• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.5
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• pp.372-378
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• 2007

GHX (Geothermal Heat Exchanger) design which determines the performance and initial cost is the most important factor in ground source heat pump system. Performance of GHX is strongly dependent on the thermal resistance of soil, grout and pipe. In general, GHX design is based on the static simulation program. In this study, dynamic simulation has been peformed to analyze the variation of system performance for various GHX parameters. Line-source theory has been applied to calculate the variation of ground temperature. The averaged weather data measured during a 10-year period $(1991\sim2000)$ in Seoul is used to calculate cooling and heating loads of a building with a floor area of $100m^2$. The simulation results indicate that thermal properties of borehole play significant effect on the overall performance. Change of grout thermal conductivity from 0.4 to $3.0W/(m^{\circ}C)$ increases COP of heating by 9.4% and cooling by 17%. Change of soil thermal conductivity from 1.5 to $4.0W/(m^{\circ}C)$ increases COP of heating by 13.3% and cooling by 4.4%. Change of GHX(length from 100 to 200 m increases COP of heating by 10.6% and cooling by 10.2%. To study long term performance, dynamic simulation has been conducted for a 20-year period and the result showed that soil temperature decreases by $1^{\circ}C$, heating COP decreases by 2.7% and cooling COP decreases by 1.4%.

• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.365-372
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• 2014

Technologies for rapid concrete curing using elevated temperature are important for saving cost and time when constricting concrete structures. Recently, a microwave heating form was developed. In this study the early strength of concrete cured by the developed form was experimentally investigated. Large scale mock up tests were conducted six times, and the results were analyzed based on the maturity theory. Logarithmic correlation curves were generated based on the measured strength and estimated maturity. It was confirmed that the strength development of the concrete cured by microwave heating form can be estimated by the equivalent age theory usually applied to steam-curing technology. By using the microwave heating form, one day at most is enough to get the required strength for the safe removal of forms, even in cold weather.

• Journal of Digital Convergence
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• v.19 no.6
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• pp.285-292
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• 2021

Due to the recent Corona 19 outbreak, camping culture is rapidly drawing attention from many people. Convective heating devices, which many campers use during winter, have the temperature stratification problem. To solve this problem, various power circulators are being used. Several non-powered circulators are also on sale, but the direction of the circulator is designed to be at the right angle relative to the convection heating mechanism and the circulator does not properly play the role of air circulation. To solve this problem, a 3D printer is used to design a non-powered circulator in the same direction as the convection heating mechanism. Electricity is generated without power using Peltier element and ceramic paper and the circulator is produced to withstand heat using HTPLA-CF filament. This study presents a method to solve the temperature stratification problem through efficient convective circulation. In addition, the purpose of this study is to manufacture products at a lower cost by using a 3D printer.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.3
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• pp.60-67
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• 2010

Korea's large-scale incinerating facilities of domestic waste were built in the late 1980's. It was found that most of the incinerators were designed during the period and even the ones constructed afterwards have been built without any changes or modifications. However, the nature of waste fed into incinerators is undergoing a radical change due to government policies on waste collection, which is upheld by a research into changes in the heating value of domestic wastes. As a result, refractories and stokers are being damaged in many of the facilities due to overheating. On the other hand, the formation of clinkers on boilers' heating surface, which curbs he at transfer, results in problems such as a fall in used heating value and a rise in the temperature of combustion chambers. Methods are being deployed to resolve the problems-such as spraying water on piles of waste, incinerating food waste by mixing together what has been separately collected, spraying water on combustion chambers, etc. Such actions are not a fundamental solution, nor redesigning and rebuilding incineration facilities is cost-effective. This research seeks to develop a fundamental solution to address the situation.

• Journal of Bio-Environment Control
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• v.8 no.2
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• pp.136-146
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• 1999

A series of experiments were carried out in winter to investigate the indoor thermal environment in greenhouses with different kinds of heating systems, and characterize the energy consumption, heat transport and thermal energy efficiency of each system. By the Quantitative calculation of heat losses which transmit through the covers of greenhouse, the fundamental data of energy-saving of the particular heating system were obtained. And from the analysis of air temperature differences between indoor and outside, it was possible to select more effective energy-saving and comfortable heating system in greenhouses. The electric heater was more stable in thermal environment and cheaper in cost, since it could be used during the surplus time of electric power from 10：00 p.M. to 8：00 A.M. But the low air temperature in greenhouses besides these times resulted in a chilling problem of the crops. The heating system by hot air had the advantage to show nearly uniform temperature difference by the height above the ground. But the system had the disadvantage to require more energy consumption than the electric heating system.

