Variation Of Gas Temperature Research Articles

Studi Numerik Pembakaran Butana (C4H10) dalam Meso Scale Combustor dengan Perforated Plate

This research was conducted to determine the combustion stability and flame temperature inside meso-scale combustor with variations of perforated plate flame holder and combustion gas temperature at combustor exit side using numerical method or Computational Fluid Dynamics (CFD). Meso-scale combustor is made of two pieces of quartz glass tube with a length of 20 mm and 10 mm. Each quartz glass tube having an internal diameter of 3.5 mm and a wall thickness of 0.7 mm. Two kinds of perforated plate flame holder made of copper i.e. perforated plate type I and perforated plate type II, inserted between two quartz glass tubes. Butane (C 4 H 10 ) and air were used in this study as fuel and oxidizer, respectively. Numerical simulations were performed using ANSYS Fluent 17.0. The result of numerical simulation showed that the most stable combustion is obtained in meso-scale combustor by using flame holder in the form of perforated plate type II at higher reactant velocity. In addition, the combustor with perforated plate flame holder type II also produces a higher flame temperature at the same reactant speed. These phenomena occured due to the temperature distribution into the reactans is more uniform and the recirculation heats into the reactans is better than the combustor with perforated plate flame holder type I. Flame and combustor walls temperatures increased with increasing recirculation heats.

Assessing the Impact of Astrochemistry on Molecular Cloud Turbulence Statistics

We analyze hydrodynamic simulations of turbulent, star-forming molecular clouds that are post-processed with the photo-dissociation region astrochemistry code 3D-PDR. We investigate the sensitivity of 15 commonly applied turbulence statistics to post-processing assumptions, namely variations in gas temperature, abundance and external radiation field. We produce synthetic $^{12}$CO(1-0) and CI($^{3}$P$_{1}$-$^{3}$P$_{0}$) observations and examine how the variations influence the resulting emission distributions. To characterize differences between the datasets, we perform statistical measurements, identify diagnostics sensitive to our chemistry parameters, and quantify the statistic responses by using a variety of distance metrics. We find that multiple turbulent statistics are sensitive not only to the chemical complexity but also to the strength of the background radiation field. The statistics with meaningful responses include principal component analysis, spatial power spectrum and bicoherence. A few of the statistics, such as the velocity coordinate spectrum, are primarily sensitive to the type of tracer being utilized, while others, like the delta-variance, strongly respond to the background radiation field. Collectively, these findings indicate that more realistic chemistry impacts the responses of turbulent statistics and is necessary for accurate statistical comparisons between models and observed molecular clouds.

Spectroscopic diagnosis of gas temperature in blown-out plasma of atmospheric-pressure microwave oxygen plasma torch

The gas temperature of atmospheric-pressure microwave oxygen plasma torch in a blown-out plasma is diagnosed by optical emission spectroscopy (OES) via the atmospheric band O2(b1Σg+ →X3Σg−). The variations of gas temperature with respect to input power and gas flow rate are investigated, as well as the spatial distribution of gas temperature along the blown-out plasma. And the limitation of OES diagnosis in the experiment is discussed extensively. Moreover, the morphology of plasma torch is also inspected at various gas flow rates and values of microwave power.

Thermodynamic analysis of design and part-load operation of a novel waste heat recovery unit

Organic Rankine Cycle (ORC) thermodynamic optimization is of critical importance while developing new plants. Optimization procedures may be imed at the highest efficiency as well as cost or sizing minimization. Optimization process is generally carried out for plant nominal rating. At the same time, part-load operation has to be carefully considered in case of waste heat recovery from flue gases coming from internal combustion engines or gas turbines. Gas mass flow and temperature variations are specific to this application, significantly influencing ORC plant performance. Secure prediction of part-load operation is of particular importance for assessment of plant power output, providing stability and safety and utilizing proper control strategy. In this paper design and off-design cycle simulation model is proposed. Off-design performance of the ORC cycle recovering waste heat from gas turbine unit installed at gas compressor station is considered. Major factors affecting system performance are outlined.

