• Journal of Korean Society of Environmental Engineers
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• v.38 no.11
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• pp.611-617
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• 2016

Remanufacturing that is the rebuilding of a product to specifications of the original manufactured product by collecting used-product, completely disassembling, cleaning and repairing or replacing with a new part and reassembling has been received attention in aspects of resource, recycling because it is a great environmental improvement. Remanufacturing is the rebuilding of a product to specifications of the original manufactured product by collecting used-product, completely disassembling, cleaning and repairing or replacing with a new part and reassembling. With a great environmental improvement and resource recycling and conservation, many studies were conducted. Up to date, remanufacturing activities are mainly applied to automobile parts and printer toner cartridge in South Korea. However, remanufacturing of rental product is not well conducted although rental products are collected in good condition and could be remanufactured in the same condition as a new product. Therefore, in this study, we conducted life cycle assessment (LCA) to an air cleaner product that is one of rental products. This study attempts to identify the processes in new products and remanufacturing life cycles that contribute the most environmental impacts. The results show that air cleaner remanufacturing could reduce about 20% of environmental impacts compared to new product. The greatest benefit related to environmental impact is with regard to ozone layer depletion potential (ODP), which is reduced by 94%. In the life cycle of air cleaner, raw material extraction stage had the most environmental impacts, especially with regard to abiotic depletion potential (ADP) and global warming potential (GWP). In the environmental impacts in each part, the ABS power had the highest environmental impacts.

• Journal of the Korean Institute of Gas
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• v.20 no.5
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• pp.57-63
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• 2016

Though a valve is a very important part in a system to control properly, it has potential failure caused by gap from valve stem to ball connection, and abrasion, crack, fixation causing operational trouble and accidents. 64% of the valve failure in the real case was the failure of airtightness and most accidents of leakage and explosion were occurred while fixing the failure. While there are no proper safety manual, maintenance procedure and regulation for industrial valves excluding safety valve, safety management for the valves is left to the discretion of the maintenance company. Strict maintenance that removes hazards and emergency response procedure are required to prevent and reduce the loss of accident. This study suggests safety enhancement measures through valve monitoring by investigating the status of use of valve and current maintenance. Enhancement of gas safety management can be acquired by a monitoring system that provides diagnosis for valve status, monitoring real-time gas leakage, management of entire cycle lifetime that can reduce maintenance cost.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.199-199
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• 2011

ATES(Aquifer Thermal Energy Storage) 열펌프 시스템은 기존의 다양한 열원 적용 시스템 대비 효율이 우수한 것으로 알려져 유럽과 미국에서 건물 냉난방 시스템으로 적용되고 있다. 특히, ATES 시스템은 기존의 냉난방 시스템 대비 경제성이 우수한 것으로 알려져 있으나 국내에서는 이에 대한 연구 결과는 전무한 실정이다. 본 연구에서는 ATES 열펌프 시스템의 실증 성능 결과를 분석하였으며, LNG 보일러와 에어컨을 사용하는 기존의 냉난방 시스템을 비교시스템으로 ATES 열펌프 시스템의 경제성 평가를 수행하였다. ATES 시스템의 연간 실증 성능 실험결과 ATES 시스템은 외기온도와 무관하게 연중 안정적인 성능을 나타내었다. 경제성 평가시에 생애주기법(Life Cycle Cost)을 적용하여 ATES 열펌프 시스템의 설치 및 운전에 필요한 총 소요비용을 산정하고, 이 결과를 바탕으로 투자회수기간법을 통해 ATES 시스템의 투자회수 기간을 산정하였다. 생애주기법 적용 시에 현재가치법을 사용하였으며, 현재가치법은 수명주기에 발생하는 모든 투자비용과 절감액을 일정한 시점을 기준으로 등가환산하는 방법을 의미한다. 현재가치법에 사용되는 현재가치는 초기비용과 현재가치계수의 곱으로 나타나는데, 여기에서 현재가치계수는 임의의 이자율로 일정기간 동안 정기적인 할부금액이 적립될 때의 현재금액을 구하기 위해 사용하는 계수를 의미한다. 전기와 LNG는 각각 2009년 7월의 (주)한국전력공사와 (주)한국가스공사의 고시요금을 적용하였다. 본 시스템은 실증 설비용량인 20RT를 대상 건물로 가정하였고, 초기투자비는 크게 공사비와 냉난방 설비 구입비로 구성되어 있으며, 기본적인 물가지표는 (사)한국물가정보(KPI)의 고시 데이터를 참조하였다. 각 시스템의 초기투자비는 ATES 시스템이 비교대상 기존 냉난방 시스템 대비 5.7배 높게 나타났다. 일일 8시간 사용기준으로 계절별 전력요금을 고려한 연간운전 비용은 ATES 시스템이 기존 시스템 대비 냉난방 시에 각각 77%와 16%를 나타내어 운전비용이 연간 절감되었고, 난방 운전 시 절감 비율이 냉방시보다 크게 나타났다. 두 시스템에 대한 생애주기비용을 산정하기 위하여 에어컨과 보일러의 기존시스템과 ATES 시스템의 가용연수를 모두 20년으로 설정하였고, 유지보수 비용은 초기투자비용의 2%로 설정하고, 할인율은 은행 예금이자를 기준으로 5%로 설정하였다. 전기와 LNG의 요금 상승률은 (사)한국물가정보를 바탕으로 각각 2%와 8%로 가정하였다. 이러한 조건에서 생애주기법을 이용한 경제성평가는 ATES 시스템의 경우 생애운전비용이 초기투자비용보다 작게 나타났으며, 기존 냉난방 시스템은 생애운전비용이 초기투자비용에 비하여 높게 나타났다. 본 연구 대상 ATES 열펌프 시스템의 실증 성능 데이터와 기존 문헌으로부터 얻은 냉난방 시스템의 성능 결과를 이용하여 생애주기 비용을 적용한 결과 ATES 시스템의 기존 시스템 대비 투자회수 기간은 6.62년으로 나타났다. 특히, 본 연구에서는 ATES 시스템이 국내 최초로 적용됨에 따라 스크린 등의 부품을 다소 고가의 제품으로 시스템에 적용하였으므로 ATES 시스템의 신뢰성과 안정성이 확보되면 초기 투자비 감소가 가능할 것으로 예상되며, 기존 시스템 대비 투자회수 기간은 더욱 감소될 수 있을 것으로 예상된다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.393-399
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• 2017