• Journal of the East Asian Society of Dietary Life
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• v.24 no.5
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• pp.680-690
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• 2014

This study investigated the performance of hygiene management according to the capacity and food cost of foodservice in kindergartens as a measure of kindergartens foodservice hygiene management. Dietitians from the education office visited 50 kindergartens under the control of Dongbu District Office of Education during January, 2011. Kindergartens were 11 public and 39 private institutions. Over half of kindergartens (n=27) provided foodservice to 50~99 children. About 21 kindergartens had a foodservice cost per student per day of 2,000 won. Regarding personal hygiene, 'whether to wear an accessory or have a manicure' showed the best performance. 'Whether to have their health examined once every 6 months or keep their health records in 2 years' was rarely performed. For food materials, 'whether to buy food appropriate for the quality control standard of food materials' showed the highest performance. The highest performances for storage management of food materials and handling of food was 'whether to store goods within butlery at intervals more than 30 cm from the ground' and 'whether to heat and cook food more than $74^{\circ}C$', respectively. The highest performance for distribution of food and management of facilities was 'the hygienic management of cooking tools and facilities' and 'the proper installation of air-conditioning, heating and ventilation facilities', respectively. The results of this study show that capacity and food cost had the strongest effects on performance of personal hygiene. Especially, smaller facility size could increase performance of foodservice management.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2779-2785
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• 2009

Among the livestock, chickens are raised because of the merit ingested protein in low-priced cost of production and are primary livestock increased the consumption of meat. The factors of influencing condition, odor is the most important factor. Odor substances are ammonia, amines, hydrogen sulfide and mercaptan which come from night soil. Livestock are prevented from rearing by means of these odor substances. Though the henhouse is heated using hot air type heater in the winter season, it is ventilated for the control of odor because of the increase of odor concentration. In the present work, composite catalytic system combined the existing facilities(hot air type heater) with catalytic system was developed, it could controled odor and hazardous gas using the oxidation/reduction reaction without extra operating cost. Moreover, the purpose of this work is to develop the catalysts which are cost competitive and can maximize energy efficiency. The catalysts are noble metal(Pt-Rh) and composite transition metal(Mn) type.

• Journal of the Korean Solar Energy Society
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• v.27 no.4
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• pp.175-182
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• 2007

Geothermal-energy has been getting popular as a natural energy source for green buildings these days. As a result Geothermal Source Heat Pump System (GSHPs) was being recognized effective alternative systems to conventional heating and cooling systems owing to their higher energy utilization efficiency. But GSHPs has not been popularized thereby the large amount of initial cost of the system and insufficiency of studies for economic estimation. Therefore GSHPs are being developed to make up for the weak points that are the large amount of initial cost of the system and much annual electricity consumption. In this paper, economic estimation was conducted by payback period method and it shows that the pay back period of Heat Storage Type GSHPs was calculated 6.8 years compared with the absorption Chiller-Heater system and 8.2 years compared with the Ice storage-Boiler system. Heat Storage Type GSHPs also has the lower annual source energy consumption than the conventional heating and cooling systems because of using nighttime electricity.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1994.11a
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• pp.21-26
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• 1994

Conventional electroexplosive devices (EED) commonly use a very small metal bridgewire to ignite explosive materials i.e. pyrotechnics, primary and secondary explosives. The use of semiconductor devices to replace “hot-wire” resistance heating elements in automotive safety systems pyrotechnic devices has been under development for several years. In a typical 1 amp/1 watt electroexplosive devices, ignition takes place a few milliseconds after a current pulse of at least 25 mJ is applied to the bridgewire. In contrast, as for a SCB devices, ignition takes place in a few tens of microseconds and only require approximately one-tenth the input energy of a conventional electroexplosive devices. Typically, when SCB device is driven by a short (20 $\mu\textrm{s}$), low energy pulse (less than 5 mJ), the SCB produces a hot plasma that ignites explosive materials. The advantages and disadvantages of this technology are strongly dependent upon the particular technology selected. To date, three distinct technologies have evolved, each of which utilizes a hot, silicon plasma as the pyrotechnic initiation element. These technologies are 1.) Heavily doped silicon as the resistive heating initiation mechanism, 2.) Tungsten enhanced silicon which utilizes a chemically vapor deposited layer of tungsten as the initiation element, and 3.) a junction diode, fabricated with standard CMOS processes, which creates the initial thermal environment by avalanche breakdown of the diode. This paper describes the three technologies, discusses the advantages and disadvantages of each as they apply to electroexplosive devises, and recommends a methodology for selection of the best device for a particular system environment. The important parameters in this analysis are: All-Fire energy, All-Fire voltage, response time, ease of integration with other semiconductor devices, cost (overall system cost), and reliability. The potential for significant cost savings by integrating several safety functions into the initiator makes this technology worthy of attention by the safety system designer.

• Journal of Energy Engineering
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• v.5 no.2
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• pp.183-192
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• 1996

This paper presents a numerical model of the optimal operation pattern of the CHP system built for duel-purpose of power generation and district heat production. The model can be differently formulated in accordance with the view of planner: society, electric utility or district-heating company. Here, the operation pattern of the system components and the effect of heat price are of major interest in the study. From the case study, it was found that the optimal use of auxiliary heating equipment is very important to achieve the minimum societal cost. And, the multi-step heat pricing scheme is desirable to induce the voluntary behavior of both companies towards the societal optimal pattern.