Giampaolo Manfrida - Academia.edu (original) (raw)

Papers by Giampaolo Manfrida

Energies, 2020

Geothermal energy could play a crucial role in the European energy market and future scenarios fo... more Geothermal energy could play a crucial role in the European energy market and future scenarios focused on sustainable development. Thanks to its constant supply of concentrated energy, it can support the transition towards a low-carbon economy. In the energy sector, the decision-making process should always be supported by a holistic science-based approach to allow a comprehensive environmental assessment of the technological system, such as the life cycle assessment (LCA) methodology. In the geothermal sector, the decision-making is particularly difficult due to the large variability of reported results on environmental performance across studies. This calls for harmonized guidelines on how to conduct LCAs of geothermal systems to enhance transparency and results comparability, by ensuring consistent methodological choices and providing indications for harmonized results reporting. This work identifies the main critical aspects of performing an LCA of geothermal systems and provide...

cce-mt.org

1. Abstract The appeal and the possible technical solutions for the removal of CO2 in power plant... more 1. Abstract The appeal and the possible technical solutions for the removal of CO2 in power plants are examined. This lecture wishes to provide a review of the status of advancement of technology in this field, and to underscore the economical and technical problems that remain to be ...

Energies, Feb 2, 2019

Modern textile stenters are designed to reduce the inefficiency of the process and to recover the... more Modern textile stenters are designed to reduce the inefficiency of the process and to recover the flow stream, which still contains a relatively high energetic value. In recent years, research has focused on the recovery of the energy content of the low-temperature exhaust flow; nonetheless, another important aspect that may increase the efficiency of the process is the reduction of the ambient air suction. In the present research, an innovative way to improve both machine insulation and energy savings, by using preheated air, was numerically evaluated. The proposed solution utilizes an air stream transverse to the fabric (generally called air curtain), either preheated or not, to create soft gates both at the inlet and at the outlet section of the drying machine. Several valuable advantages can be listed when using this solution: reduction of the dispersion of heat and humid polluted air to the work environment, limitation of air ingestion from outside, and effective heat recovery coupled to a uniform temperature profile around the textile fabric. To analyze the insulation capability of the air curtains in terms of mass and energy transfer, a two-dimensional CFD model of the machine was realized. A test matrix including three possible fabric speeds (20, 40 and 60 m/min), three tilt angles (−15 • , 0 • and 15 •), four mass flow rates (0% with no air curtains and 3%, 5% and 7% of the total flow rate through the machine, where the 5% case is equivalent to the flow rate ingested from the ambient) and two temperatures (15 • C and 70 • C) of the plane jets exiting from the air curtains was considered, thus covering a wide range of possible practical applications. The obtained results demonstrate that warm air curtains at both the inlet and outlet are very effective in a fabric speed range up to 40 m/min; at higher fabric speed, entrainment of warm gases from inside the machine at the fabric outlet becomes relevant, and the adoption of a cold air curtain (capable of better insulation) can be recommended in this position.

Energy, 2015

In this paper, a conceptual cycle has been developed by integrating a solar field consisting of p... more In this paper, a conceptual cycle has been developed by integrating a solar field consisting of parabolic trough collectors with an operating 500 MWe coal fired thermal power plant for preheating the condensate/feed water. The effect of solar aided feed water heating (SAFWH) has been studied separately for each feed water heater (except LP Heater-1 and deaerator) by placing a feed water heat exchanger (FWHE) parallel to the heater under study. Energy, exergy, economic and environmental (4E) analyses have performed on this conceptual cycle in fuel saving mode by complete substitution of bleed steam with solar energy. Performance parameters (Energy and exergy efficiency, net unit heat rate, fuel savings and solar contribution) and economic parameters (Levelised cost of electricity generation (LCoE), simple payback period) and environmental parameters (annual reductions in coal consumption, CO 2 and ash generation) have been calculated. The results have shown that levelised cost (cents/kWh) and simple payback period (years) for solar aided feed water heating in HPH-7 without and with thermal storage are 5.045/5.196 and 5.13/6.21 respectively. Sensitivity analysis has been carried out to find out the sensitivity of LCoE with respect to discount rate, plant capacity factor and fuel cost.

International Journal of Environment and Pollution, 2001

In this paper, the results from a plume diffusion experiment on a small-scale model of a two-stac... more In this paper, the results from a plume diffusion experiment on a small-scale model of a two-stack waste incinerator, carried out in a developed boundary-layer wind-tunnel, will be presented. A brief description of the tunnel, the measurement system, and the artificially developed neutral boundary layer is given. The experiments investigate ground-level concentration measurements and vertical and horizontal concentration profiles taken at different distances from the stacks. The results are compared with widely used Gaussian models like ISC3 and ADMS2.

