349 research outputs found
Exercise testing and training in cystic fibrosis clinics in the United Kingdom: a 10-year update
No full textThis is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record
Perforation Test as an Accuracy Evaluation Tool for a Constitutive Model of Austenitic Steel
No full textW artykule zaprezentowano nową metodę oceny dokładności modelu konstytutywnego. Oparto ją na wynikach uzyskanych w próbie przebijania z użyciem młota opadowego. Wyznaczenie błędu zostało przeprowadzone na podstawie porównania prędkości penetratora zmierzonej w trakcie ekspery mentu i obliczonej na podstawie symulacji MES. W celu walidacji metody przeanalizowano wybrane równania konstytutywne: Johnsona-Cooka. Zerilli-Armstronga oraz rozszerzony model Rusinka-Klepaczko w odniesieniu do stali austenitycznej X4CrMnN 16-12. Badania właściwości mecha- nicznych stali zostały przeprowadzone w szerokim zakresie prędkości odkształcania z użyciem maszyny serwo-hydraulicznej oraz pręta Hopkinsona. Błąd względny wyznaczony jako różnica zmierzonej i obliczonej na podstawie równania konstytutywnego krzywej naprężenie-odkształcenie został ustalony jako wartość błędu referencyjnego (metoda klasyczna). Następnie porównano go z błędem względnym wyznaczonym na podstawie zmierzonego i obliczonego za pomocą MES chwilowego przebiegu prędkości penetratora (nowa metoda). Stwierdzono dobrą korelację pomiędzy klasyczną a nową metodą oceny dokładności modela W po- równaniu do klastycznej metody możliwa jest walidacja zależności konstytutywnej w szerokim zakresie prędkości odkształcania oraz temperatury w trakcie jednego testu
Steam flow effects on hydrolysis reaction kinetics in the Cu–Cl cycle
No full textIn this paper, the effects of an inert carrier gas and steam flow on the reaction kinetics of a CuCl2 hydrolysis reactor are examined for the thermochemical copper-chlorine (Cu–Cl) cycle of hydrogen production. Experimental data from two packed bed reactors, at three separate vapour pressures of H2O in the gaseous input stream, are investigated in terms of the transient conversion efficiencies and reaction kinetics. The results show that the transient reaction rate reduces by over 75% as the reaction progresses and physical resistances develop in the reactor. The effects of system temperature and reactant flowrate on the reaction rate are also investigated with experimental data. The results of this paper show that by reducing the steam density, the variability in reaction rate can be decreased. These results can be used to predict the reaction kinetics, allowing residence time and transport properties to be more effectively considered.Ontario Research Excellence Fund (ORF)Canada Research Chairs (CRC) programAtomic Energy of Canada Limited (AECL
Nitrogen carrier gas flow for reduced steam requirements of water splitting in a packed bed hydrolysis reactor
No full textThis paper presents new experimental data and modeling of a copper(II) chloride (CuCl2) hydrolysis reactor for thermochemical hydrogen production with the Cu–Cl cycle. A hydrated nitrogen stream reacts with CuCl2 particles at various temperatures between 365 °C and 400 °C to investigate the reaction extent of steam in the endothermic reactor. Thermal decomposition of the solid reactant is examined by monitoring the chlorine production in the gaseous effluent. The theoretical maximum steam conversion is calculated from the Gibbs reaction energy and compared with the experimental results via the reaction quotient. The results of this paper provide significant new data to achieve higher conversion efficiencies of steam in the Cu–Cl cycle than previously obtained in past experimental and predictive data.Ontario Research Excellence Fund(ORF)Canada Research Chairs (CRC) programAtomic Energy of Canada Limited (AECL
Solid particle decomposition and hydrolysis reaction kinetics in Cu–Cl thermochemical hydrogen production
No full textThis paper examines cupric chloride solid conversion during hydrolysis in the thermochemical copper-chlorine (Cu–Cl) cycle of hydrogen production. The hydrolysis reaction is a challenging step, due to the excess steam requirement and decomposition of cupric chloride (CuCl2) into cuprous chloride (CuCl) and chlorine (Cl2). In this paper, the hydrolysis and decomposition reactions are analyzed with respect to chemical equilibrium conversion and the reaction kinetics. The effects of operating parameters are examined, including the temperature, pressure and excess steam, on equilibrium conversion. It is shown that the reaction kinetics expression that represents a reversible reaction reflects the equilibrium limitation on the solid conversion, rather than first-order kinetics.Atomic Energy of Canada LimitedOntario Research Excellence Fun
Equilibrium conversion in Cu–Cl cycle multiphase processes of hydrogen production
