• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.1
• /
• pp.29-39
• /
• 2017

In this research, thermal design data such as heat transfer coefficient on the wall surface required for ventilation system design which is to prevent the temperature rise in the underground utility tunnel that three sides are adjoined with the ground was investigated in numerical analalysis. The numerical model has been devised including the tunnel lining of the underground utility tunnel in order to take account for the heat transfer in the tunnel walls. The air temperature in the tunnel, wall temperature, and the heating value through the wall based on heating value(117~468 kW/km) of the power cable installed in the tunnel and the wind speed in the tunnel(0.5~4.0 m/s) were calculated by CFD simulation. In addition, the wall heat transfer coefficient was computed from the results analysis, and the limit distance used to keep the air temperature in the tunnel stable was examined through the research. The convective heat transfer coefficient at the wall surface shows unstable pattern at the inlet area. However, it converges to a constant value beyond approximately 100 meter. The tunnel wall heat transfer coefficient is $3.1{\sim}9.16W/m^2^{\circ}C$ depending on the wind speed, and following is the dimensionless number:$Nu=1.081Re^{0.4927}({\mu}/{\mu}_w)^{0.14}$. This study has suggested the prediction model of temperature in the tunnel based on the thermal resistance analysis technique, and it is appraised that deviation can be used in the range of 3% estimation.

• Journal of the Korean Wood Science and Technology
• /
• v.44 no.5
• /
• pp.655-663
• /
• 2016

Increasing green house gas and it consequent climate change problems are discussed as a global issue. Accordingly, future local green house gas emission will increase up to 40% of the entire local green house gas emission and therefore, efforts to reduce the emission in construction industry is urgently required. Therefore, in this study, heating energy demand was analyzed by using the EnergyPlus simulation according to wood material finishes configuration. EnergyPlus has the entry for a variety of buildings and heating, ventilation, air conditioning (HAVC) system components, in particular buildings, air conditioning systems, and performs simultaneous integrated calculated through the feedback between the heat source unit, a verification program according to the ASHRAE Standard 140-2007 to be. The climate data for the simulation we used the data IWEC in Incheon and Gwangju provided by EnergyPlus. The analysis of simulation model was farm and fishing house standard design drawings: 2012, presented at the Korea Rural Community Corporation. The results of simulation of central region and southern region were effected by wood products of simulation model into the interior finish, exterior finish, windows, wooden structure. Also, it was confirmed that the reduced heating energy demand.

• Archives of design research
• /
• v.18 no.4 s.62
• /
• pp.119-128
• /
• 2005

This paper presents an intuitive 3D modeling interlace based on a field study and prototype development. The process and tools of modeling were observed in workshops of professional design model making, day modeling, wood caning and glass crafting. The Spray Modeling interlace was developed from the observational analysis of the field study. It is a 3D modeling interface which combines particle spraying and day modeling in Virtual or Augmented Reality space. Virtual volume particles are sprayed on frames in Augmented Reality space as day modeling. It adopts a real air spay gun as a tangible interface device which provides coherent sound and air-force feedback. The prototype development and a user study showed that the interface supports new patterns of form development and expression. Control interfaces and requirements of auxiliary devices were found to be improved. This study examines the potential of the new interlace for designers working in 3D virtual and augmented reality. The new spraying interface is also expected to be used as an alternative interface in 3D computer workspace, games, education software and media art.

• Korean Journal of Food Science and Technology
• /
• v.14 no.2
• /
• pp.156-161
• /
• 1982

Three plastic film solar dryers covered with different film layer were constructed by modifying farm vinyl house and studied their performance. The collection efficiency and temperature raising of type C which was covered with double layers of transparent PE and black PVC film was most efficient, followed after B covered with double layer of transparent PE film and type A covered with single layer transparent PE film. The inside temperature of type C was average $18^{\circ}C$ higher than ambient temperature and its collection efficiency showed 31.5% with air flow rate of $3.8m^3/min$. The solar energy collection efficiency of type C was increased in proportion to air flow rate up to 60.2% at $11.3m^3/min$. In demonstration drying test of red pepper in type C, drying capacity per unit area was 2.5 times higher than that of conventional solar drying on straw mat and drying time shortened to about half.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.3
• /
• pp.286-292
• /
• 2005

This study is to investigate the industrial boiler which can be significantly affected by the restriction of NOx. Note that the application of SNCR method to industrial boiler is usually blown as not feasible due to the insufficient residence time for proper mixing. The purpose of this study is to investigate the applicability of the SNCR system application to the industrial boiler, which produces 40 tons of steam per hour using heavy oil. For the industrial boiler with 3-D rectangular coordinate, the general coding are made fur various turbulence modeling such as turbulent flow, turbulent fuel combustion, thermal NO formation and destruction together with the NO reaction with reducing agents. Further, the incorporation of drop trajectory model is successfully made in 3-D rectangular coordinate with Lagrangian frame and the main swirl burner effect on the characteristics of flame is considered. As expected a short flame was created and thereby NOx is removed more efficiently by increasing the proper region of temperature for NO reduction reaction. The validation of program was made successfully by the comparison of experimental data. Based on the reliable calculation results, the SNCR method in a industrial boiler shows the possibility as one of viable NO reduction method by the use of well designed mixing air of reducing agent.

