1,720,998 research outputs found
Reliability analysis for preliminary forecasts of hydrogeological unit productivity
Full text linkThe aim of this work is to find a probabilistic characterization of the productive capacity of a well in a geological formation hosting an aquifer. Such characterization in terms of productive capacity may allow a preliminary assessment to be made of the probability of success for a required productivity (i.e. target point). This evaluation is usually carried out by statistical analysis of a geological dataset, which is likely to be influenced by many parameters. Such datasets are often incomplete or unreliable. Therefore, a method for evaluating potential productivity, using probabilistic hydraulic conductivity data, is proposed. The hydraulic characterization of hydrogeologic units is based on the collection of information obtained mainly through pumping tests and their interpretation. The results, expressed in terms of hydraulic conductivity, are summarized in a range of variability that is strictly dependent on the number of performed tests and their spatial distribution in the unit itself. If this range is known, an estimate of well’s yield can be made on a deterministic basis, through Thiem’s relationship for steady state conditions, by setting a value of hydraulic conductivity that corresponds to the average value of the range. The proposed reliability analysis enables to overcome the limitations of the deterministic approach by correlating each calculated flow rate, which is taken to be a design flow rate exceeding the critical flow rate of the hydrogeologic unit, to its probability of failure. Therefore, this approach aims to evaluate the probability of failure of the water system. The preliminary result is to associate the values of aquifer exploitation with a probability failure function. This outcome can then be used to define the potential solutions in the optimal allocation of the withdrawal by means of reliability analysis that takes into account the uncertainty of the system
A comprehensive exergy evaluation of a deep borehole heat exchanger coupled with a ORC plant. The case study of Campi Flegrei
No full textThe paper presents a comprehensive energy and exergy analysis of a possible geothermal power plant located in the geothermal district of Campi Flegrei (Italy), made of a coaxial WellBore Heat eXchanger coupled to an Organic Rankine Cycle. We have accounted for all system components: the ground source, the WellBore Heat eXchanger, the Organic Rankine Cycle cycle, and cooling system. The energy and exergy performance indexes of each subsystems and overall system have been evaluated, thus calculating the net power, the First-Law efficiency, the Second-Law efficiency, the irreversibilities. The results indicate a good potential of the WellBore Heat eXchanger – Organic Rankine Cycle technology in the area, as the estimated performances have similar values to those of classical binary geothermal power plants: a First-Law efficiency of 11.67% and a Second-Law efficiency of about 43.80%. The overall system performances decrease respectively to 10.62% due to the fans energy requirements in the cooling tower and to 23.15% due to the large exergy destruction occurring in the WellBore Heat eXchanger. A deep exergy analysis of the WellBore Heat eXchanger has highlighted that the overall irreversibility is strongly affected by the insulation performance between the two coaxial pipes and by the temperature deviation between the ground and the fluid. The latter one is mainly due to the continuous heat extraction from the geothermal source, therefore proposed improvement strategies consist of both the increasing of thermal resistance of the material insulating the upward pipe and the reduction of the equivalent thermal radius of the well optimizing the heat extraction profiles over the plant lifetime
Multiphase Flow Metering
No full textOver the last two decades the development, evaluation and use of MFM systems has been a major focus for the Oil & Gas industry worldwide. Since the early 1990's, when the first commercial meters started to appear, there have been around 2,000 field applications of MFM for field allocation, production optimisation and well testing. So far, many alternative metering systems have been developed, but none of them can be referred to as generally applicable or universally accurate. Both established and novel technologies suitable to measure the flow rates of gas, oil and water in a three-phase flow are reviewed and assessed within this book. Those technologies already implemented in the various commercial meters are evaluated in terms of operational and economical advantages or shortcomings from an operator point of view. The lessons learned about the practical reliability, accuracy and use of the available technology is discussed. The book suggests where the research to develop the next generation of MFM devices will be focused in order to meet the as yet unsolved problems. The book provides a critical and independent review of the current status and future trends of MFM, supported by the authors' strong background on multiphase flow and by practical examples. These are based on the authors' direct experience on MFM, gained over many years of research in connection with both operators and service companies
Looking forward to a decarbonized era. Geothermal potential assessment for oil & gas fields in Italy
No full textThe target of this work is to produce a vision of the geothermal potential stored in the depleted oil & gas fields in Italy, by using the available information provided by the Ministry of Economic Development, the published data on hydrocarbon fields, and the estimated temperature at depth from the Italian National Geothermal Database. Five most promising fields have been selected and the volume method has been applied to assess their geothermal potential. Then a probabilistic approach has been adopted to obtain not a single value but a distribution of values of the technical potential TP. The results indicate that the available heat in hydrocarbons fields is encouraging and it is fundamental to analyze the production capacities of the existing wells to have a clearer idea of the possible uses of this existing and wasted heat
Producing geothermal energy with a deep borehole heat exchanger. Exergy optimization of different applications and preliminary design criteria
Full text linkThis paper aims at proposing fast and plain design tools to evaluate the best energy application for deep borehole heat exchangers, exploiting geothermal resources. Exergy efficiency has been chosen as a performance index. Five possible utilization solutions have been analyzed: district heating, adsorption cooling, ORC power production, a thermal cascade system, and combined heat and power configuration. An extensive sensitivity analysis on source characteristics and well geometry has been performed to find the design criteria that ensure the maximum exergy performance. Results show that configurations involving district heating are recommended for exclusive power production. If optimized, district heating exergy efficiency can reach values in the range 40%–50% when a geothermal source at the well bottom is lower than 300 °C. For higher values, the combined heat and power production is a preferable choice, reaching an exergy efficiency of up to 60%. Design charts are also provided to read first-attempt values of the well operative temperatures and flow rate to maximize exergy efficiency for each utilization layouts
MULTIPHASE FLOW FUNDAMENTALS
No full textDescrizione dei principi di misura nei flussi multifase per lo sviluppo di misuratori di portat
KEY MULTIPHASE FLOW METERING TECHNIQUES
No full textdescrizione delle tecniche di misura utilizzate nei sistemi di misura multifas
Back analysis of a horizontal geothermal plant implemented in a wine production process
Full text linkThe Salcheto winery has undertaken a process of reduction of its primary energy consumption and the implementation of green energy technologies. They adopted solar photovoltaic, wood biomass, and geothermal energy sources. A horizontal ground source heat exchanger (GSHE) plant is used to cool a part of the pressed grapes and control the wine production temperature. The goal of this work was to investigate some technical issues of the plant and to increase the efficiency of the whole system. The first step was the evaluation of the actual operating conditions of the GSHE plant, by performing a thermal response test. The results allowed us to find the thermal diffusivity of 3.5 × 10−7 m2 /s, and the calculation with the IGSHPA standard indicated a cooling performance of about 6 kW. A survey during the harvest highlighted a peak power of 6 kW. Therefore, to improve the plant, some modifications were proposed and analyzed. In the new layout, the geothermal plant serves the condenser of the refrigeration unit, allowing cooling of the all production lines, instead of only one. The peak power was evaluated as 32 kW, and the GSHE can fulfil this, up to 18 kW. For higher power, the evaporative tower will supply the remainder, covering a maximum of 45%. Furthermore, the refrigeration unit may cover the cooling requirements of the entire residential and office building, without other plant improvements
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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