No full textThis paper performs a thermodynamic equilibrium analysis of individual steps within the copper–chlorine (Cu–Cl) thermochemical cycle of hydrogen production. The cycle has a maximum temperature of 550 °C and it involves four reaction steps – producing hydrogen, copper, hydrogen chloride and oxygen – and a cupric chloride drying step. In this paper, the chemical reaction steps of the cycle are analyzed to determine the effects of process variables on chemical equilibrium conversion. It is found that the hydrogen production reaction can occur as a two-phase gas–solid system, rather than three phases. The optimal conditions for hydrogen production occur at a temperature below 400 °C, at atmospheric pressure. The study also found that the ideal condition to minimize excess steam, and completely consume any chlorine formed during the reaction, is a temperature of 400 °C, at atmospheric pressure. The operating conditions for complete consumption of chlorine were identified by the equilibrium partial pressure of chlorine formed, during decomposition of cupric chloride solid (CuCl2), and the equilibrium partial pressure of chlorine from the reverse chlorine consumption reaction. Furthermore, the ideal condition for the copper oxychloride decomposition reaction is a temperature around 500 °C, atmospheric pressure, which minimizes cuprous chloride (CuCl) vaporization.Atomic Energy of Canada LimitedOntario Research Excellence Fun
Comparison of sulfur–iodine and copper–chlorine thermochemical hydrogen production cycles
No full textSulfur–iodine and copper–chlorine water splitting cycles are promising methods of thermochemical hydrogen production. In this paper, these two cycles are compared from the perspectives of heat quantity, heat grade, thermal efficiency, related engineering challenges, and hydrogen production cost. The heat quantity and grade required by each step of the cycles are evaluated and the thermal efficiencies are approximated from the heat requirements. It is found that the overall heat requirements of the two cycles do not have significant differences and the overall efficiencies of the two cycles are similar, between 37 and 54%, depending on the portion of heat recovery. The copper–chlorine cycle has the advantage of a lower maximum temperature of 803 K, which is 300 K lower than the maximum temperature of 1123 K in the sulfur–iodine cycle. This indicates that the copper–chlorine cycle can link more readily with various heat sources, such as grade Generation IV nuclear and fossil fuel power stations. It is also reported that the copper–chlorine cycle can have fewer challenges of equipment materials and product separation. A cost analysis shows that the copper–chlorine and sulfur–iodine cycles have similar hydrogen production costs, which are lower than steam-methane reforming, and conventional and high temperature electrolysis, due to less use of electricity, no carbon related charges and no methane requirement in the thermochemical cycles.Atomic Energy of Canada LimitedOntario Research Fun
Comparison of different copper–chlorine thermochemical cycles for hydrogen production
No full textCopper–chlorine thermochemical cycles for hydrogen production are very promising water splitting cycles. In this paper, different types of copper–chlorine cycles with various numbers of steps are compared. The factors that determine the number and effective grouping of steps are analyzed. It is found that the water requirement in the hydrolysis step is affected by a combination of drying and hydrolysis steps. It is also found that hydrogen can be produced either from electrolysis of cuprous chloride, or from chlorination of copper by hydrogen chloride, which indicates a potential combination of disproportionation and chlorination steps. The major engineering advantages and disadvantages of these cycle variations with different amounts of steps will be analyzed and discussed.Atomic Energy of Canada LimitedOntario Research Excellence Fun
Effects of atomization conditions and flow rates on spray drying for cupric chloride particle formation
No full textThis paper examines the effects of different operating variables on cupric chloride (CuCl2) powder formation in a copper-chlorine (Cu–Cl) thermochemical cycle of hydrogen production. Experiments have been performed in two different spray drying units to identify the effects of the main operating variables on the cupric chloride powder quality. The experiments also examine the formation of powders using low temperature heat available from nuclear, solar and other industrial sources to remove moisture from solutions. The atomization liquid flow rate, atomization pressure and drying air inlet temperature are identified as independent variables. The moisture content, bulk density, particle size distribution and morphology are the dependent variables representing the powder quality. Experimental data have been analyzed for cohesive force and free flow characterization of powders using the Hausner ratio.Atomic Energy of Canada LimitedOntario Research Fun
Periodic Boundary Value Problems for Second Order Impulsive Integrodifferential Equations of Mixed Type in Banach Spaces
No full textAbstractIn this paper, the author obtains an existence theorem of minimal and maximal solutions for the periodic boundary value problems of second order impulsive integrodifferential equations of mixed type in Banach space by means of the monotone iterative technique and cone theory based on a comparison result
- …
