Improved semi-empirical correlations for the evaporation and condensation of zeotropic mixtures

该项目的目的是发展改进的模型方法，以预测流体混合物蒸发和冷凝过程中的传热。为此，在一个正在进行的项目中设计并设置了快速测试设备，可以为所提出的计算方程提供特定于混合物的参数。在应用的后续项目中，将通过在快速试验装置中进一步混合流体来深化这一程序，因此模型方法将进一步发展。两个地点的快速测试设备基于相同的实验概念。共沸混合物的沸腾行为的研究由拜罗伊特大学技术热力学和输运过程主席（br<s:1> ggemann工作组）和汉诺威莱布尼茨大学热力学研究所（Kabelac工作组）进行。将模型方法从目前的二元流体混合物扩展到三元混合物，并对实验装置进行了建设性的优化。研究了乙醇与硅氧烷的二、三元组合物六甲基二硅氧烷（MM）和八甲基三硅氧烷（MDM）。后者在ORC过程以及高温热泵中表现出作为工质的有利特性。由于汽化焓显著增大，乙醇的加入可能使传递的热通量更高。

The aim of this project is to develop improved model approaches for the prediction of heat transfer during the evaporation and condensation of fluid mixtures. To this end, rapid test apparatuses were designed and set up in an ongoing project, with which mixture-specific parameters can be provided for the proposed calculation equations. In the applied follow-up project, the procedure is to be deepened by means of further fluid mixtures in the rapid test apparatuses and the model approaches are thus to be further developed. The rapid test apparatuses at both locations are based on the same experimental concept. The investigations on the boiling behavior of zeotropic mixtures are carried out at the Chair of Technical Thermodynamics and Transport Processes of the University of Bayreuth (Brüggemann working group), the investigations on the condensation behavior at the Institute of Thermodynamics of the Leibniz University of Hannover (Kabelac working group). Extensions of the model approaches from currently binary fluid mixtures to ternary mixtures are planned as well as constructive optimizations of the experimental apparatuses. Binary and ternary combinations of ethanol and the siloxanes hexamethyldisiloxane (MM) and octamethytrisiloxane (MDM) will be investigated. The latter exhibit advantageous properties as working fluids in ORC processes as well as in high temperature heat pumps. The addition of ethanol can potentially enable higher transferred heat fluxes due to the significantly larger enthalpy of vaporization.