Experimental and numerical investigation on passive and active μDMFC

In this paper, design and fabrication of a micro direct methanol fuel cell based on stainless steel in two kind of active and passive with cross strip and parallel flow field are presented. Dropping pressure, velocity and heat transfer of the cell is simulated by a 3D modeling in fluent software. An optimum operating condition of the cell is obtained by the mass flow and temperature limitation. The cell was tested in different temperatures and mass flow rate and the cell performance is investigated in different condition. Maximum power density of the cell in active condition and at 60 °C was 170 mW/cm² and in passive condition was 85 mW/cm². A μDMFC with different flow field is investigated. Cross strip flow field has shown better performance and the effect of cell orientation on performance is also investigated.     

Resource assessment and removal analysis for corn stover and wheat straw in the Eastern and Midwestern United States—rainfall and wind-induced soil erosion methodology

The focus of this study was to develop a methodology to estimate “hectare-weighted”, county-level, corn stover and spring and winter wheat straw removable residue quantities in the USA for 1995–1997 in 37 states (north–south line from North Dakota to Texas and all states east) such that tolerable rainfall and wind soil loss limits were not exceeded.The methodology developed and employed in this study was based on the revised universal soil loss equation (RUSLE) and the wind erosion equation (WEQ), which were used to predict individual county-level corn or wheat yields required at harvest to insure that the amount of soil loss would not exceed the tolerable soil loss limit. These yields were then compared to actual county-level corn or wheat yields to determine the quantity of removable residue.Results of this study indicate an annual average of over 42 and 8 million metric tons of corn stover and straw (spring and winter wheat), respectively (46.2 and 8.8 million tons) were potentially available for removal between 1995 and 1997 in these 37 states.     

Uniaxial and biaxial ratchetting in piping materials—experiments and analysis

The performance of the Chaboche kinematic hardening model has been evaluated in this paper to predict the ratchetting responses for a broad set of uniaxial and biaxial loading histories. The investigations have been performed with reference to both uniaxial and biaxial experimental data, viz. (a) strain and stress controlled uniaxial tests on tensile specimens; (b) biaxial tests on straight pipes with constant internal pressure and cyclic bending load; and (c) a shake table test on elbow. The parameters of the Chaboche model have been calculated from the uniaxial strain controlled stable hysteresis loop. Amongst the various parameters in the Chaboche model, it has been found that the selection of the value of γ₃ plays a crucial role in achieving better simulation. The Chaboche model was observed to predict complete shakedown for γ₃=0. On the other hand, the model closely simulated the experimental results for γ₃=9. The same parameters have been used to analyze the biaxial loading condition. Ratchetting simulation studies by the Chaboche model have resulted in reasonably good agreement with experiments.     

Hydropower–water and renewable energy in Turkey: Sources and policy

Turkey's energy consumption has been growing much faster than its production. It forces Turkey to make a rapid action to supply energy demand. From the viewpoint of primary energy sources (petroleum and natural gas), Turkey is not a rich country, but it has an abundant hydropower potential to be used for generation of electricity. Hydropower is the most important kind of renewable, sustainable energy and a proven technology for electricity generation. The aim of this paper is to discuss sources and policy of hydropower, water and renewable energy in Turkey and compares the hydropower application with Europe.     

On exergy and sustainable development—Part 2: Indicators and methods

This second part is the continuation of Wall and Gong [Exergy Internat. J. 1 (3) (2001), in press]. This part is an overview of a number of different methods based on concepts presented in the first part and applies these to real systems. A number of ecological indicators will be presented and the concept of sustainable development will be further clarified. The method of Life Cycle Exergy Analysis will be presented. Exergy will be applied to emissions into the environment by case studies in order to describe and evaluate its values and limitation as an ecological indicator. Exergy is concluded to be a suitable ecological indicator and future research in this area is strongly recommended.     

Sondhauss and Rijke oscillations—thermodynamic analysis,possible applications and analogies

The phenomena of acoustical pressure oscillations generated in a gas by a steady heat source may be separated into two distinct types: (i) Sondhauss oscillations which occur in a pipe having one end closed and one open; (ii) Rijke oscillations which occur in a pipe with both ends open. After reviewing representative literature, actual and possible applications are described. Analogies and differences among these and similar systems are considered from a thermodynamic point of view.     

