eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1108
1116
72555
Effects of Flight Dynamics on Performance of One Axis Gimbal System, Considering Disturbance Torques
A. R. Vali
vali@mut.ac.ir
1
Meisam Pirzadeh
meisam.pirzadeh67@gmail.com
2
Electrical Engineering, Malek Ashtar University of Technology
Department of Control Engineering, Damavand Branch, Islamic Azad University
The gimbal stabilization mechanism system is used to provide the stability to an object mounted on the gimbal by isolating it from the base angular motion and vibration. In this paper the model of one axis gimbal system with dynamics flying object is introduced. The gimbal torque relationships are obtained using Newton’s second law equation on the assumption that gimbal is rigid body. The system is modelled using Simulink MATLAB. In fact, the purpose of this research was to analyse effects of flight dynamics on performance of one axis gimbal system. The simulation results are discussed and compared to show the validity of the gimbal system proposed at the flight path. Also, the results show that the gimbal system stabilizes the line of sight even when the disturbance torques effect on the system performance.
https://www.ije.ir/article_72555_cb296a41ace397e84739ac56a3ffd421.pdf
Key words gimbal seeker
rate gyro
servo
tracking loop
LOS rate
flight path
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1117
1123
72556
Purification and Zymography of lipase from Aspergillus niger PTCC5010
mahdieh ghamari
m.ghamary85@gmail.com
1
Food Science and Technology, Ferdowsi University of Mashhad
In this study, Aspergillus niger lipase after extraction of medium culture was precipitated with different percentages of acetone and purified by ion exchange chromatography using SP-sepharose HP and Q-sepharose HP. The process of purification of the anzyme was studied by electrophoresis and the molecular weight was detected and determined by Zymography using overlying containing phenol red and rhodamine B. The results show that the vast majority of lipase from this strain has been precipitated by acetone 70% saturation, and leads to the 1.67 fold the purified enzyme, with special activities 32.8 U/mg and 38.5%efficiency. Using two-phase chromatography, enzyme specific activity reached 246.47 U/mg and 12.59-fold purification were achieved. The results of Zymography and electrophoresis indicate a lipase band with weighing about 30 kDa.
https://www.ije.ir/article_72556_63cd28c85e5d2c79ba5ccba3ba46f16e.pdf
Lipases
Purification
Chromatography
A.niger
Zymography
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1124
1133
72557
Artificial Neural Network Approach for Modeling of Mercury Adsorption from Aqueous Solution by Sargassum Bevanom Algae (RESEARCH NOTE)
M. Sharifzadeh
mazyar.sharifzadeh@gmail.com
1
R. HosseinAlizadeh
maziarsharif@yahoo.com
2
Department of chemical engineering,, Ayatollah Amol
chemical engineering, Sciences and researches Branch, Islamic Azad Unive
In this study, the adsorption of mercury ions by Sargassum bevanom (S. bevanom) by batch method was investigated. The optimum operating parameters such adsorbent dosage, contact time, and pH, were obtained as: a biomass dose of 0.4 g in 100 ml of mercury solution, contact time of 90 mins and pH 7, respectively. Three equations Morris –Weber, Lagergren and pseudo second order are tested to verify the kinetics of the adsorption process. The data are well explained by the model of Weber Morris. The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich are subjected to sorption data to estimate sorption capacity that the Langmuir model indicated Better performance in the fitting of equilibrium data. Also, the thermodynamic parameters indicated that the adsorption process of mercury by S. bevanom is spontaneous and endothermic. Artificial Neural Networks (ANN) was used to predict the adsorption efficiency for the removal of mercury ions that the ANN model can estimate the behavior of mercury removal process.
https://www.ije.ir/article_72557_b224fbe8083307d8660e70f6e966c89f.pdf
Mercury
alga
Adsorption
Thermodynamic
Kinetic
ANN
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1134
1139
72558
Enhancement of L-asparaginase Production by Candida utilis in a 13L Fermenter and its Purification
vahid momeni
v.momeni86@yahoo.com
1
chemical engineering, sharif
L- asparaginase enzyme is a renown enzyme due to its chemotherapeutic properties. This enzyme could also be employed in food processing technology. The present study aimed, optimizing the agitation and aeration rate in L-asparaginase production, using Candida utilis, ATCC 9950 in batch fermentation system. Beet molasses used as the carbohydrate source for enzyme production. A maximum asparaginase activity of 245.6 U/ml obtained after 20h of fermentation under optimal condition of 1.25 vvm aeration rate and 300 rpm agitation speed. Purification of the enzyme was also done by Acetone Precipitation and column chromatograph. Purified L-asparaginase revealed molecular weight 75 kDa and 82.7 % yield with 10.02 fold increase in specific activity.
