• Journal of the Korean Society for Precision Engineering
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• v.29 no.7
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• pp.778-784
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• 2012

In comparison with some other light sources, LED has merits such as increased life expectancy, fast response, pollution free, and high energy efficiency. Lately, due to development of LED with high brightness and capacity, LED has widely used in many industrial fields such as automotive, aviation, display, transportation and special lighting applications. Since the high heat generation of LED chips can cause a reduction in lifetime, degradation of luminous efficiency, and variation of color temperature, studies have been carried out on the optimization of LED packaging and heat sinks. In this study, experiments on measuring the heat generation rate of LED and the cooling performance of a heat sink were carried for analyzing the thermal characteristics of LED lighting system in free convection. From the results, dimensionless correlation on the cooling performance of heat sink in natural convection was proposed with Nusselt number and Rayleigh number as a guideline for designing cooling device of LED lightings.

• Journal of the Korea Safety Management & Science
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• v.19 no.4
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• pp.149-155
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• 2017

This study is analyzed combustion phenomena based on the environmental energy facility incinerator. It is assumed that combustible components of waste are composed of carbon and hydrogen, and the combustion process of fuel is by setting as multi-component / multistage reaction. As the combustion chamber is burned, the high temperature environment is achieved, also the heat transfer accompanied by the turbulent flow and the generation of NOx, a pollutant, are interpreted to predict the thermal and fluid characteristics and pollution emissions of the grate incinerator. As the result of internal flow analysis, the slow flow around the ash chute and the mixing effect due to the complicated turbulence around the combustion chamber were predicted to show excellent performance. It is shown to the internal average temperature was about $1024^{\circ}C$, around the about $1000^{\circ}C$ homogeneous temperature distribution. Due to the sudden temperature decrease in the boiler, the flue gas temperature at the outlet was estimated to be about $220^{\circ}C$.

• Advances in concrete construction
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• v.5 no.6
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• pp.563-573
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• 2017

Transparency, excellent toughness, thermal stability and a very good dimensional stability make Polycarbonate (PC) one of the most widely used engineering thermoplastics. Polycarbonate market include electronics, automotive, construction, optical media and packaging. One alternative for reducing the environmental pollution caused by polycarbonate from electronic waste (e-waste), is to use it in cement concretes. In this work, physical and chemical characterization of recycled polycarbonate from electronic waste was made, through the analysis by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM). Then cement concrete was made with Portland cement, sand, gravel, water, and this recycled polycarbonate. Specimens without polycarbonate were produced for comparison purposes. The effect of the particle sizes and concentrations of recycled polycarbonate within the concrete, on the compressive strength and density was studied. Results show that compressive strength values and equilibrium density of concrete depend on the polycarbonate particle sizes and its concentrations; particularly the highest compressive strength values were 20% higher than that for concrete without polycarbonate particles. Moreover, morphological, structural and crystallinity characteristics of recycled polycarbonate, are suitable for to be mixed into concrete.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.8
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• pp.18-24
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• 2021

Polymers, polymer compounds, are very moldable at low temperatures and have good strength against weight, and hence, are often used in the interior and exterior materials of cars. Owing to the increasing environmental problems, emission regulations have become stricter, which has increased the use of lightweight polymers as substitutes for metal materials. Therefore, as the use of polymer increases, extensive research is being conducted on the bonding technology of polymers, such as polyurethane and epoxy. However, the increased cost and environmental pollution by adhesives caused by the polymer manufacturing plant depend on the chemical composition or the manufacturer's mix ratio. To compensate for this issue, a laser beam is irradiated through a highly permeable polymer (PC) placed on top of an absorbent polymer (ABS) to transfer the laser output to the ABS polymer and fuse them at the interface. Moreover, enabling laser penetrating bonding by placing a stainless steel wire mesh between the two polymers can achieve improved bonding strength compared to conventional heterogeneous polymer bonding.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.74-75
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• 2021

In the recent 2017 annual average fine dust concentration (PM2.5) statistics released by the Organization for Economic Cooperation and Development (OECD), Korea has a high concentration of 25.14㎍/m3, which is about twice the average of 12.5㎍/m3 in OECD countries. Fine dust (PM2.5) is the main source of secondary pollutant production by the reaction of primary pollutants emitted from automobiles and thermal power plants, mainly composed of sulfates, nitrates, and organic carbon. The permeable block is an eco-friendly product that prevents rainwater from collecting on the surface of the road because it does not penetrate the groundwater properly, and is widely constructed on sidewalks or parking lots to recharge groundwater in case of rain. In addition, the pavement of the permeable block is a fundamental solution to reduce pollution by preventing rainwater from flowing into the stream, and it also has the advantage of easy replacement as well as low replacement costs. Therefore, this study was a basic experiment to produce permeable blocks mixed with TiO2 and diatomite to improve indoor air quality, and intended to analyze the flexural strength and compressive strength of permeable blocks mixed with TiO2.