Experimental and numerical study on laminar burning velocities and flame instabilities of hydrogen–air mixtures at elevated pressures and temperatures

Experimental and numerical study on hydrogen–air flames at elevated pressures and temperatures was conducted. Meanwhile, the calculation is extended to initial pressure and temperature up to 8.0 MPa and 950 K, respectively. Laminar burning velocities and Markstein lengths were obtained at the elevated pressures and temperatures. Sensitivity analysis and flame structure were also analyzed. The results show good agreement between the computed results and experimental data. The study shows that laminar burning velocities are increased with the increase of initial temperature, and they decrease with the increase of initial pressure. With the increase of initial pressure, advancement of the onset of cellular instability is presented and Markstein length is decreased, indicating an increase of flame instability with the increase of initial pressure. The study shows insensitivity of flame instability to initial temperature. Laminar burning velocity is depended on the competition between the main chain branching reactions and chain termination reaction. The chain branching reactions are the temperature-sensitive reaction, while the termination reaction is the temperature-insensitive reaction. Through the extraction of the overall reaction orders, it is demonstrated that with increasing pressure, the overall reaction orders give a decreasing trend and then increasing trend. This behavior suggests an analogy to three explosion limits of hydrogen/oxygen mixtures. Numerical study also shows that the suppression (or enhancement) of overall chemical reaction with the increase of initial pressure (or temperature) is closely linking to the decrease (or increase) of H, O and OH mole fractions in the flames. Strong correlation is existed between burning velocity and maximum radical concentrations of H and OH radicals in the reaction zone of premixed flames. On the basis of the numerical data, an empirical formula for laminar burning velocity is correlated for the hydrogen–air premixed mixture at elevated pressures and temperatures. The correlated laminar burning velocities are in good agreement with the known experimental results and simulated results with CHEMKIN. The correlation can be used in the calculation of laminar burning velocities at evaluated pressures and temperatures.     

On exergy and sustainable development—Part 1: Conditions and concepts

The future of life on our planet is a matter of great concern. This paper is based on a vision of sustainable development. It is divided into two parts. The first part introduces conditions and concepts that are of importance for sustainable development. Environmental conditions in terms of causes and effects of emissions, the concept of exergy as a physical measure of difference or contrast and a number of different exergy forms common in nature are presented. Emissions and pollutants are differences in the environment, thus effecting the environment. Exergy is a suitable measure of these differences. The concept of sustainability is examined with relation to exergy flows on the earth. Part 2 of this paper introduces methods based on presented concepts and applies these to real systems. Exergy is applied to emissions to the environment by case studies in order to describe and evaluate its values and limitations as an ecological indicator. Exergy is considered as a useful ecological indicator by reference to the literature in the field.     

Hydrogen production from methane and solar energy – Process evaluations and comparison studies

Three conventional and novel hydrogen and liquid fuel production schemes, i.e. steam methane reforming (SMR), solar SMR, and hybrid solar-redox processes are investigated in the current study. H₂ (and liquid fuel) productivity, energy conversion efficiency, and associated CO₂ emissions are evaluated based on a consistent set of process conditions and assumptions. The conventional SMR is estimated to be 68.7% efficient (HHV) with 90% CO₂ capture. Integration of solar energy with methane in solar SMR and hybrid solar-redox processes is estimated to result in up to 85% reduction in life-cycle CO₂ emission for hydrogen production as well as 99–122% methane to fuel conversion efficiency. Compared to the reforming-based schemes, the hybrid solar-redox process offers flexibility and 6.5–8% higher equivalent efficiency for liquid fuel and hydrogen co-production. While a number of operational parameters such as solar absorption efficiency, steam to methane ratio, operating pressure, and steam conversion can affect the process performances, solar energy integrated methane conversion processes have the potential to be efficient and environmentally friendly for hydrogen (and liquid fuel) production.     

