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Prof. Kyung Chun Kim
School of Mechanical Engineering, Pusan National University, Busan 609-735, South Korea

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Research Keywords & Expertise

0 Heat Transfer
0 Turbulence
0 Fluid Mechanics
0 organic Rankine cycle
0 Energy system analysis, modelling and optimization

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organic Rankine cycle
Heat Transfer
Turbulence

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Journal article
Published: 17 August 2021 in Materials
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Heat transfer under flow boiling is better in a rectangular channel filled with open-cell metal foam than in an empty channel, but the high pressure drop is a drawback of the empty channel method. In this study, various types of metal foam insert configurations were tested to reduce the pressure drop while maintaining high heat transfer. Specifically, we measured the boiling heat transfer and pressure drop of a two-phase vertical upward flow of R245fa inside a channel. To measure the pressure and temperature differences of the metal foam, differential pressure transducers and T-type thermocouples were used at both ends of the test section. While the saturation pressure was kept constant at 5.9 bar, the steam quality at the inlet of the test section was changed from 0.05 to 0.99. The channel height, moreover, was 3 mm, and the mass flux ranged from 133 to 300 kg/m2s. The two-phase flow characteristics were observed through a high-speed visualization experiment. Heat transfer tended to increase with the mean vapor quality, and, as expected, the fully filled metal foam channel offered the highest thermal performance. The streamwise insert pattern model had the lowest heat transfer at a low mass flux. However, at a higher mass flux, the three different insert models presented almost the same heat transfer coefficients. We found that the streamwise pattern model had a very low pressure drop compared to that of the spanwise pattern models. The goodness factors of the flow area and the core volume of the streamwise patterned model were higher than those of the full-filled metal foam channel.

ACS Style

Sanghyun Nam; Dae Yeon Kim; Youngwoo Kim; Kyung Chun Kim. Effect of Metal Foam Insert Configurations on Flow Boiling Heat Transfer and Pressure Drop in a Rectangular Channel. Materials 2021, 14, 4617 .

AMA Style

Sanghyun Nam, Dae Yeon Kim, Youngwoo Kim, Kyung Chun Kim. Effect of Metal Foam Insert Configurations on Flow Boiling Heat Transfer and Pressure Drop in a Rectangular Channel. Materials. 2021; 14 (16):4617.

Chicago/Turabian Style

Sanghyun Nam; Dae Yeon Kim; Youngwoo Kim; Kyung Chun Kim. 2021. "Effect of Metal Foam Insert Configurations on Flow Boiling Heat Transfer and Pressure Drop in a Rectangular Channel." Materials 14, no. 16: 4617.

Journal article
Published: 17 August 2021 in Ocean Engineering
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The performance of coastal breakwaters in reducing wave height and energy is an important problem. This paper presents an experimental and numerical investigation of solitary wave interaction with two submerged rectangular obstacles. White light and particle image velocimetry (PIV) techniques were utilized to study the free surface profile of a solitary wave and flow field in an experimental procedure. The PIV test results revealed that two clockwise vortices are generated between and after the two obstacles, and the white light test results showed that three phenomena of wave breaking, crest-crest exchange, and air-water mixing occur in the solitary wave passage over the two obstacles. A transient two-dimensional numerical model was used to study solitary wave interaction with two rectangular obstacles. The numerical model was validated with experimental results in terms of free surface profile, velocity fields, and velocity profiles. Using this model, the effects of obstacles height and distance were investigated. The numerical results showed that when increasing the height of the obstacles, the drag force applied on the obstacles, the strength of vortices, the energy loss, and the height reduction of the solitary wave increased. The presence of the second obstacle and wave breaking occurrence constrain the movement of vortices and cause a negative drag coefficient on the obstacles in some cases. The energy loss, the height reduction of the solitary wave, and the strength of the vortex generated between the obstacles increased as the distance of the obstacles increased up to S/L = 1.5. In contrast, the strength of the vortex generated after the second obstacle was decreased by increasing the distance of two obstacles.

ACS Style

Ashkan Ghafari; Mohammad Reza Tavakoli; Mahdi Nili-Ahmadabadi; Kowsar Teimouri; Kyung Chun Kim. Investigation of interaction between solitary wave and two submerged rectangular obstacles. Ocean Engineering 2021, 237, 109659 .

AMA Style

Ashkan Ghafari, Mohammad Reza Tavakoli, Mahdi Nili-Ahmadabadi, Kowsar Teimouri, Kyung Chun Kim. Investigation of interaction between solitary wave and two submerged rectangular obstacles. Ocean Engineering. 2021; 237 ():109659.

Chicago/Turabian Style

Ashkan Ghafari; Mohammad Reza Tavakoli; Mahdi Nili-Ahmadabadi; Kowsar Teimouri; Kyung Chun Kim. 2021. "Investigation of interaction between solitary wave and two submerged rectangular obstacles." Ocean Engineering 237, no. : 109659.

