高性能三水醋酸钠-尿素-膨胀石墨混合相变材料的制备及其在电地暖中的应用性能

doi:10.11949/0438-1157.20200229

摘要/Abstract

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

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

中图分类号:

TK 02

黄睿, 方晓明, 凌子夜, 张正国. 高性能三水醋酸钠-尿素-膨胀石墨混合相变材料的制备及其在电地暖中的应用性能[J]. 化工学报, 2020, 71(6): 2713-2723.

Rui HUANG, Xiaoming FANG, Ziye LING, Zhengguo ZHANG. Preparation of high-performance sodium acetate trihydrate-urea-expanded graphite mixed phase change material and its application performance in electric floor heating[J]. CIESC Journal, 2020, 71(6): 2713-2723.

图/表 14

图1 不同厚度的SAT-urea-EG相变板

Fig.1 Photographs of SAT-urea-EG phase change panels with different thicknesses

图2 实验房与电地暖结构示意图以及实验房照片

Fig.2 Schematic of test room and electric floor heating, together with two photographs of test room

图3 SAT和尿素以及含有不同质量分数尿素的SAT-urea混合物的DSC曲线

Fig.3 DSC curves of SAT and urea as well as SAT-urea mixtures with different mass fractions of urea

表1 SAT-urea混合物的相变特性参数

Table 1 Phase change characteristics of SAT-urea mixtures with different mass fractions of urea

尿素的质量分数/%	相变温度/℃	峰值温度/℃	相变潜热/(J/g)
0(SAT)	58.70	64.10	288.4±1.6
10	32.92	36.70/54.11	241.2±2.3
20	32.84	36.35/48.17	228.5±3.7
30	32.83	35.38	228.2±0.8
32	32.74	35.04	225.2±1.8
35	32.53	34.79	211.7±2.0
38	32.41	34.64	218.1±1.1
40	32.41	35.17	215.0±1.8
42	32.61	35.17	205.9±3.1
45	32.63	35.62	193.4±2.4
50	32.85	35.24	155.6±4.1
100(urea)	132.74	135.01	231.1±2.1

图4 EG含量不同的混合相变材料的T-history曲线

Fig.4 T-history curves of mixtures with different contents of EG

表2 EG含量不同的混合相变材料的热特性参数

Table 2 Thermal characteristics of mixtures with different contents of EG

EG质量分数/%	过冷度/℃	热导率/ (W/(m·K))	熔点/℃	相变潜热/(J/g)
0	7.15	0.531	32.41	218.1±1.1
2	2.89	1.355	32.40	213.2±0.4
4	2.04	2.349	31.98	209.1±0.6
6	2.02	2.991	31.98	203.7±1.3
8	2.10	3.346	32.11	200.0±1.5
10	2.02	3.657	32.20	195.2±1.2

图5 SAT-urea-EG混合相变材料200次加热-冷却循环前后的DSC曲线

Fig.5 DSC curves of SAT-urea-EG PCM before and after 200 heating-cooling cycles

图6 放置不同厚度的相变板时实验房内不同位置温度随时间的变化

Fig.6 Time-dependent temperatures at different locations of test room when equipped with phase change panels with different PCM thicknesses

表3 实验房地暖系统中安装不同厚度相变板时的热性能参数

Table 3 Parameters of test rooms equipped with phase change panels with different PCM thicknesses

厚度/mm	t_H/min	t_C/min	T_m/℃	t_L/min	Δt/min	FTC/%	EC/ (W·h)
5	107	58	17.6	173	222	78.93	35
10	200	58	18.6	222	364	86.26	55

图7 不同加热温度下实验房内不同位置的温度随时间的变化

Fig.7 Time-dependent temperatures at different locations of test room at different set heating temperatures

表4 不同加热温度下实验房的热性能参数

Table 4 Parameters of test rooms under different set heating temperatures

加热

温度/℃

EC/

(W·h)

图8 PCM房和参考房的对比

Fig.8 Comparisons of PCM room and reference room

表5 PCM房和参考房的峰谷用电量及电费

Table 5 EC and EF of PCM room and reference room

Room	EC_P/(W·h)	EF_P×10³/CNY	EC_V/(W·h)	EF_V×10³/CNY	EC_T/(W·h)	EF_T×10³/CNY
参考房	69	42.573	72	22.104	141	64.677
PCM房	59	36.403	65	19.955	124	56.358

表6 相变板的投资成本及节能经济效益

Table 6 Economic cost and payback of phase change panel

相变板

成本/ CNY

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