Heat Transfer and hydrodynamics in Annular Chromatography：CFD—Simulation and Experiments

IntrotctiouAImular chrDmatography Provides the POssibility ofseparating multicomponent fixtures continuously inone single unit. The rotating annulus of thechromatotw can be filled with arbitw stationalsPhases depending on the existing separation Problem.The feed is introduced at a fixed and stationary sechonat the top of the unit, while the eluent is distributedeverywhere else around the upper circumference. At thebottom the separated Products can be collected atcendn stationals exit angle…     

Embodied energy and intensity in China’s (normal and processing) exports and their driving forces, 2005-2015

International trade has important impacts on a country’s energy consumption. This paper first uses the time-series (2005–2015) extended input-output database to study China’s embodied energy and intensity in both normal and processing exports. Structural decomposition analysis (SDA) is then applied to analyze the driving forces behind the embodiment changes. The empirical results show that China’s energy embodied in both normal and processing exports first increased in 2005–2008, dropped in 2009 due to the global financial crisis, and then rose again after 2009, and finally dropped in 2014–2015. The embodied energy in trade as a percentage of total energy consumption in China was relatively stable before and after the global financial crisis, at around 28% over the 2005–2008 period, and 22% over the 2009–2015 period. The contribution of the aggregate embodied intensity (AEI) of exports to China’s aggregate energy intensity dropped from 30% in 2005 to 21% in 2015. Among China’s trading partners, the United States, Japan and Korea together accounted for around half of China’s embodied energy and AEI in exports in 2005, but their shares dropped to only one third in 2015. Energy efficiency improvement played the key role in reducing the embodied energy and intensity in China’s exports. Similar analysis can be applied to other regions and indicators.     

Experimental and Numerical Investigation of Enhancement of Heat and Mass Transfer in Adsorbent Beds

ＥｘｐｅｒｉｍｅｎｔａｌａｎｄＮｕｍｅｒｉｃａｌＩｎｖｅｓｔｉｇａｔｉｏｎｏｆＥｎｈａｎｃｅｍｅｎｔｏｆＨｅａｔａｎｄＭａｓｓＴｒａｎｓｆｅｒｉｎＡｄｓｏｒｂｅｎｔＢｅｄｓＬｉｕＺｈｅｎｙａｎ；ＦｕＺｈｕｍａｎ；ＧｅＸｉｎｓｈｉ；ＳｕＹｕｅｈｏｎｇ；...     

Energy and exergy analysis of photovoltaic–thermal collector with and without glass cover

In photovoltaic–thermal (PV/T) technology, the use of glass cover on the flat-plate hybrid solar collector is favorable to the photothermic process but not to the photovoltaic process. Because of the difference in the usefulness of electricity and thermal energy, there is often no straight forward answer on whether a glazed or unglazed collector system is more suitable for a specific application. This glazing issue was tackled in this paper from the viewpoint of thermodynamics. Based on experimental data and validated numerical models, a study of the appropriateness of glass cover on a thermosyphon-based water-heating PV/T system was carried out. The influences of six selected operating parameters were evaluated. From the first law point of view, a glazed PV/T system is found always suitable if we are to maximize the quantity of either the thermal or the overall energy output. From the exergy analysis point of view however, the increase of PV cell efficiency, packing factor, water mass to collector area ratio, and wind velocity are found favorable to go for an unglazed system, whereas the increase of on-site solar radiation and ambient temperature are favorable for a glazed system.     

Isothermal and non-isothermal oil–water flow and viscous fingering in a porous medium

Immiscible flow of heavy oil in a porous formation by high temperature pressurized water has been numerically studied. The physical region is a square domain in the horizontal plane with low and high pressure points at the opposite corners along one of the diagonals. Water, the invading fluid, when introduced at high pressure displaces the in situ oil towards the low pressure production zone. The extent of displacement of oil by water through the porous medium in a given amount of time and the appearance of preferential flow paths ( fingers) is the subject of the present investigation. The resistance to water–oil movement arises from the viscous forces in the fluid phases and the capillary force at their interface. Based on their relative magnitudes, various forms of displacement mechanisms can be realized. As the viscosity ratio of heavy oil to water is large, viscous forces in the oil phase become dominant and constitute the major factor for controlling the flow distortions in the porous formation. A mathematical model that can treat the individual fluid pressures, capillary effects and heat transfer has been employed in the present work. A fully implicit, two-dimensional numerical model has been used to compute the pressure and temperature fields. The domain decomposition technique has been adopted in the numerical solution since the problem is computationally intensive. Naturally occurring oil-rich reservoirs to which the present study is applicable are inhomogeneous and layered. A qualitative study has been carried out to explore the effect of permeability variations on the flow patterns. Numerical calculations show that non-isothermal effects as well as layering promote the formation of viscous fingers and consequently the sweep efficiency of the high pressure water front.     