Journal article
Published: 15 July 2021 in Sustainable Energy Technologies and Assessments
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In this study, a biomass powered combined cooling, heating, and power system based on the organic Rankine cycles and the vapor compression cycle has been presented for small scale developing and underdevelopment communities. The system consists of an M−Xylene organic Rankine cycle as the prime mover capable of delivering 100 kW of electricity. Meanwhile, Isobutane vapor compression chiller is powered by an R245fa organic Rankine cycle. This organic Rankine cycle is powered by the residual heat from the biomass fuel. The cooling and the heating capacities of the system, as well as the overall system exergy destruction rate and the overall heat capacity of the heat exchangers were evaluated against the boiler and condenser saturation temperatures of the organic Rankine cycles and the vapor compression chiller. The system can deliver as much as 30 kW of cooling and 528 kW of heating at various combinations of parameters. The multi-objective optimization considering the Genetic Algorithm was also carried out. The system exergy destruction rate and the heat capacity of the heat exchangers at the optimum point were found to be 177 kW and 15.11 kW/K, respectively.

ACS Style

Muhammad Tauseef Nasir; Michael Chukwuemeka Ekwonu; Javad Abolfazli Esfahani; Kyung Chun Kim. Performance assessment and multi-objective optimization of an organic Rankine cycles and vapor compression cycle based combined cooling, heating, and power system. Sustainable Energy Technologies and Assessments 2021, 47, 101457 .

AMA Style

Muhammad Tauseef Nasir, Michael Chukwuemeka Ekwonu, Javad Abolfazli Esfahani, Kyung Chun Kim. Performance assessment and multi-objective optimization of an organic Rankine cycles and vapor compression cycle based combined cooling, heating, and power system. Sustainable Energy Technologies and Assessments. 2021; 47 ():101457.

Chicago/Turabian Style

Muhammad Tauseef Nasir; Michael Chukwuemeka Ekwonu; Javad Abolfazli Esfahani; Kyung Chun Kim. 2021. "Performance assessment and multi-objective optimization of an organic Rankine cycles and vapor compression cycle based combined cooling, heating, and power system." Sustainable Energy Technologies and Assessments 47, no. : 101457.

Article
Published: 08 July 2021 in ChemElectroChem
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To achieve efficient conversion of renewable energy sources through water splitting, low-cost, efficient, and eco-friendly catalysts are required for oxygen and hydrogen evolution. Herein, we demonstrate that infrared (IR)-irradiating oxide catalysts improve the evolution efficiency of H 2 and O 2 gases by approximately 3.4 times that of the conventional method. This indicates that the IR oxide catalysts contribute to lowering of the energy per mol required to break the interatomic covalent bonds in the water molecule (H 2 O) through stretching and bending vibrations, thus facilitating the efficient evolution of H 2 and O 2 gases. The comparison results of IR oxide catalysts with the catalyst-free 6M KOH solution showed that the former requires a shorter duration of 11 min compared to the 37 mins required by the catalyst-free 6M KOH solution for the evolution of 500 cc of O 2 and H 2 gases. For the system containing the IR oxide catalyst, the power consumption was 5.5 Wh for 1 L of H 2 gas evolution, whereas the catalyst-free system consumed 23 Wh of power. This four-times lower power consumption, using the IR oxide catalyst indicates a promising method for the mass evolution of O 2 and H 2 gases. These results indicate that the IR oxide can be used as an efficient and eco-friendly thermal radiation catalyst for green hydrogen and renewable energy applications.

ACS Style

Sobin Mathew; Chan Yang Kim; Min-Kyun Kim; Kyung Chun Kim; Young-Rae Cho; Won Sub Chung. Effect of Infrared Oxide Catalyst on Water Splitting for Green Energy. ChemElectroChem 2021, 1 .

AMA Style

Sobin Mathew, Chan Yang Kim, Min-Kyun Kim, Kyung Chun Kim, Young-Rae Cho, Won Sub Chung. Effect of Infrared Oxide Catalyst on Water Splitting for Green Energy. ChemElectroChem. 2021; ():1.

Chicago/Turabian Style

Sobin Mathew; Chan Yang Kim; Min-Kyun Kim; Kyung Chun Kim; Young-Rae Cho; Won Sub Chung. 2021. "Effect of Infrared Oxide Catalyst on Water Splitting for Green Energy." ChemElectroChem , no. : 1.

Journal article
Published: 29 June 2021 in International Journal of Multiphase Flow
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An experimental study was conducted on the flow characteristics and turbulence suppression in vertically issued bubbly jets with low void fraction (less than 1%, Re = 3,172). The effect of bubble distributions on the flow characteristics of the bubbly jet was investigated using planar Laser-Induced Fluorescence (PLIF) in the same measurement plane as Particle Image Velocimetry (PIV) for the phase separation. To ensure uniform size of the small bubbles, a bubble generator consisting of small needles was designed and manufactured. Due to the low void fraction, the velocity fields of each phase were successfully obtained. The slip velocity was constant in the far-field of the flow as 2.1 times of the inlet velocity in this study. In the early stage of the jet, there is an acceleration region that is attributed to the buoyancy of bubbles. As the potential core of the bubbly jets collapses, the distribution of bubbles seems to have an annular truncated cone shape, which evolves with the liquid flow structure. Most bubbles are populated the region around the velocity radius of the bubbly jet. Reynolds shear stresses and normal stresses of the dilute bubbly jet generally show smaller magnitudes than those of pure jets, buoyant jets, bubbly jets, and bubbly plumes. The case with higher void fraction (1%, Exp.330) shows similar magnitude of Reynolds axial stresses to jets, but magnitudes of other stresses are similar to the case with lower void fraction (0.66, Exp.320). The results are probably attributed to suppression of turbulence in low-void-fraction condition.

ACS Style

Hyunduk Seo; Kyung Chun Kim. Experimental study on flow and turbulence characteristics of bubbly jet with low void fraction. International Journal of Multiphase Flow 2021, 142, 103738 .

