Thermal stability of n -pentane, cyclo-pentane and toluene as working fluids in organic Rankine engines

Invernizzi, Costante Mario; Iora, Paolo; Manzolini, Giampaolo; Lasala, Silvia

doi:10.1016/j.applthermaleng.2017.04.038

Cited by 50 publications

(26 citation statements)

References 19 publications

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“…Finally, a crucial parameter for the choice of a working fluid is its thermal stability. About the hydrocarbons here considered, it seems reasonable to assume a safe operative maximum temperature of 250 • C to 280 • C [39][40][41][42], according to the fixed approach temperature difference of 50 • C in the heat exchanger HT 1 .…”

Section: The Selection Of the Working Fluidsmentioning

confidence: 99%

Pure and Hydrocarbon Binary Mixtures as Possible Alternatives Working Fluids to the Usual Organic Rankine Cycles Biomass Conversion Systems

et al. 2019

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This study investigates the use of pure and hydrocarbons binary mixtures as potential alternatives working fluids in a usual biomass powered organic Rankine cycle (ORC). A typical biomass combined heat and power plant installed in Cremona (Italy) is considered as the benchmark. Eight pure hydrocarbons (linear and cyclic) and four binary mixtures of linear hydrocarbons were selected. The critical points of the binary mixtures at different composition were calculated using an in-house code developed in MATLAB© (R2018b) environment. Based on the critical point of a working fluid, supercritical and subcritical cycle configurations of ORC were analysed. A detailed thermodynamic comparison with benchmark cycle was carried out in view of cycle efficiency, maximum operating pressure, size of the turbine and heat exchangers. The supercritical cycles showed 0.02 to 0.03 points lower efficiency, whereas, subcritical cycles showed comparable efficiencies than that of the benchmark cycle. The cycles operating with hydrocarbons (pure and mixtures) exhibited considerably lower volume flow ratios in turbine which indicates lower turbine size. Also, size parameter of regenerator is comparatively lower due to the lower molecular complexity of the hydrocarbons. A noticeable increase in turbine power output was observed with change in composition of the iso-octane/n-octane binary mixture at the same thermodynamic efficiency.

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Section: The Selection Of the Working Fluidsmentioning

confidence: 99%

Pure and Hydrocarbon Binary Mixtures as Possible Alternatives Working Fluids to the Usual Organic Rankine Cycles Biomass Conversion Systems

et al. 2019

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“…The thermal stability test method, as discussed in [55][56][57], compare the vapour pressure of the fluid before and after the thermal stress test. The test circuit, in stainless steel AISI 316, consists of a sample cylinder, one thermocouple (type K), two pressure transmitters that cover a wide range of pressure from 1 to 100 bar and some block valves to charge and isolate the investigated fluid.…”

Section: Thermal Stabilitymentioning

confidence: 99%

“…The measured values of the vapour pressure P v for the virgin fluid were fitted by Equation (2), whose coefficients A and B are reported respectively in Figures 11a and 12a. Figure 13 reports the quasi-constant of the velocity reaction k*, which is a parameter correlated to the number of decomposed moles [56], as a function of the reciprocal of the stress temperature for the fluids 2,2,2-trifluoroethanol and n-butanol. For a fixed decomposition rate k * = 1•10 −9 s −1 , the corresponding temperatures are about 300 • C and 250 • C for the first and the second fluid respectively.…”

Section: Thermal Stabilitymentioning

confidence: 99%

Water Mixtures as Working Fluids in Organic Rankine Cycles

et al. 2019

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This work explores the possibility to adopt in organic Rankine cycle (ORC) plants mixtures of water (acting as solvent) plus an organic compound (acting as solute) as the working fluid. Initially an evaluation of the thermodynamic properties of the mixtures is performed, in order to assess their properties, and to point out the molar fractions which entail a near-azeotropic behaviour. Four species from three different classes of chemical compounds are investigated: 2,2,2-trifluoroethanol and n-butanol for alcohols, where the first is fluorinated, acetonitrile for nitrile class and 2-methylpyrazine as a heterocyclic aromatic compound. Simultaneously, the thermal stability of the pure substances considered as the possible solute for the mixtures is experimentally investigated in order to estimate the temperature applicability range. The ORC plant performance, from a low-enthalpy geothermal heat source (hot water stream from 100 to 200 °C), adopting the selected mixtures as the working fluid is finally evaluated, and the analysis includes a preliminary discussion on the turbine design; results are compared with respect to the reference case of a hypothetical plant adopting water as the working fluid.

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“…However, they must be used below the decomposition temperatures to ensure system safety. Similarly, Invernizzi et al [76] investigated the thermal stability of three representative hydrocarbons used as working fluids in organic Rankine cycles (ORC): n-pentane, cyclo-pentane, and toluene, using vapour pressure as an indicator. The results showed that cyclo-pentane was very stable at 350 • C after eight hours with a decomposition rate twenty times lower than the corresponding value for n-putane.…”

Section: Working Fluids In Orcmentioning

confidence: 99%

Expander Technologies for Automotive Engine Organic Rankine Cycle Applications

Alshammari

Karvountzis-Kontakiotis

Pesyridis

et al. 2018

Energies

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The strive towards ever increasing automotive engine efficiencies for both diesel and gasoline engines has in recent years been forced by ever-stringent emissions regulations, as well as the introduction of fuel consumption regulations. The untapped availability of waste heat in the internal combustion engine (ICE) exhaust and coolant systems has become a very attractive focus of research attention by industry and academia alike. Even state of the art diesel engines operating at their optimum lose approximately 50% of their fuel energy in the form of heat. As a result, waste heat recovery (WHR) systems have gained popularity as they can deliver a reduction in fuel consumption and associated CO2 emissions. Of these, the Organic Rankine Cycle (ORC) is a well matured waste heat recovery technology that can be applied in vehicle powertrains, mainly due to the low additional exhaust backpressure on the engine and the potential opportunity to utilize various engine waste heat sources. ORCs have attracted high interest again recently but without commercial exploitation as of today due to the significant on-cost they represent to the engine and vehicle. In ORCs, expansion machines are the interface where useable power production takes place; therefore, selection of the expander technology is directly related to the thermal efficiency of the system. Moreover, the cost of the expander-generator units accounts for the largest proportion of the total cost. Therefore, selection of the most appropriate expander is of great importance at the early stage of any automotive powertrain project. This study aims to review the relevant research studies for expansion machines in ORC-ICE applications, analyzing the effects of specific speed on expander selection, exploring the operational characteristics of each expander to further assist in the selection of the most appropriate expander, and comparing the costs of various expanders based on publically available data and correlations.

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Thermal stability of n -pentane, cyclo-pentane and toluene as working fluids in organic Rankine engines

Cited by 50 publications

References 19 publications

Pure and Hydrocarbon Binary Mixtures as Possible Alternatives Working Fluids to the Usual Organic Rankine Cycles Biomass Conversion Systems

Pure and Hydrocarbon Binary Mixtures as Possible Alternatives Working Fluids to the Usual Organic Rankine Cycles Biomass Conversion Systems

Water Mixtures as Working Fluids in Organic Rankine Cycles

Expander Technologies for Automotive Engine Organic Rankine Cycle Applications

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