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1995

This paper presents the results of an extensive set of measurements on a model of an exhaust diff... more This paper presents the results of an extensive set of measurements on a model of an exhaust diffuser for gas turbines. The diffuser is of the straight-wall annular-axial type, typically employed in small-to-medium size gas turbines. It features six high-solidity struts, which support, in the real machine, one of the shaft bearings and have piping for oil supply inside. The 35%-scale model has been tested on a special test stand developed at the University of Perugia, using the suction side of a centrifugal-flow industrial fan of suitable capacity. Inlet speed

Volume 3: Heat Transfer; Electric Power, 1985

A methodology for the performance analysis of gas turbines for cogeneration applications is prese... more A methodology for the performance analysis of gas turbines for cogeneration applications is presented. Energy and exergy balances allow presentation of data in terms of either conventional or second-law parameters, as well as examination of the trends with respect to cycle variables and cogeneration options. The results show that, even though gas turbines (and particularly regenerative solutions) are very flexible for cogeneration purposes, care has to be exercised in matching thermal energy production conditions and cycle variables in order to achieve optimal performance.

Volume 3: Heat Transfer; Electric Power, 1985

The performance of gas turbines in cogeneration is examined by means of a second-law approach. Di... more The performance of gas turbines in cogeneration is examined by means of a second-law approach. Different cycle parameters, for both simple and regenerative design, are investigated together with different options for process or utility heat production. A reference electric power size of 4 MW is assumed for these comparisons. Results are presented as a set of parameters (electric power index, rational efficiency, coefficient of utilization). A new parameter, named versatility index, effectively indicates the broadness of the design thermal loads which can be handled by a gas turbine plant.

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration, 1989

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1990

The Society shall not be rbsponsible for statements or opinions advanced In papers or in discussi... more The Society shall not be rbsponsible for statements or opinions advanced In papers or in discussion-at meetings of the Society or of Its Olvislon or Sectiona, or printed in ifs publications {r. Diaeuesion is printed only if the paper la published in an ASME Journal. Papers are anaitabte 'S^l from ASME for fifteen months offer the meeting.

In the wide framework of the knowledge triangle: education-innovation-research, the accreditation... more In the wide framework of the knowledge triangle: education-innovation-research, the accreditation of environmental engineering education is here discussed. The application of the European Accreditation of Engineering Programmes EUR-ACE® model to the multidisciplinary first cycle degree in Civil, Building and Environmental Engineering and the more specific second cycle degree in Environmental Engineering, based on the European Credit Transfer System and in accordance with the Bologna Process, running at the School of Engineering, is discussed. Particularly, the critical issues to guarantee the quality and the status of environmental engineering graduates, in terms of applying knowledge capacities and technical innovative competences, according the Dublin Descriptors or the more engineering focused EUR-ACE® skill descriptors, and at local and global scale are preliminary examined and compared. The involvement of the professional working world in the definition of goals in skills, of typical expectations of achievements and abilities, and in general in comparing the teaching profile with the actual needs of the technical workforce, is also briefly described. The system for educating environmental engineers in knowledge and understanding, making informed judgments and choices, communication and learning skills, capacities to lifelong learning, is also considered.

The mechanism of combustion in diesel engines is strongly determined by the structure of the jet ... more The mechanism of combustion in diesel engines is strongly determined by the structure of the jet issuing from the injector; the actual flow being two-phase, unsteady and compressible with further features of turbulence and three-dimensionality, a direct attack by means of powerful numerical techniques can often proove to be unsuccessful or economically unaffordable. A semi-empirical method, based on the extension in the time domain of the classical theory of turbulent jets, has been developed in order to get a better insight of the physical phenomenon; the applicability of the approach to unsteady jets as encountered in engine fuel injectors has been checked and theoretically justified, and the integration in time of the equation of continuity and momentum conservation allows to calculate instantaneously the jet penetration from the input data, consisting in the time-history of the injection pressure. An experimental setup has been assembled in order to check the results of the analysis: an injection pump was mounted on an injector test bench, and one of the injectors was instrumented for the fast-response measurement of the injection pressure, needle displacement and jet penetration. The instrumentation, comprising quartz pressure transducers, a capacitive gap sensor and a conical hot film probe, was connected to a data acquisition system providing a direct microcomputer interface for data collection and handling; on the same computer the program for the calculation of the jet penetration was run. The measurements have allowed to assess the good performance of the simulation in predicting the jet penetration.

ABSTRACT A model of the vaned intake of a centrifugal compressor was instrumented and tested for ... more ABSTRACT A model of the vaned intake of a centrifugal compressor was instrumented and tested for the investigation of aero-acoustic excitation modes for specific flow conditions, in order to check the possibility of damage to the Inlet Guide Vanes (IGV). The tests demonstrate that several acoustic modes occur for such complex geometries, and that their frequencies and amplitudes should be verified in order to avoid the excitation of forced vibration of the blades.

