Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
Evaluation of potential fluids for low temperature Organic Rankine cycle
Submission Author:
Juliana Silva Brasil , CE
Co-Authors:
Juliana Silva Brasil, RICHARDSON LEANDRO NUNES, Thalles Coimbra Borba Roldão , Luben Cabezas Gómez, Cristiano Tibiriçá
Presenter: Juliana Silva Brasil
doi://10.26678/ABCM.ENCIT2022.CIT22-0478
Abstract
Organic Rankine cycle (ORC) is a potentially viable technology to recover energy of low-grade heat sources, which implies greater energy efficiency as well as a reduction in the use of fossil fuels, which are harmful to the environment. Reused heat can come either from traditional sources, such as industrial waste heat or from alternative sources (solar, geothermal). Understanding the operation of this cycle for different fluids, under given conditions, is useful to assess its suitability and indicate the most favorable operating conditions. This research evaluates the thermal efficiency of the saturated organic Rankine cycle (ORC), for 25 fluids, comparing a numerically solved equation model with an analytical model. Considering evaporation temperatures varying between 80°C and 100°C, the relative error of the cycle efficiency obtained in each of the two approaches was calculated. It was observed that toluene, cyclohexane, benzene, R600a, R141b, R123, R11 and R1233zd(E) have the highest efficiency values ranging between 0.1222 and 0.1132. It should be noted, however that R11 is a chlorofluorocarbon and its use should be avoided, as agreed in the Montreal Protocol, as well as the hydrochlorofluorocarbon fluid R141b which, despite having a relatively small ODP (Ozone Depletion Potential), has a high GWP (Global Warming Potential). R123, even with low ODP and GWP, is also a hydrochlorofluorocarbon. Toluene, cyclohexane and benzene are fluids with high flammability and toxicity. R1233zd(E), a non-flammable replacement for R123, has low GWP and zero ODP but still with high cost. R600a, a natural fluid, has low GWP and zero ODP, despite its flammability, it is a fluid of interest today due to growing concerns about climate changes, as R290, propane. Other fluids of considerable efficiency but expensive are R245fa (0.1130), R1234ze(E) (0.1106), R236fa (0.1085). R245fa, R236fa and R134a stand out for their high GWP while R1234ze(E) has low GWP and zero ODP but still with high cost. Fluids R290, R1234yf and R22 (chlorofluorocarbon) have the lowest critical temperatures, of 96.6°C, 94.7°C and 96.1°C, respectively, thus requiring attention to the working temperature range considered.
Keywords
Organic Rankine Cycle, . Low-grade thermal waste recovery, working fluids
