• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.12
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• pp.1582-1590
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• 2004

The purpose of this study is to show the existence of optimal operation conditions for minimum fuel consumption of the gas turbine based combined cycle cogeneration power plant. Optimal operational condition means the optimal distribution of the power generated by each gas turbine and the heat generated by each HRSG. Total fuel consumption is calculated by the sum of the fuels for gas turbines and supplementary boiler. Fuel consumption is calculated by numerical methods of energy equations which contain the power generated from gas and steam turbines, the heat generated by HRSG and the heat extracted from high pressure steam turbine.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.5
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• pp.670-679
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• 1998

The solution of hyperbolic equation with wave nature has sharp discontinuties in the medium at the wave front. Difficulties encounted in the numrtical solution of such problem in clude among oth-ers numerical oscillation and the representation of sharp discontinuities with good resolution at the wave front. In this work inviscid Burgers equation and modified heat conduction equation is intro-duced as hyperboic equation. These equations are caculated by numerical methods(explicit method MacCormack method Total Variation Diminishing(TVD) method) along various Courant numbers and numerical solutions are compared with the exact analytic solution. For inviscid Burgers equa-tion TVD method remains stable and produces high resolution at sharp wave front but for modified heat Conduction equation MacCormack method is recommmanded as numerical technique.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.11 s.242
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• pp.1257-1264
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• 2005

An inverse problem to determine two-dimensional total heat exchange factor is studied for the prediction of the slab temperature in the reheating furnace. Temperature measurements by the experiment are used in the inverse analysis. This inverse analysis employs the conjugate gradient method. The overall heat absorptances for 12-zones of the cross-section of the slab are estimated. The estimated temperatures at measurement locations are in good agreements with the measured temperatures.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.103-111
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• 2001

In the present study, the internal combustion engine tends to high performance, fuel economy, small-sized. Therefore, it is necessary to solve the problems on thermal load, abnormal combustion, etc in the engine. Thin film instantaneous temperature probe was made, and the measuring system was established. The instantaneous surface temperatures in the constant volume combustion chamber were measured with this system and the heat flux was obtained by Fourier analysis. Maximum instantaneous temperatures were obtained after 55∼60ms from ignition and they increased as equivalence ratio and varied differently as the position of probe. Total heat loss during combustion time was affected by the equivalence ratio and differed widely as the position of probe.

• Journal of the Korean Society for Heat Treatment
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• v.10 no.4
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• pp.232-236
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• 1997

A rectangular type circulating fluidized bed (CFB) with an internal nozzle and two partition walls was proposed. In this modified CFB, an internal nozzle and two slanted partition walls were additionally set in the riser. This cold mode apparatus was made of acrylic resin; the riser was 1500mm high and $1000{\times}1000mm^2$ in the cross sectional area, the internal nozzle was 200mm high and 10mm in the inner diameter, and the partition wall was 7mm thick. Glass beads of $91{\mu}m$ in the mean diameter were employed as bed materials. In the cold mode by using the proposed CFB with an internal nozzle, it was possible to change the particle hold up by changing the gas flow ratio of the nozzle to the total(Qn/Qt). It was found that the inflection point which devided the bed structure between the dense and the dilute phase in the riser varied with Qn/Qt.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.5
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• pp.397-405
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• 2003

Heat and fluid flow in a compressor into which liquid refrigerant is injected for the purpose of reducing discharge gas temperature in a heat pump system has been numerically studied. A mechanistic approach encompassing liquid jet breakup and droplet evaporation has been performed to investigate the effects of liquid injection on the spacial and temporal variation of the gas temperature and pressure inside the compressor cylinder. Various parameters, such as liquid injection mass, time, duration and droplet size, are considered in the present study to elucidate the flow field inside the compressor. As the injection mass is increased, discharge gas temperature is decreased, while the pressure is increased due to the added mass of the injection. For the injected liquid mass corresponding to 15% of the total vapor mass in the cylinder, the discharge gas temperature drops by 22.4 K. It is observed that the droplet size plays a major role in the evaporation rate of the droplets that determines the degree of the discharge temperature drop.

• Journal of the East Asian Society of Dietary Life
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• v.4 no.1
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• pp.95-104
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• 1994

This study was carried out to investigate the effect of sub-atmosphere on the fermentation and heat treatment after fermentation of Kimchi. When the results from the conditions of atmosphere and under-atmosphere were compared, the growth of lactic acid bacteria was increased but the growth of aerobic bacteria was decreased under 560mmHg and 360mmHg. The number of total microorganism was decreased and simultaneously damaged to the tissue of Kimchi under 0mmHg. Kimchi fermented under 560mmHg and 360mmHg had longer storage duration than that of atmosphere. Among the several conditions, the result of heat treatment under 460-260mmHg was the best. the treatment for 4 minutes at 80$^{\circ}C$, 2 minutes at 100$^{\circ}C$, and 1 minute at 120$^{\circ}C$ was good in tissue states and storage.

• Journal of the Korean Home Economics Association
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• v.23 no.2
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• pp.29-36
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• 1985

This experiment was conducted to investigate changes of the components in steamed and roasted green tea after 10 min, 20 min and 30 min of heat treatment of heat treatment at $110^{\circ}C$. Vitamin C and tannin were determined by spetrophotometry. Total nitrogen, water-soluble nitrogen and water-soluble non protein nitrogen were determined by Kjeldahl analysis system. Aromas were identified by gas chromatography. After heat treatment, contents of most compounds decreased. Tannin and caffeine decreased a little bit, while vitamin C decreased considerably. There were both decreases and increases in aromas. Aromas which increased were geraniol, trans-2-hexenol, linalool, $\alpha$-ionone and $\beta$-ionone. From these results, it was concluded that the highest quality of green tea was one steam- treated for 10 min at $110^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1437-1443
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• 2003

Most optimization problems do not consider tolerance of design variables and design parameters. Ignorance of these tolerances may not fit for the practical problems and can lead to an unexpected conclusion. That is why we suggest robust optimization considering tolerances in both design variables and problem parameters. Using robust optimization, we designed minimum weight annular finned heat transfer tube subject to constraints on limitation of pressure difference and minimum value of total heat transfer. Consequently, robust optimization satisfies tolerance considered practical problems.

• International Journal of Automotive Technology
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• v.6 no.2
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• pp.79-85
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• 2005

This work is to investigate the surface heat flux and combustion characteristics of premixed propane mixture in a constant volume chamber. The experiment of heat flux and combustion characteristics of premixed propane mixture are performed with various equivalence ratio and initial pressure conditions. Based on the experimental results, it is found that the maximum instantaneous temperature is increased with the increase of initial pressure in the chamber. There are significant differences in the burning velocity of premixed propane mixture at different measuring points in the constant volume combustion chamber. A]so, the trends of temperature difference at each measuring points are similar to the burning velocity in the combustion chamber. It is concluded that the total heat loss during the combustion period is affected by the equivalence ratio and the initial condition of fuel-air mixture.