@article{DubberkeLinnemannAbbasetal.2018, author = {Dubberke, Frithjof H. and Linnemann, Matthias and Abbas, Wameedh Khider and Baumh{\"o}gger, Elmar and Priebe, Klaus-Peter and Roedder, Maximilian and Neef, Matthias and Vrabec, Jadran}, title = {Experimental setup of a cascaded two-stage organic Rankine cycle}, series = {Applied Thermal Engineering}, volume = {131}, journal = {Applied Thermal Engineering}, publisher = {Elsevier}, doi = {10.1016/j.applthermaleng.2017.11.137}, pages = {958 -- 964}, year = {2018}, abstract = {In combination with a bottoming cycle, operated with a pure fluid in transcritical mode, the usage of a zeotropic mixture as a working fluid appears to be exergetically favorable for power cycle efficiency in cascaded two-stage organic Rankine cycles (CORC). A CORC is set up and initially tested with cyclopentane and propane as working fluids in its high temperature and low temperature cycle, respectively. A thermal oil cycle serves as the heat source and is powered electrically with a maximum heat flow of 158 kW. The design of this experimental setup allows for a rapid replacement of individual components and for a wide range of conditions in terms of fluids and thermodynamic states. The components of all cycles and the measurement and control technology are described in detail. A testing procedure is presented, followed by a discussion of the measurement results, where it is shown that the intended concept of two cascaded organic Rankine cycles is operational and that the measured data are consistent.}, language = {en} } @article{RoedderNeefLauxetal.2016, author = {Roedder, Maximilian and Neef, Matthias and Laux, Christoph and Priebe, Klaus-P.}, title = {Systematic Fluid Selection for Organic Rankine Cycles and Performance Analysis for a Combined High and Low Temperature Cycle}, series = {Journal of Engineering for Gas Turbines and Power}, volume = {138}, journal = {Journal of Engineering for Gas Turbines and Power}, number = {031701}, publisher = {ASME}, doi = {10.1115/1.4031361}, pages = {168}, year = {2016}, abstract = {The organic Rankine cycle (ORC) is an established thermodynamic process that converts waste heat to electric energy. Due to the wide range of organic working fluids available the fluid selection adds an additional degree-of-freedom to the early design phase of an ORC process. Despite thermodynamic aspects such as the temperature level of the heat source, other technical, economic, and safety aspects have to be considered. For the fluid selection process in this paper, 22 criteria were identified in six main categories while distinguishing between elimination (EC) and tolerance criteria (TC). For an ORC design, the suggested method follows a practical engineering approach and can be used as a structured way to limit the number of interesting working fluids before starting a detailed performance analysis of the most promising candidates. For the first time, the selection process is applied to a two-stage reference cycle, which uses the waste heat of a large reciprocating engine for cogeneration power plants. It consists of a high temperature (HT) and a low temperature (LT) cycle in which the condensation heat of the HT cycle provides the heat input of the LT cycle. After the fluid selection process, the detailed thermodynamic cycle design is carried out with a thermodynamic design tool that also includes a database for organic working fluids. The investigated ORC cycle shows a net thermal efficiency of about 17.4\% in the HT cycle with toluene as the working fluid and 6.2\% in LT cycle with isobutane as the working fluid. The electric efficiency of the cogeneration plant increases from 40.4\% to 46.97\% with the both stages of the two-stage ORC in operation.}, language = {en} }