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The effect of recuperator on the efficiency of ORC and TFC with very dry working fluid
Oct 8, 2021 - Oct 10, 2021DOI https://doi.org/10.1051/matecconf/202134500012
Country Czech Republic
Location Pilsen
Organic Rankine Cycles (ORC) and Trilateral Flash Cycles (TFC) are very similar power cycles; ideally, they have a reversible adiabatic (isentropic) compression, an isobaric heating, an isentropic expansion and an isobaric cooling. The main difference is that for ORC, the heating includes the full evaporation of the working fluid (prior expansion); therefore, the expansion starts in a saturated or dry vapour state, while for TFC, the heating terminates upon reaching the saturated liquid states. Therefore, for TFT, expansion liquid/vapour state (in bubbly liquid or in vapour dispersed with droplets), requiring a special two-phase expander. Being ORC a more “complete” cycle, one would expect that its thermodynamic efficiency is always higher than for a TFC, between the same temperatures and using the same working fluids. Surprisingly, it was shown that for very dry working fluids, the efficiency of TFC can exceed the efficiency of basic (i.e. recuperator- and superheater-free) ORC, choosing sufficiently high (but still subcritical) maximal cycle temperature. Therefore in these cases, TFC (having a simpler heat exchange unit for heating) can be a better choice than ORC. The presence of a recuperator can influence the situation; by recovering the proper percentage of the remaining heat (after the expansion), the efficiency of ORC can reach and even pass the efficiency of TFC.
Alkanes as natural working fluids for organic rankine cycles
Sep 8, 2020 - Sep 10, 2020DOI DOI: 10.1063/5.0041439
Country Czech Republic
Location Pilsen
The selection of working fluids for Organic Rankine Cycles is an essential part of ORC design, influencing the configuration, the power production and the economic viability. There are several materials with satisfying thermodynamic performances, but due to their environmental impacts, they are ruled out to be used due to international agreements. To have a long life-time ORC-installation, one should find working fluids which have a relatively low impact on Nature and can survive the permanently changing legislative environment. Saturated alkanes are good candidates for this purpose; therefore, a map showing the detailed working fluid classification for a large group of them has been prepared. Separate classes have different properties upon the expansion step of the ORC process. Using this map, one can estimate the applicability of other alkanes (not included to this map) to be used as working fluid. A similar estimate can be done for mixtures of near homologues; in this way, one can prepare practically infinite novel working fluids.
Efficiency improvement for solar cells panels by cooling
Dec 4, 2018 - Dec 6, 2018DOI 10.1109/ICETS.2018.8724625
Country Iraq
Location Kirkuk
The high temperatures make the efficiency of the solar panels decreases and lead to a decrease in production power. In this study the cell surface temperature was reduced to low rates to improve efficiency and increase power by cooling the surface of the solar panel with water through adding a tube to the surface of the panel and make holes in diameters of 2 mm and at different flow rates (3 L /h, 6 L /h and 9 L /h) then compare it with solar panel without cooling. observed that the efficiency for all panel is peak at (12:30 pm) also observed that the efficiency increases with cooling by water and the results show the efficiency is being high when low flow rate, the all results for solar panel without cooling, 3 liters/hour, 6liter/hour and 9 liters/hour respectively for efficiency average per day through the experiment is (12.63%), (13.54%),(13.23 %) and (13.06%), the rate of increase for efficiency in solar panels with comparison without cooling the results showed the efficiency increased of rate (6.71%) for flow rate 3 liters/hour, (4.51%) for 6 liters/hour flow and (3.28%) at flow rate 9 liters/hour.