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Modeling and optimization of an organic Rankine cycle
2002 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

A waste heat recovery system that is under development at United Technologies Research Center (USA), is utilizing the waste heat in the exhaust stream from a gas turbine. This system uses an organic Rankine cycle (ORC). The gas turbine is designed for power generation and produces 400 kW of electrical power. Connecting the ORC to the system it is expected to produce a further 80 kW. The ORC has been modeled in Matlab to help predict the behavior of the system under different running conditions. Two steady state models for the ORC have been developed: a design point model and an off design model. The design point model was used to investigate the effect on performance of component parameters such as isentropic efficiency of the pump and turbine as well as pressure ratios over the various components. The off design model was used to determine the effects on the cycle of changes to parameters concerning the surrounding such as ambient temperature. Optimization of the cycle was carried out, using the off design model to find a set of controllable parameters that would give the highest net power. The sensitivity studies using the design point model showed that turbine efficiency is of major importance for the overall performance of the ORC. It was also found from the sensitivity studies of the off design model that a change in the ambient temperature has a major effect on the net power output. On a warm day less energy is available in the exhaust gases and the net power decreases. The optimization of the ORC has shown that the highest net power is achieved at an optimum level of superheat coming out from the evaporator for a given superheat going into the condenser.

Place, publisher, year, edition, pages
Keyword [en]
Technology, modeling, Rankine cycle, power systems
Keyword [sv]
URN: urn:nbn:se:ltu:diva-56338ISRN: LTU-EX--02/025--SELocal ID: d1e5101e-1a3d-4268-8650-b34b40a89e71OAI: diva2:1029725
Subject / course
Student thesis, at least 30 credits
Educational program
Mechanical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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