AMA Style

Hyunduk Seo, Kyung Chun Kim. Experimental study on flow and turbulence characteristics of bubbly jet with low void fraction. International Journal of Multiphase Flow. 2021; 142 ():103738.

Chicago/Turabian Style

Hyunduk Seo; Kyung Chun Kim. 2021. "Experimental study on flow and turbulence characteristics of bubbly jet with low void fraction." International Journal of Multiphase Flow 142, no. : 103738.

Article
Published: 26 June 2021 in Journal of Thermal Analysis and Calorimetry
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In the current study, the artificial neural network modeling of the Nusselt number and friction factor of a heat exchanger, equipped with the twisted tapes to enhance the heat transfer capacity, has been done. In the modeling procedure, alongside the Reynolds number, four geometrical characteristics of the twisted cut tapes, including the depth of cut, the area of cut, the perimeter of cut, and the pitch length of the twisted tapes, have been considered. The required data were gathered from both experiments and the CFD method. The results clarified that compared to the experimental procedures and numerical methods, the artificial neural network model has an outstanding performance in considerably less time and cost. Despite a variety of cuts, the present work introduced generalized and unique tools to design and control these systems. The work interestingly reveals that the model can forecast the friction factor and the heat transfer augmentation only by the specification parameter of cuts rather than the shape of cuts. Further sensitivity studies also proved that, if necessary, some variables could be removed from the input vectors, and the models predicting ability remains acceptable.

ACS Style

Mohammad Mahdi Tafarroj; Golnaz Zarabian Ghaeini; Javad Abolfazli Esfahani; Kyung Chun Kim. Multi-purpose prediction of the various edge cut twisted tape insert characteristics: multilayer perceptron network modeling. Journal of Thermal Analysis and Calorimetry 2021, 145, 2005 -2020.

AMA Style

Mohammad Mahdi Tafarroj, Golnaz Zarabian Ghaeini, Javad Abolfazli Esfahani, Kyung Chun Kim. Multi-purpose prediction of the various edge cut twisted tape insert characteristics: multilayer perceptron network modeling. Journal of Thermal Analysis and Calorimetry. 2021; 145 (4):2005-2020.

Chicago/Turabian Style

Mohammad Mahdi Tafarroj; Golnaz Zarabian Ghaeini; Javad Abolfazli Esfahani; Kyung Chun Kim. 2021. "Multi-purpose prediction of the various edge cut twisted tape insert characteristics: multilayer perceptron network modeling." Journal of Thermal Analysis and Calorimetry 145, no. 4: 2005-2020.

Journal article
Published: 25 June 2021 in Materials
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Open-cell metal foams are porous medium for thermo-fluidic systems. However, their complex geometry makes it difficult to perform time-resolved (TR) measurements inside them. In this study, a TR particle image velocimetry (PIV) method is introduced for use inside open-cell metal foam structures. Stereolithography 3D printing methods and conventional post-processing methods cannot be applied to metal foam structures; therefore, PolyJet 3D printing and post-processing methods were employed to fabricate a transparent metal foam replica. The key to obtaining acceptable transparency in this method is the complete removal of the support material from the printing surfaces. The flow characteristics inside a 10-pore-per-inch (PPI) metal foam were analyzed in which porosity is 0.92 while laminar flow condition is applied to inlet. The flow inside the foam replica is randomly divided and combined by the interconnected pore network. Robust crosswise motion occurs inside foam with approximately 23% bulk speed. Strong influence on transverse motion by metal foam is evident. In addition, span-wise vorticity evolution is similar to the integral time length scale of the stream-wise center plane. The span-wise vorticity fluctuation through the foam arrangement is presented. It is believed that this turbulent characteristic is caused by the interaction of jets that have different flow directions inside the metal foam structure. The finite-time Lyapunov exponent method is employed to visualize the vortex ridges. Fluctuating attracting and repelling material lines are expected to enhance the heat and mass transfer. The results presented in this study could be useful for understanding the flow characteristics inside metal foams.

ACS Style

Youngwoo Kim; Chanhee Moon; Omid Nematollahi; Hyun Kim; Kyung Kim. Time-Resolved PIV Measurements and Turbulence Characteristics of Flow Inside an Open-Cell Metal Foam. Materials 2021, 14, 3566 .

AMA Style

Youngwoo Kim, Chanhee Moon, Omid Nematollahi, Hyun Kim, Kyung Kim. Time-Resolved PIV Measurements and Turbulence Characteristics of Flow Inside an Open-Cell Metal Foam. Materials. 2021; 14 (13):3566.

Chicago/Turabian Style

Youngwoo Kim; Chanhee Moon; Omid Nematollahi; Hyun Kim; Kyung Kim. 2021. "Time-Resolved PIV Measurements and Turbulence Characteristics of Flow Inside an Open-Cell Metal Foam." Materials 14, no. 13: 3566.

