Heat storage and release characteristics of solar phase change Kang and influence factors

doi:10.11949/j.issn.0438-1157.20181199

Abstract

Abstract:

The system combining the solar water and phase change heat storage Kang is put forward. Instead of water tank, Kang plate and phase change material are used as heat storage devices to availably improve the heating efficiency in this system. Based on Fluent, two-dimensional unsteady heat transfer model of the Kang is established. The heat storage and release characteristics of phase change Kang is studied and compared with the thermal properties of concrete material Kang. The effects of phase change temperature and latent heat of phase change materials on the heat storage and release characteristic of Kang are also analyzed. Under the working condition of this article, the stable temperatures of the upper surface of Kang of day and night increase by 2℃ and 4℃, respectively. The largest surface temperature difference of Kang decreases from 3.7℃ to 0.8℃. The heat increased by 66.36%. The phase change heat storage Kang has the advantages of high temperature of the upper surface of Kang, uniform temperature distribution, good heat-insulation property and large heat storage capacity. Results show that the temperature of the upper surface of Kang at night increase significantly, with the increase of phase change temperature, but the heat gain of Kang is reduced. Increasing the latent heat has little effect on the temperature of the upper surface of Kang, while significant effect on the heat gain of the Kang.

Key words: solar energy, phase change heat storage Kang, phase change temperature, phase change latent heat, numerical simulation

摘要：

提出一种太阳能热水相变蓄热炕的新型供暖系统，系统无须设置水箱，仅使用炕板与相变材料作为蓄热装置，可有效提高供暖效率。基于Fluent数值模拟平台，建立相变炕的二维非稳态传热模型，研究相变炕的蓄放热性能，并与混凝土炕的热性能进行对比；还分析了相变材料的相变温度和潜热对相变炕蓄放热性能的影响。结果表明，在设定工况下，与混凝土炕相比，上炕面的日间与夜间稳定温度分别提高2℃和4℃，上炕面最大温差由3.7℃降至0.8℃，全天得热量提高了66.36%。因此，相变炕具有上炕面温度较高、温度分布均匀、得热量大以及保温性能好等优点；提高相变温度，炕体得热量会有所减少，但对提升上炕面温度作用显著；增大相变潜热，可以显著提高炕体得热量，但对提升上炕面温度作用不明显。

关键词: 太阳能, 相变炕体, 相变温度, 相变潜热, 数值模拟

CLC Number:

TK 512

Wenyu LI, Liangliang SUN, Yanping YUAN, Xiaoling CAO, Bo XIANG. Heat storage and release characteristics of solar phase change Kang and influence factors[J]. CIESC Journal, 2019, 70(5): 1761-1771.

李文玉, 孙亮亮, 袁艳平, 曹晓玲, 向波. 太阳能热水相变炕体蓄放热性能及影响因素[J]. 化工学报, 2019, 70(5): 1761-1771.

Figures/Tables 18

Fig.1 Composite system of phase change heat storage Kang

Fig.2 Schematic of cross section of Kang

Table 1 Physical properties and geometric properties of Kang material

材料名称	厚度/ mm	密度/ (kg·m^-3)	比热容/ (J·(kg·K)^-1)	热导率/ (W·(m·K)^-1)
水泥砂浆	30	1800	1050	0.93
卵石混凝土	60	2300	920	1.51
聚苯乙烯	20	30	1380	0.042
钢筋混凝土	100	2500	920	1.74

Table 2 Physical properties of phase change material

密度/

(kg·m^-3)

比热容/

(J·(kg·K)^-1)

热导率/

(W·(m·K)^-1)

运动黏度/

(m²·s^-1)

Fig.3 Basic heat transfer unit of Kang

Fig.4 Validation of mesh and time steps independency

Fig.5 Temperature of measured points of wall under different filling conditions

Table 3 Physical properties of material

材料

密度/

(kg·m^-3)

热导率/

(W·(m·K)^-1)

比热容/

(J·(kg·K)^-1)

Table 4 Error analysis of numerical simulation

测点	误差范围/%	平均误差/%
相变墙A点	0.08~3.11	0.91
混凝土墙A点	0.48~4.96	2.63
相变墙B点	0.31~5.04	2.11
混凝土墙B点	2.8~5.18	4.17

Fig.6 Change of average temperature of upper surface of Kang under different filling conditions

Fig.7 Change of measuring points temperature of upper surface of Kang under different filling conditions

Fig.8 Change of average temperature of under surface of Kang under different filling conditions

Fig.9 Heat flux of pipe and liquid fraction varies with time

Fig.10 Melting image of phase change materials

Fig.11 Effect of phase change temperature and liquid fraction on average temperature of upper surface of Kang

Fig.12 Total heat gain, heat release of day and night under different phase change temperatures

Fig.13 Effect of phase change latent heat on average temperature of upper surface of Kang

Fig.14 Total heat gain, heat release of day and night under different phase change latent heat

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