Influence of feedstock powder and cold spray processing parameters on microstructure and mechanical properties of Ti-6Al-4V cold spray depositions

A high pressure cold spray system was used to deposit three Ti-6Al-4V feedstock powders (i.e., hydride de-hydride, plasma atomized, and gas atomized) on Ti-6Al-4V substrates while varying gas temperature and nozzle length. Particle impact temperature and particle velocity were calculated using a 1-D axial model. The microstructure of the feedstock powders and the cold spray depositions were characterized via optical and scanning electron microscopy. The hardness of the as-received powders was determined using nanoindentation. To assess deposition quality, coatings were characterized in terms of porosity, microhardness, and adhesion strength. Results showed that hydride de-hydride powders were characterized by an equiaxed alpha grain structure with intergranular beta phase regions while atomized powders were characterized by martensitic α phase structures. Cold sprayed coatings revealed two distinct microstructures. Regions that experienced low/moderate plastic strain retained the as-received powder microstructure while regions that experienced significant plastic strain were characterized either by a featureless microstructure (atomized coatings) or the presence of fine, elongated beta precipitates (hydride de-hydride coatings). Depositions performed using a long nozzle resulted in the best deposition quality, with porosity as low as 0.3% and adhesion strengths >69MPa. While atomized powders resulted in comparatively higher quality coatings for all process conditions, hydride de-hydride coatings of excellent quality (average porosity≈0.6%, adhesion strength >65MPa) were achieved under optimal conditions. Thus, hydride de-hydride powders may hold promise as a cost effective alternative to atomized powders for Ti-6Al-4V cold spray depositions.

Dynamic modeling and simulations of the behavior of a fixed‐bed reactor‐exchanger used for CO2 methanation

A multidimensional heterogeneous and dynamic model of a fixed‐bed heat exchanger reactor used for CO2 methanation has been developed in this work that is based on mass, energy and momentum balances in the gas phase and mass and energy balances for the catalyst phase. The dynamic behavior of this reactor is simulated for transient variations in inlet gas temperature, cooling temperature, gas inlet flow rate, and outlet pressure. Simulation results showed that wrong‐way behaviors can occur for any abrupt temperature changes. Conversely, temperature ramp changes enable to attenuate and even fade the wrong‐way behavior. Traveling hot spots appear only when the change of an operating condition shifts the reactor from an ignited steady state to a non‐ignited one. Inlet gas flow rate variations reveal overshoots and undershoots of the reactor maximum temperature. © 2017 American Institute of Chemical Engineers AIChE J, 64: 468–480, 2018

Possible Effect of Main Roof Settlement on Outburst Hazard in Case of Gas Hydrate Dissociation during Coal Mining

The results of physical modeling of geomechanical processes in outer zones of coal beds with the main roof caveable with difficulty. The scope of the modeling embraces the inlfuence seams on gas release by gas temperature and pressure variation during stage-wise outlet of gas from a pressure bomb, which simulates cyclical mechanical impact on a coal seam in the zones of a gas pocket. It is found that the low-frequency (2.0–4.5 Hz) attenuating vibrations generated in the main roof can induce both secondary rock mass disintegration as well as methane desorption and decomposition of gas hydrates (if present) accompanied by an increases in gas pressure and in number of gas-dynamic events in outer zones of coal beds.

Numerical modeling of the interaction of pressurized large diameter gas buried pipelines with normal fault ruptures

There is a growing attention towards the seismic response of large diameter pipelines, owing to the potential adverse impact on economy and civilized life of a structural collapse under earthquake effects, such as strong ground shaking, and other earthquake related effects such as fault rupture, landsliding and liquefaction. The intersection of a fault rupture with a pipeline is of special concern, because the safety verification is affected by significant uncertainties in the loading condition, related to the unknown exact location where the fault offset may occur, the unknown amount of the offset itself, as well as the intersection angle of the fault rupture with the pipe axis. Besides, the inherent analytical/numerical complexity of the problem may require 3D finite element models with non-linear constitutive laws and large deformations.In this paper a summary is presented of a comprehensive set of 3D numerical simulations of the interaction of a large diameter gas pipeline with a normal fault rupture, with the main objectives of: 1) throwing light on the pipeline performance under increasing levels of fault offset, including cross-sectional buckling and ovalization; 2) providing a parametric set of results, including the variability of the fault-pipe intersection angles, of the mechanical properties of the pipe-soil interface, as well as of the operating conditions, in terms of internal gas pressure and temperature variations.

Studying gas temperature variation upon aerosol injection

Variation of the temperature of gaseous combustion products upon pulsed injection of aqueous aerosols (water, NaCl solution, clay suspension) with droplet sizes within 40–400 μm has been experimentally studied at initial gas temperatures from 520 to 910 K. The motion of aerosol droplets in the counterflow of combustion products was visualized by panoramic optical techniques. It is established that the process of gas cooling depends on the degree of aerosol dispersion, NaCl concentration in solution, clay content in suspension, and the conditions of liquid phase injection.