• Advances in nano research
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• v.13 no.5
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• pp.475-485
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• 2022

Crystalline silicon photovoltaic cells have advantages of zero pollution, large scale and high reliability. A major challenge is that sunlight wavelength with photon energy lower than semiconductor band gap is converted into heat and increase its temperature and reduce its conversion efficiency. Traditional cooling PV method is using water flowing below the modules to cool down PV temperature. In this paper, the idea is proposed to reduce the temperature of the module and improve the energy conversion efficiency of the module through the modulation of the solar spectrum. A spectrally selective nanofilm reflector located directly on the surface of PV is designed, which can reflect sunlight wavelength with low photon energy, and even enhance absorption of sunlight wavelength with high photon energy. The results indicate that nanofilm reflector can reduce spectral reflectivity integral from 9.0% to 6.93% in 400~1100 nm wavelength range, and improve spectral reflectivity integral from 23.1% to 78.34% in long wavelength range. The nanofilm reflector can reduce temperature of PV by 4.51℃ and relatively improved energy conversion efficiency of PV by 1.25% when solar irradiance is 1000 W/m². Furthermore, the nanofilm reflector is insensitive in sunlight's angle and polarization state, and be suitable for high irradiance environment.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.12
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• pp.715-732
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• 2009

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2008. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends in thermal and fluid engineering have been surveyed in the categories of general fluid flow, fluid machinery and piping, new and renewable energy, and fire. Well-developed CFD technologies were widely applied in developing facilities and their systems. New research topics include fire, fuel cell, and solar energy. Research was mainly focused on flow distribution and optimization in the fields of fluid machinery and piping. Topics related to the development of fans and compressors had been popular, but were no longer investigated widely. Research papers on micro heat exchangers using nanofluids and micro pumps were also not presented during this period. There were some studies on thermal reliability and performance in the fields of new and renewable energy. Numerical simulations of smoke ventilation and the spread of fire were the main topics in the field of fire. (2) Research works on heat transfer presented in 2008 have been reviewed in the categories of heat transfer characteristics, industrial heat exchangers, and ground heat exchangers. Research on heat transfer characteristics included thermal transport in cryogenic vessels, dish solar collectors, radiative thermal reflectors, variable conductance heat pipes, and flow condensation and evaporation of refrigerants. In the area of industrial heat exchangers, examined are research on micro-channel plate heat exchangers, liquid cooled cold plates, fin-tube heat exchangers, and frost behavior of heat exchanger fins. Measurements on ground thermal conductivity and on the thermal diffusion characteristics of ground heat exchangers were reported. (3) In the field of refrigeration, many studies were presented on simultaneous heating and cooling heat pump systems. Switching between various operation modes and optimizing the refrigerant charge were considered in this research. Studies of heat pump systems using unutilized energy sources such as sewage water and river water were reported. Evaporative cooling was studied both theoretically and experimentally as a potential alternative to the conventional methods. (4) Research papers on building facilities have been reviewed and divided into studies on heat and cold sources, air conditioning and air cleaning, ventilation, automatic control of heat sources with piping systems, and sound reduction in hydraulic turbine dynamo rooms. In particular, considered were efficient and effective uses of energy resulting in reduced environmental pollution and operating costs. (5) In the field of building environments, many studies focused on health and comfort. Ventilation. system performance was considered to be important in improving indoor air conditions. Due to high oil prices, various tests were planned to examine building energy consumption and to cut life cycle costs.

