石蜡基相变储能墙结构设计与控温实验研究

Structural Design and Experimental Study on Temperature Control of Paraffin-Based Latent Thermal Energy Storage Wall

基于相变储能(LTES)理论筛选牌号为25℃的石蜡掺入质量分数为5%的碳纤维制备复合相变材料,利用金属波纹管封装后蛇形敷设于墙体中,在墙体与室内相邻一侧的混凝土材料中掺入质量分数为2%的钢纤维,设计制备相变储能墙。将LTES墙与普通混凝土墙分别用于2组温室模型制备LTES温室与普通温室,进行控温对比实验。提出相变维持时间、温度延迟时间、温度衰减倍数、升温速率和降温速率5个指标定量评价LTES墙综合控温性能。结果表明:牌号为25℃的石蜡,实际相变温度区间为22.2~30.0℃,与植物生长所需环境温度区段相匹配,适于温室使用;LTES墙施工便捷、成本低、封装量高、热交换速率快,结构设计方法切实可行;LTES温室环境温度波动小,相变材料的储热与放热过程对于温室环境温度起到“削峰填谷”效果,减少了辅热或制冷设备产生的附加能耗,可起到节能减排作用;LTES墙较普通墙具有很长一段相变维持时间,且外温传递的延迟时间长、衰减幅度大、升温和降温的速度慢,将其用于温室结构可以起到明显控温效果。

The composite phase change material is prepared from grade 25℃paraffin with mass fraction of 5%carbon fiber,based on the theory of phase change energy storage.The paraffin,which is encapsulated by metal bellows,is arranged in the wall with serpentine arrangement.Steel fiber with a mass fraction of 2%is added to the concrete on the interior side of the wall.Latent thermal energy storage(LTES)wall is designed and fabricated by the methods above.LTES wall and concrete wall are used to prepare LTES greenhouse and ordinary greenhouse in two sets of greenhouse models,respectively.And the temperature control experiment is conducted.Five evaluation indexes including phase change maintenance time,temperature delay time,temperature attenuation multiple,heating rate and cooling rate are proposed to quantitatively measure the comprehensive temperature control performance of LTES wall.The experimental results show that the actual phase transition temperature range of paraffin with grade 25℃is 22.2℃to 30.0℃,which matches the environmental temperature range required for the growth of greenhouse plants,is suitable for the use of greenhouse.The structural design method is feasible because LTES wall has advantages such as convenient,low cost,high encapsulation amount,and high heat exchange rate.The process of heat storage and heat release of phase change materials play a"cutting peak and filling valley"effect on the greenhouse environment temperature,which reduce the additional energy consumption generated by auxiliary heat or refrigeration equipment,play a role in energy conservation and emission reduction.Compared with ordinary walls,LTES wall has a long period of phase change maintenance time,the delay time of external temperature transfer is longer,the attenuation range is larger,and the rate of heating and cooling is slower.It can be used in greenhouse structure to control the temperature obviously.