In a reciprocating compressor, the piston and connecting rod are important parts. Excess mechanical stress on these parts may cause damage, and broken parts are expensive and difficult to replace. Therefore, it is necessary to analyze the mechanical stress affecting durability and longevity. The main purpose of this study was to identify locations of maximum stress on pistons and connecting rods. Based on dynamic calculation of the working process of a specific air compressor, an analysis of piston and connecting rod performance has been completed. A three-dimensional model for the air compressor's pistons and connecting rods was built separately, and FEM analysis of these components was carried out using a numerical method. The pistons were loaded by pressure which was changed according to crankshaft angle without thermal boundary conditions. The simulation results were used to predict and estimate stress concentration as well as the value of this stress on pistons and connecting rods. The maximum equivalent stress calculated are over 190 MPa on pistons and 123 MPa on connecting rods at crank angle $135^{\circ}$ and $225^{\circ}$ but these are under tensile yield strength. Besides, the calculated safety factors of connecting rods and pistons is higher than 1. Moreover, the results obtained can be used to provide manufacturers with references to optimize the design of pistons and connecting rods for reciprocating compressors.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.9
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• pp.527-533
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• 2017

Environmental concern about smart phone is growing because it has short product life span while having intensive production technology and cost. In this study environmental impact of the smart phone is quantified using the LCA methodology based on the ISO 14040 series standards. The assessment considers potential environmental impacts across the whole life cycle of the smart phone including; pre-manufacturing; manufacturing; distribution; product use; and end-of-life stages. The pre-manufacturing stage is the most dominant life cycle stage causing the highest environmental impacts among all 10 impact categories assessed. The global warming impacts of the smart phone in the pre-manufacturing, distribution, use, manufacturing, and end-of-life stages were 52.6% 23.9%, 15.7%, 7.0%, and 0.8%, respectively. Sensitivity of the life cycle impact assessment results to the system boundary definition and assumptions made were quite high. Three components of the smart phone, PCB, battery, and display module were identified as the key components causing majority of the potential environmental impact in the pre-manufacturing stage. As such the slim and light-weight design and the use of environmental friendly materials are important design factors for reducing the environmental impact of the smart phone.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.493-500
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• 2017