Acetophenone hydrogenation on Rh/Al2O3 catalyst: Flow regime effect and trickle bed reactor modeling

Flow regime effect and reactor modeling studies in a gas-liquid downward flow fixed bed reactor were conducted for acetophenone hydrogenation on 1% Rh/Al2O3 catalyst, a relatively complex reaction scheme typical of pharmaceutical applications, using a 7.1mm ID stainless steel reactor with 0.5mm catalyst spheres at elevated pressures. A flow regime transition map for trickle and bubbly flows was determined visually in a transparent reactor surrogate and confirmed by monitoring pressure drop fluctuations for different gas/liquid systems, tube/particle materials, and operating pressure and temperature. The flow regime at each operating condition for the opaque stainless steel reactor was identified solely using pressure drop fluctuations. The beneficial effect of bubbly flow on reaction rate was confirmed experimentally at gas and liquid superficial velocity ranges of 0.02–0.19m/s and 2.5–12mm/s, respectively, under 80–100°C, 11–26bar and 0.04–0.6M initial substrate concentration. Gas flow rate, temperature, and pressure variations were used to study the effects on reaction performance of partial wetting of the catalyst and of liquid-solid diffusion limited reaction. A reactor model including external/internal mass transfer and flow regime effects was developed using an adjustable parameter to account for partial wetting and flow regime effects. The parameter was fitted using a subset of the experiments, and the model provided good prediction (R2>95%) of all remaining experiments.

The influence of negative ions in helium–oxygen barrier discharges: II. 1D fluid simulation and adaption to the experiment

A 1D fluid simulation was developed to investigate the influence of negative ions in a helium–oxygen barrier discharge between two glass plates at a distance of . The paper describes setting up the simulation for a pressure of and an admixture of oxygen to helium. In order to enable the comparison with laser photodetachment experiments, the simulation is adapted to the experimentally observed discharge current and gap voltage by varying gas temperature, flux of thermally desorpted electrons and secondary electron emission coefficients. The discharge is characterized by evaluation of the most important elementary collision processes as well as the kinetics of the charged species. Besides, the influence of long-living species on the discharge behavior is taken into account by long-time simulations. The negative ions are characterized by their spatio-temporal distribution in the gap and their production and loss processes. The comparison between simulations without and with consideration of negative ions reveals the importance of negative ions on the discharge development.

Applying perturbation technique to analysis of a free piston Stirling engine possessing nonlinear springs

This paper describes a novel design approach of the free piston Stirling engines (FPSEs) based on multiple-scale perturbation method. First, a comprehensive mathematical model for an FPSE possessing nonlinear springs is presented. Then, the method of multiple scales is used to obtain the steady-state response of the engine system. Thus, some useful analytical relationships to predict frequency, strokes of pistons, and phase angle, as well as output power and efficiency of the nonlinear FPSE, are presented. Furthermore, a systematic mathematical approach for estimating the gas temperatures within expansion and compression spaces of the FPSE is proposed based on the perturbation technique. Next, a simulation study is carried out to investigate how much the engine frequency, strokes of pistons, and phase angle of the FPSE are sensitive to the variation of gas temperature. Besides, the effect of changes in the engine design parameters such as mass and stiffness of the pistons on the output power of the FPSE is studied using simulation. Finally, a test engine is developed and experimented to verify the proposed design technique. It is found that the experimental results are in a good agreement with the simulation outcomes of the analytical model through which validity of the proposed design scheme is clearly demonstrated.

