The non-isothermal test was conducted on thermal storage/release performance of sugar alcohols and their binary eutectic mixtures as applied to low to medium temperature thermal energy storage.Four familiar sugar alcohols (xylitol,d-sorbitol,meso-erythritol and d-dulcitol) having fusion temperatures between 90 ℃ and 200 ℃,were selected as the candidates due to their low prices in market,and six binary eutectic mixtures were prepared accordingly.The phase change temperature and phase change enthalpy of the sugar alcohols and their binary eutectic mixtures were measured by differential scanning calorimetry.Results show that xylitol,d-sorbitol and the binary eutectic mixtures containing one of them tend to form super-cooled liquids and cannot recrystallize from their melt during cool-down.The 95mol％ meso-erythritol/5mol％ d-dulcitol,the only binary eutectic mixture that can recrystallize,experiences cold crystallization during re-heating instead of crystallization during cool-down.In spite of the favorable recrystallization performance,meso-erythritol and d-dulcitol were observed to have severe supercooling and their supercooling degrees were determined to reach up to 101.9 ℃ and 70.4 ℃,respectively,at the cooling rate of 5 ℃/min.Although these sugar alcohols and their binary eutectic mixtures possess desirably high thermal energy storage density,they all suffer from specific issues associated with crystallization that must be addressed in practical applications.%对可用于中低温相变储热的糖醇及二元共晶混合物的储释热特性进行非等温测试.选取熔点为90～200℃时的4种常见且价格低廉的糖醇(木糖醇、d-山梨糖醇、内消旋-赤藓糖醇和d-半乳糖醇)为候选对象,制备相应的6种两两组合的二元共晶糖醇.采用差示扫描量热仪,对糖醇及二元共晶混合物的相变温度和相变焓进行测试.结果表明,木糖醇、d-山梨糖醇以及含两者其中之一的5种二元共晶糖醇在熔化之后重新冷却的过程中不能结晶,形成过冷液态;唯一1种能够重新结晶的二元共晶糖醇(95mol％内消旋-赤藓糖醇/5mol％ d-半乳糖醇)的结晶现象并非出现在冷却过程中,而是在再次升温过程中发生冷结晶.虽然内消旋-赤藓糖醇和d-半乳糖醇的重结晶性能较好,但存在较严重的过冷现象;当冷却速率为5℃/min时,两者的过冷度分别高达101.9和70.4℃.上述糖醇及二元共晶混合物虽然具有可观的储热密度,但在结晶过程中均存在各自的问题,须在实际应用中予以解决.
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