Journal article
Published: 23 June 2021 in Computers in Biology and Medicine
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In a new therapeutic technique, called magnetic drug targeting (MDT), magnetic particles carrying therapeutic agents are directed to the target tissue by applying an external magnetic field. Meanwhile, this magnetic field also affects the blood as a biomagnetic fluid. Therefore, it is necessary to select a magnetic field with an acceptable range of influence on the blood flow. This study investigates the effect of an external magnetic field on the pulsatile blood flow in a stenosed curved artery to identify a safe magnetic field. The effects of a number of parameters, including the magnetic susceptibility of blood in oxygenated and deoxygenated states and the magnetic field strength, were studied. Moreover, the effect of the plaque morphology, including the occlusion percentage and the chord length of the stenosis, on changes in blood flow induced by the magnetic field was investigated. The results show that applying a magnetic field increases the wall shear stress (WSS) and the pressure of the deoxygenated blood. Comparing the wall shear stresses of the deoxygenated and oxygenated blood shows that the effect of magnetic field on the deoxygenated blood is more significant than its effect on the oxygenated blood due to its higher magnetic susceptibility. The study of the stenosis geometry shows that the influence of magnetic field on the blood flow is increased by decreasing the occlusion percentage of the artery. Furthermore, among the evaluated lengths, the 50° chord length results in the highest variation under the influence of the magnetic field. Finally, the magnetic field of Mn = 2.5 can be utilized as a safe field for MDT purposes in such a stenosed curved artery.

ACS Style

Kowsar Teimouri; Mohammad Reza Tavakoli; Ashkan Ghafari; Kyung Chun Kim. Investigation of the Plaque Morphology Effect on Changes of Pulsatile Blood Flow in a Stenosed Curved Artery Induced by an External Magnetic Field. Computers in Biology and Medicine 2021, 135, 104600 .

AMA Style

Kowsar Teimouri, Mohammad Reza Tavakoli, Ashkan Ghafari, Kyung Chun Kim. Investigation of the Plaque Morphology Effect on Changes of Pulsatile Blood Flow in a Stenosed Curved Artery Induced by an External Magnetic Field. Computers in Biology and Medicine. 2021; 135 ():104600.

Chicago/Turabian Style

Kowsar Teimouri; Mohammad Reza Tavakoli; Ashkan Ghafari; Kyung Chun Kim. 2021. "Investigation of the Plaque Morphology Effect on Changes of Pulsatile Blood Flow in a Stenosed Curved Artery Induced by an External Magnetic Field." Computers in Biology and Medicine 135, no. : 104600.

Journal article
Published: 16 June 2021 in Journal of Cleaner Production
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Flat-plate solar collectors are a cost-effective technology for water heating in residential buildings. Comprehensive sensitivity analysis and multi-objective optimization of five crucial factors in a flat-plate solar collector equipped with twisted tapes are investigated. The studied factors are the Nusselt number (Nu), friction factor (f), solar collector efficiency (η), thermal performance factor (ξ), and the temperature difference of the heat transfer fluid across the device (ΔT). The simulation of functions is carried out by four soft computing methods, such as the linear and cubic form of multivariate adaptive regression splines (MARS), group method of data handling (GMDH), and multivariate polynomial regression (MPR). The linear form of the MARS algorithm shows the highest accuracy in predicting Nu, f, and η by R2 = 0.99986, 0.9984, and 0.98821, respectively. The Reynolds number (Re) is from 4000 to 14,000, and the twisted tape ratio (Y) is between 0 and 15. The simulated annealing optimization is employed to find the global optima. According to the study, Nu, η, ξ, and ΔT reach their maximum when f is minimum, which occurs for Y = 5 and Re in the 13,200 to 13,400 range for different global solar radiation levels. The maximum temperature difference happens at noon, about 6.54 K at the Re = 5362.5 and Y = 5 with the collector surface area by 2 m2. When the appropriate working conditions are met so that these factors are simultaneously optimal, ΔT, hence the efficiency, can be increased.

ACS Style

Behnam Mohseni-Gharyehsafa; Javad Abolfazli Esfahani; Kyung Chun Kim; Henni Ouerdane. Soft computing analysis of thermohydraulic enhancement using twisted tapes in a flat-plate solar collector: Sensitivity analysis and multi-objective optimization. Journal of Cleaner Production 2021, 314, 127947 .

AMA Style

Behnam Mohseni-Gharyehsafa, Javad Abolfazli Esfahani, Kyung Chun Kim, Henni Ouerdane. Soft computing analysis of thermohydraulic enhancement using twisted tapes in a flat-plate solar collector: Sensitivity analysis and multi-objective optimization. Journal of Cleaner Production. 2021; 314 ():127947.

Chicago/Turabian Style

Behnam Mohseni-Gharyehsafa; Javad Abolfazli Esfahani; Kyung Chun Kim; Henni Ouerdane. 2021. "Soft computing analysis of thermohydraulic enhancement using twisted tapes in a flat-plate solar collector: Sensitivity analysis and multi-objective optimization." Journal of Cleaner Production 314, no. : 127947.

Journal article
Published: 27 May 2021 in Scientific Reports
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This paper proposes a data augmentation method based on artificial intelligence (AI) to obtain sound level spectrum as predicting the spatial and temporal data of time-resolved three-dimensional Particle Tracking Velocimetry (4D PTV) data. A 4D PTV has used to measure flow characteristics of three side mirror models adopting the Shake-The-Box (STB) algorithm with four high-speed cameras on a robotic arm for measuring industrial scale. Helium filled soap bubbles are used as tracers in the wind tunnel experiment to characterize flow structures around automobile side mirror models. Full volumetric velocity fields and evolution of vortex structures are obtained and analyzed. Instantaneous pressure fields are deduced by solving a Poisson equation based on the 4D PTV data. To predict spatial and temporal data of velocity field, artificial intelligence (AI)-based data prediction method has applied. Adaptive Neural Fuzzy Inference System (ANFIS) based machine learning algorithm works well to find 4D missing data behind the automobile side mirror model. Using the ANFIS model, power spectrum of velocity fluctuations and sound level spectrum of pressure fluctuations are successfully obtained to assess flow and noise characteristics of three different side mirror models.

