Constructal Theory

The use of the internet in a creative and enriching way to provide new opportunities to students improve their leaning, and to natural update teachers into the new discoveries, theories and (green) science, technology, society and environment awareness, also for a starting line, to the pedagogical, creative, exploration and better changing of information into knowledge and vice-versa, new pedagogical projects development with sustainable development and good practices awareness, and following the Portuguese National Education Curriculum.
We can find various contends like Constructal Theory; Green Energy, Energy Efficiency, Industrial Property; Interactive Internet; Portuguese Cultural Heritage for basic, secondary and post secondary education, being suitable also for Teachers Training Centres, providing ideas for teachers training centers.

Product design techniques that support mass customization include product platform design, computer-aided parametric design and modular design, among others. Unfortunately, no rigorous method has appeared until now to help designers combine these approaches systematically and maximize the quality and economic benefits of component commonality, particularly for very large number of product variants. In this paper we describe one method that addresses these issues, based on the formulation of the product design of customizable products as a problem of access in a geometric space. The method is illustrated with a case study, namely, the design of a line of customizable hand exercisers.

We live in the information age but we can only increase the benefit if we look to permanently promote more efficiently the use of the cyberspace for creative thinking; pedagogical innovation; sustainable development education; the new constructal pedagogical supervision; scientific, technological, and engineering advances share like the constructal law, green chemistry, and green energy; Portuguese Cultural Heritage; economic growth; and biotechnology through the quality pedagogical resources and Web 2.0 already putted in place in there and all those that are to come available. So more "state-of-the-art" teachers training for continuous update are needed, and we know too that adequate training can lead to better judgments and better performance. In Portugal, the pedagogical supervision theories thrive with lots of different institutions like universities and polytechnics offering MSc. and PhD programs in these subjects, to these theories is add now the constructal pedagogical supervision theory for sustainable development. New training courses are needed for teachers so can have a bigger variety for their choices, while achieving the United Nations goals for sustainable development.

In the present paper we focus on two items, Energy, and Environment. We propose to restore and extend the view of CARNOT, relative to thermomechanical systems and processes, starting from thermostatics (equilibrium thermodynamics), through what was first developed as Finite Time Thermodynamics (FTT), since the 1980s (nice radical of Chambadal-Novikov-Curzon-Ahlborn), until now. The CARNOT machine is revisited in the presence of heat transfer irreversibilities as well as internal irreversibility, and heat loss. Classical results are recovered. New bounds are developed when constraints are added; these constraints are related to useful effect, energy consumption, or machine efficiency. A new form of 'nice radical' is proposed when energy consumption is imposed. New results are proposed with different added constraints.

Several optimization models of irreversible reverse cycle machines have been developed based on different optimization criteria in the literature, most of them using linear heat transfer laws at the source and sink. This raises the issue how close to actual operation conditions they are, since the heat transfer law on the phase-change processes is dependent on ∆T 3. This paper addresses this issue by proposing a general model for study and optimization of thermal machines with two heat reservoirs applied to a Carnot-like refrigerator, with non-linear heat transfer laws and internal and external irreversibility. The optimization was performed using First and Second Law of Thermodynamics and the Lagrange multipliers method. Thus, several constraints were imposed to the system, also different objective functions were considered, allowing finding the optimum operating conditions, as well as the limited variation ranges of the system parameters. Results show that the nature of the heat transfer laws affects the optimum values of system parameters for obtaining maximum performances and also their magnitude. Sensitivity studies with respect to system several parameters are presented. The results contribute to the understanding of the system limits in operation under different constraints and allow choosing the most convenient variables in given circumstances.

In the present work, the effect of the hydrogen and the air temperature values on the temperature distribution in a Planar Solid Oxide Fuel Cell is studied by the aid of a twodimensional mathematical model. Two different configurations of the Solid Oxide Fuel Cells are examined: i) the Anode Supported Planar Solid Oxide Fuel Cell (ASP_SOFC) and ii) the Electrolyte Supported Planar Solid Oxide Fuel Cell (ESP_SOFC). In order to describe the temperature distribution within the SOFC, the coupling of the mass and energy transport phenomena along with the electrochemistry is required. The studied parameters are: a) the hydrogen and the air temperature values and b) the geometry configurations. The complex system of the governing equations is numerically solved with the finite differences method and the calculation of the temperature distribution within each domain of the SOFCs is calculated via the 2-D mathematical model processed by FORTRAN language. Finally, the mathematical model predictions for the temperature distribution under the influence of the studied parameters are thoroughly discussed.

