• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.323-324
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• 2006

The nanostructure control of $Si_3N_4$ ceramics can be achieved by using fine starting powder and retardation of grain growth. The spark plasma sintering technique is useful to retard the grain growth by rapid heating. In the present work, the change of microstructure was investigated with emphasis on the particle size of starting powder, the amount of sintering additive and the heating schedule. The rapid heating by spark plasma sintering gave the fine microstructure consisting of equiaxed grains with the same size as starting particles. The spark plasma sintering of $Si_3N_4$ fine powder was effective to control the microstrucutre on nano-meter level.

• Land and Housing Review
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• v.10 no.1
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• pp.25-32
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• 2019

In this study, the case analysis data on underground temperature are presented. In addition, numerical analysis of the ventilation load reduction plan was derived according to the residence schedule change for the building with cool tube. The research scope and method are as follows. The overall system principle was examined through reviewing the theory of the Cool tube system. Case study and analysis were conducted. Numerical simulation was used to examine the change in energy usage. Also, the change of load energy in case of varying amount of ventilation was derived based on actual building room schedule. When the Cool tube system was applied to the residential buildings, the cooling load was reduced from 3,331 kW to 193 kW, which showed a reduction effect of about 90%.The heating load was reduced from 42,276kW to 32,575kW by 23%.Also, result shows that the cooling load decreased by 24% and the heating load decreased by 66% when the number of ventilation according to the occupancy schedule was applied.

• KIEAE Journal
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• v.14 no.4
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• pp.47-52
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• 2014

The problem of energy consumption is more serious in university buildings than primary, middle and high school buildings. Because university buildings have generally heating and cooling systems, and various incidental facilities. In university, the library is one of the building that many people use and the most energy is spent. So, investigation on energy saving is very important and urgent. This study aims finally to present the guideline for low-energy design of University library by aiding a designer to select best solution in the side of energy-saving. In this paper, composition of space, utilization schedule and performance of construction materials are grasped, some primary factors that effect to energy saving are analyzed by energy simulation. The result of this study is as follows; First, the subject library has more cooling load than heating load because of cooling load generated during middle season. Second, green roofs is the most effective to heating load saving, but not to cooling energy. Third, outdoor air cooling is the most effective to cooling energy saving among the investigated strategies included in this study.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.33-38
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• 2009

Energy loss from windows accounts for large scores of heating and cooling loads also in energy saving apartments that is reduced over 30% of total energy consumption. Movable reflective insulations, insulation shutters, blinds, insulated shades are used to reduce energy loads from windows. In this study, energy saving performance of insulated shades was simulated by control methods. According to installation of insulated shades, heating loads were decreased about $10.5{\sim}11.3%$, and cooling loads are decreased about $11.0{\sim}15.5%$ on an energy saving apartment. The heating peak load was reduced about 9.5% by insulated shades, but the cooling peak load is hardly ever decreased. Because in the condition of cooling peak load, latent cooling loads accounts for large score of cooling loads. Difference of the energy loads by a schedule control method and an outdoor detection control was no more than 5% for a base model. In the case of insulated shades with automatic control system, simple time schedule control system would be more efficient than outdoor detection control system that should use several sensors.

• Journal of the Korean Ceramic Society
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• v.34 no.6
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• pp.553-560
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• 1997

A fine $\alpha$-Al2O3 powder was prepared by sol-gel process for membrane application. And it was carried out by adding 1.5wt% $\alpha$-Al2O3 powders(mean size : 87 nm) as seeds to the prepared sols and by controlling the heating schedule (the heating rate and the soaking time) to prevent the microstructural change, which occured during $\theta$-to $\alpha$Al2O3 phase transformation. The seeded $\alpha$-Al2O3 particles acted as the heterogeneous nucleation sites for the $\alpha$-Al2O3 nucleation during the transformation of $\theta$- to $\alpha$-Al2O3 and resulted in increasing the driving force of phase transformation to activate the formation of $\alpha$-Al2O3 phase at 82$0^{\circ}C$. By $\alpha$-Al2O3 seeding and controlling of heating condition the phase transformation of $\theta$- to $\alpha$-Al2O3 was accomplished at low temperature and the grain growth process was depressed. Therefore, the unsupported membrane could be fabricated in $\alpha$-Al2O3 . The average diameter of pores in the fabricated membrane was 7 nm and the porosity was 47%.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.230-233
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• 2004