ACS Style

Dong Kim; Arman Safdari; Kyung Chun Kim. Sound pressure level spectrum analysis by combination of 4D PTV and ANFIS method around automotive side-view mirror models. Scientific Reports 2021, 11, 1 -15.

AMA Style

Dong Kim, Arman Safdari, Kyung Chun Kim. Sound pressure level spectrum analysis by combination of 4D PTV and ANFIS method around automotive side-view mirror models. Scientific Reports. 2021; 11 (1):1-15.

Chicago/Turabian Style

Dong Kim; Arman Safdari; Kyung Chun Kim. 2021. "Sound pressure level spectrum analysis by combination of 4D PTV and ANFIS method around automotive side-view mirror models." Scientific Reports 11, no. 1: 1-15.

Journal article
Published: 25 May 2021 in Applied Sciences
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The upgraded elastic surface algorithm (UESA) is a physical inverse design method that was recently developed for a compressor cascade with double-circular-arc blades. In this method, the blade walls are modeled as elastic Timoshenko beams that smoothly deform because of the difference between the target and current pressure distributions. Nevertheless, the UESA is completely unstable for a compressor cascade with an intense normal shock, which causes a divergence due to the high pressure difference near the shock and the displacement of shock during the geometry corrections. In this study, the UESA was stabilized for the inverse design of a compressor cascade with normal shock, with no geometrical filtration. In the new version of this method, a distribution for the elastic modulus along the Timoshenko beam was chosen to increase its stiffness near the normal shock and to control the high deformations and oscillations in this region. Furthermore, to prevent surface oscillations, nodes need to be constrained to move perpendicularly to the chord line. With these modifications, the instability and oscillation were removed through the shape modification process. Two design cases were examined to evaluate the method for a transonic cascade with normal shock. The method was also capable of finding a physical pressure distribution that was nearest to the target one.

ACS Style

Mohammad Noorsalehi; Mahdi Nili-Ahmadabadi; Seyed Nasrazadani; Kyung-Chun Kim. Aerodynamic Inverse Design of Transonic Compressor Cascades with Stabilizing Elastic Surface Algorithm. Applied Sciences 2021, 11, 4845 .

AMA Style

Mohammad Noorsalehi, Mahdi Nili-Ahmadabadi, Seyed Nasrazadani, Kyung-Chun Kim. Aerodynamic Inverse Design of Transonic Compressor Cascades with Stabilizing Elastic Surface Algorithm. Applied Sciences. 2021; 11 (11):4845.

Chicago/Turabian Style

Mohammad Noorsalehi; Mahdi Nili-Ahmadabadi; Seyed Nasrazadani; Kyung-Chun Kim. 2021. "Aerodynamic Inverse Design of Transonic Compressor Cascades with Stabilizing Elastic Surface Algorithm." Applied Sciences 11, no. 11: 4845.

Accepted manuscript
Published: 24 May 2021 in Measurement Science and Technology
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A two-dimensional phosphorescence-based method is presented for simultaneous measurement of strain and temperature. 6 μm Mg4FGeO6:Mn4+ phosphor particles were sprayed on the surface of the test target for use as a sensor. A measurement system was established, which included a high-speed camera, a 385-nm LED, and a signal generator. The signal generator controls the LED to output a 100-Hz light pulse to excite the phosphor. The phosphorescence is then detected by the high-speed camera with a frequency of 10 kHz. The temperature information is obtained from the phosphorescence decay rate using the lifetime method. A digital image correlation method was then used with the random markings formed by spraying. The 100 Hz temperature and strain measurement technique was implemented based on the current experimental conditions with an accuracy of 2% in temperature measurement and 16% and 9.3% in u- and v-direction respectively in strain measurement. The measurement procedure was used for measurements of temperature and deformation of an aluminum plate with a pulsed current in a temperature range of 0~600 oC and a displacement range of 0-300 μm. The results from experiments show the possibility of 2D measurements of surface temperature and strain in a harsh environment with a non-invasive method.

ACS Style

Tao Cai; Shabnam Mohammadshahi; Taekyung Lee; Kyung Chun Kim. Simultaneous measurement of two-dimensional temperature and strain fields based on thermographic phosphor and digital image correlation. Measurement Science and Technology 2021, 32, 095204 .

AMA Style

Tao Cai, Shabnam Mohammadshahi, Taekyung Lee, Kyung Chun Kim. Simultaneous measurement of two-dimensional temperature and strain fields based on thermographic phosphor and digital image correlation. Measurement Science and Technology. 2021; 32 (9):095204.

Chicago/Turabian Style

Tao Cai; Shabnam Mohammadshahi; Taekyung Lee; Kyung Chun Kim. 2021. "Simultaneous measurement of two-dimensional temperature and strain fields based on thermographic phosphor and digital image correlation." Measurement Science and Technology 32, no. 9: 095204.