Product design techniques that support mass customization include product platform design, computer-aided parametric design and modular design, among others. Unfortunately, no rigorous method has appeared until now to help designers combine these approaches systematically and maximize the quality and economic benefits of component commonality, particularly for very large number of product variants. In this paper we describe one method that addresses these issues, based on the formulation of the product design of customizable products as a problem of access in a geometric space. The method is illustrated with a case study, namely, the design of a line of customizable hand exercisers.

We live in the information age but we can only increase the benefit if we look to permanently promote more efficiently the use of the cyberspace for creative thinking; pedagogical innovation; sustainable development education; the new constructal pedagogical supervision; scientific, technological, and engineering advances share like the constructal law, green chemistry, and green energy; Portuguese Cultural Heritage; economic growth; and biotechnology through the quality pedagogical resources and Web 2.0 already putted in place in there and all those that are to come available. So more "state-of-the-art" teachers training for continuous update are needed, and we know too that adequate training can lead to better judgments and better performance. In Portugal, the pedagogical supervision theories thrive with lots of different institutions like universities and polytechnics offering MSc. and PhD programs in these subjects, to these theories is add now the constructal pedagogical supervision theory for sustainable development. New training courses are needed for teachers so can have a bigger variety for their choices, while achieving the United Nations goals for sustainable development.

For most engineering students, thermodynamics probably seems like an abstract subject. Introductory discussions about heat engines and the Carnot cycle, as prerequisites for the entropy concept, are difficult to understand and perhaps even more difficult to teach. This is understandable because most contemporary teachers have not struggled with the problem of constructing the most efficient steam engine. However, the same holds true for thermodynamics of solutions and phase equilibria, not to mention the mysterious subject of "irreversible thermodynamics." This is also understandable because even today most teachers have not used thermodynamics as a tool for solving practical problems in chemistry or materials science. Perhaps the situation is slowly changing now.

A thermodynamic analysis of the irreversibility on solar absorption refrigerators is presented. Under the hierarchical decomposition and the hypothesis of an endoreversible model, many functional and practical domains are defined. The effect of external heat source temperature on the entropy rate and on the inverse specific cooling load (ISCL) multiplied by the total area of the refrigerator A/Q e are studied. This may help a constructor to well dimension the solar machine under an optimal technico-economical criterion A/Q e and with reasonable irreversibility on the refrigerator. The solar concentrator temperature effect on the total exchanged area, on the technico-economical ratio A/Q e , and on the internal entropy rate are illustrated and discussed. The originality of these results is that they allow a conceptual study of a solar absorption refrigeration cycle.

Sunlight is a natural resource that can be harnessed by the photovoltaic conversion of sunlight into electricity-utilizing solar cells. The production of most common solar cells consists of a homojunction of a p-type and n-type silicon. The p-n junction is realized by the diffusion of impurities through one surface of the wafer. Silicon wafers have a typical dimension of 156 × 156 mm 2 and a thickness of 0.15-0.2 mm. Groups of 50-100 solar cells are electrically connected and encapsulated to form a module. The required area for interconnection does not contribute to power generation, and the performance of larger area devices usually suffers from higher resistive losses. In the present work, a theoretical model of the geometric arrangement of the top contact metallic electrodes branched network in a photovoltaic cell is developed. The network structure of the electrodes is obtained from applying the constructal design methodology by the minimization of the overall resistance. As a result, the optimal lengths and geometrical relationships of an electrode branching network with a branching angle are determined. A geometric distribution of the electrode network on the solar cell analyzed by the total resistance of every level of branching is defined. The top metallic contact network presents a tree-shaped geometric arrangement with the main objective of covering a generation area for an enhanced collection of the generated electrical current. The theoretical results obtained are expressed as the total voltage of the arrangement and the lengths of the branched electrode network.

The article presents a partial synthesis of progress in control thermodynamics by laying out the main results as a sequence of principles. We state and discuss nine general principles (0-8) for finding bounds on the effectiveness of energy conversion in finite-time.

