Caratenuto Andrew, Zheng Yi
Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA.
Department of Chemical Engineering, Northeastern University, Boston, MA 02115, USA.
Sci Adv. 2024 Sep 20;10(38):eadn6368. doi: 10.1126/sciadv.adn6368. Epub 2024 Sep 18.
Comparative evaporation rate testing in a dark environment, commonly used to characterize a reduced vaporization enthalpy in interfacial solar evaporators, requires the assumption of equal energy input between cases. However, this assumption is not generally valid, leading to misleading characterization results. Interfacial evaporators yield larger evaporation rates in dark conditions due to enlarged liquid-vapor surface areas, resulting in increased evaporative cooling and larger environmental temperature differentials. Theoretical and experimental evidence is provided, which shows that these temperature differences invalidate the equal energy input assumption. The results indicate that differences in evaporation rates correspond to energy input variations, without requiring enthalpy to be reduced below theoretical values. These findings offer alternative explanations for previous claims of reduced vaporization enthalpy and contradict enthalpy-related conclusions drawn from differential scanning calorimetry. We conclude that postulating a reduced vaporization enthalpy using the dark environment method is inaccurate and that re-evaluation of vaporization enthalpy reduction is required.
在黑暗环境中进行的比较蒸发速率测试通常用于表征界面太阳能蒸发器中降低的汽化焓，但这种测试需要假设不同测试案例之间的能量输入相等。然而，这一假设通常并不成立，会导致具有误导性的表征结果。由于液-气表面积增大，界面蒸发器在黑暗条件下会产生更高的蒸发速率，从而导致蒸发冷却增加以及更大的环境温差。本文提供了理论和实验证据，表明这些温差使能量输入相等的假设无效。结果表明，蒸发速率的差异对应于能量输入的变化，而无需将焓降低到理论值以下。这些发现为先前关于汽化焓降低的说法提供了替代解释，并与差示扫描量热法得出的与焓相关的结论相矛盾。我们得出结论，使用黑暗环境方法假设汽化焓降低是不准确的，需要重新评估汽化焓的降低情况。
