating temperature is suitably set at 45°C. Compared to the reference room with a comparable thermal comfort, the test room equipped with the sodium acetate trihydrate-urea-expanded graphite mixed phase change panel with 10 mm in thickness presents the advantages of less electricity consumption and lower electricity cost, according to the time-of-use electricity price in Shanghai. It is revealed that the sodium acetate-urea-expanded graphite mixed PCM shows good potential for use in electric floor heating.

Key words: latent thermal energy storage, phase change material, sodium acetate trihydrate, electric floor heating, hydrate, composites, renewable energy

摘要：

采用尿素调节三水醋酸钠的相变温度到合适范围再添加膨胀石墨来降低过冷度，研制了高性能的三水醋酸钠-尿素-膨胀石墨混合相变材料，并对其在电地暖中的应用性能进行了研究。结果表明，当尿素质量分数为36.5%、膨胀石墨添加量为4%(质量)时，所得混合相变材料的熔化焓高达209.1 J/g，熔点在31.98℃，过冷度仅为2.04℃，热导率为2.349 W/(m·K)，热可靠性良好；将用该混合相变材料制成的相变板安装在实验房的电地暖中时，实验房的热舒适度随着相变材料层厚度的增加而增加，但也带来加热时间和用电量的增加；当相变材料层厚度为10 mm时，电加热温度适宜设置在45℃；在热舒适度相当的条件下，有相变板的实验房与无相变板的参比房相比具有用电量小及电费低的优势。

关键词: 潜热储热, 相变材料, 三水醋酸钠, 电加热地板采暖, 水合物, 复合材料, 再生能源