There has been a large amount of work being conducted on the thermo-dynamics of the Direct Contact Condensation (DCC), however, not much attention was given to the phenomena particularly active near the steam’s nozzle exit. A transparent rectangular upright duct of 4 ft high, was built with a supersonic nozzle positioned at the bottom of the channel to characterize flow behavior near the steam nozzle’s exit. Particle image velocimetry (PIV) was applied to draw information on the steam’s jet penetration into the water as well as the entrainment and mixing between the two phases under the steam’s inlet pressure ranging from 1.5 – 3.0 bars. PIV normalized contour measurements depicted not appreciable changes in the radial velocity of the jet. Whereas, in the core region of the jet, the change in the jet’s velocity was not much till Y/De ~ 4.3 and the vertical velocity of the jet decreased slowly till Y/De ~ 8. The jet’s normalized upward velocity attained an optimized value between Y/D...

The scarcity of drinkable water supplies is becoming a serious and troubling challenge to long-term development. This issue emphasises the urgency of implementing rapid water desalination options. However, desalination is a capital-intensive process that requires a significant amount of energy, and since it is now mostly powered by fossil fuels across the globe, it has the potential to leave a significant carbon footprint. In this light, transitioning to green energy sources for desalination is a necessity in today’s society. Humidification–dehumidification (HD) is one of the most effective desalination procedures to consider for distant places with modest fresh water demands for household and agricultural demands. This is mostly because it requires minimal operational and maintenance concerns. The current article examines the many kinds of HD desalination systems driven by solar energy sources and their key components. The current study established that the seawater HD system is vi...

As more and more complex and sophisticated hardware and software tools are available, complex problems described by consistent mathematical models are successfully approached by numerical simulation: modelling and simulation are present at almost each level in education, research, and production. Numerical "experiments" have predictive value, and complement physical experiments. They are unique in providing valuable insights in Gedankenexperiment-class (thought experiment) investigations. This chapter presents numerical simulation results related to a structural optimization problem that arises in systems with gradients and fluxes. Although the discussion concerns the optimal electrical design of photovoltaic systems, it may be extended to a larger class of applications in electrical and mechanical engineering: diffusion and conduction problems. The first concern in simulation is the proper formulation of the physical model of the system under investigation that should lead to consistent mathematical models, or well-posed problems (in Hadamard sense) (Morega, 1998). When available, analytic solutions-even for simplified mathematical models-may outline useful insights into the physics of the processes, and may also help deciding the numerical approach to the solution to more realistic models for the systems under investigation. Homemade and third party simulation tools are equally useful as long as they are available and provide for accurate solutions. Recent technological progresses brought into attention the Spherical PhotoVoltaic Cells (SPVC), known for their capability of capturing light three-dimensionally not only from direct sunlight but also as diffuse light scattered by the clouds or reflected by the buildings. This chapter reports the structural optimization of several types of spherical photovoltaic cells (SPVC) by applying the constructal principle to the minimization of their electrical series resistance. A numerically assisted step-by-step construction of optimal, minimum series resistance SPVC ensembles, from the smallest cell (called elemental) to the largest assembly that relies on the minimization of the maximum voltage drop subject to volume (material) constraints is presented. In this completely deterministic approach the SPVC ensembles shapes and structures are the outcome of the optimization of a volume to point access problem imposed as a design request. Specific to the constructal theory, the optimal shape (geometry) and structure of both natural and engineered systems are morphed out of their functionality and resources, and of the constraints to which they are subject.

Chemical engineering, a highly intellectual scientific discipline, is changing. While a large number of processes are well established, optimized and standardized, new needs have to be addressed. A summary of the new challenges and pressures faced by chemical engineering research is presented here. '. .. a form of sustainable development which meets the needs of the present without compromising the ability of future generations to meet their own needs'.

Biomimicry is not considered a developed design discipline yet, even with a methodology and supporting theories well established. In most cases, biomimicry is only considered an emerging discipline. The epistemology of biomimicry is a project under development, a discipline under construction. This article proposes a brief review on conceptual and contextual aspects of biomimicry, a review on its methodological content, and an analysis of present and possible future of this emerging discipline.

In recent decades, the approach known as Finite-Dimension Thermodynamics has provided a fruitful theoretical framework for the optimization of heat engines operating between a heat source (at temperature T hs) and a heat sink (at temperature T cs). We will show in this paper that the approach detailed in a previous paper [1] can be used to analytically model irreversible heat engines (with an additional assumption on the linearity of the heat transfer laws). By defining two dimensionless parameters, the intensity of internal dissipation and heat leakage within a heat engine were quantified. We then established the analogy between an endoreversible heat engine and an irreversible heat engine by using the apparent temperatures (T cs → T λ,φ cs , T hs → T λ,φ hs) and apparent conductances (K h → K λ h , K c → K λ c). We thus found the analytical expression of the maximum power of an irreversible heat engine. However, these apparent temperatures should not be used to calculate the conversion efficiency at the optimal operating point by analogy with the case of an endoreversible heat engine.