• Journal of the Korean Institute of Landscape Architecture
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• v.30 no.4
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• pp.37-46
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• 2002

The main purpose of this research is to discuss the urban heat island which will be caused by urbanization, especially by the construction of new town on a wide green zone. Over the last ten years, five new towns have been developed around the Seoul metropolitan area. However these new towns become bedroom communities and create traffic problems between Seoul and its surrounding areas because of an increase in population and a lack of roads and other infrastructures. The construction of another such new town is under consideration in the Pan-gyo area. But it is important that Pan-gyo remains a wide green zone. Many studies show that green space can play an important role in improving urban eco-meteorological, ameliorative capability and air hygiene. The objective of this study is to analyze the urban heat islands of Bund-Dang Si which was constructed in 1996 and of the Pan-Gyo area planned as new town. To investigate the local thermal environment and its negative effects caused by change of the land use type and urbanization we used LANDSAT TM images for extraction of urban surface temperature according to change of land use over 15 years. These data were analyzed together with digital land use and topographic data. As a study result, we found that the thermal island of this area from 1985 to 1999 rapidly increased with a difference of mean temperature of more than 12'E. Before construction of Bun-Dang Si the temperature of this area was the same as the forest, but during the new town construction in 1991, an urban heat island developed. The temperature of forest with a size of over 50% of the investigation area was lowest, which leads us to conclude that the forest cools the urban and its surroundings. The mean temperature of the residential and commercial area is more than +4.5$^{\circ}C$ higher then forest, so this method of land use is the main factor increasing the urban heat island. Urban heat islands and green space play an important role in urban wind systems, i.e. Thermal Induced Air Exchange and Structural Wind Circulation, because of their special properties with regard to energy balance between constructed urban and land. The skill to allocate land use types in urban areas is a very important planning device to reduce air pollution and induce the fresh cold air from green space. An urban climatic experiment featuring a numerical wind simulation study to show the air corridor will be published in a following research paper.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.6
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• pp.586-599
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• 2014

During the last two decades, indoor air quality and volatile organic compounds (VOCs) have been of concern in Korean society due to their nature of potential health impacts. In order to investigate the pollution levels of VOCss in indoor environments, establishment of a solid test method for monitoring the airborne VOCss is essential. In Korea, a method based on adsorbent sampling and GC analysis coupled with thermal desorption was proclaimed as the Korea Standard Method for Indoor Air Quality Test. This study was carried out to examine some inherent problems of the VOCs measurement method. The VOCs method does not describe in detail preparing the standard samples. The standard samples may be prepared by impregnation of either liquid standard solutions or a mixture of standard gases. In this study, we investigated the optimal temperature condition for transferring the liquid standards onto a standard adsorbent tube. As a result, keeping the impregnation temperature at $250^{\circ}C$ will be recommended in regard of the boiling points of multiple target analytes and the thermal stability of the adsorbent. We also demonstrated some problems associated with handling of a syringe used for transferring the standard solutions onto the adsorbent tubes, and a best way to get rid of the syringe problems was suggested. Finally, a number of field works were conducted to evaluate the performance of adsorbent sampling methods. Comparison of different adsorbent tubes, i.e. tube packed with single sorbent (Tenax) and double sorbents (Tenax with Carbotrap), revealed that 30 to 40% differences between the two groups, implying that sampling efficiency is depending on the volatility and the strength of adsorbents. However, duplicate precisions for VOCs sampling with a same type of adsorbent and at same flow rates appeared to be satisfactory to be all within 20%, which is a quality control guideline. Distributed volume precisions were also found to be within a guideline value, 25%, although the precision was in general inferior to the duplicate precision. The Korea indoor VOCs test method should be more refined and improved in many aspects, particularly procedure and instrumentation for preparing the standard samples and specification of quality control assessment.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.6
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• pp.626-632
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• 2015

The International Maritime Organization (IMO) has adopted several regulations for the prevention of air pollution from ships. In addition, there is a requirement for shipping liners to reduce greenhouse gas emissions. Accordingly, we need to take measurements to ensure that the steps taken are both efficient and environmentally friendly. It has been determined that the application of the Miller cycle in diesel engines has the effect of both reducing the amount of NOx and improving thermal efficiency. However, this method requires a considerably larger charge air pressure. Therefore, we consider a two-stage turbo-charging system, which not only results in a high charging pressure, but also improves the part load performance with an exhaust-gas bypass system or the application of the Miller cycle. Because of complications associated with the two-stage turbo-charging system, it is complex and difficult to realize a design that optimizes matching between diesel engine and turbo-chargers. Accordingly, it is necessary to perform a quantitative analysis to determine the effects and optimal conditions of these different systems in the early stage of system design. In this paper, we develop a simulation program to model these systems, and we verify that the results of this program are reliable. Further, we discuss methods that can be employed to improve its efficiency.