Solidification inside a sphere—an experimental study

This paper presents the investigations of the solidification of an n-hexadecane inside a spherical enclosure. The effect of solidification process was investigated for three different constant surface temperature conditions (13 °C, 8 °C and 3 °C) and for three different initial superheats of n-hexadecane (8 °C, 2 °C and 0 °C). It was observed that the solidification phase front propagates uniformly inwards towards the centre of the sphere. The concentricity of the solid–liquid phase front deteriorates as time progresses due to shrinkages causing formation of voids inside the sphere. A lower constant surface temperature results in a larger solidified mass fraction. The effect of the initial liquid superheats of the PCM on the solidification is insignificant.     

An experimental study on hydrogen–methane mixtured fuels

In this study, temperature distributions from turbulent chemical reactive flow inside a model combustor have been presented for various mixtured hydrogen–methane fuels. The gas emissions were also obtained at the combustor exit. A platinum–platinum 13% rhodium thermocouple (R type) was used for measurement of axial and radial temperatures. The axial and radial temperature measurements were taken from six various distances and four distances, respectively. Experimental measurements were made at excess air ratios of 1.2 and 1.7, two various thermal powers including 40 and 60 kW and two various hydrogen–methane blending fuels (volumetrically 30% H₂–70% CH₄ and 70% H₂–30% CH₄). The results show that the temperature level increases, CO and CO₂ emissions decrease when the hydrogen content is increased in mixtured fuel, hydrogen–methane mixtured fuels are successfully used without any important modification in natural gas burner.     

Furnace for biomass combustion – Comparison of model with experimental data

As one of the most easily accessible renewable energy resources, straw can be burned to provide heat energy. In this paper, results of theoretical and experimental research conducted under the proceedings of mathematical – numerical modeling of turbulent reacting flows has been presented. Two-dimensional turbulent flow model with homogeneous chemical reactions has been developed. The proposed model has been analyzed on the example of adiabatic combustion chamber for combustion of agricultural biomass. Turbulent flow is considered using time averaging Navier–Stokes equations that are closed by k–ε turbulence model. Calculations based on the proposed models were conducted using commercial CFD package FLUENT 6.3.26. For the purposes of experimental research, measurements of fluid flow and thermal parameters, such as continuous measurement of temperature in different points in the workspace furnace, air flow, flue gas flow, continual analysis of combustion products as well as setting heat and material balance, were carried out. Comparative analysis of the results of experiments and calculations indicate satisfactory agreement between the model and experiment.     

China ADS sub-critical experimental assembly—Venus-1 and preliminary experiment

China s accelerator-driven sub-critical system (ADS) sub-critical experimental assembly Venus-1 and the preliminary experiment is presented. The core of Venus-1 is a coupled one of a fast neutron zone and a thermal neutron zone. The fast neutron zone is at the centre of the core and formed by natural uranium fuel. A fast neutron spectrum field can be produced in the fast neutron zone and used for the transmutation of minor actinides (MAs). The thermal neutron zone surrounds the fast neutron zone and is formed by low-enriched uranium fuel. It is a fission zone. An epithermal neutron zone between the fast neutron zone and the thermal neutron zone can be established for the transmutation of long-lived fission products (LLFP). On July 18, 2005, the first fuel element was loaded into the Venus-1 sub-critical assembly and some preliminary experiments about the sub-critical neutronics were performed. The Venus-1 can be driven by an Am-Be source or other steady neutron source (Cf-252, D-D reaction and D-T reaction) to study the effect of the external neutron source with different energies or a D-T pulsed neutron source on the dynamic characteristics.     

Lessons from Rotor 37

INTanDUCTIONhi1992theturbomachinerycommittee0ftheIoter-nationalGasTurbineInstitute(IGTI)decidedtosetuPatestcaseforCFDcalculations.Aftersomedebateitwasdecidedthatthetestcasesh0uldbecalculated'blind',i.e.thattheexperimentalresultssh0uldn0tbemadeawilableulltilafterthesolutionshadbeensubndtted.NASA(LewisResearchCenter)offeredasuitabletestca-seintheformofahighlyloadedtransoniccompressorrot0rwhichwasthenbeingtestedwitheXtensiveuseoflaseranemometrytomeasuretheiliternalflow.Themeasurementsw…     

Development of hydrogen absorption–desorption experimental test bench for hydrogen storage material

A volumetric experimental set-up used for measuring hydrogen absorption–desorption characteristics of hydrogen storage material will be presented. Although the experimental set-up is mainly employed to do hydrogen absorption–desorption cycling (including pressure cycling and thermal cycling) measurement automatically, it also can incidentally provide general measurements such as pressure-composition-temperature (P–C–T) curves and kinetics measurements in manual way in the ranges of 0.004–12 MPa and 213–773 K. The experimental set-up can be used to investigate the influence of hydrogen absorption–desorption cycles to hydrogen storage properties of material. The leakage rate of the whole experimental set-up was evaluated systemically. The usability and reliability of the experimental set-up were checked with LaNi₅ and Pd/K (kieselguhr).     