Energies, 2020

Geothermal energy could play a crucial role in the European energy market and future scenarios fo... more Geothermal energy could play a crucial role in the European energy market and future scenarios focused on sustainable development. Thanks to its constant supply of concentrated energy, it can support the transition towards a low-carbon economy. In the energy sector, the decision-making process should always be supported by a holistic science-based approach to allow a comprehensive environmental assessment of the technological system, such as the life cycle assessment (LCA) methodology. In the geothermal sector, the decision-making is particularly difficult due to the large variability of reported results on environmental performance across studies. This calls for harmonized guidelines on how to conduct LCAs of geothermal systems to enhance transparency and results comparability, by ensuring consistent methodological choices and providing indications for harmonized results reporting. This work identifies the main critical aspects of performing an LCA of geothermal systems and provide...

cce-mt.org

1. Abstract The appeal and the possible technical solutions for the removal of CO2 in power plant... more 1. Abstract The appeal and the possible technical solutions for the removal of CO2 in power plants are examined. This lecture wishes to provide a review of the status of advancement of technology in this field, and to underscore the economical and technical problems that remain to be ...

Energies, Feb 2, 2019

Modern textile stenters are designed to reduce the inefficiency of the process and to recover the... more Modern textile stenters are designed to reduce the inefficiency of the process and to recover the flow stream, which still contains a relatively high energetic value. In recent years, research has focused on the recovery of the energy content of the low-temperature exhaust flow; nonetheless, another important aspect that may increase the efficiency of the process is the reduction of the ambient air suction. In the present research, an innovative way to improve both machine insulation and energy savings, by using preheated air, was numerically evaluated. The proposed solution utilizes an air stream transverse to the fabric (generally called air curtain), either preheated or not, to create soft gates both at the inlet and at the outlet section of the drying machine. Several valuable advantages can be listed when using this solution: reduction of the dispersion of heat and humid polluted air to the work environment, limitation of air ingestion from outside, and effective heat recovery coupled to a uniform temperature profile around the textile fabric. To analyze the insulation capability of the air curtains in terms of mass and energy transfer, a two-dimensional CFD model of the machine was realized. A test matrix including three possible fabric speeds (20, 40 and 60 m/min), three tilt angles (−15 • , 0 • and 15 •), four mass flow rates (0% with no air curtains and 3%, 5% and 7% of the total flow rate through the machine, where the 5% case is equivalent to the flow rate ingested from the ambient) and two temperatures (15 • C and 70 • C) of the plane jets exiting from the air curtains was considered, thus covering a wide range of possible practical applications. The obtained results demonstrate that warm air curtains at both the inlet and outlet are very effective in a fabric speed range up to 40 m/min; at higher fabric speed, entrainment of warm gases from inside the machine at the fabric outlet becomes relevant, and the adoption of a cold air curtain (capable of better insulation) can be recommended in this position.

Energy, 2015

In this paper, a conceptual cycle has been developed by integrating a solar field consisting of p... more In this paper, a conceptual cycle has been developed by integrating a solar field consisting of parabolic trough collectors with an operating 500 MWe coal fired thermal power plant for preheating the condensate/feed water. The effect of solar aided feed water heating (SAFWH) has been studied separately for each feed water heater (except LP Heater-1 and deaerator) by placing a feed water heat exchanger (FWHE) parallel to the heater under study. Energy, exergy, economic and environmental (4E) analyses have performed on this conceptual cycle in fuel saving mode by complete substitution of bleed steam with solar energy. Performance parameters (Energy and exergy efficiency, net unit heat rate, fuel savings and solar contribution) and economic parameters (Levelised cost of electricity generation (LCoE), simple payback period) and environmental parameters (annual reductions in coal consumption, CO 2 and ash generation) have been calculated. The results have shown that levelised cost (cents/kWh) and simple payback period (years) for solar aided feed water heating in HPH-7 without and with thermal storage are 5.045/5.196 and 5.13/6.21 respectively. Sensitivity analysis has been carried out to find out the sensitivity of LCoE with respect to discount rate, plant capacity factor and fuel cost.

International Journal of Environment and Pollution, 2001

In this paper, the results from a plume diffusion experiment on a small-scale model of a two-stac... more In this paper, the results from a plume diffusion experiment on a small-scale model of a two-stack waste incinerator, carried out in a developed boundary-layer wind-tunnel, will be presented. A brief description of the tunnel, the measurement system, and the artificially developed neutral boundary layer is given. The experiments investigate ground-level concentration measurements and vertical and horizontal concentration profiles taken at different distances from the stacks. The results are compared with widely used Gaussian models like ISC3 and ADMS2.

