Increment Of Flow Rate Research Articles

Energy and exergy analyses of a fluidized bed coal combustor steam plant in textile industry

In this study, the analyses of first and second laws of thermodynamic are presented for a 6.5MW power plant located in Adana, Turkey. The system components, examined in the present study, are listed as a fluidized bed coal combustor (FBCC), a heat recovery steam generator (HRSG), an economizer (ECO), fans, pumps, a cyclone and a chimney. All of the system components are examined one by one and the energy and exergy analyses are carried out for all of the system components. The highest value of irreversibility is observed in the FBCC, about 93% of the entire system irreversibility tracked by HRSG and ECO with 3% and 1%, respectively. The high excess air value, which is the primary origin of irreversibility, causes the heat losses from the FBCC, due to the increment in mass flow rate of the combustion gas. Moreover, the high excess air value gives rise to occurrence of low combustion efficiency in FBCC which can be decreased through decreasing flow rate of air with decreasing oxygen. Secondly, changes in the energy and exergy efficiencies are examined employing different ambient temperature. As the ambient temperature increases, the second law efficiencies of FBCC and HRSG increases but efficiency of ECO decreases.

Optimization of heat transfer and pressure drop characteristics via air bubble injection inside a shell and coiled tube heat exchanger

Most recently, a couple of academic investigations have focused on air bubble injection (with a constant air flow rate) inside the shell-and-coiled-tube heat exchangers in order to increase the performance and effectiveness of these heat exchangers. However, the amount of air flow rate has great effects on these applications which have not been probed in previous studies. Moreover, in former papers, air flow has been injected inside the only shell side and not coil side of heat exchanger. Hence, in this experimental research, air bubbles is flowed inside the shell or coil side of heat exchanger with variant air flow rates to detect an optimum condition and also fill out this topic. Air flow rate was changed between 1LPM and 5LPM. Coil side water flow rate was kept at 1LPM (inlet temperature of 40°C) and shell side water flow rate was varied between 1LPM and 5LPM (inlet temperature of 15°C). Furthermore, pressure drop due to bubble injection is measured in this paper for aforesaid heat exchangers as another new parameter. Observations showed that the air flow rate and injection side (shell and coil) play key roles on the effect of bubble injection into the heat exchangers. Findings showed that, increment of air flow rate causes enhancement of overall heat transfer coefficient. Air injection into the shell side of the heat exchanger increased the overall heat transfer coefficient 6–187% depending on air flow rate.

Characterization of Flow-resistant Tubes Used for Semi-occluded Vocal Tract Voice Training and Therapy

This study aimed to characterize the pressure-flow relationship of tubes used for semi-occluded vocal tract voice training/therapy, as well as to answer these major questions: (1) What is the relative importance of tube length to tube diameter? (2) What is the range of oral pressures achieved with tubes at phonation flow rates? (3) Does mouth configuration behind the tubes matter? Plastic tubes of various diameters and lengths were mounted in line with an upstream pipe, and the pressure drop across each tube was measured at stepwise increments in flow rate. Basic flow theory and modified flow theory equations were used to describe the pressure-flow relationship of the tubes based on diameter and length. Additionally, the upstream pipe diameter was varied to explore how mouth shape affects tube resistance. The modified equation provided an excellent prediction of the pressure-flow relationship across all tube sizes (6% error compared with the experimental data). Variation in upstream pipe diameter yielded up to 10% deviation in pressure for tube sizes typically used in voice training/therapy. Using the presented equations, we can characterize resistance for any tube based on diameter, length, and flow rate. With regard to the original questions, we found that (1) For commonly used tubes, diameter is the critical variable for governing flow resistance; (2) For phonation flow rates, a range of tube dimensions produced pressures between 0 and 7.0 kPa; and (3) The mouth pressure behind the lips will vary slightly with different mouth shapes, but this effect can be considered relatively insignificant.