Regular article
Published: 17 May 2021 in The European Physical Journal Plus
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An analysis of the second law of thermodynamics was performed for Al2O3/H2O nanofluid in different plate-pin fin-splitter heat sinks in the present study. The square pin fins with rectangular, arched, and wavy splitters behind them were inserted inside the plate-fin heat sink. We investigated the effects of nanofluid, volume fraction of nanoparticles, Reynolds number, splitter shape, pin width, and splitter length on the heat transfer, fluid flow, thermal, frictional entropy generation rates or irreversibilities, the sensitivity analysis, and Bejan number inside the plate-pin fin-splitter heat sink. The nanofluid was simulated using a two-phase mixture model. The numerical results were validated with both empirical correlations and experimental data. The results indicate that the thermal performance is improved by about 15% for pure water, and the f factor is reduced by about 0.6% using rectangular splitters behind pin fins. Also, Nu is increased by about 25% with the simultaneous use of 2% vol. Al2O3/H2O nanofluid and a rectangular splitter. It is increased more by using arched splitters compared to rectangular and wavy splitters. The rectangular, arched, and wavy splitters generate up to 39.34%, 42.36%, and 38.61% lower thermal entropy generation than the smooth heat sink, respectively. Among splitter geometries, the arched splitters have the highest amount of frictional entropy generation. The thermal irreversibility is increased by about 71% and 43.2%, and the frictional irreversibility is reduced by about 4.1% and 0.3% with reduced pin width and splitter length in the plate-pin fin-rectangular splitter heat sink, respectively. The use of nanofluid reduces thermal irreversibility and increases frictional irreversibility. By increasing the volume fraction of nanoparticles from 0.5 to 3%, the thermal irreversibility is reduced by about 63.3%. Thus, the frictional irreversibility is increased by about 6.8% in the plate-pin fin-arched splitter heat sink. Moreover, the results show that thermal performance and thermal irreversibility are sensitive to changes in the pin width, splitter length, Re, and nanofluid volume fraction.

ACS Style

Elham Hosseinirad; Javad Abolfazli Esfahani; Faramarz Hormozi; Kyung Chun Kim. Analysis of entropy generation and thermal–hydraulic of various plate-pin fin-splitter heat recovery systems using Al2O3/H2O nanofluid. The European Physical Journal Plus 2021, 136, 1 -30.

AMA Style

Elham Hosseinirad, Javad Abolfazli Esfahani, Faramarz Hormozi, Kyung Chun Kim. Analysis of entropy generation and thermal–hydraulic of various plate-pin fin-splitter heat recovery systems using Al2O3/H2O nanofluid. The European Physical Journal Plus. 2021; 136 (5):1-30.

Chicago/Turabian Style

Elham Hosseinirad; Javad Abolfazli Esfahani; Faramarz Hormozi; Kyung Chun Kim. 2021. "Analysis of entropy generation and thermal–hydraulic of various plate-pin fin-splitter heat recovery systems using Al2O3/H2O nanofluid." The European Physical Journal Plus 136, no. 5: 1-30.

Journal article
Published: 15 May 2021 in International Journal of Hydrogen Energy
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In this study, a steady-state analytical model for heat and mass transfer in a 2D micro-reactor coated with a Nickel-based catalyst is developed to investigate microscale hydrogen production. Appropriate correlations for each species’ net rate of production or consumption, mass diffusivity, and the heat of reactions are developed using a detailed reaction mechanism of methane steam reforming. The energy and species conservation equations are then solved for the reactive mixture coupled with the wall energy equation. Finally, the response surface methodology (RSM) is employed to study the effects of channel height, inlet velocity and temperature, wall thickness and conductivity, and external heat flux on CH4 conversion. It is found that the inlet gas temperature, among different parameters, has the most influence on the overall performance of the microchannel hydrogen production. Also, the maximum necessary heat of reforming reaction increases by 84% and 26% if the CH4 conversion changes from 50% to 60% and 60% to 70%, respectively. The developed analytical simulation can be a useful tool for designing experiments in micro-scale hydrogen production.

ACS Style

Mostafa Pourali; Javad Abolfazli Esfahani; Mohammad Amin Sadeghi; Kyung Chun Kim; Jeff Gostick. Simulation of methane steam reforming in a catalytic micro-reactor using a combined analytical approach and response surface methodology. International Journal of Hydrogen Energy 2021, 46, 22763 -22776.

AMA Style

Mostafa Pourali, Javad Abolfazli Esfahani, Mohammad Amin Sadeghi, Kyung Chun Kim, Jeff Gostick. Simulation of methane steam reforming in a catalytic micro-reactor using a combined analytical approach and response surface methodology. International Journal of Hydrogen Energy. 2021; 46 (44):22763-22776.

Chicago/Turabian Style

Mostafa Pourali; Javad Abolfazli Esfahani; Mohammad Amin Sadeghi; Kyung Chun Kim; Jeff Gostick. 2021. "Simulation of methane steam reforming in a catalytic micro-reactor using a combined analytical approach and response surface methodology." International Journal of Hydrogen Energy 46, no. 44: 22763-22776.

Journal article
Published: 13 May 2021 in International Journal of Mechanical Sciences
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The effects of using nature-inspired needle-shaped vortex generators (VGs) on the aerodynamic features of a 65°/35° double-delta wing were investigated experimentally in a wind tunnel. Particle Image Velocimetry (PIV) visualization was conducted on 7 chord-wise sections as well as 7 span-wise sections at an Angle of Attack (AOA) of 30° and on a plane adjacent to the wing surface at AOAs of 30° and 35° The experiments were carried out at Re = 2 × 105. The double-delta wing was equipped with a series of VGs at the leading edge of the apex and kink area. The effect of VGs on the time-averaged vortical flow features was investigated and then compared to those of the plain wing model. The assessment of the vortices’ diameter, vorticity and velocity distribution, streamline topology, circulation (Γ), and parameter Γ/Av showed that the use of the needle shaped VGs has an enhancing effect on the improvement in flow structure of the double-delta wing. The causes of the flow structure improvement were the increased flow momentum over and behind the wing, energized near-surface flow, a more concentrated vortex system, and delayed vortex breakdown.