https://www.ije.ir/article_72558_b0427c3d691854659170caa53ac1bb23.pdf
Asparaginase
Candida utilis
Agitation speed
Aeration rate
Purification
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1140
1144
72559
Climate Change Impact on Precipitation Extreme Events in Uncertainty Situation; Passing from Global Scale to Regional Scale
Mohammad Khordadi
khordadi.mj@gmail.com
1
Water Engineering, Ferdowsi University of Mashhad, I.R. Iran
Global warming and then climate change are important topics studied by researchers throughout the world in the recent decades. In these studies, climatic parameters changes are investigated. Considering large-scaled output of AOGCMs and low precision in computational cells, uncertainty analysis is one of the principles in doing hydrological studies. For this reason, it is tried that investigating the uncertainty due to precision of computational cells and in passing from global scale to regional scale through LARS-WG model and CRU institute, precipitation changes in Mashhad synoptic station located in Ghareghom basin are studied. The results show enough ability of the model to simulate precipitation parameter in the base period. Using downscaled output of HadCM3 generated by CRU with high precision shows gradual decreasing of precipitation trend for frequency and sum values. Comparing the downscaled output of the AOGCM with 2.5*3.75 resolution and the output of CRU with 0.5*0.5 resolution, the uncertainty is due to precision of computational cells from global to regional scale which the latter scale is closer to real values.
https://www.ije.ir/article_72559_14ee9dba82b54259e27d6c6fa1b60526.pdf
Climate change
CRU
Downscaling
LARS
WG
Uncertainty
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1145
1153
72560
Impact of the Confluence Angle on Flow Field and Flowmeter Accuracy in Open Channel Junctions
Amir Hossein Zaji
amirzaji@gmail.com
1
Hossein Bonakdari
bonakdari@yahoo.com
2
Hossein Bonakdari
sharifipourminoo@gmail.com
3
Civil Engieering, Razi University
Civil Engieering, Razi University
Civil Engieering, Razi University
Open channel junction is one of the most common hydraulic structures that are used in various practical situations such as sewer, drainage, and flood control systems. Knowing the fluid flow behavior, is one of the most important topics in designing the efficient open channel junctions. The complexity and deviation of flow in the junction’s zone disrupts the proper functioning of the flowmeter devices which are located in the cross section and causing error in their measurements. Various three-dimensional Computational Fluid Dynamic (CFD) models were developed in this paper in order to study in the velocity field and flowmeter accuracy of junctions in different hydraulic conditions and confluence angles. The results showed that by increasing the confluence angle, the junction’s downstream flow becomes more complicated, and consequently, the difference between the flowmeter measured discharge values and the real discharge value becomes greater. For the junction with 30° confluence, the flowmeter discharge prediction error is equal to 2 and 6.45% in the junction’s upstream and downstream, respectively. These values increase to 6 and 38.65% for the junction’s upstream and downstream with 90° confluence, respectively.
https://www.ije.ir/article_72560_2e79782d418886d9bb886c29114df241.pdf
CFD
Confluence angle
Flow Field
Flowmeter
Open channel junction
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1154
1159
72561
Predicting the buckling Capacity of Steel Cylindrical Shells with Rectangular Stringers under Axial Loading by using Artificial Neural Networks
Zahra Kalantari
zahrakalantari@yahoo.com
1
Mehran Seyed Razzaghi
razzaghi.m@gmail.com
2
Civil Engineering and Surveying,, Qazvin Branch Islamic Azad University
Civil Engineering and Surveying,, Qazvin Branch Islamic Azad University
A parametric study was carried out in order to investigate the buckling capacity of the vertically stiffened cylindrical shells. To this end ANSYS software was used. Cylindrical steel shells with different yield stresses, diameter-to-thickness ratios (D/t) and number of stiffeners were modeled and their buckling capacities were calculated by displacement control nonlinear static analysis. Radial basis function (RBF) neural networks were used to predict the buckling capacity of shells. Herein 70 percent of the results of numerical analyses were used to train the neural network and the remainders were used to test and validate the results of neural networks. Results of this study showed that RBF neural networks are useful tools to predict the buckling capacity of vertically stiffened cylindrical shells. It was also shown that buckling capacities of stiffened shells exponentially vary by distance of adjacent stiffeners (unstiffened length).
