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Optimized performances comparison of organic Rankine cycles for low grade waste heat recovery
Wang Enhua 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.8
An organic Rankine cycle (ORC) can be applied to recover the low-grade waste heat. In this paper, the performances of five different types of ORC are evaluated. These configurations include a simple ORC, an ORC with an internal heat exchanger (IHE), an ORC with an open feed organic fluid heater (OFOH), an ORC with a closed feed organic fluid heater (CFOH), and an ORC with a reheater. First,the feasible working region is defined for an ORC operating together with an internal combustion engine. Subsequently, the thermal efficiency of each ORC is maximized using a genetic algorithm. Finally, the characteristics of each ORC are analyzed and compared using a combination of the first law and second law method. Our analysis indicates that the ORC with an IHE showed the best thermodynamic performance. The ORC with an OFOH and the ORC with a CFOH are sub-optimal while the simple ORC and the ORC with a reheater are the last choice. The effects of the expander inlet pressure, the condenser outlet temperature and the expander isentropic efficiency on system performance of each ORC were also analyzed.
Shin, Woonsup,Zhu, Enhua,Nagarale, Rajaram Krishna,Kim, Chang Hwan,Lee, Jong Myung,Shin, Samuel Jaeho,Heller, Adam American Chemical Society 2011 ANALYTICAL CHEMISTRY - Vol.83 No.12
<P>When a current or a voltage is applied across the ceramic membrane of the nongassing Ag/Ag<SUB>2</SUB>O-SiO<SUB>2</SUB>-Ag/Ag<SUB>2</SUB>O pump, protons produced in the anodic reaction 2Ag(s) + H<SUB>2</SUB>O → Ag<SUB>2</SUB>O(s) + 2H<SUP>+</SUP> + 2e<SUP>–</SUP> are driven to the cathode, where they are consumed by the reaction Ag<SUB>2</SUB>O(s) + H<SUB>2</SUB>O + 2e<SUP>–</SUP> → 2Ag(s) + 2 OH<SUP>–</SUP>. The flow of water is induced by momentum transfer from the electric field-driven proton-sheet at the surface of the ceramic membrane. About 10<SUP>4</SUP> water molecules flowed per reacted electron. Because dissolved ions decrease the field at the membrane surface, the flow decreases upon increasing the ionic strength. For this reason Ag<SUP>+</SUP> ions introduced through the anodic reaction and by dissolution of Ag<SUB>2</SUB>O decrease the flow. Their accumulation is reduced by applying Nafion-films to the electrodes. The 20 μL min<SUP>–1</SUP> flow rate of 6 mm i.d. pumps with Nafion coated electrodes operate daily for 5 min at 1 V for 1 month, for 70 h when the pump is pulsed for 30 s every 30 min, and for 2 h when operating continuously.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2011/ancham.2011.83.issue-12/ac201118t/production/images/medium/ac-2011-01118t_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac201118t'>ACS Electronic Supporting Info</A></P>