ACS Style

Hamed Khodabakhshian Naeini; Mahdi Nili-Ahmadabadi; Yoon Seong Park; Kyung Chun Kim. Effect of nature-inspired needle-shaped vortex generators on the aerodynamic features of a double-delta wing. International Journal of Mechanical Sciences 2021, 202-203, 106502 .

AMA Style

Hamed Khodabakhshian Naeini, Mahdi Nili-Ahmadabadi, Yoon Seong Park, Kyung Chun Kim. Effect of nature-inspired needle-shaped vortex generators on the aerodynamic features of a double-delta wing. International Journal of Mechanical Sciences. 2021; 202-203 ():106502.

Chicago/Turabian Style

Hamed Khodabakhshian Naeini; Mahdi Nili-Ahmadabadi; Yoon Seong Park; Kyung Chun Kim. 2021. "Effect of nature-inspired needle-shaped vortex generators on the aerodynamic features of a double-delta wing." International Journal of Mechanical Sciences 202-203, no. : 106502.

Conference paper
Published: 06 May 2021 in Recent Advances in Computational Mechanics and Simulations
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Open-cell metal foam is a promising porous media for thermo-fluid systems. Flow characteristics inside a 10 PPI (Pores per inch) metal foam with a porosity of 0.92 are analyzed with a laminar inlet flow condition. The flow inside the metal foam structure is chaotically furcated and interflowed by the interconnected pore network. Strong transverse motion is shown inside metal foam with about 23% of bulk velocity. This spanwise velocity is similar value to the result of Onstad et al. (Exp Fluids 50(6):1571–1585, 2011 [4]) who investigated flow inside metal foam using magnetic resonance velocimetry in a turbulent inlet flow condition. It is evidence that the metal foam structure has a dominant influence on transverse motion. Considerable velocity and vorticity fluctuation inside metal foam structure were found. The fluctuations are decayed at downstream. Irregular structure of metal foam generates turbulence. The results presented in this study are useful to understand turbulent characteristics of flow through metal foams.

ACS Style

Chanhee Moon; Kyung Chun Kim. Structure Generated Turbulence: Laminar Flow Through Metal Foam Replica. Recent Advances in Computational Mechanics and Simulations 2021, 275 -281.

AMA Style

Chanhee Moon, Kyung Chun Kim. Structure Generated Turbulence: Laminar Flow Through Metal Foam Replica. Recent Advances in Computational Mechanics and Simulations. 2021; ():275-281.

Chicago/Turabian Style

Chanhee Moon; Kyung Chun Kim. 2021. "Structure Generated Turbulence: Laminar Flow Through Metal Foam Replica." Recent Advances in Computational Mechanics and Simulations , no. : 275-281.

Research article
Published: 28 April 2021 in Inverse Problems in Science and Engineering
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Elastic Surface Algorithm (ESA), which was proposed for the inverse design in external flows, substitutes the airfoil wall by an elastic curved beam that deforms due to a difference between the target and current pressure distributions. The original ESA, such as all inverse design methods, which use only pressure as the target parameter, cannot converge in separated flows because of an almost constant pressure inside the separated region. This study developed the ESA for the inverse design in external separated flows by considering a linear combination of normalized pressure and shear stress distribution as the target flow parameter. Removing the geometrical filtrations, the automatic determination of the beam elasticity modulus, and the definition of dynamic spines instead of the vertical spines were the other essential modifications to upgrade the ESA for separated flows. The method was verified for blunt-leading-edged airfoils in subsonic turbulent flow under different angles of attack, and different initially-guessed geometries. The method reduced the separation by modifying the wall shear stress along the separation region.

ACS Style

Mohammad Hossein Noorsalehi; Mahdi Nili-Ahmadabadi; Kyung Chun Kim. Inverse shape design method based on pressure and shear stress for separated flow via Elastic Surface Algorithm. Inverse Problems in Science and Engineering 2021, 1 -44.

AMA Style

Mohammad Hossein Noorsalehi, Mahdi Nili-Ahmadabadi, Kyung Chun Kim. Inverse shape design method based on pressure and shear stress for separated flow via Elastic Surface Algorithm. Inverse Problems in Science and Engineering. 2021; ():1-44.

Chicago/Turabian Style

Mohammad Hossein Noorsalehi; Mahdi Nili-Ahmadabadi; Kyung Chun Kim. 2021. "Inverse shape design method based on pressure and shear stress for separated flow via Elastic Surface Algorithm." Inverse Problems in Science and Engineering , no. : 1-44.

Journal article
Published: 25 April 2021 in Energies
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A flow visualization study was carried out for flow boiling in a rectangular channel filled with and without metallic random porous media. Four main flow patterns are observed as intermittent slug-churn flow, churn-annular flow, annular-mist flow, and mist flow regimes. These flow patterns are clearly classified based on the high-speed images of the channel flow. The results of the flow pattern map according to the mass flow rate were presented using saturation temperatures and the materials of porous media as variables. As the saturation temperatures increased, the annular-mist flow regime occupied a larger area than the lower saturation temperatures condition. Therefore, the churn flow regime is narrower, and the slug flow more quickly turns to annular flow with the increasing vapor quality. The pattern map is not significantly affected by the materials of porous media.