https://www.ije.ir/article_72561_2a18f71480a3f0d5d33b79c152d92020.pdf
Buckling
cylindrical shells
Stiffener
Artificial Neural Networks
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1160
1168
72562
Proposing a Novel Cost Sensitive Imbalanced Classification Method based on Hybrid of New Fuzzy Cost Assigning Approaches, Fuzzy Clustering and Evolutionary Algorithms
mahdi eftekhari
meftekhari@mail.uk.ac.ir
1
mahboubeh mahdizadeh
mh.mahdizadeh@gmail.com
2
Department of Computer Engineering, Department of Computer Engineering
Department of Computer Engineering, Shahid Bahonar University
In this paper, a new hybrid methodology is introduced to design a cost-sensitive fuzzy rule-based classification system. A novel cost metric is proposed based on the combination of three different concepts: Entropy, Gini index and DKM criterion. In order to calculate the effective cost of patterns, a hybrid of fuzzy c-means clustering and particle swarm optimization algorithm is utilized. This hybrid algorithm finds difficult minority instances; then, their misclassification cost will be calculated using the proposed cost measure. Also, to improve classification performance, the lateral tuning of membership functions (in data base) is employed by means of a genetic algorithm. The performance of the proposed method is compared with some cost-sensitive classification approaches taken from the literature. Experiments are performed over 22 highly imbalanced datasets from KEEL dataset repository; the classification results are evaluated using the Area Under the Curve (AUC) as a performance measure. Some statistical non-parametric tests are used to compare the classification performance of different methods in different datasets. Results reveal that our hybrid cost-sensitive fuzzy rule-based classifier outperforms other methods in terms of classification accuracy.
https://www.ije.ir/article_72562_717cda731c566ec49449e3a5f53b85ba.pdf
cost sensitive learning
Fuzzy Clustering
fuzzy rule
based classification systems
evolutionary algorithms
lateral tuning
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1169
1174
72563
Improving Electrochromic Properties of WO3 Thin Film with Gold Nanoparticle Additive
Elham Mansoori
mansori.elham@yahoo.com
1
Maede Ameri
maed.ameri@gmail.com
2
Alireza Nikfarjam
a.nikfarjam@ut.ac.ir
3
Key armin Rahmanzade
k.a.rahmanzadeh@gmail.com
4
, Islamic Azad University, Science and Research Bran
, Islamic Azad University, Science and Research Bran
Mechateronics, University of Tehran
, Islamic Azad University, Science and Research Bran
In this research, WO3 and Au-WO3 thin films were prepared at different temperatures using the sol gel method. The effect of gold nanoparticles (GNPs) on the electrochromic properties of WO3 was also studied. 2.5 nm GNP was synthesized through sodium citrate reduction of gold chloride in an aqueous solution. These films were characterized by XRD, SEM, TEM, and spectrophotometer analyses. The films annealed at 200ÚC were amorphous and crystallized at high temperatures. According to the scanning electron microscopy (SEM) image, the films annealed at 200ÚC were dense. Moreover, the particles were uniformly distributed on them. Spectrophotometer analysis of WO3 thin films annealed at 200ÚC showed their high electrochromic properties (transmission modulation (ΔT) was 72% and response time was 3.25s for 80% coloring). Spectrophotometer analysis of Au-WO3 thin films annealed at 200ÚC showed that their coloration properties increased (ΔT = 78%) and response duration decreased (1.65s) when gold nanoparticles were added. This enhancement is attributed to the increased conductivity caused by the addition of gold nanoparticles as well as the surface plasmon resonance based absorption of GNPs.