The purpose of this study is to establish the optimal induction heating conditions of various preform types used for TR forging. The finite element model coupled electro-magnetic and transient heat transfer was employed to evaluate the distribution of temperature at the billet. Power control method was applied to control temperature of preform in induction heating because TR forging is not a continuous process. Power schedule that consists of heating and holding stage was suggested. In heating stage, power is inversely proportional to diameter of preform but the time of heating stage is directly proportional to the diameter of preform. But, in holding stage, the required power for thermal equilibrium per unit volume of the billet decreases with an increase in a diameter of billet due to the increase of efficiency.

• Journal of Power System Engineering
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• v.20 no.4
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• pp.63-68
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• 2016

In this study, through portion of the blind control which the user can adjust the deration and the main loads, night for energy reduction during the review of the energy difference between the cooling and heating load periods in order to present the best operation schedules of the blind control. The result, Cooling period, the venetian blind is installed the day or the day and night CASE adjusted to $0^{\circ}$ was identified as optimal for the operating schedule. Heating period, the day, without installed the blinds, the Venetian blind is installed only at night CASE adjusted to $0^{\circ}$ or $45^{\circ}$ angle of the slats, which have been identified as optimal for the operating schedule.

• Solar Energy
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• v.11 no.2
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• pp.29-33
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• 1991

The present paper deals with two types of heating methods widely used for the Radiant Floor heating systems in Korea. Of these, one method circulates hot water according to the predefined schedule ("intermittent heating") while the other runs the system with the aid of thermostats ("continuous heating"). The standard version of SERI-RES has been modified for the numerical simulation of the problem. Preliminary results show relatively large temperature swings in the case of intermittent heating with solar availability. On the other hand, the case of continuous heating would avoid such undesirable temperature fluctuations. These results are also verified by experimental evaluations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1419-1426
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• 2012

The heating and cooling energy load of the KNU plant factory was analyzed using the DesignBuilder. Indoor temperature set-point, LED supplemental lighting schedule, LED heat gain, and type of double skin window were selected as simulation parameters. For the cases without LED supplemental lighting, the proper growth temperature of lettuce $20^{\circ}C$ was selected as indoor temperature set-point together with $15^{\circ}C$ and $25^{\circ}C$. The annual heating and cooling loads which are required to maintain a constant indoor temperature were calculated for all the given temperatures. The cooling load was highest for $15^{\circ}C$ and heating load was highest for $25^{\circ}C$. For the cases with LED supplemental lighting, the heating load was decreased and the cooling load was 6 times higher than the case without LED. In addition, night time lighting schedule gave better result as compared to day time lighting schedule. To investigate the effect of window type on annual energy load, 5 different double skin window types were selected. As the U-value of double skin window decreases, the heating load decreases and the cooling load increases. To optimize the total energy consumption in the plant factory, it is required to set a proper indoor temperature for the selected plantation crop, to select a suitable window type depending on LED heat gain, and to apply passive and active energy saving technology.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.928-933
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• 2009

The purpose of this study is to examine the energy consumption, carbon dioxide emission & energy cost of district heating using sewage source. The annual TOE of heat pump using sewage source save 37.1 percent than city gas boiler. And annual carbon dioxide emission of heat pump cut down 41.3 percent than city gas boiler. If it charges the rate schedule for district heating to apartment resident, collected amount are 3,127,170 thousand won. As energy cost of heat pump & circulation pump are 1,378,072 thousand won. the profits are 1,749,098 thousand won. As payback period is 8.97years, applicability is low level. However, it has advantages in energy consumption, carbon dioxide emission & energy cost. Therefore, it needs to proceed through government assistance.