• Transactions of the KSME C: Technology and Education
• /
• v.4 no.1
• /
• pp.35-41
• /
• 2016

Geothermal heat pump (GHP) systems have been proved to be one of the most efficient systems for heating and cooling in buildings. However, an optimal energy performance depends on a good control of the system components, including heat pumps and circulation pumps, which affect to the total energy consumption of system. This paper presents the simulation results of the heat pump performance for two different control schemes, i.e. constant setting temperature (Control-A) and variable setting temperatures (Control-B) in buffer tank. A dynamic simulation tool, TRNSYS 17, was used to model the entire system and to assess the performance of the system. Simulation results show that the Control-B, which controls the temperature in buffer tank with outdoor air temperature, is a effective way to reduce the energy consumptions in heat pump (7.7%) and circulation pump (7.5%).

• Journal of the Korean Institute of Gas
• /
• v.20 no.5
• /
• pp.50-56
• /
• 2016

In this work, the open-drive oil free air compressor is modified to activate an organic Rankine cycle system as an expanding machine. The shape of the modified scroll expander case is a rectangular parallelepiped and the size of the case is $0.0394m^3$. The scroll expander is operated in an ORC using R245fa as working fluid with various working conditions for the performance test. The test data points are used to calculate the parameters of the scroll expander semi-empirical simulation model. The simulation results are compared with the experimental results to validate the simulation model.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2017.04a
• /
• pp.151-151
• /
• 2017

본 연구는 인력을 이용한 품질검사를 수행하고 있는 현장에서 불량 및 품질에 대한 신뢰성이 떨어지고 있는 현상을 해소하기 위해 자동으로 평면도를 측정하고자 하였다. 설계는 Auto CAD를 이용하였다. 평면도 측정기의 크기는 가로${\times}$세로${\times}$높이를 $1000{\times}600{\times}1800mm$로 하였다. 프레임은 $60{\times}60$ 프로파일을 이용하였고 다른 구성 부품은 SUS304 재질을 이용하였다. 측정대상을 올려놓은 상태에서 녹색 버튼을 누루면 작동되도록 되어 있다. 그림 8은 측정결과를 나타낸 것이다. 측정기는 국내업체인 데바의 모델명 EA-20N의 Air Micrometer을 사용하였으며 측정핀의 위치는 조정이 가능하도록 하였다. 평면도 측정 중 설정치수와 같이 않으면 NG 명령과 함께 부저가 울리도록 프로그램하였다. 불량이 발생하면 그림 8과 같이 나타났다. 불량 측정을 위해 측정부의 결과 값이 나타나며 불량이 발생하면 어느 위치에서 불량이 발생했는지를 알 수 있도록 하였다. 또한 결과 값은 자동으로 저장되도록 하였다. 품질확보를 위해 100EA를 측정한 결과 0.00258, 0.00259, 0.00259, 0.00263, 0.00251, 0.00286, 0.00275의 평균값을 나타냈다. 측정값의 검증은 하이트게이지로 측정한 결과 0.002 이내의 결과를 나타냈다. 따라서 본 평면도 측정기를 이용한다면 생산성 향상이 가능하여 가격경쟁력이 있다고 판단된다.

• Journal of Radiation Protection and Research
• /
• v.22 no.1
• /
• pp.47-58
• /
• 1997

The conversion coefficients of effective dose per unit air kerma and equivalent dose per unit fluence were calculated by MCNP4A code for antero-posterior(AP) and postero- anterior(PA) incidence of broad, unidirectional beams of photons into anthropomorphic MIRD phantom. Calculations have been performed for 20 monoenergetic photons of energy ranging from 0.03 to 10 MeV. The conversion coefficients showed a good agreement with the corresponding values given in the draft publication of joint task group of ICRP and ICRU within 10%. The deviations may arise from the differences of geometry in the MIRD phantom and the ADAM/EVE phantoms, and the differences in the codes and cross-section data used. Inclusion of a specific oesophagus model results in effective dose slightly different(5% at most) from the effective doses obtained by adopting the equivalent doses for the thymus or pancreas. Deletion of the ULI from the remainder organ appeared not to be significant for the cases of photon dosimetry covered in this study.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.1
• /
• pp.107-119
• /
• 1991