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1995

This paper presents the results of an extensive set of measurements on a model of an exhaust diff... more This paper presents the results of an extensive set of measurements on a model of an exhaust diffuser for gas turbines. The diffuser is of the straight-wall annular-axial type, typically employed in small-to-medium size gas turbines. It features six high-solidity struts, which support, in the real machine, one of the shaft bearings and have piping for oil supply inside. The 35%-scale model has been tested on a special test stand developed at the University of Perugia, using the suction side of a centrifugal-flow industrial fan of suitable capacity. Inlet speed

Volume 3: Heat Transfer; Electric Power, 1985

A methodology for the performance analysis of gas turbines for cogeneration applications is prese... more A methodology for the performance analysis of gas turbines for cogeneration applications is presented. Energy and exergy balances allow presentation of data in terms of either conventional or second-law parameters, as well as examination of the trends with respect to cycle variables and cogeneration options. The results show that, even though gas turbines (and particularly regenerative solutions) are very flexible for cogeneration purposes, care has to be exercised in matching thermal energy production conditions and cycle variables in order to achieve optimal performance.

Volume 3: Heat Transfer; Electric Power, 1985

The performance of gas turbines in cogeneration is examined by means of a second-law approach. Di... more The performance of gas turbines in cogeneration is examined by means of a second-law approach. Different cycle parameters, for both simple and regenerative design, are investigated together with different options for process or utility heat production. A reference electric power size of 4 MW is assumed for these comparisons. Results are presented as a set of parameters (electric power index, rational efficiency, coefficient of utilization). A new parameter, named versatility index, effectively indicates the broadness of the design thermal loads which can be handled by a gas turbine plant.

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration, 1989

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1990

The Society shall not be rbsponsible for statements or opinions advanced In papers or in discussi... more The Society shall not be rbsponsible for statements or opinions advanced In papers or in discussion-at meetings of the Society or of Its Olvislon or Sectiona, or printed in ifs publications {r. Diaeuesion is printed only if the paper la published in an ASME Journal. Papers are anaitabte 'S^l from ASME for fifteen months offer the meeting.

In the wide framework of the knowledge triangle: education-innovation-research, the accreditation... more In the wide framework of the knowledge triangle: education-innovation-research, the accreditation of environmental engineering education is here discussed. The application of the European Accreditation of Engineering Programmes EUR-ACE® model to the multidisciplinary first cycle degree in Civil, Building and Environmental Engineering and the more specific second cycle degree in Environmental Engineering, based on the European Credit Transfer System and in accordance with the Bologna Process, running at the School of Engineering, is discussed. Particularly, the critical issues to guarantee the quality and the status of environmental engineering graduates, in terms of applying knowledge capacities and technical innovative competences, according the Dublin Descriptors or the more engineering focused EUR-ACE® skill descriptors, and at local and global scale are preliminary examined and compared. The involvement of the professional working world in the definition of goals in skills, of typical expectations of achievements and abilities, and in general in comparing the teaching profile with the actual needs of the technical workforce, is also briefly described. The system for educating environmental engineers in knowledge and understanding, making informed judgments and choices, communication and learning skills, capacities to lifelong learning, is also considered.

The mechanism of combustion in diesel engines is strongly determined by the structure of the jet ... more The mechanism of combustion in diesel engines is strongly determined by the structure of the jet issuing from the injector; the actual flow being two-phase, unsteady and compressible with further features of turbulence and three-dimensionality, a direct attack by means of powerful numerical techniques can often proove to be unsuccessful or economically unaffordable. A semi-empirical method, based on the extension in the time domain of the classical theory of turbulent jets, has been developed in order to get a better insight of the physical phenomenon; the applicability of the approach to unsteady jets as encountered in engine fuel injectors has been checked and theoretically justified, and the integration in time of the equation of continuity and momentum conservation allows to calculate instantaneously the jet penetration from the input data, consisting in the time-history of the injection pressure. An experimental setup has been assembled in order to check the results of the analysis: an injection pump was mounted on an injector test bench, and one of the injectors was instrumented for the fast-response measurement of the injection pressure, needle displacement and jet penetration. The instrumentation, comprising quartz pressure transducers, a capacitive gap sensor and a conical hot film probe, was connected to a data acquisition system providing a direct microcomputer interface for data collection and handling; on the same computer the program for the calculation of the jet penetration was run. The measurements have allowed to assess the good performance of the simulation in predicting the jet penetration.

ABSTRACT A model of the vaned intake of a centrifugal compressor was instrumented and tested for ... more ABSTRACT A model of the vaned intake of a centrifugal compressor was instrumented and tested for the investigation of aero-acoustic excitation modes for specific flow conditions, in order to check the possibility of damage to the Inlet Guide Vanes (IGV). The tests demonstrate that several acoustic modes occur for such complex geometries, and that their frequencies and amplitudes should be verified in order to avoid the excitation of forced vibration of the blades.