• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1161-1166
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• 2008

The objective of this research was to investigate the enhancement of heat transfer by mesh in water/air direct contact air conditioning system. Mesh is inserted as a turbulent promoter in front of the water injection nozzle. The heat transfer characteristics with and without mesh and the effect of the number of inserted mesh and mesh porosity size have been studied experimentally. Inserted mesh improves heat transfer efficiency compared to non-inserted mesh system and heat transfer efficiency increased as the number of mesh is increased. Meanwhile, heat transfer efficiency decreased as the porosity of the mesh is increased. With inserted mesh, inlet and outlet temperature difference of air increased more than 50%. Heat exchange time of water/air to reach the 100% humidity decreased less than 30%. This result shows inserted mesh can enhance the performance of the water/air direct contact air conditioning system.

• Journal of the Korean Society of Combustion
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• v.14 no.4
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• pp.17-24
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• 2009

Reburning is one of the most useful technologies for reducing nitric oxide in economically and technically. The reburning process was demonstrated as an effective NOx reduction method through injection of a secondary hydrocarbon fuel. An experimental study has been conducted to evaluate the effect of biomass reburning on NOx and CO formation in a light oil flamed combustion furnace. Reburning tests on NOx reduction of air-carried rice husk powder as the reburn fuel and light oil as the main fuel were performed in flames stabilized by a co-flow swirl and fuel staged burner, which was mounted at the front of the furnace. The results included flue gas emissions and temperature distribution in the furnace for several kinds of experimental conditions. It was observed clearly that NOx concentrations in the exhaust have considerably decreased due to effect of biomass reburning. The maximum NOx reduction rate was 42% when the reburn fuel fraction was 0.18. The CO emissions were kept under 42 ppmv in all experimental tests. And this paper makes clear that in order to decrease NOx concentration in the exhaust when the biomass reburning system is adapted, the control of some factors such as reburn fuel fraction and reburn zone fraction is very important.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.1
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• pp.75-80
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• 2008

The objective of this research was to investigate the enhancement of heat transfer by mesh in water/air direct contact air conditioning system. Mesh is inserted as a turbulent promoter in front of the water injection nozzle. The heat transfer characteristics with and without mesh and the effect of the number of inserted mesh and mesh porosity size have been studied experimentally. Inserted mesh improves heat transfer efficiency compared to non~inserted mesh system and heat transfer efficiency increased as the number of mesh is increased. Meanwhile, heat transfer efficiency decreased as the porosity of the mesh is increased. With inserted mesh, inlet and outlet temperature difference of air increased more than 50%. Heat exchange time of water/air to reach the 100% humidity decreased less than 30%. This result shows inserted mesh can enhance the performance of the water/air direct contact air conditioning system.

• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.47-55
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• 2011

The optimum mold design and the optimum process condition were constructed upon executing process simulation of rubber injection molding with the commercial CAE program of MOLDFLOW (Ver. 5.2) in order to solve the process-problems of K company relating to cracks, which occurs at the inner cavity wall of C. V. joint boots. As a result it was confirmed that the real cracks occurs at the exactly same position of the cavity as exhibits the defects of weld and meld line and unsatisfactory curing according to the result of simulation. In order to prevent the occurrence of weld and meld line at the defect-position, the location of gate was altered to the optimum position of the cavity. Consequently the filling pattern was established to minimize the degree of the melt-fronts confronting or the melt-flows melding to prevent the occurrence of weld and meld line at the defect-position. It was observed that both gate-positions to maximize the degree of the formation of weld and meld line and air traps are located, respectively, in opposite direction each other with reference to the optimum gate position. In addition, the temperature of mold was raised by $10^{\circ}C$ and maintained at $170^{\circ}C$ for satisfactory curing.

• Journal of radiological science and technology
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• v.36 no.1
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• pp.49-55
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• 2013

Currently, commercially available phantom can reproduce and evaluate only a static situation, the study is incomplete research on phantom and system which is can confirmed functional situation in the kidney by time through dynamic phantom and blood flow velocity, various difference according to the amount of radioactive. Therefore, through this study, it has produced the dynamic kidney phantom to reproduce images through the dynamic flow of the kidney, it desires to evaluate the usefulness of nuclear medicine imaging. The production of the kidney phantom was fabricated based on the normal adult kidney, in order to reproduce the dynamic situation based on the fabricated kidney phantom, in this study, it was applied the volume pump that can adjust the speed of blood flow, so it can be integrated continuously radioactive isotopes in the kidney by using $^{99m}Tc$-pertechnate. Used the radioactive isotope was supplied through the two pump. It was confirmed the changes according to the infusion rate, radioactive isotopes and the different injection speeds on the left and right, analysis of the acquired images was done by drawn five times ROI in order to check the reproducibility of each on the front and rear of the kidney and bladder. Depending on the speed of injection, radioisotope was a lot of integrated and emissions up when adjusting the pressure of the pump as 30 stroke, it was the least integrated and emissions up when adjusting as 40 stroke. The integration of the left & right kidney was not reached in the amount of the highest when adjusting as 10 stroke. In the changes according to the amount of the radioactive isotope, 0.6 mCi(22.2 MBq), 0.8 mCi (29.6 MBq)was showed up similar tendency but, in the result of the different injection 0.8 mCi, it was showed up counts close to double of 0.6 mCi. In the result of the differently injection speed of the left & right kidney, as a result of different conditions that injection speed was 20 stroke through left kidney phantom, the injection speed was 30 stroke through right kidney phantom, it was enough difference in the resulting image can be easily distinguished with the naked eye. Through this study, the results showed that the dynamic kidney phantom system is able to similarly reproduce renogram in the actual clinical practice. Especially, the depicted over time for the flow to be excreted through the kidney into the bladder was adequately reproduce, it is expected to be utilized as basic data to check the quality of the dynamic images. In addition, it is considered to help in the field of functional imaging and quality control.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.1
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• pp.103-110
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• 2012