This dissertation analyzes the running mechanism of flexible and thin tape above rotating head through the experiment. The scope of study is confined to measure the vertical deformation of running tape under hydrodynamic pressure invoking phenomena of elasto-hydrodynamic lubrication between the protruded bump on a rotating cylinder ad the running tape. Experimental system is devised to measure the vertical deflection of the running tape by opto-electronical displacement gauge, which enables to detect microscopic surface deflection of high frequency. Thorough the tests of small specimens of groove and bump, the accuracy and reliability of this experimental method is confirmed and achieved an accuracy within 5%(2.mu.m) error for the microscopic deflection with high frequency. In experimental works, the effects of bump size on flying characteristics of the tape were evaluated and examined. For the vertical deformation of the running tape. the numerical results and its trend agree qualitatively with the experimental ones.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.9
• /
• pp.2339-2358
• /
• 1993

Since the rate and completeness of combustion in direct injection engines were controlled by the characteristics of gas flow fields and sprays, an understanding of those was essential to the design of the direct injection engines. In this study the numerical simulations of injection pressure effects on the characteristics of gas flow fields and sprays were preformed using the spray model that could predict the interactions between gas fields and spray droplets. The governing equations were discretized by the finite volume method and the modified k-.epsilon. model which included the compressibility effects due to the compression/expansion of piston was used. The results of the numerical calculation of the spray characteristics in the quiescent environment were compared with the experimental data. There were good agreements between the results of calculation and the experimental data, except in the early stages of the spray. In the motoring condition, the results showed that a substantial air entrainment into the spray volume was emerged and hence the squish motion was relatively unimportant during the fuel injection periods. It was found that as the injection pressure increased, the evaporation rate of droplets was decreased due to the narrow width of spray and the increased number of droplets impinged on the bottom of the piston bowl.

• Journal of Advanced Marine Engineering and Technology
• /
• v.34 no.1
• /
• pp.62-68
• /
• 2010

The requirement of high efficiency and low emission for marine diesel engines are being enforced because of air pollution and climate change on the earth. In connection with these, many new technologies are considered. But they are mainly for new building ship. It is necessary to be concerned about the improvement of engine performance for existing ship. In this paper, the simulation program for performance of marine two-stroke diesel engine was developed to predict the deteriorating performance according to elapsed time for existing ship. The result was compared with the result of the program named TOP-CODE which was used by engine maker and checked to be shown good agreement between them.

• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.6
• /
• pp.765-772
• /
• 2011

In this research, the fuel cell system model capable of generating codes in real time was developed to construct of a HIL (Hardware-In-the-Loop) for a SOFC-powered ship. Moreover, the effects of the distribution of the exhaust gas flow rates in a stack, the flow rates of fuels and temperature of air supplied on the temperature characteristics of fuels supplied to the cathode and the anode, the output power of the stack and system efficiency are examined to minimize the temperature difference between fuels supplied to the stack used in a 500kW SOFC system using methane as a fuel. As a result, the temperatures of fuels supplied to the cathode and the anode maintain at 830K when the opening factor of three-way valve located at outlet of turbine is 0.839. Also the process for optimization of methane flow rate considering the fuel cell stack and system efficiency is required to increase the temperatures of fuels supplied to the stack.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.3
• /
• pp.315-324
• /
• 2012

This paper presents a numerical investigation of the deflagration-to-detonation transition (DDT) of flame acceleration by a shock wave filled with an ethylene/air mixture as the combustible gas, considering geometrical changes by using obstacles and bent tubes. The model used consists of the reactive compressible Navier-Stokes equations and the ghost fluid method (GFM) for complex boundary treatment. Simulations with a variety of bent tubes with obstacles show the generation of hot spots through flame and strong shock-wave interactions, and restrained or accelerated flame propagation due to geometrical effects. In addition, the simulation results show that the DDT occurs with a nearly constant chemical heat-release rate of 20 MJ/($g{\bullet}s$) in our numerical setup. Furthermore, the DDT triggering time can be delayed by the absence of unreacted material together with insufficient pressures and temperatures induced by different flame shapes, although hot spots are formed in the same positions.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.42 no.2
• /
• pp.99-107
• /
• 2014

In this study, aerodynamic characteristics of Kline-Fogleman airfoils are numerically investigatied which has been widely used in remote control aircraft operating at low Reynolds numbers. The comparison of aerodynamic characteristics was conducted between NACA4415 and Kline-Fogleman airfoil based on NACA4415. ANSYS Fluent was employed with the incompressible assumption and $k-{\omega}$ SST turbulence model. It was found that lift coefficient was significantly enhanced in the range of Reynolds number from $3{\times}10^3$ to $3{\times}10^6$. Especially in the region of Reynolds number below $2.4{\times}10^5$, the lift-to-drag-ratio was improved by 26% using the Kline-Folgeman airfoil compared with NACA4415 airfoil.