https://www.ije.ir/article_72563_b78509b528c6e63db925d13a71ac74dd.pdf
nano particles
sol
gel
Surface plasmon resonance
Thin film
WO3
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1175
1185
72564
A Hybrid Meta-heuristic for the Dynamic Layout Problem with Transportation System Design
Aliakbar Hasani
aa.hasani@shahroodut.ac.ir
1
Roya Soltani
roya.soltani@gmail.com
2
Industrial Engineering and Management, Shahrood University of Technology, Shahrood, Iran
Department of Industrial Engineering, Islamic Azad University
This paper primarily presents a comprehensive dynamic layout design model which integrates layout and transportation system design via considering more realistic assumptions, such as taking account of fixed-position departments and distance between departments that endanger each other. In addition, specific criteria such as capacity, cost and reliability of facilities are considered in transportation system design decision. The combinatorial nature of the problem necessitates using a meta-heuristic approach to deal with this issue. Therefore, an efficient hybrid meta-heuristic based on variable neighborhood search (VNS) and simulated annealing (SA) is proposed to design a proper dynamic layout for a specific planning horizon. The validity of the superiority of the proposed solution method is proven through comparing with all of the other solution methods upon the original model available in the literature. Finally, an extensive computational results lead to the conclusion that the proposed method outperforms other existing methods. In addition, solving an example from the dynamic layout design of a home appliance manufacturer demonstrates the efficiency of the proposed model and solution algorithm in terms of solution quality to solve real-world instances.
https://www.ije.ir/article_72564_cfe3b4862076778d67e5f54f16d1a80e.pdf
Dynamic plant layout problem
Transportation system design
Hybrid meta
heuristic
Variable neighborhood search
Simulated Annealing
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1186
1192
72565
Process Capability Index for Logistic Regression Profile Based on Spmk Index
Amirhossein Amiri
amirhossein.amiri@gmail.com
1
Mina Rezaye abbasi charkhi
mina_abbasi90@yahoo.com
2
Department of Industrial Engineering, Shahed University
Department of Industrial Engineering and Managemen, Amirkabir University of Technology (Polytechnic)
Profile is a relationship between a response variable and one or more independent variables which can describe quality of a process or a product. On the other hand, for an in-control process, capability indices are criteria for the process quality improvement that allows to meet customers’ expectations. Despite a considerable number of applications and monitoring methods already proposed for profiles, a few researches have been focused on the process capability index of profiles. In this paper, we propose a new Spmk index to measure the process capability when the quality of the process is characterized by a logistic regression profile. The performance of the proposed index is evaluated through simulations. Finally, the application of the proposed index is illustrated through a real case.
https://www.ije.ir/article_72565_372dc62378401a348fe304de494d341a.pdf
profile monitoring
logistic profile
processes capability index
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1193
1198
72566
Duplex Surface Treatment of AISI 1045 Steel via Plasma Nitriding of Titanized Layer
Ali Habibolahzadeh
ahabibolahzadeh@yahoo.com
1
Sina Sanjari
sa_30na1987@yahoo.com
2
Department of Metallurgy and Materials Engineering, Semnan University
Department of Metallurgy and Materials Engineering, Semnan University
In this Study, surface of medium carbon steel (AISI 1045) was modified by titanizing followed by plasma nitriding. Titanizing was performed using pack cementation method, in a pack mixture of ferrotitanium, ammonium chloride and alumina, at 1223 K for 45 and 180 min. Plasma-nitriding was conducted at two temperatures of 803 and 823 K for 5 h, in a gas mixture of 75%N2+25%H2. The samples were characterized by scanning electron microscope (SEM), x-ray diffractometre (XRD), Vickers microhardness and pin-on-disk wear tests. The thicknesses of titanized layers was 8-10μm, the thicknesses had no significant change after plasma nitriding. The duplex treated layers consisted of Fe4N, TiN and TiCN phases. Lower titanizing time and higher plasma nitriding temperature provided superior wear resistance and hardness. The highest wear resistance and the lowest friction coefficient were achieved in the sample which was titanized for 45 min and then plasma nitrided at 823 K, with 2130 HV microhardness.