The flow field, fuel-air mixing, and behaviors of turbulent flames have been investigated using the large eddy simulation (LES) numerical technique in a premixed swirl combustor equipped with EV double cone burners. Recirculation zones are generated by the swirl burner, and lean premixed flames are formed within a distance of 0.2 m from the tip of the burner. NOx emission of 0.46 ppm is predicted at 1 atm and an air/fuel ratio of 38.7. However, most of the CO generated in a flame front continues to be oxidized as it moves toward the exit, and CO emission of 5.45 ppm is predicted at the exit. The NOx emission can be reduced by decreasing the pressure and air/fuel ratio. The characteristics of NOx emission have been investigated through RANS simulations for various fuel injection types, and it is found thereby that five-lance-hole injection produces the lowest NOx emission rate.

• Journal of the Korean Society of Radiology
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• v.12 no.6
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• pp.777-783
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• 2018

The purpose of this study was to investigate the degree of tearing of the rubber when the spike of the syringe connector was connected to the bottle of the contrast medium composed of the rubber compound type and to investigate the presence of the synthetic rubber due to tearing and grinding and the size of the pulverized product when the pulverized matters rubber was detected. As a result, in the case of tearing degree, the front side of the first contact with the end of the syringe connector was torn more than the back side by about $3.14{\pm}0.04mm$, and the pulverized matters was detected on average 7 to 15 on the 10 contrast mediums. The average particle size was measured to be about $7.89{\pm}0.31{\mu}m$. In addition, it is necessary to develop a micro_filter type automatic injection system for blocking off the pulverized matters as well as additional experiments through various experiments and analysis methods, and it is considered that interest of related organizations will be needed in preparation of fatal accidents when pulverized matters is introduced.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.6
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• pp.50-57
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• 2007

Pressure Sensitive Paint(PSP) means a reacting paint in pressure. PSP can measure continuous pressure field by analyzing the oxygen quantity using optical method. The surface pressure of down stream after the sonic jet that injected transversely into the supersonic freestream was measured by PSP technique. Moreover the effect of various rectangular shaped cavities in front of the jet was measured by PSP technique. A comparison of the PSP results with conventional pressure tap and CFD indicates good agreement. Until now, the results of numerical analysis were compared with the discrete points such as the results of pressure tap. In this study, the whole region pressure was measured using PSP technique and its results were similar to CFD. Therefore, the flow phenonenon of cavity downstream was clearly grasped.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.359-363
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• 2005

In SCRamjet engine, combustion occurs in supersonic flow with airbreathing. SCRamjet is characterized by very short combustion time in combustor, so it is very important to be mixing the air and fuel in short duration. Several methods are suggested for mixing enhancement. Among these, cavity is selected to study for enhancement of mixing. The numerical simulation is performed in the case of freestream Mach number of 2.5 and cavity located in front of fuel jet injection. CFD-Fastran, commercial code with three-dimensional Navier-Stokes equation with the Menter SST turbulence model were used. The results are obtained validate experiment results for same condition. Therefore, the numerical results show the mixing enhancement characteristics with a cavity.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.1
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• pp.57-62
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• 2011

The effects of swirl chamber's diameter and length on injector's dynamic characteristics were investigated through an experimental study. A mechanical pulsator was installed in front of the manifold of a swirl injector which produces pressure oscillations in the feed line. Pressure in the manifold, liquid film thickness in the orifice and the pressure in the orifice were measured in order to understand the dynamic characteristic of the simplex swirl injector with varying geometry. A direct pressure measuring method (DPMM) was used to calculate the axial velocity of the propellant in the orifice and the mass flow rate through the orifice. These measured and calculated values were analyzed to observe the amplitude and phase differences between the input value in the manifold and the output values in the orifice. As a result, a phase-amplitude diagram was obtained which exhibits the injector's response to certain pressure fluctuation inputs. The mass flow rate was calculated by the DPMM and measured directly through the actual injection. The effect of mean manifold pressure change was insignificant with the frequency range of manifold pressure oscillation used in this experiment. Mass flow rate was measured with the variation of injector's geometries and amplitude of the mass flow rate was observed with geometry and pulsation frequency variation. It was confirmed that the swirl chamber diameter and length affect an injector's dynamic characteristics. Furthermore, the direction of geometry change for achieving dynamic stability in the injector was suggested.