• The Microorganisms and Industry
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• v.19 no.2
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• pp.28-33
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• 1993

이번 여행을 통해, 여러 각도에서 국제사회가 어떻게 변해가는 가를 주시하여야 할 것이라는 생각이 들었다. 특히 생명공학 분야에서 가까운 ㅇ리본 뿐 아니라, 중국 대만에서도 많은 연구가 이루어지고 있으니, 독불장군 style의 연구태도를 지양하여 국제화된 사회로서, 국제적인 새로운 지식의 교환으로서 좀 더 광범위한 빠른 지식의 장을 열 수 있으리라. 이런 면을 고려해 볼때, 이번 한.중 미생물학회는 서로의 지식을 교환할 수 있는 좋은 매개체 역할을 하였다 생각되며, 앞으로도 이런 기회가 자주 열렸으면 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.11a
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• pp.393-396
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• 2020

드론 기술의 발전은 우리 실생활에서 IoD를 활용한 다양한 서비스 제공을 가능하게 해주었다. IoD 환경을 실질적으로 활용하기 위해서는 드론과 사용자 간의 인증 및 프라이버시 보호가 보장되어야 한다. 본 논문에서는 안전한 드론 운용환경 제공을 위하여 발표된 키 교환 프로토콜들을 분석하여 문제점을 도출하였다. 두 프로토콜 모두 IoD 환경에서 사용자와 드론 간 안전한 키 교환을 목적으로 제안되었으나, 세션키 또는 사용자의 익명 아이디가 노출되어 사용자의 프라이버시가 노출될 수 있다는 문제점과 키 교환 간 사용자의 참여가 요구되어 재해·재난 환경 등 자동화된 프로토콜을 요구하는 실제 환경에 활용되기 부적합하다는 한계를 보여주었다. 따라서 향후 IoD 환경에 적합한 키 교환 프로토콜은 강한 익명성을 동반한 프라이버시 보장뿐 아니라, 드론이 직접 키 교환 요청을 할 수 있어야 한다.

• Journal of the KSME
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• v.35 no.7
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• pp.638-646
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• 1995

직접접촉 얼교환 기술은 냉각탑, 접촉급수 가열기 및 공기분리기 등과 같은 장치에 예전부터 이용되어 왔는데, 그 주요한 적용이유는 가열유체와 수열유체의 사이에 일어나는 전열이 일반 열교환기와는 달리 고체벽(금속 열전달표면)을 통과하지 않고 열교환을 함으로써, 종래의 열교 환기에 비하여 상대적으로 설비의 간단화, 부식 및 스케일 부착문제가 경감됨에 따른 적은 유 지보수비 및 높은 열전달률을 얻을수 있는 이점이 있으며, 저 온도차에서의 효율적인 사용이 가능하기 때문이다. 이 글에서는 직접접촉응축 현상의 장점을 이용하는 직접접촉식 교환기의 구조와 형태, 그리고 그 응용분야에 대해서 알아보고자 한다.

• Journal of Power System Engineering
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• v.9 no.4
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• pp.11-17
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• 2005

This paper reports an experimental study on the performance evaluation of air-to-air heat exchanger with rotary type newly developed in this study. Air flow rate is varied from 10 to 120 m3/h. The range of RPM of the porous rotating discs mounted inside the heat exchanger unit is 0 to 50. The temperature of the return air side is set by adjusting heat supply at heater. The material of the porous rotating discs is cooper and its thickness is 1.0 mm. The heat transfer rate increased with the increase in air flow rate. It was found that the heat transfer rate, as the temperature of the return air side was increased, was improved due to higher temperature difference. The heat exchange performance increased with the increase in the temperature of the return air side at the conditions of the same RPM. The sensible heat exchange efficiency was maximum 68 to 76 percent, and enthalpy exchange efficiency 64 to 74 percent.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.1
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• pp.1-6
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• 2017

In order to better save energy, many buildings have been constructed with high levels of insulation and airtightness in recent years. Additionally, having high quality indoor air has become more relevant, necessitating a ventilating system. This study is aimed at evaluating the performance of a humidity exchanger through computational fluid dynamics (CFD) analysis of elements for the purpose of providing comfortable indoor air and reduced energy consumption. The simulation was conducted with three different shapes (triangle, rectangular, and curve) of heat exchanger elements, in order to find the most effective element. A follow-up simulation then proved the efficiency of the chosen humidity exchanger, which was selected by analyzing the results of the preceding simulation, comparing study data with measurement data from the Korea Testing Laboratory (KTL). The resulting analysis revealed that the rectangular element showed the lowest level of efficiency in both heating and cooling, while the curved element showed the highest level of efficiency in both heating and cooling.