The literature reviewed in this article shows that the evolution of vehicles is in line with the evolution of animal locomotion and that it is predictable from the constructal law of design and evolution in nature. The evolution of ships and airplanes illustrates the evolutionary design of the "human-and-machine species" as it moves and spreads on Earth: farther, faster, more efficiently, and with greater lasting power (sustainability). Every vehicle size has its design. The bigger vehicle is not a magnified facsimile of the smaller. The size fraction that the lifting organs occupy in the overall vehicle increases with the body size. Every vehicle size has its niche, the supporting territory, and population to which it belongs. All the designs of movement on the globe evolve. Vehicles do not evolve by themselves; they evolve hand in glove with the humans who design and use them. The result is hierarchy, and it is why hierarchy is natural and unavoidable. We see it in geophysical movement (river basins), animal movement (food chain), human social movement (global air and maritime traffic), and everywhere else. The appearance of a new hierarchical design of movement on earth does not eliminate the existing hierarchical designs of movement. The new hierarchy joins the old, and what works is kept. No evolving system deviates from the features dictated by the law of physics of evolution in nature.

This paper describes human application of their knowledge and technological ability to fly and continue to enhance that power. Through application of their knowledge and technological ability, human beings have evolved the ability to fly and continue to enhance that power. Aircraft technology evolution is about the evolving design of the human movement on the Earth’s surface: people, goods, materials, and everything else. As the whole vehicle or animal evolves toward becoming better at moving mass on the landscape, the organs remain imperfect, because each represents a compromise. The whole vehicle or animal is a construct of organs that are ‘imperfect’ only when examined in isolation. The vehicle design evolves over time and becomes a better construct for moving the vehicle mass on the world map. Flow architectures are evolving right now, throughout nature and in technologies. The legacy of all flow systems (animate and inanimate) is: they have moved weight horizontally and improve...

The problem study here is concerned with the geometrical evaluation of an isothermal Y-shaped cavity intruded into conducting solid wall with internal heat generation. The cavity acts as a sink of the heat generated into the solid. The main purpose here is to minimize the maximal excess of temperature (θmax) in the solid. Constructal Design, which is based on the objective and constraints principle, is employed to evaluate the geometries of Y-shaped cavity. Meanwhile, Simulated Annealing (SA) algorithm is employed as optimization method to seek for the best shapes. To validate the SA methodology, the results obtained with SA are compared with those achieved with Genetic Algorithm (GA) and Exaustive Search (ES) in recent studies of literature. The comparison between the optimization methods (SA, GA and ES) showed that Simulated Annealing is highly effective in the search for the optimal shapes of the studied case.

The dissolution and microfluidic mass transfer of carbon dioxide in water at high-pressure conditions are crucial for a myriad of technological applications, including microreactors, extractions, and carbon capture, utilization, and sequestration (CCUS) processes. In this experimental work, we use a high-pressure microfluidic method to elucidate the mass transfer process of CO 2 in water at high pressure. An intriguing multiphase CO 2 flow and dispersions are observed when operating at the pressure-temperature (P-T) condition close to the CO 2 gas-liquid phase boundary (P = 6.5 MPa and T = 23.5 ± 0.5˝C). We propose a series of strategies to unravel this complex multi-phase dynamics by calculating each phase's volume and mass change in a gas-liquid coexistent CO 2 dispersion, estimating the possible CO 2 concentration change in water, and comparing with the CO 2 solubility data. Finally, we quantify the CO 2 mass transfer by directly calculating the CO 2 dissolution rate in water and estimating the volumetric mass transfer coe cient (k L a). The results show that the mass transfer may be influenced by the specific area (a), CO 2 concentration gradient in the water slug, and the traveling speed of a dispersion.