Dynamic simulation and optimization of an industrial-scale absorption tower for CO2 capturing from ethane gas

Abstract This article considers a process technology based on absorption for CO2 capturing of ethane gas in phase 9 and 10 of south pars in Iran using diethanolamine (DEA) as absorbent solvent. This CO2 capture plant was designed to achieve 85% CO2 recovery and obtain 19 ppm the CO2 concentration in the outlet of absorber. ASPEN–HYSYS software was used for the dynamic simulation of a commercial-scale CO2 capture plant and amine Pkg equation was chosen from the fluid property package for calculating the thermodynamic properties of the process. A static approach for optimization was used to evaluate the optimum conditions. This research revealed that pressure variation does not have any considerable changes in the absorption process, while both amine inlet temperature and volumetric flow rate increment enhance the absorption tower efficiency. The effect of temperature was very significant as shown in the dynamic study plots. The optimum condition for CO2 absorption from a stream of ethane gas with molar flow rate of 2118 kg mol h−1 was obtained 75 m3 h−1 of amine at 53 °C and 24 bar. This optimized condition is acceptable from economical, safe as well as feasible point of view.

Experimental study on heat pipe assisted heat exchanger used for industrial waste heat recovery

Steel industry plays an important role economically in China. A great amount of hot waste liquids and gases are discharged into environment during many steelmaking processes. These waste liquids and gases have crucial energy saving potential, especially for steel slag cooling process. It could be possible to provide energy saving by employing a waste heat recovery system (WHRS). The optimum operation condition was assessed by integrating the first and the second law of thermodynamics for a water–water heat pipe heat exchanger (HPHE) for a slag cooling process in steel industry. The performance characteristics of a HPHE has been investigated experimentally by analyzing heat transfer rate, heat transfer coefficient, effectiveness, exergy efficiency and number of heat transfer units (NTU). A specially designed on-line cleaning device was used to clean the heat exchange tubes and enhance heat transfer. The results indicated that the exergy efficiency increased with the increment of waste water mass flow rate at constant fresh water mass flow rate, while the effectiveness decreased at the same operation condition. As the waste water mass flow rate varied from 0.83m3/h to 1.87m3/h, the effectiveness and exergy efficiency varied from 0.19 to 0.09 and from 34% to 41%, respectively. In the present work, the optimal flow rates of waste water and fresh water were 1.20m3/h and 3.00m3/h, respectively. The on-line cleaning device had an obvious effect on the heat transfer, by performing the device, heat transfer rate, heat transfer coefficient, effectiveness and exergy efficiency were improved by 6.11%, 9.49%, 7.19% and 7.93%, respectively.

Numerical simulation and experimental validation of a high concentration photovoltaic/thermal module based on point-focus Fresnel lens

Characteristics of a high concentration photovoltaic/thermal (HCPV/T) module equipped with point-focus Fresnel lens have been investigated in this paper. Both electrical and thermal models of the module are developed by numerical methods. The electrical model is based on the Shockley diode equation, and the thermal model is grounded on a two-dimensional steady-state heat transfer model. Influences of environmental parameters and coolant water are considered in the models. The inputs of the models consist of irradiance, ambient temperature, wind speed, water temperature and mass flow rate. The outputs mainly include electrical efficiency and thermal efficiency. The simulated results are compared with experimental results and a great agreement is obtained. By the virtue of the validated models, influences of different parameters on module performance are analyzed in detail. The results show that an electrical efficiency of 28% and a thermal efficiency of 60% can be obtained by the HCPV/T module. The electrical efficiency is mainly influenced by solar irradiation rather than cell temperature. The thermal efficiency increases with the increment of irradiance, ambient temperature and water mass flow rate. On the contrary, increasing water temperature and wind speed will lower the thermal efficiency. Also, the HCPV/T module can produce hot water as high as 70°C without decreasing the electrical efficiency seriously.

