1,721,081 research outputs found
A semi-empirical method for assessing the performance of an open-drive screw refrigeration compressor
No full text
Modelling the performance of a scroll expander for small organic Rankine cycles when changing the working fluid
Full text link
Proposal of a Profile Geometry Suitable for Claw Rotor Compressors
No full textClaw rotor compressors are rotary positive displacement machines with built-in compression. They are characterized by greater performance if compared to Roots blowers and are more efficient in discharging gas at pressures substantially higher than at suction. This paper aims at proposing a rotor profile suitable for the claw-type mechanism, with thorough indication of the profile geometry. After presenting some graphical cases of rotor profiles, drawn according to the proposed geometry, comparisons with a reference profile suggest that the proposed one seems to be preferable from a filling point of view
Improving the semi-empirical modelling of a single-screw expander for small organic Rankine cycles
Full text linkThe common semi-empirical modelling adopted for positive-displacement rotary expanders is revised in this paper. Paying particular attention to the leakage flow rates, the mechanical losses at the shaft and the ambient heat losses by the proposal of a more physically sound modelling, this paper aims at improving the performance simulation of a single-screw expander for which there exists a wide experimental campaign in literature. In detail, the mechanical losses are modelled with an approach consistent with the Stribeck's theory, whereas the contributions of both natural convection and radiation are taken into account for a proper modelling of the ambient heat losses. After calibration and validation of the modelling procedure, based on experimental data of the expander operation with R245fa, mean absolute percentage errors of 0.69%, 1.77% and 0.33% as regards mass flow rate, electric power output and exhaust fluid temperature, respectively, are calculated. These errors are lower than the ones reported by other researchers, so the current simulations are more consistent with the experimental data. Considering the higher reliability for a better performance simulation by the new modelling procedure, the model is finally used to study the behavior of the expander. In particular, attention is paid to the mass flow rate, the shaft and the electric power outputs, the expander efficiency, as well as the ambient heat losses, and to their relations with the operation parameters such as the degree of fluid superheat at the expander inlet, the fluid pressure at the expander inlet, the pressure ratio and the rotational speed
A geometric study of different curves for the rotor profiles of a twin-screw compressor
Full text linkThis paper presents the results of comparisons among some patented solutions for profiling the contours of the rotors in twin-screw compressors. Referring to a base case where all the generating curves are circumferences, patents suggesting to replace arcs of circumference with arcs of conic sections, i.e. parabola, ellipse and hyperbola, but even a straight line segment, are presented and guidelines for rotor profile construction are reported. After setting the size of the compressor, attention is paid to the inter-lobe area, as the sum of the area between two consecutive lobes in the male rotor and of the area of the groove in the female rotor. Actually, this area is strictly related to the volume displacement. Limited to the current case study, the profile including an elliptic segment seems to be the preferable solution for higher inter-lobe area, then for higher displacement, though a number of considerations should be necessary for a broader context
Sulla relazione fra il raggio della camma e l’alzata della paletta in una pompa a palette con rotore equilibrato
No full text
Investigations of an air-blown integrated gasification combined cycle fired with high-sulphur coal with post-combustion carbon capture by aqueous ammonia
Full text linkThis work deals with CO2 capture plants for an advanced air-blown gasification-based combined cycle where a coal with high sulphur content, which is really relevant for the coal market, is used as feedstock. The sulphur removed as H2S from the coal-derived gas enters a wet sulphuric acid process. Later, the resulting acid is used to control ammonia slip in a post-combustion CO2 capture plant based on ammonia scrubbing and designed for a reduced energy demand. Thus, limiting the energy impact of the CO2 capture technology will improve the power plant efficiency, according to a presumable lower cost of the generated electricity, as a high-sulphur coal is used as fuel input.In detail, a cooled ammonia-based process is found to be more attractive than a more conventional chilled ammonia-based solution: in case of 90% of CO2 avoided, the overall power plant efficiency is equal to 41.7% and the SPECCA (specific primary energy consumption for CO2 avoided) as low as 2.3MJ/kgCO2. Moreover, the calculation results show the SPECCA for CO2 avoided ranging from 80% to 90% is almost constant, even though the power plant efficiency increases if lower levels of CO2 capture are considered
- …