Prevention of fouling and scaling in stationary and circulating liquid–solid fluidized bed heat exchangers: Particle impact measurements and analysis

Fluidized particles in liquid–solid fluidized bed heat exchangers are able to remove deposits from the walls and thus to prevent fouling or scaling. This fouling prevention ability is believed to depend strongly on the frequency and force of particle–wall collisions. This paper presents piezoelectric measurements of impacts on the wall in both stationary and circulating fluidized beds of various particle sizes and bed voidages. Two types of impacts were measured, namely by collisions of particles on the sensor and by liquid pressure fronts induced by particle–particle collisions close to the sensor. The characteristics of both impact types are used to analyze the total impulse and energy exerted by impacts on the wall for various fluidized beds.     

Research and Development on PFBC—CC in China and Jiawnag Pilot plant Project

ＲｅｓｅａｒｃｈａｎｄＤｅｖｅｌｏｐｍｅｎｔｏｎＰＦＢＣ－ＣＣｉｎＣｈｉｎａａｎｄＪｉａｗａｎｇＰｉｌｏｔＰｌａｎｔＰｒｏｊｅｃｔＮｉｎｇｓｈｅｎｇＣａｉ；ＭｉｎｇｙａｏＺｈａｎｇ；ＤａｎＬｉ；ＷｅｎｔｉｎｇＦｕ（ＴｈｅｒｍａｌＥｎｅｒｇｙＥｎｇｉｎ...     

Flow Field and Performance of Cross Flow Fans——Experimental and Theoretical Investigations

Due to the construction and the operating principle the prediction of performance of Cross Flow Fans (CFF) is difficult and the knowledge about the internal flow regime is limited. To investigate the impact of geometrical parameters on the performance of CFF, experimental investigations, using Particle Imaging Velocimetry (PIV), and CFD calculations were carried out. Some results of PIV measurements and CFD calculations are presented, which give an impression of the internal flow and confirm the numerical calculations.     

Nucleate Boiling Enhancements on Porous Graphite and Microporous and Macro–Finned Copper Surfaces

Enhancements in nucleate boiling heat removal with dielectric liquids, by increasing either the bubbles nucleation sites density and/or the wetted surface area, are desirable for immersion cooling of high-power computer chips. This article presents the results of recent investigations of nucleate boiling enhancement of FC-72, HFE-7100, and PF-5060 dielectric liquids on porous graphite, copper microporous surfaces, and copper surfaces with square corner pins, 3 mm × 3 mm in cross-section and 2, 3, and 5 mm tall. All surfaces have a footprint measuring 10 × 10 mm. These investigations examined the effects of liquid subcooling up to 30 K and surface inclination, from upward-facing to downward-facing, on nucleate boiling heat transfer coefficient and critical heat flux. Natural convection of dielectric liquids for cooling chips while in the stand-by mode, at a surface average heat flux <20 kW/m², is also investigated for the different surfaces.     

Constitutive equations and wave propagation in Green–Naghdi type II and III thermoelectroelasticity

In this article we extend the theory of thermoelasticity devised by Green and Naghdi to the framework of finite thermoelectroelasticity. Both isotropic and transversely isotropic bodies are considered and thermodynamic restrictions on their constitutive relations are obtained by virtue of the reduced energy equality. In the second part, a linearized theory for transversely isotropic thermopiezoelectricity is derived from thermodynamic restrictions by constructing the free energy as a quadratic function of the 11 second-order invariants of the basic fields. The resulting theory provides a natural extension of the (linear) Green and Naghdi theory for types II and III rigid heat conductors. As a particular case, we derive the linear system which rules the processes depending on the symmetry axis coordinate only.