Modelling of Bubble Aggregation, Breakage and Transport in Slab Continuous Casting Mold

The bubble-liquid flow, especially the aggregation and breakage behavior, plays a significant role in the slab continuous casting process. A 1/4th water model was employed to investigate the two-phase flow characteristics and the bubble size distribution. A mathematical model based on the Euler-Euler approach was developed to analyze the bubble aggregation and breakage in the bubbly flow. The population balance model (PBM) was applied to calculate bubble size distribution, and the simulation was implemented through the MUSIG (multiple size group) model. The numerical predictions were verified by the water model experiment. The results show that the PBM is a useful approach for analyzing bubble size distribution and can be taken into industrial applications of gas-liquid two phase flow inside the continuous casting mold. The ratio of big bubbles and bubble mean diameter in the upper recirculation zone are found to decrease with the increment of water flow rate and increase with the increment of gas flow rate. The bubble aggregation and breakage behavior, bubble size distribution and the effect of gas bubbles on flow field in the continuous casting mold are revealed. The numerical results are compared with the experiment and they show good agreement.

Investigations of Droplet‐Plasma Interaction using Multi‐Dimensional Coupled Model

AbstractRecently developed multi‐dimensional coupled fluid‐droplet model is used to investigate the behavior of complex interaction between the liquid precursor droplets and atmospheric pressure plasma (APP). The significance of this droplet‐plasma interaction is not well understood under diverse realm of working conditions in two‐phase flow. In this study, we explain the implication of vaporization of liquid droplets in APP which are subsequently responsible to control major characteristics of surface coating depositions. Coalescence of water droplets is more dominant than Hexamethyldisiloxane (HMDSO) droplets because of its sluggish rate of evaporation. A disparity in the performance of evaporation is identified in two independent mediums, such as gas mixture and discharge plasma using HMDSO precursor. The length of evaporation of droplets is amplified by an increment of gas flow rate indicating with a reduction in the gas temperature and electron mean energy. In particular, the spatio‐temporal density distributions of charged particles show a clear pattern in which the typical nitrogen impurity ions are primarily effective as compared to other helium ionic species along the pulse of droplets in APP. Finally, we contrast the behavior of discharge species in the pure helium and He‐N2 gas mixtures revealing the importance of stepwise and Penning ionization processes. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Numerical simulation of CO2 separation from gas mixtures in membrane modules: Effect of chemical absorbent

In this study, a mathematical model is proposed for prediction of CO2 absorption from N2/CO2 mixture by potassium threonate in a hollow-fiber membrane contactor (HFMC). CFD technique using numerical method of finite element was applied to solve the governing equations of model. Effect of different factors on CO2 absorption was analyzed and for investigation of absorbent type effect, functioning of potassium threonate was compared with diethanolamine (DEA). Axial and radial diffusion can be described with the two dimensional model established in this work. The obtained simulation results were compared with the reported experimental data to ensure accuracy of the model predictions. Comparison of model results with experimental data revealed that the developed model can well predict CO2 capture by potassium threonate in HFMCs. Increment of absorbent flow rate and concentration eventuate in enhancement of CO2 absorption. On the other hand, capture of CO2 will be reduced with increment of gas flow rate. According to the model results, potassium threonate can be considered as a more efficient absorbent as compared with DEA.

직접분사식 디젤엔진에서 아산화질소의 생성에 관한 실험적 연구

It has been generally recognized that (Nitrous Oxide) emission from marine diesel engines has a close correlation with (Sulfur Dioxide) emission, and diversity of fuel elements using ships affects characteristics of the emission. According to recent reports, in case of existence of an enough large NO(Nitric Oxide) generated as fuel combustion, effect of the emission in exhaust gas on the formation is more vast than effect of the NO. Therefore, formation due to the element operates on a important factor in EGR(Exhaust Gas Recirculation) systems for NOx reduction. An aim of this experimental study is to investigate that intake gas of the diesel engine with increasing of flow rate affects emission in exhaust gas. A test engine using this experiment was a 4-stroke direct injection diesel engine with maximum output of 12 kW at 2600rpm, and operating condition was set up at a 75% load. A standard gas with 0.499%() was used for changing of concentration in intake gas. In conclusion, the diesel fuel included out sulfur elements did mot emit the emission, and the emission in exhaust gas according as increment of the standard gas had almost the same ratio compared with rate in mixture inlet gas. Furthermore, the element in exhaust gas was formed as mixture in intake gas because increment of flow rate in intake gas increased emission. Hence, diesel fuels included sulfur compounds were combined into in combustion, and in exhaust gas should be generated to react with NO and which exist in a combustion chamber.

