Dynamic Simulation and Control Design for Small Scale Waste Heat Organic Rankine Cycle Plants

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dc.contributor.advisor Yu, W en
dc.contributor.advisor Young, B en
dc.contributor.author Lie, Matthew en
dc.date.accessioned 2017-08-04T04:11:22Z en
dc.date.issued 2017 en
dc.identifier.uri http://hdl.handle.net/2292/34818 en
dc.description Full text is available to authenticated members of The University of Auckland only. en
dc.description.abstract The Organic Rankine Cycle (ORC) is a thermodynamic process capable of utilising low temperature heat sources such as geothermal reservoirs and industrial waste heat. For an ORC system to be effectively controlled and operated, it is important to develop an understanding of the dynamic behaviour of the system and its components. This thesis investigates the use of dynamic simulation models as tools for plant and control design. Dynamic simulation models of a 75 kW waste heat ORC plant were built using VMGSim, a process flowsheet simulator. From these models, a control strategy using PID controllers was designed to maintain safe operation of the plant by regulating the expander inlet pressure and degree of superheat in the working fluid vapour. The set point tracking and disturbance rejection ability of the proposed control system was examined. Dynamic testing revealed that the superheat response exhibited some non-linear behaviour that can be linked to the vapouriser. Examining the response of the plant under cooling air disturbances showed significant variations in plant performance. Alterations to plant operation are suggested to compensate for different cooling air temperatures across the year to achieve consistent plant performance. Finally, by introducing decreases in exhaust gas flow rate to varying levels and monitoring the response of the process variables, the point at which the plant was taken out of the range of operation of the control system was found. The proposed control system was shown to be sufficient in keeping the plant within safe operating bounds under process disturbances that occur during day-to-day operation. The suggested alterations to plant operation to account for changing cooling air temperatures in different seasons were successful in maintaining consistent plant performance. The simulation of a process disturbance occurring outside the normal operating bounds of the plant shown in this thesis can be used to quantify the probability and consequence of such events for use in safety analyses. It was thus demonstrated that simulation tools can be effectively used to develop understanding of dynamic behaviour as well as aiding the plant and control design process. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof Masters Thesis - University of Auckland en
dc.relation.isreferencedby UoA99264933512102091 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. en
dc.rights Restricted Item. Available to authenticated members of The University of Auckland. en
dc.rights http://creativecommons.org/licenses/by-nc-sa/3.0/nz/ en
dc.rights.uri https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm en
dc.title Dynamic Simulation and Control Design for Small Scale Waste Heat Organic Rankine Cycle Plants en
dc.type Thesis en
thesis.degree.discipline Chemical and Materials Engineering en
thesis.degree.grantor The University of Auckland en
thesis.degree.level Masters en
dc.rights.holder Copyright: The author en
pubs.elements-id 644594 en
pubs.record-created-at-source-date 2017-08-04 en

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