Redirection of sunlight by microstructured components – Simulation,fabrication and experimental results

This paper presents a non-tracking microstructured light redirecting device, which can be integrated into architectural glass. When fixed in the upper area of a window above eye level it redirects the light from solar altitudes between 15° and 65° and illuminates a room without causing glare.Ray-tracing calculations are employed as a tool for identifying suitable configurations and geometries. The results of the simulations show the advantage of combinations of lens-like with prism-like geometries in comparison to conventional microprism arrays regarding the overall light redirection efficiency as well as the producibility. The redirecting device is more lightweight, gives better integration options and is producible in a more economic manufacturing process as systems with similar performance. Measurements of cast silicone prototypes (100 mm × 100 mm × 4 mm) confirmed the simulation results. By now the performance has also been shown by large scale industrially produced acrylic panels with dimensions of 1500 mm × 400 mm × 4 mm.     

Fundamental aspects of the Ti–H system: theoretical and experimental behaviour

We study the interaction of hydrogen with titanium in order to characterize some important microscopic and macroscopic properties of this system. It is technologically important because, among other applications, the Ti–H system is used as structural material in many applications due to the combination of two important mechanical properties, which are resistance to the corrosion and hardness. Using a calculus program based on the jellium model for the material, we obtain values of properties that are important in the determination of the macroscopic behaviour of the Ti–H system, such as the variation of the electronic density and of the induced density of states due to the presence of the hydrogen in the matrix of Ti. From an experimental point of view, we hydride a titanium matrix in order to determine the effects of the process on the properties of the material structure.The general features of these theoretical and experimental methods are discussed and the corresponding results are compared with experimental data.     

Crystallization fouling of CaCO3 – Analysis of experimental thermal resistance and its uncertainty

Crystallization fouling occurs when dissolved salts precipitate from an aqueous solution. In the case of inversely soluble salts, like calcium carbonate (CaCO₃), this may lead to crystal growth on heated walls. Crystallization may also take place in the bulk solution either via homogeneous nucleation or heterogeneous nucleation on suspended material.In this paper, surface crystallization of CaCO₃ and crystallization in the bulk fluid and its effect on the fouling rate on a heated wall are studied. The fouling experiments are done in a laboratory scale set-up of a flat plate heat exchanger. Accuracy of the results is analyzed by uncertainty analysis. SEM and XRD are used to determine the morphology and the composition of the deposited material.The uncertainty analysis shows that the bias and precision uncertainties in the measured wall temperature are the largest source of uncertainty in the experiments. The total uncertainty in the fouling resistance in the studied case was found to be ±13.5% at the 95% confidence level, which is considered to be acceptable.Surface crystallization rate is found to be controlled by the wall temperature indicating that the surface integration dominates the fouling process. The flow velocity affects the fouling rate especially at high wall temperature by decreasing the fouling rate with increasing flow velocity. Crystallization to the bulk fluid is found to enhance significantly the fouling rate on the surface when compared to a case in which fouling is due to crystal growth on the surface.     

Electricity generation using solar parabolic dish system with thermoelectric generator—An experimental investigation

The present electricity grid installation cost as well as the tariff is quite high in India, particularly remote rural areas, to electrify houses. These problems can be easily solved by installing standalone systems that operate on one of the clean energy sources such as solar energy. An experimental analysis of generating electricity from a thermoelectric generator (TEG) powered by a solar parabolic dish concentrator device with aperture area and focal length of 12.6 m² and 2.42 m, respectively, is presented in this article. A TEG is made up of a thermoelectric module connected to a flat receiver by an absorber layer. The studies were carried out in Indian climatic conditions at the National Institute of Technology, Puducherry. Over a spectrum of beam radiation, the system's maximum energy conversion efficiency, as well as efficient electrical output, are evaluated and presented. The proposed system's average effective electrical efficiency is 0.424%, corresponding to the TEG's average energy conversion efficiency of 2.76%.     