Experimental analysis of the influence of urea injection upon NOx emissions in internal combustion engines fueled with biodiesels

The effect of urea injection on NOx emissions in a six-cylinder, four-stroke internal combustion engine fueled with B80 biodiesel has been experimentally investigated. The results reveal that urea injection leads to a reduction of NOx emissions of B80 biodiesel fuel. Moreover, the influence of injection parameters on NOx reductions has been studied. The findings show that increasing the injection temperature results in lower NOx emissions. Also urea mass flow rate increment leads to more NOx reduction. The same result has been obtained by an increase in spray angle. In addition, increasing the number of nozzles indicates more depletion in NOx emissions while a “three-nozzles spray system” has the most considerable effect on NOx reductions.

A Numerical Study on the Effect of Bleed System on Starting Ability and Flow Performance of Rampressor Inlet

A unique supersonic compressor rotor with high pressure ratio, termed the Rampressor, is presented by Ramgen Power Systems, Inc., (RPS). Based on the models of Rampressor inlet, the inlet flow field with bleed system is numerically studied. Validation of the employed computational fluid dynamics (CFD) scheme is provided through test cases. The effects of boundary layer bleed location and bleed amount on Rampressor rotor inlet start and flow performance are analyzed. The results indicate that the boundary layer bleed has a significant effect for start and flow performance of Rampressor inlet. Boundary layer bleed technique has been applied to eliminate the emerging flow separation zone for enhancing Rampressor rotor inlet performance and enlarging its stable working range. The starting ability and flow performance of Rampressor inlet are efficiently improved by bleeding system, but the improvement effect is different for Rampressor inlet with different bleed location. Along the position of bleeding system moves forward, the range of Rampressor inlet normal work rotation speed is enlarged. The flow performance of Rampressor inlet improves obviously with the increment of bleed flow rate, and exit stability of Rampressor inlet enhances. And in the same back pressure work condition of Rampressor inlet, bleed system has been shown to be effective that exit stability of Rampressor inlet ameliorates, but the loss of compressed air from the bleed system has a negative effect on overall Rampressor inlet efficiency.

Performance response and recovery of temporal and spatial phase separated process for nutrients removal in short-term shock loadings

This study was conducted to evaluate the stability and performance response under short-term hydraulic and organic shock load conditions in temporal and spatial phase separated process. The overall removals of BOD, TN, and TP declined slightly despite the hydraulic shock loading, and rapid recovery could be observed again after four cycles of 16h. It seems that rapid recovery may be achieved by the unique characteristics of the system operated in a fed-batch manner. The effect of shock load on nitrogen removal due to increment of flow rate was higher than that of phosphorus, because of the insufficient reaction time for the nitrification and denitrification. After the organic shock, however, recovery time for phosphorus removal was needed rather than that of organics and nitrogen, because the overload to micro organisms related to the phosphorus release is attained by short-term organic shock loading.

