• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.9
• /
• pp.206-211
• /
• 2016

Various applications require dry air at low temperature, such automation equipment, semiconductor manufacturing, chemical production lines, and coating processes for the shipbuilding industry. Four evaporators for low temperature (below $0^{\circ}C$) were installed for a dehumidification system. Moist air is cooled sequentially over three evaporators. The first evaporator has an evaporation temperature of $13^{\circ}C$, that of the second evaporator is $5^{\circ}C$, and that of the third evaporator is maintained at $-1.3^{\circ}C$. In the fourth evaporator implantation thereby the moisture contained in the moisture air. A pressure regulator (CPCE 12) is used at this point and is defrosted when the vapor pressure is below a set value. The non-implantation moisture of the air is a heating system that uses the waste heat of a condenser with high temperature. It develops the cooling type's dehumidifier, which is important equipment that prevents the destruction of protein and measures the temperature and humidity at each interval by changing the front air velocity from 1.0 m/s to 4.0 m/s. The cooling capacity was also calculated. The greatest cooling capacity was 1.77 kcal/h for a front air velocity of 2.0 m/s

• Journal of Power Electronics
• /
• v.11 no.2
• /
• pp.194-201
• /
• 2011

The air flow supplied to a fuel cell system is one of the most significant factors in determining fuel efficiency. The conventional method of controlling the air flow is to fix the oxygen supply at an estimated constant rate for optimal efficiency. However, the actual optimal point can deviated from the pre-set value due to temperature, load conditions and so on. In this paper, the maximum efficiency point tracking (MEPT) algorithm is proposed for finding the optimal air supply rate in real time to maximize the net-power generation of fuel cell systems. The fixed step MEPT algorithm has slow dynamics, thus it affects the overall efficiency. As a result, the variable step MEPT algorithm is proposed to compensate for this problem instead of a fixed one. The complete small signal model of a PEM Fuel cell system is developed to perform a stability analysis and to present a design guideline. For a design example, a 1kW PEM fuel cell system with a DSP 56F807 (Motorola Inc) was built and tested using the proposed MEPT algorithm. This control algorithm is very effective for a soft current change load like a grid connected system or a hybrid electric vehicle system with a secondary energy source.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2009.11a
• /
• pp.561-565
• /
• 2009

The performance of supersonic impulse turbine was investigated experimentally. Experiment was performed with the compressed air instead of the high temperature burned gas because of the limitation of test facility and danger. As a result of the experiment with the compressed air, the performance in the real gas(burned gas) was predicted by the similarity method. The nozzle area of prototype turbine was calculated based on the real gas. So, it is difficult to satisfy the similarity conditions completely. Two similarity conditions were set and the design point for real gas was existed between two similarity conditions. And, the new turbine test model with calculated nozzle area based on the compressed air was tested. Therefore, similarity point of the new turbine test model was also existed between above two similarity points. It means that the design point for real gas was similar to the test point with the new turbine model.

• Journal of Korean Academy of Nursing
• /
• v.5 no.2
• /
• pp.38-50
• /
• 1975

This study was conducted to find the shortest optimum time for taking oral temperature and axillary temperature, which does not affect reliability of body temperature. For this purpose, first, the time at which all the samples are reaching maximum temperature is identified Second, the mean maximum temperature is compared with the mean temperature of each consecutive measurement by T-test to find the time at which no significant changes in temperature occurs along time sequence. Third, optimum temperatures are set at points of -0.2℉, -0.4℉, -0.6℉, -0.8℉, -1.0℉, -1.2℉, -1.4℉, from maximum temperature. A point of time at which 90% of samples reach at optimum temperature is identified and defined as optimum time. The study sample, a total of 164 cases were divided into two groups according to their measured body temperature. The group with body temperature below 37 $^{\circ}C$(A group) and above 37$^{\circ}$1'C (B group) were compared on the time required to reach maximum temperature and optimum temperature. The results are as follow. 1. The time required for total sample to reach maximum temperature was 13 minutes in both groups by oral method, 15 minutes in A group and 13 minutes in B group by axillary method. Time required for 90 % of cases reach maximum temperature by oral method was 10 minutes in both group. By axillary method, 12 minutes in A group. (Ref: table 2) 2. Statistical analysis by means of T-test, the time which does not show a significant change by oral method were 12 minutes in A group and 11 minutes in B group, and by axillary method 14 minutes in A group and 11 minutes in B group. (Ref: table 5, 6.) 3. Where optimum temperature was defined as maximum temperature minus 0.2 ℉, optimum time was found 8 minutes in both groups by oral method, and 11 minutes in A group and 9 minutes in B group by axillary method 4. Where optimum temperature was defined as maximum temperature minus 0.4 ℉, optimum time was found 7 minutes in A group and 6 minutes in B group by oral method, and 9 minutes in A group and 7 minutes in B group by axillary method 5. Where optimum temperature was defined as maximum temperature minus 0.8 ℉, optimum time was found 6 minutes in A group and 6 minutes in B group by axillary method (Ref: table 7, 8, 9, 10) 6. The commonly practiced temperature taking time, 3 minutes in oral method and 5 minutes in axillary method can be accepted as pertinent when physiological variation of body temperature at the mean level of -1, 2 ℉ is accepted. 7. The difference in time required to resister maximum temperature was compared between the group with body temperature below 37$^{\circ}C$ and above 37$^{\circ}$1'C, and found no significant difference in oral mettled and 1 - 4 minute difference in axillary method with shorter time requirement in feverish group.