• Journal of Sensor Science and Technology
• /
• v.5 no.4
• /
• pp.17-24
• /
• 1996

Planar multi-junction thermal converters were fabricated for precise measurements of the ac voltage and current by an ac-dc transfer method. A heater and a thermocouple array were fabricated onto a sandwiched membrane, $Si_{3}N_{4}$ (200 nm) / $SiO_{2}$ (400 nm) / $Si_{3}N_{4}$ (200 nm), a thickness of $0.8\;{\mu}m$ and a size of $2{\times}4\;mm^{2}$, which is supported by a surrounding frame. The NiCr heater is located at the center of the membrane vertically. Hot junctions of $48{\sim}156$ pairs of thermocouples (Cu-CuNi44) are located near or onto the heater, and cold junctions are located onto the silicon frame. Output of the thermal converters for 10 mA dc input was $76\;mV{\sim}382\;mV$ dependent on a model, and short term stability of the outputs was ${\pm}5{\sim}15\;ppm$/ 10 min with 5 mA dc input. Responsivity in air was in the range of $3.9{\sim}14.5V/W$. Responsivity of the model BF48 in air which has 48 thermocouples was 2 times or greater than that of 3 dimensional multi-junction thermal converter in vacuum which has 56 thermocouples. AC-DC transfer differences with an input of 10 mA or less were less than ${\pm}1\;ppm$ in the frequency range from 5 Hz to 2 kHz, and about $2{\sim}3\;ppm$ at 5 kHz and 10 kHz.

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.6
• /
• pp.658-665
• /
• 2014

Natural gas for marine diesel engine is considered as an important and clean source of energy because of simultaneously reducing the emission of NOx, SOx and GHG. Especially with a appearance of shale gas, the using of natural gas has been investigated aggressively and expected to expand rapidly. By the reports, gas engine and diesel engine were both in a similar performance in the power aspect, and the SFOC of gas engine was shown a little better than that of diesel engine. But the characteristics of exhaust gas emission were different according to various combustion technologies. And with lean burn technology, the emission of NOx could be reduced to 85% lower than that of diesel engine. In this paper, it was described that a simulation program has been developed to predict NOx emission. The developed program is adopted two-zone model and Wiebe function for combustion in cylinder. The effects of premixed and diffusive combustion could be simulated by using the excess air ratio as input data. And it was confirmed that the results of simulation were agreed with the general trends of exhaust gas emission according to various combustion conditions such as lean burn, premixed and diffusive combustion.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.12
• /
• pp.608-613
• /
• 2019

NOx (Nitrogen oxide) in the exhaust gas from vehicle engines is considered one of the most harmful substances in air pollution problems. NOx is made when combustion occurs under high temperature conditions and EGR (exhaust gas recirculation) is normally used to lower the combustion temperature. As the EGR ratio increases, the NOx level becomes low, but a high EGR ratio makes the combustion unstable and causes further air pollution problems, such as CO and unburned hydrocarbon level increase. This study showed that fuel droplets could move more freely by the radiation of sonic wave for the stable combustion. In addition, the engine performance improved with increasing EGR ratio. As a basic study, the effect of sonic wave radiation on the velocity of fuel droplets was studied using CFD software. The results showed that the velocity of small droplets increased more under high frequency sonic wave conditions and the velocity of the large droplets increased at low frequency sonic wave conditions. In addition, an engine analysis model was used to study the effects of the increased combustion stability. These results showed that a 15% increase in EGR ratio in combustion resulted in a 45% decrease in NOx and a 10% increase in thermal efficiency.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.35 no.6
• /
• pp.780-785
• /
• 2006

The composition analysis of various radish (Rapharnus sativus L.) leaves and the effects of drying condition on the quality characteristics of hot-air dried radish leaves were carried out by a response surface methodology. Independent variables put in drying temperature $(X_1)$ and drying time $(X_2)$, dependent variables put in color, calcium, iron, vitamin, etc. In the proximate composition of radish leaves by varieties, there were no significant differences in the ash, protein, lipid, calcium and iron content of samples, but there were significant differences in the vitamins, chlorophyll and color value of samples. The quality characteristics on dried radish leaves by central composite design, it was significant value on the moisture content, chlorophyll and color value according to drying temperature and drying times. But there were no significant differences in the contents of calcium $(31.41{\sim}35.80\;mg/g,\;dry\;base)$ and iron $(0.21{\sim}0.29\;mg/g\;dry\;base)$. The multiplex regression coefficients analysis were calculated with independent variables $(X_1,\;X_2)$ and dependent variables (moisture, chlorophyll, color value). The calculated coefficient correlations for the each samples were $R^2>0.97$. The effects of drying temperature were greater than drying time in the total chlorophyll content changes of radish leaves. Based on the present study, the optimum drying condition for the lowest color changes and effective reduction of moisture of radish leaves were expected to be $5{\sim}6$ hours at $70^{\circ}C$.

• Korean Journal of Food Science and Technology
• /
• v.36 no.6
• /
• pp.1020-1025
• /
• 2004

In previous paper, contaminations of food-borne pathogenic bacteria of Saengshik was found to occur during processing, because detection rates of food-borne pathogenic bacteria in final products were higher than those of raw materials. In this study, methods to reduce food-borne pathogenic bacteria and improved manufacturing process were developed for microbial safety of Saengshik. Food-borne pathogenic bacteria in raw materials were reduced to about 0.5-2.0 log cfu/g when seven kinds of raw materials were washed with electrolyzed water and ozonated water, but food-borne pathogenic bacteria could not be removed completely. After improvement of manufacturing process, numbers of food-borne pathogenic bacteria were same or decreased to levels of raw materials. Gaseous ozone and Biocon could control air-borne bacteria under $1{\times}10^1$ cfu/1000 L of air in pulverization and mixing rooms.