What can we learn from high-frequency appliance-level energy metering? Results from a field experiment

This study uses high-frequency appliance-level electricity consumption data for 124 apartments over 24 months to provide a better understanding of appliance-level electricity consumption behavior. We conduct our analysis in a standardized set of apartments with similar appliances, which allows us to identify behavioral differences in electricity use. The Results show that households' estimations of appliance-level consumption are inaccurate and that they overestimate lighting use by 75% and underestimate plug-load use by 29%. We find that similar households using the same major appliances exhibit substantial variation in appliance-level electricity consumption. For example, households in the 75th percentile of HVAC usage use over four times as much electricity as a user in the 25th percentile. Additionally, we show that behavior accounts for 25–58% of this variation. Lastly, we find that replacing the existing refrigerator with a more energy-efficient model leads to overall energy savings of approximately 11%. This is equivalent to results from behavioral interventions targeting all appliances but might not be as cost effective. Our findings have important implications for behavior-based energy conservation policies.     

A complete model of the drying curve for porous bodies—experimental and theoretical studies

Non-hygroscopic, capillary porous bodies, saturated with liquids were dried in an experimental device. By systematically varying the drying agent, the liquids and the differently structured samples, a wide range of drying rate curves were found experimentally and evaluated. The basic equation for the model of the constant-rate drying period refers—according to Krischer—to capillary liquid transportation only. The liquid-diffusion coefficient dependent on moisture content is calculated on the basis of the model considerations of Rumpf. For the falling-rate period the well-known receding drying front model is modified with regard to the capillary liquid movement.     

Effective ways to reduce CO2 emissions from China's heavy industry? Evidence from semiparametric regression models

Using China's province-level panel data from 2005 to 2017, this article uses a semiparametric regression model to investigate CO₂ emissions in China's heavy industry. Empirical results show that while economic growth exerted carbon reduction effects in the eastern region, it stimulated the growth of CO₂ emissions in the central and western regions. This is mainly due to regional differences in industrial structure and the high-tech industry. Energy efficiency has made a greater contribution to reducing CO₂ emissions in the central region because the R&D investment and patent rights granted in this region has grown faster. The energy consumption structure has a more complex impact. It exerts a “pulling first, then restricting” (Ո-shaped) nonlinear effect on CO₂ emissions in the eastern and western regions, but an inverted “N-shaped” effect in the central region. This is mainly due to the differences in the composition of energy consumption across regions. Environmental regulations have a positive “U-shaped” nonlinear impact on CO₂ emissions in the eastern and western regions. It means that environmental regulations help cut down CO₂ emissions in the early stage, and the facilitation effect gradually disappears at the later stage. Conversely, environmental regulations produce an inverted “U-shaped” impact in the central region.     

Ni catalysts derived from Mg–Al layered double hydroxides for hydrogen production from landfill gas conversion

A layered double hydroxide (LDH) precursor with a hydrotalcite-like structure containing Ni/Mg/Al cations was prepared. A series of Ni catalysts containing mixed-oxides and spinel phases were then obtained through thermal treatment of the LDH precursor. X-ray diffraction (XRD), transmission electron microscopy (TEM), and temperature-programmed reduction (TPR) revealed that the LDH derived Ni catalysts have well-dispersed nickel phases upon reduction. The thermal treatment temperatures have noticeable effects on the specific surface area, pore volume, phase transformation, particle size, and reducibility of the catalysts. Thermal treatment temperatures up to 700 °C promote the generation of mesopores which facilitate an increase in specific area and pore volume. Beyond 700 °C sintering occurs, mesopores collapse, and specific area and pore volume decrease. High thermal treatment temperatures favor the phase transformation to spinel solid solutions and the particle size growth. Metal-support interaction is enhanced but reducibility is hindered due to the formation of spinel solid solution phases. The LDH derived Ni catalysts were tested for landfill gas conversion at 750 °C and have shown excellent activity and stability in terms of methane conversion. At gas hourly space velocity (GHSV) of 240,000 h⁻¹ and pressure of 1 atm, 81% methane conversion was achieved during a 48 h test period without apparent catalyst deactivation.     

