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Oxidative Removal of Volatile Organic Compounds over the Supported Bimetallic Catalysts
Get PDF Volatile organic compounds (VOCs) and methane are pollutants that are harmful to the atmosphere and human health. It is highly required to control emissions of VOCs. Catalytic oxidation is one of the most effective pathways for the elimination of VOCs, in which the key issue is the development of novel and high-performance catalysts. In this review article, we briefly summarize the preparation strategies, physicochemical properties, catalytic activities, and stability for the oxidative removal of VOCs of the supported bimetallic catalysts that have been investigated by our group and other researchers. The supported bimetallic catalysts include the supported noble bimetal, supported noble metal-transition metal, and supported non-precious bimetal catalysts. It was found that catalytic performance was related to one or several factors, such as specific surface area, pore structure, particle size and dispersion, adsorbed oxygen species concentration, reducibility, lattice oxygen mobility, acidity, reactant activation ability, and/or interaction between bimetals or between metal and support. The stability and ability of anti-poisoning to water, carbon dioxide or chlorine were related to the nature of the bimetal and support in the catalysts. In addition, we also envision the development trend of such a topic in the future work
One Dimensional Kardar-Parisi-Zhang Equation in Various Initial Condition Amplitudes
Get PDFThe Kardar-Parisi-Zhang (KPZ) equation with different initial conditions has been investigated in this paper. The numerical solutions using fixed data are performed without noise term and with two kinds of noise terms, i.e., Gaussian noise term and white noise term. The solutions to the equation have been simulated with different initial conditions of the form A sin (x/16) Our study introduces the obtained shape of the solutions to the KPZ equation according to noise terms with three different amplitudes A. The effect of the noise and the amplitude of the noises are presented and investigated
Parametric Study of an Earth-Air Heat Exchanger Assisted by a Green Wall for Passive Cooling in Hot Climates
Get PDF Cooling of buildings during summers in hot climates is an important issue for architects and builders and in terms of energy consumption, residential and tertiary buildings are among the highest consumers. This paper presents a numerical study, focused on a new design for a passive cooling system that uses an earth-air heat exchanger (EAHE), which was assisted by a green wall/air heat exchanger (GAHE) in hot climatic conditions. The tubes buried in the ground and the shadow of a vertical green wall offer considerable advantages for saving energy. The depth of the pipes in the ground was calculated by taking into account the physical properties of the soil. A parametric study was carried out by taking into account the pipe diameter, pipe length, pipe depth in the ground, and the velocity of air in the pipes. The vertical pipe in the green wall allowed a significant additional drop in the air temperature at low air velocities or small pipe depths in the ground. This means that shorter pipe lengths can be used in the earth-air heat exchanger to keep the air outlet temperature of the same order. For an earth air heat exchanger assisted by a green wall operating in hot climates, the design and operation parameters recommended are; pipe diameter 120 mm, length of the buried pipe 4 m, depth in the ground 30 m and air velocity 1 m/s
Mixed Convective Transport Around Staggered Rows of Square Cylinders
Get PDF The unsteady mixed convective transport around multiple bluff objects placed in a staggered configuration with respect to a uniform free stream flow is analyzed through two-dimensional numerical computation. The bluff objects are identical in shape and size with square cross-section and arranged in two different rows within an unconfined domain. A small temperature difference between the objects and the free stream results in the free convection in addition to the forced flow. Simulation is carried out using a finite volume based method considering a uniform cross flow of air (Prandtl number = 0.71) at a moderate Reynolds number (= 100). The transverse spacing between the cylinders may anticipated to influence significantly the wake dynamics, which in turn affects the thermal transport. Simultaneously, the mixed convective strength also influences the wake dynamics and vortex structure formation. An interplay between these two effects aptly dictates the resulting flow dynamics and associated thermal transport. Accordingly, the dimensionless transverse spacing is varied (= 1, 3 and 5) along with the mixed convective strength (Richardson number = 0-2). It is observed that the flow and thermal fields show chaotic nature at smaller transverse spacing. However, at larger spacing, the usual unsteady vortex dynamics persists. Very interestingly it is observed that the chaotic flow at smaller transverse spacing reduces its instability to become unsteady periodic at larger strength of the thermal buoyancy. The average heat transfer from the cylinders is found more at smaller transverse spacings and it increases with increasing mixed convective strength
Experimental Characterization of Low-Temperature Inorganic. Phase Change Materials by Differential Scanning Calorimetry