https://www.ije.ir/article_72566_77444f1b27415177500b147ddf98af34.pdf
medium carbon steel
duplex treatment
plasma nitriding
titanizing
microhardness
Wear
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1199
1208
72567
Studying the Effect of Reformer Gas and Exhaust Gas Recirculation on Homogeneous Charge Compression Ignition Engine Operation
Mohsen Pourfallah
m.pourfalah@gmail.com
1
Mechanical & Indusrial Engineering, Babol Noshirvani University of Technology
Combustion in homogeneous charge compression ignition (HCCI) engine is controlled auto ignition of well-mixed fuel, air and residual gas. Since onset of HCCI combustion depends on the auto ignition of fuel/air mixture, there is no direct control on the start of combustion process. Therefore, HCCI combustion becomes unstable rather easily especially at lower and higher engine load. Charge stratification has the potential to extend the load limits of HCCI combustion by improving the control over the combustion phase as well as reducing the maximum of pressure rise. In this study, a combination of experiment and numerical simulation was carried out to investigate the effect of fuel stratification using reformer gas and EGR on HCCI natural gas combustion. It was found that fuel stratification in this case increased the autoignition property of natural gas. On the lean operation boundary, reformer gas and EGR blending enhanced the autoignition by advancing combustion timing at identical initial conditions compared to pure natural gas that expanded the lean boundary of the operating region.
https://www.ije.ir/article_72567_9ae51bb1e09814b289b71e7ae64a4992.pdf
HCCI Engine
charge stratification
Reformer gas
Combustion Control
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1209
1218
72568
Prediction of Residual Stresses for a Hollow Product in Cold Radial Forging Process
Bahman Ghasemi
bahmangh7@gmail.com
1
Hossein Alijani
hossein.alijani@yahoo.com
2
Mehrdad Poursina
poursina@eng.ui.ac.ir
3
Mechanical Engineering, Khomeini shahr Azad University
Mechanical Eng., University of Isfahan
Mechanical Engineering, University of Isfahan
Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axles and also for creating internal profiles such as rifling the gun barrels. The radial forging of tube is usually performed over a mandrel to create an internal profile and/or size the internal diameter. Most of the previous studies conducted on the radial forging process have used axisymmetric models. In this research, residual stresses of a short hollow tube in a cold radial forging process are investigated using 3-D finite element simulation. In this study, a mandrel with six helical grooves and two steps along its length is used. This kind of mandrel is innovated in this research. The workpiece is modeled as an elastic-plastic material and the commercial finite element software, ABAQUS is used to simulate of the process. The accuracy of the model is tested by comparing the predicted results with available experimental work and also validated by both slab and upper bound methods. Residual stresses in the radial forged product and the influence of the process parameters on stress distribution, such as workpiece motions, friction and percentage of reduction are studied to determine the optimized parameters of simulation and improve the condition of this process.
https://www.ije.ir/article_72568_243f8727137aac4927efe038d6dbd6e0.pdf
Cold Radial Forging
Residual Stress
Mandrel Forging
3
D FEM
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1219
1225
72569
An Improved N-dimensional NURBs-based Metamodel
Zhixian Zhong
2005zhzhx@163.com
1
Yuhong Long
longyuhong@guet.edu.cn
2
Zhansi Jiang
jiangzhansi@gmail.com
3
Liquan Ma
jzs@guet.edu.cn
4
College of Mechanical and Control Engineering, Guilin University of Technology
Department of Electromechanical Engineering, Guilin University of Electronic Technology
Department of Electromechanical Engineering, Guilin University of Electronic Technology
Department of Electromechanical Engineering, Guilin University of Electronic Technology
Non Uniform Rational B-splines (NURBs) are proved to be very promising for metamodeling in engineering problems, because they have unique properties such as local modification scheme, strong convex hull property, and infinitely differentiability, etc. Since NURBs are defined by control points, knot vector, and weights associated with control points, the precision of NURBs is influenced by all of the parameters. In order to improve the precision and calculating efficiency, an enhanced method of building NURBs metamodel is presented. Some improvements are made in many aspects, such as: improving the date parameterization method and the calculating method of weight coefficient. Compared with the existing methods, this method can calculation the weight coefficient of each control point more quickly, because it avoids the inverse operation of correlation matrix, which may cause singular. Several classic numerical examples show that the presented method is effective for building approximate model with higher accuracy than existing NURBs metamodel.