구리기판을 이용한 그래핀 박막 특성 및 그래핀을 이용한 트랜지스터의 특성 분석

화학적 증착방법으로 구리기판 위에 그래핀을 형성하고 일반적인 전사방법을 이용하여 그래핀 박막을 제작하였다. 메탄과 수소 가스의 유량비에 따른 특성에 대하여 라만 분석법을 이용하여 조사하였다. 메탄의 유량이 많을수록 그래핀의 형성이 잘 이루어지는 것을 확인하였다. 수소의 양이 증가할수록 D (<TEX>$1350cm^{-1}$</TEX>), G (<TEX>$1580cm^{-1}$</TEX>) 대역이 증가하였으며, 상대적으로 메탄의 유량비가 증가할수록 2D (<TEX>$2700cm^{-1}$</TEX>)의 픽이 강도가 증하였다. D (<TEX>$1350cm^{-1}$</TEX>)은 결함과 관련되어 있는 픽이다. 그래핀의 단층확인은 G/2D의 비율이 작을수록 그래핀이 단일박막임을 알 수 있고, 200도에서 열처리 후 0.55의 값을 나타내는 것을 확인하였다. 그래핀 채널 트랜지스터를 제작한 결과 p 형 반도체로서의 전달특성이 나타나는 것을 확인하였다. Graphene thin film was prepared on the copper foils by chemical deposition, and the characteristic of graphene depending on <TEX>$H_2$</TEX> and CH4 gas flow rates was analyzed by the Raman spectra. The graphene formation was improved with increment of methan gas flow rates. The increment of hydrogen gas flow rate made high intensity of D(<TEX>$1350cm^{-1}$</TEX>) and G(<TEX>$1580cm^{-1}$</TEX>). The peak of D(<TEX>$1350cm^{-1}$</TEX>) is related with the defects, and the 2D(<TEX>$2700cm^{-1}$</TEX>) increased depending on the increment of amount of methan gas flow rate. The rate of G/2D indicates the quality of garphene to like a monolayer, and the small value of G/2D means better grapheme. The G/2D of graphene after annealed at <TEX>$200^{\circ}C$</TEX> was 0.55 and improved the characteristic of graphene than the deposited-grapnene. Thin film transistor with graphene as an active channel was p-type semiconductor.

CFD Optimization Analysis of a Cooling Fan for Mining Dump Truck

Axial flow fans are widely used in our daily lives such as automotive cooling systems, electronic appliances and air conditioning. The factors that affect the aerodynamic performance of axial flow fans include blade number, fan diameter, hub ratio, blade angle, rotating speed, etc. This paper investigates effects of hub ratio and bladenumber on the aerodynamic performance of the axial flow fan of the radiator of a dump truck we previously designed for mining. With the computational fluid dynamics (CFD) method, the fans operation condition, such as entry static pressure, effective power and flow rate, are numerically simulated with various hub ratios and blade numbers. The results of the numerical simulations are quantitatively analyzed and curves of fans performance changing with hub ratio and blade number are given. An optimization design for the cooling fan is conducted. The results of numerical simulation give conclusion that an increase of 5.6% of the vacuum static pressure and an increase of 3% of flow rate can be obtained when the hub ratio is between 500-600mm, with the same or even less power consumption. The flow rate increment reaches its peak at 8%, while power consumption efficiency is almost linearly increased, when the blade number increases to be in the range of 8 to 10. That is to say when the blade number is between 8 to 10, the fan is apparently making better use of energy. Compared with experimental method, computational fluid dynamics (CFD) method can reduce design circle and lower cost. The CFD results provide guidance to improvement of design efficiency and energy utilization.

Analysis of the crystalline characteristics of nc-Si:H thin film using a hyperthermal neutral beam generated by an inclined slot-excited antenna

The deposition of hydrogenated nano-crystal silicon (nc-Si:H) thin film for manufacturing quantum dot solar cells, which has received attention due to the use of this film third-generation solar cells, is studied here. A hyperthermal neutral beam (HNB) generated by an inclined slot-excited antenna plasma source is used to reduce damage to the silicon thin film and deposition of the crystalline thin film is carried out on a substrate at a low temperature (<200°C). The size and the crystalline fraction of the nc-Si:H of the deposited thin film were analyzed by scanning transmission electron microscopy and a Raman microscope. As a result, silicon crystals 1–10nm in size were observed in the amorphous silicon matrix. According to previous studies, the size and the crystalline fraction of nc-Si:H in deposited thin films increase as the hydrogen flow rate is increased. However, the increment of hydrogen flow rate decreases the deposition rate rapidly. The size and the crystalline fraction of nc-Si:H are adjustable by varying the substrate temperature and HNB energy without a change of the hydrogen flow rate. There are optimum conditions between the HNB energy and the substrate temperature for an appropriate amount of nc-Si:H in silicon thin film.