Based on the data accumulated through EMU fault management, this paper examines the reliability of old railway car parts and proposes measurements to improve safety. Subway Line 7 of the Seoul Metropolitan Rapid Transit Corporation, auxiliary power unit (Static Inverter) of the EMU second version is a core equipment to supply power to various room-service units in cars and make an effect directly on passenger satisfaction. To analyze the pattern of failure throughout the field data over a long period of time, this analysis of statistics and reliability considers the operating environment and stress factors. This statistical analysis presents the correlation between failure and the temperature stress factors related to frequent failure occurring intensively in summer. In addition, throughout the analysis of the life of the IGBT inverter, the effect of the temperature stress factor was observed before and after the repair. As a result of an analysis of the optimal operating conditions considering two variations of EMU, such as variable load and outside temperature, a difference in the cooling capacity between the optimal operating conditions and frequent failure conditions was observed. Based on this analysis, this paper suggests a way to minimize cooling capacity difference for the optimal operational conditions.

• Clean Technology
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• v.17 no.2
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• pp.85-96
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• 2011

Self-healing materials are a class of smart materials that have the structurally incorporated ability to repair damage caused by mechanical usage over time. A material (polymers, ceramics, metals, etc.) that can intrinsically correct damage caused by normal usage could lower production costs of a number of different industrial processes through longer part lifetime, reduction of inefficiency over time caused by degradation, as well as prevent costs incurred by material failure. The recent announcement from Nissan on the commercial release of scratch healing paints for use on car bodies has gained public interest on such a wonderful property of materials. This article is a second part of healing materials dealing with inorganic engineering materials such as metals, ceramics, and concrete. The healing mechanisms developed for the inorganic materials are to be discussed with the future prospect.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.7
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• pp.914-919
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• 2004

When the motor is rotating, the torque and rpm are varying as the loads or the driving status connecting through reduction units are changing. On the contrary, one can monitor the changes of the loads or the driving status in the manner of measuring motor torque and rpm. There is a torque measuring method using the strain gauge and bridge circuit. But, because this is the contact method, it has the life time which is dependent on rotating velocity and used time. So this system demands on replacement of some Parts or whole system itself for maintenance. And this system is also relatively big and expensive, requiring preceding annoying process. In this paper, we are going to suppose non-contact method to measure torque and rpm using the Hall effects sensor For this we have made the planetary geared reduction motor with Hall sensors and with the monitoring system. The monitoring system displays the sensing data(torque, rpm) and calculated data( power) and also has the network capability with Bluetooth protocol. Our solution is much more inexpensive ;md simple method to measure torque and rpm than before.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.4
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• pp.13-16
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• 2013

A lot of various researches have been going on to use heat spreader for LED module. Nano porous aluminum anodic oxide (AAO) applied LED, which is produced from anodization, is easy and economically advantageous. Convensional LED module is consist of aluminum/adhesive/copper circuit. The polymer adhesive in this module is used as heat spreader. However the thermal emission of LED component is degraded because of low heat conductivity of polymer and also reliability of LED component is reduced. Therefore, AAO in this work was applied to heat spreader of LED module which has higher heat conductivity compare to polymer. Bonding strength between AAO and copper circuit was improved with Ti/Cu seed layer by copper sputtering process (DBC) before the bonding. And this copper circuit has been fabricated by electro plating method. Peel strength of AAO and copper circuit in this work showed range between 1.18~1.45 kgf/cm with anodizing process which is very suitable for high power LED application.

• Journal of Energy Engineering
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• v.25 no.3
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• pp.27-33
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• 2016

The heat recovery system that was applied in this study, is the energy-saving type that can produce the maximum cooling capacity less power in use. In order to have a more precise control function the temperature and humidity of the constant temperature and humidity machine, control algorithm is applied to designed a fuzzy PID controller, and the outside air compensation device (air-cooled) demonstrated excellent ability to dehumidify the moisture, $-20^{\circ}C$ in winter. High efficiency and the low-noise type sirocco fan operate quitely and designed to fit the bottom-up and top-down in accordance with the characteristics of equipment. as a result of experiment data, the conversion efficiency is 95% or more, power recovery time is within 5sec, stop delay time is within 30sec, pump down time is 10sec, pump delay time is 5sec, heating delay time is 5sec, temperature deviation is ${\pm}2^{\circ}C$ (cooling deviation: $2^{\circ}C$, Heating deviation : $2^{\circ}C$), humidity deviation is a ${\pm}5%$ (humidification deviation 3.0%, dehumidification deviation 3.0%). Recently, ubiquitous technology is important. so, the constant temperature and humidity machine designed to be able to remotely control to via the mobile phone, and more scalable to support MMI software and automatic interface. Further, the life of the parts and equipment is extended by the failure.