https://www.ije.ir/article_72569_e247b063c1685c36904469a03e4dd312.pdf
Non Uniform Rational B
splines
Metamodel
Weight Coefficient
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1226
1232
72570
Approximate Closed-form Formulae for Buckling Analysis of Rectangular Tubes under Torsion
Arash Omidvari
omidvariarash@yahoo.com
1
Mechanical Engineering, Shiraz University
The buckling torque may be much less than the yield torque in very thin rectangular tubes under torsion. In this paper, simple closed-form formulae are presented for buckling analysis of long hollow rectangular tubes under torsion. By the presented formulae, one can obtain the critical torque or the critical angle of twist of the tube in terms of its geometrical parameters and material constants. First, an approximate function for critical angle of twist, including a part in terms of the Poisson’s ratio and another part in terms of geometrical parameters with unknown coefficients are considered. Then, the unknown coefficients are found by a minimax optimization method and also by using the accurate results obtained by the finite element method. The formulae can be used for a wide range of dimensions of hollow rectangular tubes. The numerical studies show that the maximum error of the presented formulae is less than 10%.
https://www.ije.ir/article_72570_d6fd99b37b27fa0ba3a7d45698261a4d.pdf
Torsion
Buckling
rectangular hollow tube
warping
optimization
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1233
1240
72571
H∞ Robust Controller Design and Experimental Analysis of Active Magnetic Bearings with Flexible Rotor System
changsheng Zhu
zhu_zhang@zju.edu.cn
1
Zhixian Zhong
2005zhzhx@163.com
2
College of Electrical Engineering, Zhejiang University
College of Mechanical and Control Engineering, Guilin University of Technology
H∞ controller for active magnetic bearings (AMBs) with flexible rotor system was designed in this paper. The motion equations of AMBs and flexible rotor system are built based on finite element methods (FEM). Weighting function matrices of H∞ controller for AMBs are studied for both the sensitivity and the complementary sensitivity of H∞ control theory. The simulation shows that the H∞ control method has a good dynamic characteristics, good robust and ability to depress vibration. The experiments are completed on a four-degree freedom magnetic bearings-flexible rotor test rig, and the obtained experimental results show that H∞ controller is characterized by the effectiveness of interference immunity and robust stability. The peak to peak vibration amplitudes of flexible rotor are less than 60μm at the first critical speed of flexible rotors, and the results indicate that H∞ controller for the active magnetic bearings with flexible rotor system is stable through the first critical speed of the flexible rotor system.
https://www.ije.ir/article_72571_9e1df2ba3bf6987e5b31b148a0d412f4.pdf
Active magnetic bearing (AMB)
H∞ control
Flexible rotor
Finite element methods
eng
Materials and Energy Research Center
International Journal of Engineering
1025-2495
1735-9244
2015-08-01
28
8
1241
1250
72572
Experimental Study for Investigating the Mechanism of Heat Transfer near the Critical Heat Flux in Nucleate Pool Boiling
Sanjeev Kumar Sharma
sksharma6@amity.edu
1
R. K. Shukla
rkshukla@amity.edu
2
basant Sikarwar
bssikarwar@amity.edu
3
Mechanical Engineering, Amity university, Noida
Mechanical Engineering, Amity university, Noida
Mechanical Engineering, Amity University Uttar Pradesh Noida India
Heat transfer coefficient in nucleate pool boiling near critical heat flux at least one orderhigher than the convectional heat transfer modes. In this paper, an experimental setup isdesigned and fabricated to investigate the mechanism of heat transfer from boiling surface tobulk liquid near critical heat flux. The images of pool boiling near the high heat flux regionreveals that the individual bubble coalesce due to very high bubble site density and formvapor mass entrapping a relatively thicker film of liquid known as ‘macro-layer’ between thegrowing vapor mass and the heating surface. Hence, the nucleate boiling at high heat flux ischaracterized by the existence of a liquid layer known as the macrolayer between the heatingsurface and the vapour mass. The rate of evaporation of macro-layer and transientconduction through macro-layer is the prime parameter to transfer heat from the heatedsurface. Using images processing, initial macrolayer thickness and vapour mass frequency atvarious wall superheats temperature were measured. The thickness of the macro-layer foundto lay the range of 153 μm to 88 μm respectively for range of 60% to 95% critical heat fluxof water on brass surface. As the heat flux increases the thickness of macro-layer decreases.The vapor mass frequency varied from 4 Hz to 8.80 Hz for water in the range of 60 to 90 %of critical heat flux. The vapor mass frequency increases as heat flux increases due to higherevaporation rate associated with higher heat flux.
https://www.ije.ir/article_72572_0cf038b2b51168b8d45648d6a7db7c73.pdf
pool
Boiling
heat transfer
nucleate
Vapor
Mushroom region
Heat Transfer Coefficient and critical heat flux