Here we explore the idea that the highest heat transfer rate between two fluids in a given volume is achieved when plate channel lengths are given by the thermal entrance length, i.e., when the thermal boundary layers meet at the exit of each channel. The overall design can be thought of an elemental construct of a dendritic heat exchanger, which consists of two tree-shaped streams arranged in cross flow. Every channel is as long as the thermal entrance length of the developing flow that resides in that channel. The results indicate that the overall design will change with the total volume and total number of channels. We found that the lengths of the surfaces swept in cross flow would have to decrease sizably as number of channels increases, while exhibiting mild decreases as total volume increases. The aspect ratio of each surface swept by fluid in cross flow should be approximately square, independent of total number of channels and volume. We also found that the minimum pumping power decreases sensibly as the total number of channels and the volume increase. The maximized heat transfer rate per unit volume increases sharply as the total volume decreases, in agreement with the natural evolution toward miniaturization in technology.

The work presented in this paper is dealing with numerical simulation of energy separation mechanism and flow phenomena within a Ranque-Hilsch vortex tube. Simulation of turbulent, compressible, highly swirling flow inside vortex tube is performed using RANS approach, with Favre averaged conservation equations. For turbulence closure, k-ε and k-ω shear-stress transport models are used. It is assumed that the mean flow is axisymmetric, so the 2-D computational domain is used. Computations were performed using open-source CFD software Open-FOAM. All compressible solvers available within OpenFOAM were tested, and it was found that most of the solvers cannot predict energy separation. Code of two chosen solvers, which proved as the most robust, is modified in terms of mean energy equation implementation. Newly created solvers predict physically accepted behavior in vortex tube, with good agreement with experimental results. Comparison between performances of solvers is also presented.

Kerbside collection is most common method in Turkey for solid waste collection. Çorlu has increasing population rate due to growing industrial activities and investments. Information used in the study such as; average waste collection amount in a month, truck properties (volume, engine power) and travelled distance during waste collection were obtained from Çorlu Municipality. Total fuel consumption of trucks during collection of 1-ton waste for 1-km is between 2.12-5.47 L diesel / ton in Çorlu. Greenhouse gas emissions for different scenarios were calculated in this study. First, GHG emission estimation done for same volume trucks using different fuel types, second estimation done for trucks with the same engine power using different fuel types. GHG emissions for Çorlu were calculated using emission coefficients for; diesel, gasoline, heavy oil, light oil, natural gas fuels from literature sources. Maximum emission is found as 35 kg CO2-eq /ton, in case of using heavy oil in the 3.5 m 3 vehicle and minimum emission is occurred 5,08 kg CO2-eq while using natural gas in 13+1,5 m 3 truck. Contrary to expectations, kg CO2-eq / ton value (which is show the GHG emission rate) is decrease while the engine power (horsepower) increases. It has been determined that there are significant differences in GHG emissions when the truck and/or fuel type are changed, even without changing factors such as route, waste collection frequency and number of stops (number of containers).

This paper reports the results of three-dimensional numerical optimisation of microchannel heat exchanger with square and circular cooling channels. The objective of the optimisation is to maximise the global thermal conductance or minimise global thermal resistance. Response surface optimisation methodology (RSM) is used in the numerical optimisation. A high-density heat flux (2.5×106W/m2) is imposed at the bottom surface of the unit cell microchannel and numerical simulation carried out using ANSYS Fluent commercial software package.The elemental volume and axial length N=10mm of the microchannel were all fixed, while the width was free to morph. The cooling technique employs single-phase water which flows through the rectangular block microchannel heat sink to remove the heat at the bottom of the microchannels in a forced convection laminar flow regime. The velocity of the fluid pumped across the microchannel axial length is the range 400≤Rew≤500. Finite volume method (FVM) is us...

In this work it is applied the Constructal Theory for the study of the geometry of an "+"-shaped isothermal cavity inserted in a conductive solid body. Main goal is to minimize the maximum temperature in the solid. The total volume of the solid and the total volume of the cavity are kept fixed while the dimensions of the cavity geometry vary according to constraints and degrees of freedom defined by the Constructal Design. The solid body has internal heat generation and its external surfaces are insulated. Cavity walls are isothermal with constant temperature T min. Obtained results indicate that the optimal performance of "+"-shape cavity is 37.2% better that the optimal performance of "C"-shape cavity and 10.8% better than the "T"-shaped cavity for the same thermal conditions.