• Journal of Energy Engineering
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• v.9 no.4
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• pp.366-371
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• 2000

본 연구는 동적형 빙축열시스템에 있어서 증발판이 축열조 상부에 설치되어 생성된 얼음을 주기적으로 분리, 이탈시켜 하부에 설치된 축열조에 저장하는 기존의 하베스트형 빙축열시스템과는 반대로 축열조 내에 증발판을 설치하여 수중에서 얼음을 생성시키고 분리시켜 부럭에 의해 얼음을 띄워 저장하는 새로운 방식의 수중 하베스트형 빙축열시스템 개발에 관한 연구이다. 본 방식은 축열조 내에 증발판이 설치되어 제빙과 탈빙이 이루어짐으로서 기존 시스템에 설치되는 순환펌프나 순환수 분배기 및 배관 등의 설비가 불필요하고, 또한 조내 물과 증발판이 직접접촉에 의해 열교환이 이루어지므로 기존 공기 중에서의 열교환 방식보다 전열효율이 우수한 장점을 가지고 있다. 따라서 본 연구에서는 상기의 수중 빙제조 방식에있어 빙 제조시와 방냉시 축열조의 열특성을 실험적으로 밝혀 시스템 최적화 및 성능 향상에 대한 기초 자료를 제공하고자 하였다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.3
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• pp.218-229
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• 2004

In this study, dry and wet surface pressure drop and heat transfer characteristics of heat exchangers having plain fins were investigated. Nine samples having different fin pitches and rows were tested. The wet surface heat transfer coefficient was reduced from experimental data using enthalpy-potential method. The wet surface heat transfer coefficients were approximately equal to the dry surface values except for one row configuration. For one row configuration, the wet surface heat transfer coefficients were approximately 30% lower than the dry surface values. For the pressure drop, the wet surface yielded approximately 30% higher values compared with the dry surface counterpart. Data were compared with existing correlations.

• Journal of Energy Engineering
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• v.14 no.4 s.44
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• pp.248-258
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• 2005

In the present study, in order to estimate possibility as a waste heat recovery system, three different heat exchangers are developed. The developed heat exchangers are tile system to supply the hot water using fermentation of waste biomass. For the experiments, various biomass materials were examined to obtain the best heat recovery. Waste heat recovery system was studied numerically and experimentally. Heat exchanger system was designed specially to obtain the optimum heat exchanging performance. The biomass heat exchanger was operated for 20 minutes, after 1 hour from start-up, the temperature of the biomass dump has been raised to the possible operation temperature. From the three time operations per day, the system would be able to supply the amount of energy, about 62,400 kcal/day.

• The Journal of Engineering Geology
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• v.25 no.1
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• pp.131-148
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• 2015

The purpose of this study is to analyze and compare the heat transfer efficiency of using copper pipe, stainless pipe and traditional PE pipe commonly used for geothermal heat exchanger, with aims at seeking improved methods. In addition, the varying efficiency of heat transfer from ground heat and groundwater heat was assessed and its applicability was discussed. Design parameters for empirical field study were derived by controlling flow rate, velocity and caliber of pipes of the heat exchanger after the thermal efficiency of the heat exchanger material was evaluated. The heat exchange efficiency and effective thermal conductivity were measured with changing pattern through field thermal efficiency and thermal response test. Experimental results show that the metal material showed higher heat transfer efficiency than the PE pipe. Although the heat transfer efficiency was not high with the increase of the pipe diameter in the flow rate, it was high with the increase of the pipe diameter in the velocity.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.60-67
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• 2021

This study presented techno-economic analysis of a 500 MWe oxy-coal power plant with CO2 capture. The power plant included a circulating fluidized-bed (CFB), ultra-supercritical steam turbine, flue gas conditioning (FGC), air separation unit (ASU), and CO2 processing unit (CPU). The dry flue gas recirculation (FGR) was used to control the combustion temperature of CFB. One FGR heat exchanger, one heat exchanger for N2 stream exiting ASU, and a heat recovery from CPU compressor were considered to enhance heat efficiency. The decrease in the temperature difference (ΔT) of the FGR heat exchanger that means the increase in heat recovery from flue gas enhanced the electricity and exergy efficiencies. The annual cost including the FGR heat exchanger and FGC cooling water was minimized at ΔT = 10 ℃, where the electricity efficiency, total capital cost, total production cost, and return on investment were 39%, 1371 M$, 90 M$, and 7%/y, respectively.