Modeling Coandã effect has been a fundamental issue in fluid dynamic research in the XX century. It has lost some interest because of the improvement in CFD, even if it could be still important in ...the area of the preliminary design of aerodynamic devices that benefits of fluid deflection by convex surfaces. An effective model of Coandã effect has not been defined, and fundamental questions are still open. The influence of convective heat exchange on Coandã adhesion of a fluid stream on a convex surface in the presence of a temperature gradient between the fluid and the convex surface is a problem, which affects many practical cases, but it is still marginally approached by scientific literature. This paper aims to start an effective research direction on the effects of convective heat exchange on Coandã effect. It approaches the problem with a set of CFD simulations. It analyses the previous hypotheses, which are based on Prandtl number and evidences the need of a more effective model that accounts also for the Reynolds number.
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DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Two fundamental questions are still open about the complex relation between fluid dynamics and thermodynamics. Is it possible (and convenient) to describe fluid dynamic in terms of second law based ...thermodynamic equations? Is it possible to solve and manage fluid dynamics problems by mean of second law of thermodynamics? This chapter analyses the problem of the relationships between the laws of fluid dynamics and thermodynamics in both first and second law of thermodynamics in the light of constructal law. In particular, taking into account constructal law and the diffusive formulation of Bejan number, it defines a preliminary step through an extensive thermodynamic vision of fluid dynamic phenomena.
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DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The use of energy by the major modes and the environmental impact of freight transportation is a problem of increasing importance for future transportation policies. This paper aims to study the ...relative energy efficiency of the major transport modes, setting up an impartial analysis, improving previous literature substantially. Gabrielli and von Karman have studied the relationship between speed and energy consumption of the most common transport modes. From this pioneering activity different methods for evaluating the energetic performance of vehicles have developed. Initially the maximum vehicle power and theoretical performance limits have been calculated in terms of weight and payload. Energy efficiency has then been evaluated in terms of the first principle of thermodynamics as the mass of the vehicle times distance moved divided by thermal energy used. A more effective analysis can be performed both in terms of vehicle life cycle and in terms of second principle considering the quality and the amount of dissipated amount of useful energy. This paper defines an LCA based model, which could allow an effective comparison between different transport modes classifying them in terms of exergy destruction. In this case, an effective comparison, which considers the quality of used energy, can be performed allowing precise politics for a future more effective evaluation of the transport modes.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This paper analyses the ACHEON Coanda effect nozzle for aircraft propulsion, based on the dynamic equilibrium of two jet streams. The ACHEON concept, and, in particular, the HOMER nozzle, which is ...its main component, are presented, together with the literature milestones from which the idea originally stems. A sub-system analysis inspired by the principles of Constructal Theory is presented for the current architecture. A mathematical model of a 2D case of the system is developed, focusing on the combined effect of the mixing of the two streams and the Coanda adhesion over a convex surface. A validation of the model is also reported, based on 2D CFD analyses, under the hypothesis of incompressible flow. Results highlight that, in spite of its relative simplicity, the model produces accurate results.
After a few decades in which airships have been depromoted to the level of being only considered as a mere curiosity they seem now to reappear. The main reasons for this are related to the recent ...progress in technology of materials, aerodynamics, energy and propulsion. Airships are also presenting themselves as green friendly air vehicles, in particular if solar powered airships are considered. Their ability to remain aloft for long time periods have also expanded the range of mission profiles for which they are suited. Herein we have concentrated on a critical overview of propulsion mechanisms for airships. These include a detailed overview of past, present, and future enabling technologies for airship propulsion. Diverse concepts are revisited and the link between the airship geometry and flight mechanics is made for diverse propulsion system mechanisms.
The advantages associated to Vertical Short-Take-Off and Landing (V/STOL) have been demonstrated since the early days of aviation, with the initial technolology being based on airships and later on ...helicopters and planes. Its operational advantages are enormous, being it in the field of military, humanitarian and rescue operations, or even in general aviation. Helicopters have limits in their maximum horizontal speed and classic V/STOL airplanes have problems associated with their large weight, due to the implementation of moving elements, when based on tilting rotors or turbojet vector mechanical oriented nozzles. A new alternative is proposed within the European Union Project ACHEON (Aerial Coanda High Efficiency Orienting-jet Nozzle). The project introduces a novel scheme to orient the jet that is free of moving elements. This is based on a Coanda effect nozzle supported in two fluid streams, also incorporating boundary layer plasma actuators to achieve larger deflection angles. Herein we introduce a state-of-the-art review of the concepts that have been proposed in the framework of jet orienting propulsion systems. This review allows to demonstrate the advantages of the new concept in comparison to competing technologies in use at present day, or of competing technologies under development worldwide.