Anambra drainage basin is decimated by a plethora of rivers emanating from heavy rainfall and fluviogeomorphic surface processes. Apparently, hydrologic and sedimentologic processes influences basin form and processes which are governed by laws of drainage basin composition postulated by Horton. Metrical dimension provides linearity, topographic and area variables used to validate Horton's postulates in the Anambra drainage basin. Topographic tools and ARC GIS 10.2 were utilized. The stream number, length and areal quantities showed that the three laws of drainage basin composition postulated by Horton are valid. It is a 6th order dendritic pattern with elongated shape and coarse texture. The drainage density, stream frequency and infiltration number were with low values: 0.10, 0.10 and 0.27 respectively while the overland processes recorded 0.51, implying heavy dissection. The constant of channel maintenance is 0.99 km 2. The relief characteristics indicated a low relief. The significance of the morphometric attributes of the Anambra drainage basin has a lot of implications in agricultural practice and erosion processes.

The universal phenomenon of evolution consists of change after change in flow configuration in a time direction that is perceptible to the observer. This reality clashes with the doctrine of precise optima, minima, and maxima, now rigidly in place because of calculus and computational simulations of all kinds of flowing and changing configurations. With two dissimilar examples, access on an area (a human settlement) and along a line (animal locomotion), it is shown that even a 1-percent imperfection in performance is accompanied by a sizable bandwidth of freedom to hit the ‘target’, that is, an easily accessible design with close to perfect performance. The evolutionary designs reveal the physics behind the phenomenon of diminishing returns in the vicinity of the mathematical optimum. In evolution what works is kept.

An ejector is a device that entrains a secondary flow into a high speed stream that is generated by expansion of high pressure motive gas [1]. These ejectors can be broadly classified into central ejectors and annular ejectors. A large majority of applications involve central ejectors where the motive gas flow is injected along the centre of the flow passage of the secondary flow. Dutton and Carroll [2] proposed an optimization procedure for such ejectors without taking the mixed supersonic flow region into account and generated the design curves considering the constant Total temperature, Molecular weight and Specific heat ratios. However in some applications involving high temperature gases such as in ramjet/scramjet and gas turbine test facilities, an annular supersonic ejector is more appropriate where annular injection of the motive gas at the periphery of the flow passage is desired to avoid the exposure of the motive gas flow nozzle to the high temperature combustion product ...

This article addresses the main research areas
identified in the call for contributions to this special
issue. With examples from published articles and
books, the present article shows that all the identified
areas are already covered by the universal principle
underlying all evolution: the constructal law (1996),
i.e. the physics law of design evolution in nature (free
morphing, flowing, moving systems). The universal
principle of evolution belongs in thermodynamics
because thermodynamics is a universal science and
evolution is a universal phenomenon. The principle
unites the natural sciences with the social sciences,
and the living with the non-living. It unifies
the world of science and its languages (energy,
economy, evolution, sustainability, etc.), and brings
together the natural and artificial flow architectures,
the human made and the not human made. The
principle establishes firmly in physics the reality
that humans are part of nature. With the principle,
physics extends its coverage over phenomena that
were previously considered out of reach: social
organization, economics and human perceptions.
Such phenomena are physical, i.e. facts. The entire
world depends on the science of useful things,
and benefits greatly from a physics discipline with
freedom, life, wealth, time, beauty and future.

Here we illustrate the free search for the optimal geometry of flow channel cross-sections that meet two objectives simultaneously: reduced resistances to heat transfer and fluid flow. The element cross section and the wall material are fixed, while the shape of the fluid flow opening, or the wetted perimeter is free to vary. Two element cross sections are considered, square and equilateral triangular. We find that the two objectives are best met when the solid wall thickness is uniform, i.e., when the wetted perimeters are square and triangular, respectively. We also consider arrays of square elements and triangular elements, on the basis of equal mass flow rate per unit of array cross sectional area. The conclusion is that the array of triangular elements meets the two objectives better than the array of square elements.

Two-phase air-water flows in a microscale fractal-like flow network were experimentally studied and results were compared to predictions from existing macroscale void fraction correlations and flow regime maps. Void fraction was assessed using (1) two-dimensional analysis of high-speed images (direct method) and (2) experimentally determined using gas velocities (indirect method). Fixed downstreamto-upstream length and width ratios of 1.4 and 0.71, respectively, characterize the five-level flow network. Channels were fabricated in a 38 mm diameter silicon disk, 250 lm deep disk with a terminal channel width of 100 lm. A Pyrex top allowed for flow visualization. Superficial air and water velocities through the various branch levels were varied from 0.007 m/s to 1.8 m/s and from 0.05 m/s to 0.42 m/s, respectively. Two-phase flow regime maps were generated for each level of the flow network and are well predicted by the Taitel and Dukler model. Void fraction assessed using the indirect method shows very good agreement with the homogeneous void fraction model for all branch levels for the given range of flow conditions. Void fraction determined directly varies considerably from that assessed indirectly, showing better agreement with the void fraction correlation of Zivi.

