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Power Production from Low Temperature Heat Sources
Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, Department of Energy and Process Engineering.
2010 (English)MasteroppgaveStudent thesis
Abstract [en]

Summary This Master Thesis is a conclusion on work done as part of the Resource Optimization and recovery in the Materials industry project (Roma). This project is involved in the development of a new technology for power production from low temperature heat sources for off gases from aluminum production cells. The technology is based on an transcritical Rankine cycle with CO2 as a working fluid, as the work recovery circuit. The center of the test facility is the expander, a prototype provided by Obrist Engineering . 81 tests were perfomed to investigate the behavoir of the expander cycle. Effect of three main parameters were investigated: • Effect CO2 massflow rate • Effect of heat source temperature • Effect of CO2 condensation pressure For each parameter combination, the high pressure side of the expander cycle was varied in order to find the maximum power output. This study clearly showed limitation of the turbine which cannot maintain large pressure difference probably due to large internal leakages. As a result, turbine outlet is highly superheated. This superheat is lost energy for the power cycle, and is simply dumped into the heat sink. One possible improvement would be to include a recuperator that recovers superheat after the pump. The results also indicate that the fan of the air loop is too small: increasing the CO2 flow rate to limit superheat at turbine outlet leads to turbine inlet temperature reduction. Last, for large CO2 mass flow rate (3.5 kg min) which is required for proper operation of the turbine, the power generated is too large for the generator installed on the loop. Its temperature reached 120 °C for some conditions. A new solution should be seeked. Based on experimental results, a mode of the power cycle was implemented in Pro/II and simulations were run in order to find an improved design. The main goal is to be able to run the cycle at high CO2 mass flow rate: 3.5 kg min. It was found that the air loop fan should be able to deliver up to 1 260 m3 h . The new generator or braking system should be able to absorb up to 297 W.

Place, publisher, year, edition, pages
Institutt for energi- og prosessteknikk , 2010. , 118 p.
Keyword [no]
ntnudaim:5855, MTENERG energi og miljø, Varme- og energiprosesser
URN: urn:nbn:no:ntnu:diva-18330Local ID: ntnudaim:5855OAI: diva2:565825
Available from: 2012-11-08 Created: 2012-11-08

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