• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.2
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• pp.187-197
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• 1996

A computer program for thermal design analysis has been developed to predict the operating characteristics and performance of an absorption heat pump to recover $30{\sim}40^{\circ}C$ of waste hot water. The effects of heat transfer area of the system components, temperature and mass flow rate of heat transfer medium, and solution circulation rate on the system performance are investigated in detail. The results obtained indicate that the COP is increased with a decrease in the temperature of driving steam and with an increase in the temperature of waste hot water while the COP is little affected by the variation of a hot water temperature. It is also found that the heating output is increased with an increase in the temperature of waste hot water and driving steam as well as with a decrease in the temperature of hot water. The simulation results are also compared with the experimental results for a periodic operation of the system and obtained a satisfactory agreement.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1631-1636
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• 2003

The purpose of this study is to analyze the phenomena of the thermally-induced vibration for the flexible space structure due to abrupt change of radiation heating circumstance using the numerical analyze and experiment test. In order to verify this structure, numerical approaches on the simplified flexible tube were compared with experimental test results at the ground experimental facility In this analyze, it was found that the thermal deformation occurs firstly due to fast radiation heating of flexible structure and then the thermally-induced vibration would be induced due to small periodic change of temperature. According to comparison of numerical and experimental result, in case of no tip mass, the first mode vibration by the numerical analyze was O.78Hz same as that of the experimental result However in case of increase tip-masses of 8g l6g, 50g and 100g, the first modes vibration theoretical analyze were 1.75Hz, 1.3Hz, 0.87Hz and O.73Hz, in decrease trend respectively and those by experimental test were 234Hz, 1.5Hz, O.78Hz and O.78Hz in decrease trend respectively Although using the simpled equation for the estimation, the estimation results were similar to experimental results.

• 한국태양에너지학회:학술대회논문집
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• 2011.04a
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• pp.256-262
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• 2011

Environmental pollution by Using of a fossil fuel, a reckless and growth-oriented development since the Industrial Revolution has caused global change of environment. An issue largest among this is a climate change. A global mean temperature since 19th century has climbed up $0.4{\sim}0.8^{\circ}C$. After The Kyoto Protocol regarding a greenhouse gas reduction goal took effect, be situations that decrease of greenhouse gas was acutely required. Interest of utilization of the new & renewable energy is increasing every day. This study shows that at first divided a country to nine range by natural geography, and second executed Meteorological data analysis of recent 30 years considering level of significance by nine range. The results of this study are that in heating load calculation of building, periodic temperature data management is required because facility capacity and cost are affected greatly by outdoor temperature, and temperature by climate range needs consideration of pertinent area. Lastly, ground temperature was assumed of the weather in region, the ground and soil.

• Journal of the Korean Institute of Gas
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• v.11 no.3
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• pp.19-25
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• 2007

The heat transfer phenomena in a coil-typed LPG vaporizer with a hot water bath employed an electrical heating system were experimentally analyzed. The heat energy is initially used to sensible heat region to heat LPG and then is done to latent heat region to vaporize LPG and to heat up the vaporized gas. A two-phase flow region could be found from periodic temperature fluctuations, and only sensible heat effect was found after passing through the region. The overall heat capacity was defined as multiplying the overall heat transfer coefficient by the heat transfer area and we found a correlation employing the heating water temperature and LPG flow rate. The results of this work can effectively be applied for the design of field scale LPG vaporizers in the near future because they can predict the features of heat transfer on a kind of coil type LPG vaporizer.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.112-119
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• 2002

Three dimensional numerical heat transfer analysis was carried out against periodically arranged fuel injectors of the liquid rocket engine. A finite volume method based on SIMPLE algorithm was adapted which gave a good agreement with the published results of the heat transfer problem of a backward facing step. The Nusselt number and pressure drop increased as the distance between the injector elements decreased. When the Reynolds number increased, the Nusselt number increased but nondimensionalized pressure drop decreased slightly.

• Journal of the Korean Professional Engineers Association
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• v.34 no.4
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• pp.69-73
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• 2001

Due to the rapid increase of automobiles and daily driving distances, air pollution by automobiles is still dominant problem of large city in spite of strict emission refutation and development of reduction technologies. Among the air pollution resources of automobile , industry. electricity generation and heating. automobile keeps 51% of total nationwide air pollution in 1998 and this proportion Is increasing in large cities from 65% to 85%. To reduce these air pollution. catalytic converter and electronic engine control, exhaust gas re-circulation and evaporative emission control system have continuously developed and applied to automobiles since 1987. Also strong emission standards and emission durability warranty have enforced and monitored annually by sampling several vehicle models. But technologies and regulations are incomplete, driver should participate in reducing air pollution for himself by planning driving, avoiding unnecessary idle and air conditioning, keeping periodic maintenance and using mass transportation.

• Journal of the Korean housing association
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• v.13 no.4
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• pp.27-33
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• 2002

In Gumi area, the heating and cooling loads for underground building could have not been correctly evaluated since there were no systems accurate underground temperature. For solving this problem two ways of predicting the underground temperature were propose. Firstly, it is to estimate the underground temperature of Gumi area by averaging out the underground temperature of the areas around Gumi city. However, the underground temperature data of the areas around Gumi city was only limited to 0.5m and 1.0m under the ground. Secondly, it is to calculate the underground temperature of Gumi area by using a periodic equation with variable about underground properties. Among these methods, the method of the average date was more correct, but the method of the variable date was more available.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1337-1341
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• 2003

This paper suggests and demonstrates a novel flow measurement technique, tunable AC mode hotwire anemometry that allows simple integration, robust measurement, and extremely high accuracy. The principle and simple theoretical analysis of the technique are shown. To find the optimal frequency at which the phase lag becomes most sensitive to flow speed change, the phase lag was measured scanning the heating frequency from 1 to 100 Hz, while the flow speed of ethanol was increased stepwise from 0 to 10 mm/s. To optimize the sensitivity of technique, the periodic thermal characteristic of the hotwire should be understood and is currently under study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2762-2770
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• 2000

The refuse incineration plant has an important role in saving the combustion energy for local heating system. But harmful combustion gas(NOx etc.) leads to some serious environmental problem. To reduce the gas, a SCR(Selective Catalytic Reduction)system is installed and it is controlled by adjusting the flow of ammonia gas(NH3) . In this paper, we apply a repetitive control method to reduce NOx by adjusting the flow of ammonia gas for SCR system in a refuse incineration plant which is located in Haeundae, Pusan, Firstly, we analyze the inlet NOx period by FFt method, and verify its periodic variations. Secondly, we design a repetitive control system by using state space model method. Lastly, the effectiveness of repetitive control system is shown by comparing to a conventional PID control in simulation and experimental results.

• Journal of the Korean Society for Nondestructive Testing
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• v.14 no.4
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• pp.219-227
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• 1995

A two-dimensional photoacoustic microscope utilizing photoacoustic signals generated by periodic heating of specimen surface with Argon ion laser and measured by accelerometer has been developed. Several aluminum specimens with various defects have been examined, characteristics of the microscope have been evaluated and optimal experimental conditions have been determined by examining the dependence on several experimental conditions including the modulation frequency and the beam width of laser.