Built an idealized thermodynamic model for solar tower thermal power plants. Analyze the influence of various parameters on thermal and exergy efficiencies. The optimum temperature would increase with the concentration ratio. The endoreversible engine efficiency would have an optimum value.

The long lots system, also known as the ribbons farming system, is a historical land use pattern, which can be encountered in some specific regions of the world, including in North America, both in the Nouvelle-France, and in the New-Mexico regions. In this paper, we show that, in the late 1990s, the first publications on Constructal Theory, which discussed topics such as urban street patterns or airport systems design, already contained the principles underlying the emergence of the man-made long lots system, but had not yet been linked to land use patterns such as the ribbons farming system. We show that this farming pattern is driven by the Constructal Law. It leads to land use geometries similar, at a human scale, to computer cooling systems. In brief, like many natural designs, the long lots system emerges as a "urge to organize" under local and global constraints specific to the economy of agricultural products trade, and according to the Constructal Law of evolving flow systems. The design of long lots systems can thus be viewed as a historical precursor of the Constructal Design approach, an approach worth considering in the design of sustainable cities.

To seek the thermodynamic basis for the well-known Maximum Entropy Production (MEP) principle has recently received considerable attention in the scientific community. However, a little success has been achieved in the reconciliation between the MEP and the currently existing physical laws. In fact, the MEP is not a fundamental physical principle, because it is not consistent with the minimization of energy expenditure rate (MEE) principle that has been supported by observations for water flow on the ground surface. A fundamental physical principle should be able to explain observations from different areas. To resolve the inconsistence, Liu (2014), based on observations from different geological systems, proposed a new thermodynamic hypothesis that states that a nonlinear natural system that is not isolated and involves positive feedbacks tends to minimize its resistance to the flow process through it that is imposed by its environment. He also shows that the MEP is actually a by-product of the minimization of heat transfer resistance in the Earth-atmosphere system under a relatively restrictive condition. This communication further derives that previous result in the more general case for the Earth-atmosphere system. The consistence between the thermodynamic hypothesis of Liu (2014) and Darwin's evolution theory is also briefly touched on. All these support the validity of the hypothesis of Liu (2014).

This work is on measurement of automobile performance on Nigerian roads using the method of fuel economy. The current located area is the road linking Maiduguri city to Bama town all in Bono State, Nigeria. The emphasis is made on performance of automobile in relation to fuel consumption with fuel economy. Road safety enhancement is also highlighted. Two particular methods (by two groups of physicists) were first identified for measurement of automobile performance. For reasons of accuracy, one of them was decided for the current study area covering a distance of sixty-six kilometers (66 km). Three samples of vehicles namely, Golf II, Hiace II and 505 Peugeot Station Wagon were chosen because the 1985 models were found to be commoner. Conditions of the road affected the results. Further, when global averages of the samples were analyzed, except for small deviation, the method verified well. Other useful parameters associated with fuel consumption and fuel economy were also determined. This study particularly finds that the average fuel economy, average energetic performance of both Golf II and 505 Peugeot Station Wagon is equivalent but higher than that of Hiace II.

Buildings account for more than 40% of EU final energy demand. Most of the existing buildings will be standing over 30 years time, when the new construction rate is still low. This means that the existing building refurbishment represents a key factor for the primary energy saving potential of EU, up to 2050. The heat exchange measurements in situ are so crucial for real dynamic behaviour characterization for standard and new solutions, such as the operative settings investigation due to user and external constrains. A new heat flux sensor development, called Tile, is exposed in this paper. The research started from the study of a commercial sensitive element based on semiconductor materials. Its thermal and electrical properties were experimental investigated. An effective and dedicated frame was set up, aiming at accuracy and stability advantages in terms of its influence on the measured values. Some prototypes of Tile sensor were realized and checked.

