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Abstract Timed injection of coolant during the onset of the compression stroke in a reciprocating compressor aimed at achieving quasi-isobaric conditions during the initial part of the compression stroke was investigated as a means of improving compressor efficiency. It is found that an isobaric cooling process followed by an isothermal compression process requires less energy than an isothermal compression process for the same boundary conditions. Achieving isobaric cooling in a real reciprocating compressor would require sudden and significant cooling during the onset of compression. A simplified process model of a real reciprocating compressor was created. It modelled the timed cooling process as a polytropic process with reduced polytropic index. An experimental compressor, equipped with a coolant injection system, was constructed. Dry baseline tests and tests with continuous and timed coolant injection were conducted. It was found that timed injection during the onset of compression, while also keeping the suction valve closed to prevent additional suction air inflow, yields an additional compression work-saving advantage over continuous coolant injection for the same set of boundary conditions. The simplified process model and numerical simulation were validated against the experimental results and were found to agree well with the experimental results.

Abstract To optimize costs and ensure safety, investigation and modeling of battery aging is very important. Calendar aging analysis consist of a periodic sequence of calendar aging and cell characterization. The influence of the characterization on the results of the calendar aging investigation has been assumed to be negligible so far. Nevertheless, the characterization measurements of different studies, especially the important capacity measurement, differ fundamentally. This could have an impact on the results of capacity and resistance change in calendar aging. In this paper, the effect of characterization is quantified for the first time, using periodic characterization measurements. A significant influence in the form of capacity increase and resistance decrease is found. It can be explained by an increase in the active electrode surface area caused by the characterization measurement. Therefore, the cell characterization is a new possible source for capacity increase in calendar aging. As an important result, in future studies capacity measurements should be performed with small currents below 1C to reduce the influence of characterization on the results. Additionally, a correction of the characterization effect can be done according to the presented method.

For many non-renewable resources, reliable production data are only available from a certain point in time but not from the beginning of production periods. In order to constrain the unknown historic production of such resources for those ancient times for which no reliable annual production data are available we present a novel mathematical technique, based on Verhulst’s logistic function. The method is validated by the United States’ crude oil production for which the complete production cycle, starting in 1859, is well documented. Assuming that the oil production in the USA between 1859 and 1929 is unknown, our method yields values for this period of 16.0 gigabarrels (Gb) based on a second-order polynomial fit and 13.5 Gb based on a third-order polynomial fit of post-1929 production data, respectively. Especially the latter amount compares well with the actual value of 12.1 Gb, thus illustrating the strength of the method. For global gold (Au) production, our method yields an ancient production up to the year 1850, when official and reliable production statistics began, of approximately 10,000 metric tons (t) based on a second-order polynomial fit. For mercury (Hg) a production of 64,000 t was determined for the time up to the year 1900, when annual production figures started to become available, again using a second-order polynomial fit. While the results obtained by the application of second-order polynomial functions could be confirmed by higher-order polynomial functions in the cases of both USA oil as well as global Au production, this was not possible in the case of global Hg production because of a highly irregular production curve.

South Africa generates most of its energy requirements from coal, and is now the leading carbon emitter in Africa, and has one of the highest rates of emissions of all nations in the world. In an attempt to decrease its CO 2 emissions, South Africa continues to research and develop alternative forms of energy, expand on the development of nuclear and has began to explore potentially vast shale gas reserves. In this mix, geothermal has not been considered to date as an alternative energy source. This omission appears to stem largely from the popular belief that South Africa is tectonically too stable. In this study, we investigated low-enthalpy geothermal energy from one of a number of anomalously elevated heat flow regions in South Africa. Here, we consider a 75-MW enhanced geothermal systems plant in the Limpopo Province, sustainable over a 30-year period. All parameters were inculcated within a levelised cost of electricity model that calculates the single unit cost of electricity and tests its viability and potential impact toward South Africa’s future energy security and CO 2 reduction. The cost of electricity produced is estimated at 14 USc/KWh, almost double that of coal-generated energy. However, a USD25/MWh renewable energy tax incentive has the potential of making enhanced geothermal systems comparable with other renewable energy sources. It also has the potential of CO 2 mitigation by up to 1.5 gCO 2 /KWh. Considering the aggressive nature of the global climate change combat and South Africa’s need for a larger renewable energy base, low-enthalpy geothermal energy could potentially form another energy option in South Africa’s alternative energy basket.