Get PDF Recently, phase change materials (PCMs) have received significant attention due to their potential for high-density thermal energy storage. While high-temperature PCMs have received the most focus in the thermal energy storage community, there are potential uses for PCMs with phase transition temperatures close to typical ambient temperatures (15-35°C). For a PCM to be widely used in a large-scale thermal energy storage system, it must meet the cost, safety, and energy density criteria in addition to having an appropriate phase change temperature. Inorganic, hydrated salt PCMs are the most promising, low-temperature PCMs, which can meet all of these criteria. After completing a review of known inorganic PCMs with phase change temperatures in the desired range, six of the more promising PCMs were tested by differential scanning calorimetry (DSC) to determine both their phase change temperatures (Tm) and latent heats of fusion (Hf). The first of these PCMs (potassium fluoride tetrahydrate) was eliminated after successful DSC testing as it became apparent that this PCM had serious health and safety concerns. Two new calcium chloride hexahydrate (CaCl2•6H2O)-based PCMs were also tested: CaCl2•6H2O + potassium nitrate (KNO3) and CaCl2•6H2O + magnesium chloride hexahydrate (MgCl2•6H2O). For CaCl2•6H2O + KNO3, it was found that the melt temperature of the PCM could be varied by changing the percentage of KNO3. In the case of the CaCl2•6H2O + MgCl2•6H2O, phase diagram modeling and physical experiments were used to determine the correct eutectic mixture, which leads to congruent melting/freezing of this PCM. CaCl2•6H2O was also tested by DSC, with found Tm and Hf results similar to those presented in the literature. Finally, sodium sulfate decahydrate (Na2SO4•10H2O) and Na2SO4•10H2O + 25 wt% H2O were tested by DSC. For both of these PCMs, significant phase separation was observed, which must be addressed if these PCMs are to be used commercially
Seismic Behavior of Historical Masonry Bridges: The Case Study of Irgandi Bridge
Get PDF In Anatolia, numerous bridges have been constructed throughout history for essential reasons. It is important to preserve the bridges and hand them down to the future generations as they have hints regarding the materials and construction techniques used in the past. Irgandi Bridge located on Gökdere in Bursa city, which is the first capital of the Ottoman Empire, has a special importance among bridges around the world. It is one of the few bridges around the world, which have had commercial activities with shops on it along with the purpose of transportation. This symbolic structure in terms of cultural, historical and constructional aspects is located in Bursa which includes 1st degree seismic hazard zone. Therefore, preservation of the bridge requires investigation of its seismic performance and taking necessary precautions. Irgandi Bridge was modeled by ANSYS software using finite element method (FEM). Convergence study was performed to determine the accurate number of elements. Modal and linear dynamic analysis of the Irgandi Bridge was conducted after the number of elements were determined by the convergence study. Therefore, seven earthquake records were scaled and performed to the system according to EC-8 (Eurocode-8). Stress distributions and displacements were examined as a result of linear dynamic analysis. It was determined that the maximum displacement occurred at the top of the bridge and the principal stress occurred in the support regions. As a result of the analyses, it was proposed to strengthen the support parts of the bridge, which were determined to be damaged under earthquake impact
Flocculation Behavior of Borax Clayey Tailings in Mono- and Dual- Flocculant Systems: Effect of Tailings Slurry Characteristics and polyDADMAC Type
Get PDFThe effect of tailings slurry characteristics such as solid ratio and solid particle size both, in mono- and dualflocculant systems, were studied as well as the effect of POLYDADMAC type in dual-flocculant system. Oppositely charged flocculants, a polyacrylamide (PAM)-typed anionic and two poly diallyl-dimethyl-ammonium chloride(polyDADMAC)-typed cationic polymers, were employed for the flocculation. Tailings slurry samples were taken on different dates from the discharge point of Kırka Borax Concentrator. Flocculation performance was characterized by the initial settling rate as well as the residual turbidity of supernatant and the extent of sediment compaction. All tests were performed at the natural pH of the tailings slurry (~pH 9.4) at which borax buffered the suspension. The results showed that an increase in solid load of the tailings slurry results in a dramatic decrease in settling rate of flocculated tailings regardless of flocculant system employed. This can be attributed to the possible change in rheological property of the slurry due to the increasing clay content of the slurry with solid ratio. While the solid ratio has an influence on the settling rate of the flocculated tailings, the amount of slimes determines the optimum dosage of cationic flocculant to obtain clear supernatant in dual-flocculant system. When anionic and cationic flocculants were used in combination, the best synergy was achieved with low weight cationic flocculant. Increasing molecular weight of the cationic flocculant from low to medium resulted in two-fold increase in the required dosage to obtain the same flocculation performance. In dualflocculant system, optimum results were obtained by anionic and cationic flocculant combination at around 0.4 kg/ton and 0.8 kg/ton solid dosages, respectively, indicating 11.7 cm/min of settling rate and 85.7% of transmittance value
A Review of Fault Detection and Diagnosis Methodologies for Air-Handling Units