Physical Modeling of Fluid Flow in Ladles of Aluminum Equipped with Impeller and Gas Purging For Degassing

In the current study a transparent water physical model was developed to study fluid flow and turbulent structure of aluminum ladles for degassing treatment with a rotating impeller and gas injection. Flow patterns and turbulent structure in the ladle were measured with the particle image velocimetry technique. The effects of process parameters such as rotor speed, gas flow rate, and type of rotor on the flow patterns and on the vortex formation were analyzed using this model, which control degassing kinetics. In addition, a comparison between two points of gas injection was performed: (a) conventional gas injection through the shaft and (b) a “novel” gas injection technique through the bottom of the ladle. Results show that the most significant process variable on the stirring degree of the bath was the angular speed of the impeller, which promotes better stirred baths with smaller and better distributed bubbles. A gas flow rate increment is detrimental to stirring. Finally, although the injection point was the less-significant variable, it was found that the “novel” injection from the bottom of the ladle improves the stirring in the ladle, promotes a better distribution of bubbles, and shows to be a promising alternative for gas injection.

Mass flow rate prediction of pressure–temperature-driven gas flows through micro/nanoscale channels

In this paper, we study mass flow rate of rarefied gas flow through micro/nanoscale channels under simultaneous thermal and pressure gradients using the direct simulation Monte Carlo (DSMC) method. We first compare our DSMC solutions for mass flow rate of pure temperature-driven flow with those of Boltzmann-Krook-Walender equation and Bhatnagar-Gross-Krook solutions. Then, we focus on pressure–temperature-driven flows. The effects of different parameters such as flow rarefaction, channel pressure ratio, wall temperature gradient and flow bulk temperature on the thermal mass flow rate of the pressure–temperature-driven flow are examined. Based on our analysis, we propose a correlated relation that expresses normalized mass flow rate increment due to thermal creep as a function of flow rarefaction, normalized wall temperature gradient and pressure ratio over a wide range of Knudsen number. We examine our predictive relation by simulation of pressure-driven flows under uniform wall heat flux (UWH) boundary condition. Walls under UWH condition have non-uniform temperature distribution, that is, thermal creep effects exist. Our investigation shows that developed analytical relation could predict mass flow rate of rarefied pressure-driven gas flows under UWH condition at early transition regime, that is, up to Knudsen numbers of 0.5.

Feed Rate on Velocity Field of Liquid Film in a Wiped Film Molecular Distillatory

Effect of feed flow rate on velocity field of evaporating liquid film in a wiped film molecular distillatory was studied with a computational fluid dynamics (CFD) method. Three assumptions were introduced in order to simplify modeling processes. According to our previous study, the RNG k-εturbulent model treating near-wall flow was properly used in this simulation. The volume of fluid (VOF) multiphase model was also applied to track the liquid-gas surface. A near-wall modeling method, enhanced wall treatment, was used to consider the effect of walls. Simulations were carried out in rotating coordinate system. All simulation results are reasonably identical with real situation and were discussed in several aspects. It was concluded that increment of feed flow rate would reduce the turbulence of liquid film on the evaporator surface and then reduce the evaporation rate.

Thermal-Pressure-Driven Gas Flows through Micro Channels

In this paper we study mass flow rate of rarefied gas flow through micro/nanoscale channels under simultaneous thermal and pressure gradients using an improved direct simulation Monte Carlo (DSMC) method. Before targeting thermal/pressure driven flows, we first analyze pressure-driven flows and verify our DSMC solver. Next, we study micro-/ nanochannels flows under simultaneous pressure-temperature gradients while our main objective is to predict mass flow rate increment due to thermal creep effects. The effects of thermal creep are studied over a wide range of flow rarefaction from the slip to free molecular regime. Our results showed that the non-dimensional thermal creep mass flow rate increments of the Poiseuille flow increases and approaches the value of 0.578 at free molecular limit.