Höhlein Stephan, König-Haagen Andreas, Brüggemann Dieter
Chair of Engineering Thermodynamics and Transport Processes (LTTT), Center of Energy Technology (ZET), University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany.
Materials (Basel). 2017 Apr 24;10(4):444. doi: 10.3390/ma10040444.
The application range of existing real scale mobile thermal storage units with phase change materials (PCM) is restricted by the low phase change temperature of 58 ∘ C for sodium acetate trihydrate, which is a commonly used storage material. Therefore, only low temperature heat sinks like swimming pools or greenhouses can be supplied. With increasing phase change temperatures, more applications like domestic heating or industrial process heat could be operated. The aim of this study is to find alternative PCM with phase change temperatures between 90 and 150 ∘ C . Temperature dependent thermophysical properties like phase change temperatures and enthalpies, densities and thermal diffusivities are measured for the technical grade purity materials xylitol (C 5 H 12 O 5 ), erythritol (C 4 H 10 O 4 ) and magnesiumchloride hexahydrate (MCHH, MgCl 2 · 6H 2 O). The sugar alcohols xylitol and erythritol indicate a large supercooling and different melting regimes. The salt hydrate MgCl 2 · 6H 2 O seems to be a suitable candidate for practical applications. It has a melting temperature of 115.1 ± 0.1 ∘ C and a phase change enthalpy of 166.9 ± 1.2 J / g with only 2.8 K supercooling at sample sizes of 100 g . The PCM is stable over 500 repeated melting and solidification cycles at differential scanning calorimeter (DSC) scale with only small changes of the melting enthalpy and temperature.
现有的配备相变材料（PCM）的实际规模移动储热装置的应用范围受到三水合醋酸钠这一常用储热材料58℃的低相变温度的限制。因此，只能为诸如游泳池或温室等低温散热器供热。随着相变温度的升高，可以运行更多像家庭供暖或工业过程热这样的应用。本研究的目的是找到相变温度在90至150℃之间的替代相变材料。对工业级纯度的木糖醇（C₅H₁₂O₅）、赤藓糖醇（C₄H₁₀O₄）和六水合氯化镁（MCHH，MgCl₂·6H₂O）等材料测量了随温度变化的热物理性质，如相变温度、焓、密度和热扩散率。糖醇木糖醇和赤藓糖醇表现出较大的过冷度和不同的熔化状态。水合盐MgCl₂·6H₂O似乎是实际应用的合适候选材料。它的熔化温度为115.1±0.1℃，相变焓为166.9±1.2 J/g，在100 g样品量时过冷度仅为2.8 K。在差示扫描量热仪（DSC）规模下，该相变材料在500次重复熔化和凝固循环中保持稳定，熔化焓和温度仅有微小变化。