This paper aims to numerically study the heat transfer in a two dimensional finned channel under laminar, incompressible and forced convective flow with adiabatic walls. The main purpose is to maximize the convection heat transfer by changing the fin’s dimensions by means of Constructal Design. Numerical computations are performed for different Bejan numbers ranging from 0.182 up to 18.2. For all simulations the Prandlt number is kept constant, Pr = 0.71. The fluid motion throughout the channel is caused by imposition of pressure difference between inlet/outlet surfaces. Concerning heat transfer, it is caused by the difference of temperature between the inlet stream of fluid and the heated fins placed at the channel surfaces. The first fin is positioned in the lower surface of the channel while the second one is placed in the upper one. The problem is submitted to three constraints, the channel area (H × L), area of two fins and occupancy areas for the fins. It is considered here th...

In this paper, a study of the elemental construct of an I-shaped fin cooling a heat generating plate is conducted in the framework of the constructal design method. Using the minimization of the maximum excess of temperature as an objective and considering that heat is generated in the conductive strip within a certain surface and with a different amplitude from the plate, the constructal design method permits to obtain a new optimal shape ratio (more general than the optimums found in the literature considering no-generation in the conductive strip or heat generated with the same amplitude in the two materials). Then, the thermal model used until here in stationary state (hypotheses on heat diffusion) is extended to take into account the time. The analytical solution obtained (verified numerically) is compared to classical heat diffusion through an engineering application (cooling an electronic device) where it keeps a good precision for times larger than 1% of the stationary time.

Thermodynamics serves several functions for chemistry and ita sister sciences and technologies. The first of these historically, and still one of the most important, is the provision of limits on the performance of proceases and devices. The very origins of thermodynamics developed from the creative ways people addressed the problem of how beat to pump water out of mines.' The provision of limits of performance is the main concern of the work we describe here. Research during the past 9 years has led to new ways of finding natural bounds on performance under the constraint that the system operate at a nonzero rate, thereby giving more realistic bounds than those derived from reversible processes. Some approaches tell us only the limits; others tell us also the process that would yield those limits. Frequently, we can infer how the lower bound on the energy we pay for operating at a nonzero rate depends on that rate of operation. There even exist processes for which no zero-rate reversible counterpart exists.2 The difference between the performance of a reversible process and a real-time process may be considerable, so great that relying on the bounds based on reversible models can be quite misleading. For example, a theoretical heat engine operating between 300 K and 2700 K with friction, finite heat conductance between the engine and its reservoirs, and a heat leak: all chosen to correspond approximately to an automobile engine, has an ideal Carnot efficiency of (2700-300)/2700 = 0.89. The efficiency of the engine when operating to generate maximum power is only 0.33. Another example is the frequent use of roasting with subsequent reduction in ore processing, both processes Bjarne Andresen was born In copenhagen in 1949. He studied at We& leyan Unhrerstty and at Cal Tech prlor to receMng hls Ph.D. from the University of Copenhagen in 1974. He is now a Lecturer in physics at the H. C. 0rsted Institute, University of Copenhagen. R. Stephen Berry was born in Denver. Colorado. In 1931. He recehred his A.B. (1952) and hk Ph.D. (1956) from W a r d Unlverslty. He was an Instructor at Haward and the Unhrerslty of Mchlgan and then moved to Yale UniversHy as an Assistant Professor. In 1964 he moved to the Unhrersity of Chicago and became a Professor thefe in 1967, and he remains there. Mary Jo W e c h e n was born In PMladelphia in 1953. She recehred her B.A. at Reed College In 1974 and her Ph.D. at Northwestern University in 1978. She is now an Asslstanl Professor at Noctheastern University.

In this study, fluid flow and energy separation in a micro-scale Ranque-HilschVortex Tube are numerically investigated. The flow is assumed as 2D, steady,compressible ideal gas, and shear-stress-transport SST k-W is found to be a bestchoice for modeling of turbulence phenomena. The results are in a good agreementwith the experimental results reported in the literature. The results show that fluidflow and energy separation inside the micro-scale vortex tube is quite similar tothose of traditional ones. Moreover, it is found that non-dimensional forms of coldtemperature difference and refrigerating capacity are only dependent on cold massfraction. In addition, two correlations have been proposed to estimate nondimensional forms of cold temperature difference and refrigeration capacity in themicro-scale vortex tube.

In studies of finite-time thermodynamics, most performance analyses concern the maximum power output and the corresponding efficiency for heat engines. In this paper, instead of just maximizing power for a cycle, the power density (the ratio of the power to the maximum specific volume in the cycle) is maximized for an Atkinson engine. The results showed that the efficiency at maximum power density is always greater than that at maximum power, and the design parameters at maximum power density lead to smaller and more efficient Atkinson engines with larger pressure ratios.