Get PDF HVAC (Heating, Ventilation and Air-Conditioning) systems for space heating, space cooling and ventilation of buildings consume nearly 40% of the world energy demand and present the least expensive opportunities for reducing the greenhouse gases emission. Fault Detection and Diagnosis (FDD) methods could monitor the operation of various processes and/or components allowing to detect and, if possible, even predict the presence of defects (deviations from normal or expected operation) as well as ideally identify (diagnose) the fault and/or its location, giving instructions for undertaking corrective actions. FDD techniques could be successfully used for managing the predictive maintenance and/or optimizing the energy/economic/environmental performance of HVAC units while assuring the comfort of occupants. This paper examines the current state of the art of the research on the development and implementation of FDD systems when applied to Air-Handling Units (AHUs), the main and most important device of HVAC systems. This paper describes the existing methodologies, approaches and tools for the utilization of FDD techniques, summarizes the most important findings available in current literature in reference to several case studies where FDD systems have been applied with reference to AHUs and indicates the main gaps to be further investigated
Management of Condenser Fan Speed and its Influence on the Split Air Conditioner Performance
Get PDF Energy saving is the challenge of decreasing the quantity of energy consumption needed. This can be done by employing reliable and smart control system. In this article, an experimental study has been carried out to investigate the performance of a split air conditioning unit having a variable speed condenser fan. The rate of heat rejection airflow has been controlled according to the outdoor air temperature via a Proportional Integral Differential (PID) controller. The control algorithm allows increasing the condenser fan speed with the increase of outdoor air temperature and vice verse. The maximum rate of air flow of the fan is 0.43 m3/s at 42ºC outdoor air temperature and the minimum flow is 0.28m3/s. To facilitate variation of refrigerant flow rate according to the evaporator load, the traditional capillary tube was replaced with a suitable thermostatic expansion valve and liquid refrigerant reserve. The influence of condenser airflow modulation and its temperature on the air conditioner performance and also on the compressor power consumption has been investigated and presented at different evaporator loads. It has been found that a 10 % reduction in compressor power is achieved by increasing the condenser air flow by about 50%
In the Framework of Global Trade, Sustainability and Industry Demand for Innovative Process and Technologies, what kind of Modern “Green” Chemical Engineering is Required for the Design of “the Factory of the Future”?
Get PDF The chemical, petroleum, gas, energy and related industries are today confronted with the globalization of the markets, acceleration of partnerships and demand for innovative process and technologies for economic growth, and they are required to offer a contribution to the fight against environmental destruction and not always sustainable behavior of the today world production. This militates for the evolution of chemical engineering in favor of a modern green process engineering voluntarily concerned by sustainability that will face new challenges and stakes bearing on complex length and time multiscale systems at the molecular scale, at the product scale and at the process scale. Indeed, the existing and the future industry processes are progressively adapted to the principles of the « green (bio) chemistry ». This involves a modern approach of chemical engineering that satisfies both the market requirements for specific nano and microscale end-use properties of competitive targeted green (sustainable) products, and the social and environmental constraints of sustainable industrial meso and macroscale production processes at the scales of the units and sites of production. These multiscale constraints require an integrated system approach of complex multidisciplinary, non-linear, non equilibrium processes and transport phenomena occurring on the different time and length scales of the chemical supply chain. This means a good understanding of how phenomena at a smaller length-scale relates to properties and behavior at a longer length-scale, from the molecular and active aggregates-scales up to the production-scales (i.e. the design of a refinery from the Schrödinger’s equations...). It will be seen that the success of this integrated multiscale approach for process innovation (the 3rd paradigm of chemical engineering) is mainly due to the considerable developments in the analytical scientific techniques coupled with image processing, in the powerful computational tools and capabilities (clusters, supercomputers, cloud computers, graphic processing units, numerical codes parallelization etc.) and in the development and application of descriptive models of steady state and dynamic behavior of the objects at the scale of interest. This modern scientific multiscale approach of chemical engineering « the green approach of process engineering » that combines both market pull and technology push is strongly oriented on process intensification and on the couple green products/green processes “to produce much more and better in using much less”, i.e. to sustainabily produce molecules and products responding to environmental and economic challenges. It will be pointed out that process intensification due to innovative continuous flow process processes (novel process windows) and innovative technologies and new equipment construction technologies (additive manufacturing) will contribute to the design of the eco-efficient “factory of the future ”:i.e. a plant in a shoe box for polymer production or in a mobile banana container platform for small-scale production of specialty chemicals, or more generally modular plants leading to flexible chemical production by modularization and standardization in the pharmaceutical and specialty chemical industries and in a great number of other fields such as materials, petroleum and gas, water treatment and desalination and environmental management, among others