ACS Style

Youngwoo Kim; Dae Kim; Kyung Kim. Flow Pattern Map of Flow Boiling in a Rectangular Channel Filled with Porous Media. Energies 2021, 14, 2440 .

AMA Style

Youngwoo Kim, Dae Kim, Kyung Kim. Flow Pattern Map of Flow Boiling in a Rectangular Channel Filled with Porous Media. Energies. 2021; 14 (9):2440.

Chicago/Turabian Style

Youngwoo Kim; Dae Kim; Kyung Kim. 2021. "Flow Pattern Map of Flow Boiling in a Rectangular Channel Filled with Porous Media." Energies 14, no. 9: 2440.

Research article
Published: 22 April 2021 in ACS Applied Polymer Materials
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A phosphorescence-based flexible optical temperature-sensing skin was developed for temperature sensing in intelligent bionic robots and automated medical treatment. 4,4-Diamino diphenyl ether and 4,4′-oxydiphthalic anhydride were combined as polyimide for use as the substrate of the flexible sensor. The substrate was doped with 6 μm MFG particles as temperature probes. Ultrasonic dispersion and thermal imidization were used to prepare a 45-μm-thick flexible temperature sensor. Compared with a traditional electronic-based flexible temperature sensor, the flexible temperature sensor has the advantages of noncontact measurement, a wide range of measurement temperature (−150 to 300 °C), high spatial resolution, and accuracy. It can also survive in harsh environments, including extremely low temperatures and high temperatures, and can withstand large deformations and large stresses. Its flexibility, extreme environmental resistance, and excellent mechanical properties show that it has great potential for wireless temperature measurement.

ACS Style

Tao Cai; Yong-Zhu Yan; Yoonseong Park; Taekyung Lee; Di Peng; Yingzheng Liu; Chang-Sik Ha; Kyung Chun Kim. Phosphorescence-Based Flexible and Transparent Optical Temperature-Sensing Skin Capable of Operating in Extreme Environments. ACS Applied Polymer Materials 2021, 3, 2461 -2469.

AMA Style

Tao Cai, Yong-Zhu Yan, Yoonseong Park, Taekyung Lee, Di Peng, Yingzheng Liu, Chang-Sik Ha, Kyung Chun Kim. Phosphorescence-Based Flexible and Transparent Optical Temperature-Sensing Skin Capable of Operating in Extreme Environments. ACS Applied Polymer Materials. 2021; 3 (5):2461-2469.

Chicago/Turabian Style

Tao Cai; Yong-Zhu Yan; Yoonseong Park; Taekyung Lee; Di Peng; Yingzheng Liu; Chang-Sik Ha; Kyung Chun Kim. 2021. "Phosphorescence-Based Flexible and Transparent Optical Temperature-Sensing Skin Capable of Operating in Extreme Environments." ACS Applied Polymer Materials 3, no. 5: 2461-2469.

Journal article
Published: 23 March 2021 in International Journal of Heat and Mass Transfer
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In the present paper, flow characteristics of an oscillating jet in a cross-flow (OJICF) emitted from a double feedback fluidic oscillator were investigated. The results were compared with a steady jet in a cross-flow (JICF) from a jet nozzle with length and diameter equal to those of the fluidic oscillator. Smoke visualization in a low-speed wind tunnel was used. The measurements were done in the symmetry plane with 3 cross sections for 4 different blowing ratios (BR) of 1 to 3.33. The OJICF shows high potential to enhance the effectiveness of film cooling since it penetrates to a lesser height and leads to considerable spanwise penetration. Then, heat transfer behaviors of an impinging OJICF (IOJICF) and impinging JICF (IJICF) were compared via thermographic phosphor thermometry (TPT). The cross-flow Reynolds number based on the hydraulic diameter of the jet exit and cross-flow velocity was varied between 510 and 2,700, and the spacing between the jet and target surface was 3 times the jet throat's hydraulic diameter. The results show that for the IOJICF, heat transfer is dominated by the cross flow, and changing the BR does not have a significant effect. However, the IJICF promotes heat transfer around 2 times more than the IOJICF, and the more the BR is, the greater the Nu number. Therefore, the OJICF could be applied for film cooling rather than impinging applications.

ACS Style

Shabnam Mohammadshahi; Hadi Samsam-Khayani; Tao Cai; Mahdi Nili-Ahmadabadi; Kyung Chun Kim. Experimental study on flow characteristics and heat transfer of an oscillating jet in a cross flow. International Journal of Heat and Mass Transfer 2021, 173, 121208 .

AMA Style

Shabnam Mohammadshahi, Hadi Samsam-Khayani, Tao Cai, Mahdi Nili-Ahmadabadi, Kyung Chun Kim. Experimental study on flow characteristics and heat transfer of an oscillating jet in a cross flow. International Journal of Heat and Mass Transfer. 2021; 173 ():121208.

Chicago/Turabian Style

Shabnam Mohammadshahi; Hadi Samsam-Khayani; Tao Cai; Mahdi Nili-Ahmadabadi; Kyung Chun Kim. 2021. "Experimental study on flow characteristics and heat transfer of an oscillating jet in a cross flow." International Journal of Heat and Mass Transfer 173, no. : 121208.