We are living an extraordinary season of uncertainty and danger, which is caused by SARS-Cov-2 infection and consequent COVID-19 infection. This preliminary study comes from both a mix of ...entrepreneurial experience and scientific research. It is aimed by the exigency to reach a new and more effective analysis of the risks on the filed and to reduce them inside a necessary cooperation process which may regard both research and some of the economic activities which are damaged by passive protection measures such as indiscriminate lockdowns. This global emergency requires specific efforts by any discipline that regards specific problems which need to be solved urgently. The characteristic airborne diffusion patterns of COVID-19 shows that the airborne presence of viruses depends on multiple factors which include the dimension of microdroplets emitted by a contagious person, the atmospheric temperature and humidity, the presence of atmospheric particulate and pollution, which may act as a transport vehicle for the virus. The pandemic diffusion shows a particular correlation with the air quality and levels of atmospheric pollution. Specific problems need to solved to understand better the virus, its reliability, diffusion, replication, how it attacks the persons and the conditions, which drives to both positive and deadly evolution of the illness. Most of these problems may benefit from the contribution from both heat and mass transfer and the unsteady thermodynamics of living systems which evolves according to constructal law. After the bibliographic research on the virus, emissive and spread modes, and consequent today adopted protection, a detailed analysis of the contributions which may be assessed by research in thermodynamics, heat and mass transfer, technical and chemical physics. Some possible areas of research have been identified and discussed to start an effective mobilization which may support the effort of the research toward a significant reduction of the impacts of the pandemic infection and the economic risks of new generalized lockdowns.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper results from a critical literature overview on systems theory and socio-technical engineering. It has allowed exploring a vast interdisciplinary domain along an interdisciplinary path. It ...starts from a preliminary analysis of Kondratieff cycles and today's transition from mature to innovative technologies, which will characterize the future decades. Then, it discusses the genesis of the socio-technical problems from its philosophical roots and the evolution along a non-linear path that involves philosophy and system theory, psychology, philosophy, and engineering. The results evidence the foundations of both system theory and socio-technical engineering. Different criteria for building a robust and consistent socio-technical model have been identified and discussed. Therefore, it analyses the possible links between contemporary philosophy, psychology, engineering, thermodynamics, and physics, which have the possibility of active cooperation toward supporting the design of more effective socio-technical systems. The importance of modern thermodynamics and constructal law has been discussed. Finally, the actual social trends are discussed: the populisms which agitate society against scientific objectivity and social and environmental responsibility. On the other hand, Pope Francis moral teaching and Greta Thunberg's movement promote the paradigms toward responsibility and change. Hence, some reflections on the possible future role of socio-technical engineering have been proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Technologies for increasing the indoor comfort conditions.•Microscale thermoelectric acclimatization in large indoor environments.•Comfort conditions in large open-space offices.
The improvement of ...indoor comfort conditions in large open-space environments with large vertical radiant or glazed surfaces is still an unsolved problem. Global standards, such as ISO7730, and essential technological research in the area of home automation are producing a general improvement in this field. Home-automation is developing different sensor systems for controlling indoor acclimatization parameters (temperature, humidity, airspeed, etc.) at room level. Those systems allow managing and controlling the acclimatization at room level. These technical solutions do not achieve optimal results in large “open-space” office environments. These limits are amplified by large vertical glazed surfaces, which accentuate the problems which relate to thermal uniformity. The incoming solar radiation increases the local temperature near the glazed surfaces and generates an uneven thermal distribution with related issues of localized discomfort. A useful improvement of the comfort conditions is significant because this layout is often used in offices and other working environments. This goal requires the introduction of a new physical parameter “local mean radiant temperature.” It allows evaluating local punctual comfort conditions inside large indoor environments. This magnitude indicates the necessary attention toward a localized control of comfort conditions in large environments with particular attention to the ones with large vertical glazed surfaces. After analyzing different methods for evaluating the comfort conditions according to actual standards, this paper evaluates the influence of the distance from the radiating surface. A practical solution for improving the thermal distribution is proposed and analyzed. It includes two major subsystems: a Wi-Fi sensing subsystem that measures airspeed and temperature in several positions and an active punctual air conditioning system made by Peltier cells. The sensing system pilots the local acclimatization inside the “open-space” environment to increase the comfort conditions and the air quality with a remarkable energy saving if it is compared to any traditional air-conditioning plant. The nature of the Peltier cells produces the same effect of a micro heat pump that provides localized and punctual HVAC. The increase in comfort conditions has been evaluated through the traditional parameters, such as PMV and PPD in different conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Purpose
Transport vehicle industry is suffering a diffused technological maturity. Energy efficiency is increasing with a certain velocity. But many factors in car development are playing against.
...Method
A critical literature review about technological maturity symptoms and industrial grade design methods is presented for the current research paper. In particular Multidisciplinary Design Optimization and Modular System Design has been considered. A technical and scientific discussion, is performed focusing on the technological effect they are generating.
Results
A possible answer comes from the MAAT 7th framework Program which defined a novel design method initially conceived for airships. It has been defined CDE, Constructal Design for Efficiency. It is specifically based on Constructal law and second Principle of Thermodynamics and aims to produce an original methodological synthesis of Modular Design principles and Multidisciplinary Optimization harmonizing them by thermodynamic principles. The result of this process allows tuning CDE on the road through an effective generalization of the preliminary CDE concept. The schematization of the necessary design process of a vehicle has presented and discussed.
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