Numerical Simulation of Corn Drying in a Hybrid Fluidized Bed‐Infrared Dryer

AbstractThis study deals with numerical modeling and experimental validation of hybrid fluidized bed‐infrared drying of bulk grain. A mathematical model of simultaneous heat and mass transfer for the aforementioned dryer was developed: first single phase model was used to establish heat and mass transfer equations over the fluidized bed, then the effect of infrared heating was incorporated into the single phase model as a source term to develop the model for a hybrid fluidized bed‐infrared dryer. The model is capable of predicting the moisture content of bulk corn as well as the drying air parameters (i.e., out let air temperature and out let air absolute humidity) during drying. The model was validated by comparison with experimentally obtained drying kinetics for different combinations of inlet air temperature, infrared power density and bed height. The results of verification test for all drying conditions indicated that the mean relative deviation for prediction of grain moisture content, out let air temperature and absolute humidity were less than 8, 11 and 7%, respectively, which reflects an acceptable accuracy (<15%). Other results showed that the application of infrared power in conjunction with fluidized bed drying to reduce corn moisture content from 0.23 to 0.12 kg H2O/kg dry solid led to a 45–87% saving in drying time and 36–68% saving in specific energy consumption compared to conventional fluidized bed configurations. The model indicated acceptable performance and hence the model could be suggested as a mathematical tool providing precise prognostications dealing with fluidized bed drying equipped with infrared heat source.Practical ApplicationsThe suggested model is an efficient method to simulate drying process of bulk grain in infrared‐fluidized bed dryers. This model provides precise prognostications regarding the variations in grain moisture content, gas temperature and gas absolute humidity. Additionally the features of the model introduced in the present study might qualify it for use in automatic control of fluidized bed dryers and online prediction of drying time to reach a desired value of moisture content.

Pressure broadening and shift rates for Ar (s–p) transitions observed in an Ar–He discharge

The pressure broadening and shift rates have been measured for the 801.699nm (s5→p8), 800.836nm (s4→p6) and 795.036nm (s3→p4) transitions in argon perturbed by 10–200Torr of helium and argon at a temperature of 440±20K using a radio-frequency, capacitively coupled discharge. For a 10% Ar in He plasma the pressure broadening and shift rates were measured as 14.18±0.65 and 1.81±0.30MHz/Torr, 17.85±0.78 and 0.72±0.32MHz/Torr, and 16.59±1.22 and 2.94±0.48MHz/Torr for the 801.699nm, 800.836nm and 795.036 nm transitions, respectively. The influence of the slightly varying gas temperature on the broadening and shift rates is less than 1%. Stark broadening and shifting by electrons in the discharge are not measurable due to low electron densities and temperatures. Phase-changing collisional cross-sections in the literature decrease with temperature, in good agreement with the Lindholm–Foley T−0.2 trend based on the Lennard–Jones potential. Further investigation of the Ar⁎–Ar and Ar⁎–He interaction potentials is necessary to understand the behavior of the cross sections.

Dynamic simulation of mixed refrigerant process for small-scale LNG plant in skid mount packages

The utilization of small natural gas reservoirs has attracted more and more attention. Most of the optimization studies concentrated on mixed refrigerant liquefaction process at steady-state simulation. Only a few studies have reported dynamic simulation of mixed refrigerant LNG (liquefied natural gas) process. The main purpose of this study was to design a dynamic model of mixed refrigerant LNG process for small-scale LNG plant in skid mount packages and to investigate the dynamic behaviors of this process. The variations of natural gas temperature, composition, pressure, flow rate and water-cooler temperature were selected as disturbances to test the stability and dynamic responses of the process. The dynamic responses of LNG temperature and total compressor energy consumption were the criteria to investigate the influences of disturbances on the process. Finally, the dynamic responses of disturbances were obtained and discussed. The simulation results showed that LNG temperature could go back to its set point value after a few minutes, while compressor duty varied with the disturbances. It indicated that the mixed refrigerant liquefaction process for small-scale LNG plant in skid mount packages could overcome some disturbances and operate at stable state.

Experimental investigation on the thermal performance of heat recovery system with gravity assisted heat pipe charged with R134a and R410A

The purpose of this study is to investigate the thermal performance of heat recovery system with gravity assisted heat pipe charged R134a and R410A working fluids and also determine the usefulness of heat pipe bundle system in heat recovery applications. For this purpose an experimental test rig was designed and built. Series of experimental tests were carried out by varying the flue gas temperature (75, 100, 125, 150 and 175 °C), flue gas velocity (1, 1.5, 2 and 2.5 m/s) and cooling water flow rates (1, 2, 3 and 4 l/min). Values of the overall effectiveness of the heat pipe heat recovery system are shown to vary with the flue gas velocity, as expected, but the results also allow the prediction of effectiveness variation with the variation of the flue gas temperature. Effectiveness of the heat pipe for both working fluids R134a and R410A has been varied averagely between 35.6% and 57.7% with a good agreement with the published results. Quantitatively, it is found that R134a working fluid is 14% more effective than R410A in heat pipe bundle system.