Abstract India’s ever increasing population has made it necessary to develop alternative modes of transportation with electric vehicles being the most preferred option. The major obstacle is the deteriorating impact on the utility distribution system brought about by improper setup of these charging stations. This paper deals with the optimal planning (siting and sizing) of charging station infrastructure in the city of Allahabad, India. This city is one of the upcoming smart cities, where electric vehicle transportation pilot project is going on under Government of India initiative. In this context, a hybrid algorithm based on genetic algorithm and improved version of conventional particle swarm optimization is utilized for finding optimal placement of charging station in the Allahabad distribution system. The particle swarm optimization algorithm re-optimizes the received sub-optimal solution (site and the size of the station) which leads to an improvement in the algorithm functionality and enhances quality of solution. The genetic algorithm and improved version of conventional particle swarm optimization algorithm will also be compared with a conventional genetic algorithm and particle swarm optimization. Through simulation studies on a real time system of Allahabad city, the superior performance of the aforementioned technique with respect to genetic algorithm and particle swarm optimization in terms of improvement in voltage profile and quality.

Abstract Owing to the challenges associated with the application of synthetic/non-modified Botryococcus Braunii Microalgae Biodiesel (BBMB), its poor performance in CI engines has resulted in increased tendencies for non-commercialization of its fuel. The properties of a synthetic BBMB were controlled by acetylene addition. In this study, acetylene was induced with air at mass flow rates of 100, 150, 200 and 300 g/hr in order to monitor the combustion, emission and performance behaviour of a 4-stroke (Kirloskar AV1), 5.2 kW diesel engine with enhanced injection timing, in which the algal biodiesel was introduced as its main fuel. The obtained results compared favourably with those of a conventional dual-fuel CI engine in terms of combustion, emissions and performance. The brake thermal efficiency (BTE) of the acetylated biodiesel improved by 3, 4, 3.6 and 5% due to acetylene addition. NOx emissions were higher for the acetylated-biodiesel, whereas, the release of CO2, HC, and CO were seen to decrease due to the addition of acetylene. Based on the results, the performance, combustion and gaseous emissions of the biodiesel obtained from Botryococcus braunii improved as a result of adding acetylene thus making it a suitable replacement for the conventional diesel fuel used in CI engines.

Abstract The presented derivative thermogravimetric and mass spectral data, obtained simultaneously for the pyrolysis of three different tyre rubbers, corroborate the assumption that the devolatilisation of a tyre rubber proceeds via two consecutive zones of weight loss and that these zones are characterised by different products and thus different reactions. The spectral data of the depolymerisation products moreover confirm that depolymerisation occurs exclusively (in case of polyisoprene rubber) or predominantly (in case of the polybutadiene rubbers) during primary devolatilisation.

Theoretical and experimental aspects of the project were conducted to investigate the effect of the mixing of a swirling steam jet into cross-flowing water. It was observed that based on the theoretical adiabatic estimations for the equilibrium temperature of steam–water mixing and by varying Psteam = 1–3 bar, Pwater = 1 bar and RPM = 60–300 around 97% (experimentally compared to the area it has at initial condition) and 85% (CFD study compared to the area it has at initial condition), an increase in the area under the influence of perfect adiabatic mixing was found. A virtual cover over the steam duct was seen. The area of this virtual cover based on the void fraction of swirling steam had a weak relationship with the total area of the region, inhibiting the perfect mixing for which an analytical relationship had been developed. The effect of mixing on the stability of swirling steam–water cross-flows was overall more than twice that of the effect on the area under the influence of the stability profile protrusions. Thus, an overall rise in inlet pressure contributed to improper mixing, whereas a rise in the RPM contributed to proper mixing inside a fixed window of observations. The effect of spatial scaling of a swirling steam trajectory on mixing in cross-flowing water was also investigated across the vertical plane. Also, the scaling of the vertical trajectories of the swirling steam jets under all operating conditions resulted in merging the regions of perfect mixing to some extent. Thus, the area under the influence of perfect mixing was reduced to around 3–4.7% under all operating conditions with scaling. This type of scaling has enormous potential for the characterization of larger fluid domains in environmental and process engineering studies.