• 한국연소학회:학술대회논문집
• /
• 2003.05a
• /
• pp.35-39
• /
• 2003

A numerical study is carried out to investigate combustion phenomena in a model SCRamjet engine, which has been experimentally studied at the Australian National University using a T3 free-piston shock tunnel. The Mach number is 3.8, the static pressure 110kPa and the static temperature 1100K in the main air flow. The fuel is hydrogen, which is injected in the cavity. Equivalence ratio is set to either 0.25 or 0.5 to access its effect on the fuel-air mixing combustion phenomena. The results show that the cavity generates several recirculation zones, which increase the fuel-air mixing. Self ignition occurs near the point of fuel injection. The flame is anchored by the cavity and generates the precombustion shock on the step. For a high equivalence ratio, the recirculation zones are bigger and the flame is present throughout the combustor.

• Structural Engineering and Mechanics
• /
• v.22 no.3
• /
• pp.331-349
• /
• 2006

The stresses and deflections in a laminated rectangular plate under thermal vibration are determined by using the moving least squares differential quadrature (MLSDQ) method based on the first order shear deformation theory. The weighting coefficients used in MLSDQ approximation are obtained through a fast computation of the MLS shape functions and their partial derivatives. By using this method, the governing differential equations are transformed into sets of linear homogeneous algebraic equations in terms of the displacement components at each discrete point. Boundary conditions are implemented through discrete grid points by constraining displacements, bending moments and rotations of the plate. Solving this set of algebraic equations yields the displacement components. Then substituting these displacements into the constitutive equation, we obtain the stresses. The approximate solutions for stress and deflection of laminated plate with cross layer under thermal load are obtained. Numerical results show that the MLSDQ method provides rapidly convergent and accurate solutions for calculating the stresses and deflections in a multi-layered plate of cross ply laminate subjected to thermal vibration of sinusoidal temperature including shear deformation with a few grid points.

• Journal of Environmental Science International
• /
• v.4 no.2
• /
• pp.169-180
• /
• 1995

This Daper presents effective simulation of the dispersion of thermal discharge which can be relesed at Boryong power plant. Applied numerical models are finite difference method for hydrodynamic analysis and Masch-model comprised of conditions for ambient current velocity. Application of these models is done in Cheonsu Bay Summing up the results of this study are as follows; 1. It is found that the result for measurements of temperature appears high at southwardly Songdo on flood. The reason is that tidal currents which flowed north direction were accompanied with southwardly dispersed thermal discharge. A minute Particle of thermal Plume has a tendency to dispels inward Deacheon Bay. 2. According to the results of numerical experiment, maximum distance for thermal discharge dispersion appeared 10.8 km at lower part and 8.6 km at upper part with power plant outlet as starting point. 3. Comparative the numerical simulation and Airbone Multispectral Scanner indicated that thermal discharge should be verified separative phenomena. The simulated results were compared with field data set showing good agreement. It is concluded that these model can be simulated well.

• Journal of Powder Materials
• /
• v.14 no.5
• /
• pp.327-332
• /
• 2007

In a view point of environment, the advanced electric contact material without environmental load element such as cadmium has to be developed. Extensive studies have been carried out on $Ag-SnO_2$ electric contact material as a substitute of Ag-CdO contact materials. In the present study, powder metallurgy including compaction and sintering is introduced to solve the incomplete oxidation problems in manufacturing process of $Ag-SnO_2$ electrical contact material. The $Ag-SnO_2$ contact material, fabricated in this study, was actually set in an electric switchgear of which working voltage is 462V and current is between 25 and 40A, for the purpose of testing its performance. As a result, it exceeded the existing Ag-CdO contact materials in terminal-temperature ascent and main contact resistance.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2003.02a
• /
• pp.189-192
• /
• 2003

Inductivity Superconducting Fault Current Limiter is the Magnet that uses high temperature Superconductivity Coil. It is an important work that it controls Electric Power Converter of Inductivity SFCL. So, we wish to design the point part FPGA by One-Chip. Design of that can divide as following. One part that generate clock that offer to thyristor. One part that set 60Hz voltage to input Clock and do count. One part that change the value that require in CPU to the integer. And finally. there is part that send output (the fixed Clock) to the thyristor.

• Journal of the Korean Solar Energy Society
• /
• v.31 no.5
• /
• pp.41-46
• /
• 2011

In the present work, a new freeze protection method has been proposed for a natural circulation system of solar water heater. Though electrothermal wire is popularly used for the purpose, there are freezing troubles by wire cut-off and excessive electric power consumption. In the experimental device, hot water in a storage tank was circulated by a small pump and used to heat the outdoor pipes if the cold water pipe surface temperature falls lower than a set point. As a result, It was observed that there was no hot water waste while the solar water heating system operated without freeze and burst.