Numerical Analysis of Influential Parameters on the Performance of Vertical-Cylindrical Refinery Furnaces

An integrated heat transfer modeling of vertical-cylindrical refinery furnaces was carried out to determine the influential parameters on the fired heaters efficiency as well as the process and flue gas temperature variations. The model was developed considering separate sections of the heater encompassing heat of the flue gas. The model was solved by an iterative procedure with initial boundary conditions. The developed model along with its solution was compiled in MATLAB R2013a environment. The parameters involved into the devised model form the basis for the determination of the most influential parameters on the performance of fired heaters. The sensitivity analysis was accomplished via examining five parameters including excess air, tube pitch, inlet air temperature, fuel composition, and fuel flow rate. Model validation reveals that the model results reasonably agree with the experimental data with less than 4% deviation. The sensitivity analysis demonstrated that varying the five influential parameters by 5% from a base case altered the furnace efficiency by 2.69%, 0.93%, 0.22%, 0.21%, and 0.07%, respectively. The devised model can be employed to reduce computing time and technical costs afforded by the use of computational fluid dynamics (CFD) analysis.

High-precision surface-level CO2 and CH4 using off-axis integrated cavity output spectroscopy (OA-ICOS) over Shadnagar, India

An enhanced performance model of the greenhouse gas analyser (GGA) instrument from Los Gatos Research (LGR), which uses off-axis integrated cavity output spectroscopy (OA-ICOS) technology to obtain highly precise and accurate measurements, has been installed at the National Remote Sensing Center (NRSC), Shadnagar with the objective of generating a long-term record of measurements conforming to standards set by the World Meteorological Organisation (WMO). A calibration procedure to ensure the precision and accuracy of measurements was formulated using National Oceanic and Atmospheric Administration-Earth System Research Laboratory (NOAA-ESRL) calibration gases bearing WMO certification. The 10 s (1 σ) average precision of carbon dioxide (CO2) and (methane (CH4)) measurements by the GGA was 101 parts per billion volume (0.30 ppbv) and accuracy 78 ppbv (0.24 ppbv), respectively. The 5 s average of 1 Hz measurements was used to compute precision, which varied from 92.52 to 116.36 ppbv (1σ, 1 Hz = 0.66 parts per million volume (ppmv), WMO-2009)) for CO2 and CH4 0.45 ppbv to 0.55 ppbv (1 σ, 1 Hz = 2.48 ppbv, WMO-2009) respectively. Diurnal variation of greenhouse gas concentrations, temperature, and pressure, showed high fluctuations when cavity pressure and temperature varied from the standard values. The residuals of dry mixing ratios with respect to (w.r.t.) the NOAA span gases varied from +30 to −60 ppbv for CO2 and ±0.35 ppbv for CH4. A case study using the corrected observations over 1 year revealed the role of wind velocity and anthropogenic emissions, as well as the seasonal variations in the ambient concentrations of CO2 and CH4 gases near the surface.

Experimental investigation of the important influence of pretreatment process of thermally exfoliated graphene on their microstructure and supercapacitor performance

Thermal exfoliation is a popular approach to prepare thin-layered graphene in large scale. Generally believed that the microstructure and surface chemistry of the products could tailored by the variation of ambient gas pressure, temperature, acid and organic substances during thermal exfoliation of graphite oxide (GO). In this work, we investigated the effect of physical pre-treatment process and acid assisting on the texture, surface state and electrochemical performance of the resulting thermal exfoliated graphene, and found that the different physical pre-treatment process had great influence on the microstructure and specific surface area of graphene. Especially the graphene formed by sonication treatment consisted by thin layers with lots of wrinkles delivered the highest specific surface area of 678m2/g. Adding volatile acid in the process of pre-treatment could decrease their specific surface area. But the graphene obtained with acid assisting was possessed of larger pore volume and improved conductivity which promoted their electrochemical performance effectively. The important role of physical pre-treatment process and acid assisting process in expansion-exfoliation of GO was discussed in detail in this work.

The Response of Nitriding Chemistry to Different Initial Gas Compositions

The response of the kinetics of surface-catalyzed reactions to different initial conditions in a gas nitriding furnace has been studied. The predictions are made under the conditions with both high and low concentrations of ammonia and a process temperature of around 520 °C. Results are presented in temporal variations of gas temperature and concentrations and coverages of surface species. It has been shown that in the composition where NH3 content is richer, there is a strong possibility of developing substantially higher Nad coverage and so diffusion into the material. Reducing the ammonia content, which means an increase in the proportion of N2 in the initial mixture, leads to a quicker saturation of the furnace atmosphere to the desorption of the reaction product, N2, which eventually suppresses the advance of reaction in the forward direction. Low coverage values of Had have proved that the adsorbed hydrogen is the most unstable species on the surface.