An experimental study of fuel–air mixing section on unstable combustion in a dump combustor

The main objective of this study is effect of the various fuel–air mixing section geometries on the unstable combustion. For the purpose of observing the combustion pressure oscillation and phase difference at each of the dynamic pressure results, the multi-channel dynamic pressure transducers were located on the combustor and inlet mixing section. By using an optically accessible quartz-type combustor, we were able to OH* measurements to characterize the flame structure and heat release oscillation with the use of a high-speed ICCD camera. In this study, we observed two dominant instability frequencies. Lower frequencies were measured around 240–380 Hz, which were associated with a fundamental longitudinal mode of combustor length. Higher frequencies were measured around 410–830 Hz. These were related to the secondary longitudinal mode in the combustion chamber and the secondary quarter-wave mode in the inlet mixing section. These second instability mode characteristics are coupled with the conditions of the combustor and inlet mixing section acoustic geometry. Also, these higher combustion instability characteristics include dynamic pressure oscillation of the inlet mixing section part, which was larger than the combustor section. As a result, combustion instability was strongly affected by the acoustically coupling of the combustor and inlet mixing section geometry.     

An experimental study on performance and emission characteristics of a methane–hydrogen fuelled gasoline engine

In this paper, the performance and emission characteristics of a conventional twin-cylinder, four stroke, spark-ignited (SI) engine that is running with methane–hydrogen blends have been investigated experimentally. The engine was modified to realize hydrogen port injection by installing hydrogen feeding line in the intake manifolds. The experimental results have been demonstrated that the brake specific fuel consumption (BSFC) increased with the increase of hydrogen fraction in fuel blends at low speeds. On the other hand, as hydrogen percentage in the mixture increased, BSFC values decreased at high speeds. Furthermore, brake thermal efficiencies were found to decrease with the increase in percentage of hydrogen added. In addition, it has been found that CO₂, NO_x and HC emissions decrease with increasing hydrogen. However, CO emissions tended to increase with the addition of hydrogen generally increase. It has been showed that hydrogen is a very good choice as a gasoline engine fuel. The data are also very useful for operational changes needed to optimize the hydrogen fuelled SI engine design.     

Survey of experimental data and assessment of calculation methods of properties for the air–water mixture

Thermodynamic properties of the air–water mixture at elevated temperatures and pressures are of importance in the design and simulation of the advanced gas turbine systems with water addition. In this paper, comprehensive available experimental data and calculation methods for the air–water mixture were reviewed. It is found that the available experimental data are limited, and the determined temperature is within 75 °C. New experimental data are needed to supply in order to verify the model further. Three kinds of models (ideal model, ideal mixing model and real model) were used to calculate saturated vapor composition and enthalpy for the air–water mixture, and the calculated results of these models were compared with experimental data and each other. The comparison shows that for the calculation of saturated vapor composition, the reliable range of the ideal model and ideal mixing model is up to 10 bar. The real model is reliable over a wide temperature and pressure range, and the model proposed by Hyland and Wexler is the best one of today. However, the reliability of the Hyland and Wexler model approved by experimental data is only up to 75 °C and 50 bar, and it is necessary to propose a new predictive model based on the available experimental data to be used up to elevated temperatures and pressures. In the calculation of enthalpy, compared to the ideal model, the calculated results of the ideal mixing model are closer to those of real model.     

Laminar-burning velocities of hydrogen–air and hydrogen–methane–air mixtures: An experimental study

The laminar burning velocities of hydrogen–air and hydrogen–methane–air mixtures are very important in designing and predicting the progress of combustion and performance of combustion systems where hydrogen is used as fuel. In this work, laminar flame velocities of hydrogen–air and different composition of hydrogen–methane–air mixtures (from 100% hydrogen to 100% methane) have been measured at ambient temperatures for variable equivalence ratios (ER=0.8–3.2$\mathrm{ER}=0.8–3.2$). A modified test rig has been developed from the former Cardiff University ‘Cloud Chamber’ for this experimental study. The rig comprises of a 250 mm length cylindrical stainless steel explosion bomb enclosed at one end with a stainless steel plug which houses an internal stirrer to allow mixing. The other end is sealed with a 120 mm diameter round quartz window. Optical access for filming flame propagation is afforded via two diametrically opposed quartz windows in both sides. Flame speeds are determined within the bomb using a high-speed Schlieren photographic technique. This method is an accurate way to determine the flame–speed and the burning velocities were then derived using a CHEMKIN computer model to provide the expansion ratio. The design of the test facility ensures the flame is laminar which results in a spherical flame which is not affected by buoyancy. The experimental study demonstrated that increasing the hydrogen percentage in the hydrogen–methane mixture brought about an increase in the resultant burning velocity and caused a widening of the flammability limits. This experiments also suggest that a hydrogen–methane mixture (i.e. 30% hydrogen+70% methane) could be a competitive alternative fuel for existing combustion plants.