• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1389-1394
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• 2003

$CO_2$ is a well-known green house gas, which is the major source of global warming. Many researchers have studied to reduce $CO_2$ emission in combustion processes. Among the method for reducing $CO_2$ emission, oxygen-enriched combustion has been proposed. But the adiabatic flame temperature is too high. So existing facilities must be changed, or the adiabatic flame temperature in the combustion zone should be reduced. The combustion characteristics, composition in the flame zone, temperature profile and emission gases were studied experimentally for the various oxygen-enriched mtios(OER) by addition of $CO_2$ under coustant $O_2$ flowrate. Results showed that the reaction zone was quenched, broadened, as addition of $CO_2$ was increased. Temperature has a large effect on the NOx emission. The emission of NOx in flue gas decreased due to the decreased temperature of reaction zone. It was also shown that the reaction was delayed by the cooling effect. As the addition of $CO_2$ was increased, the composition of CO in the flame zone increased due to the increase of reaction rate by increasing mixing effect of oxidant/fuel at OER=0, but the composition of CO decreased by quenching effect at OER=50 and 100%.

• Korean Journal of Soil Science and Fertilizer
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• v.25 no.3
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• pp.242-248
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• 1992

This study was carried out to investigate the effects of root-zone temperature in hydroponics on the plant growth and nutrient uptake of lettuce(Lactuca sativa L), tomato (Lycopersicon esculentum Mill), and cucumber (Cucumis sativus L). Respiration rate in roots increased with increase in root-zone temperature. At $10^{\circ}C$ of root-zone temperature, respiration rate in lettuce root was higher than those in tomato and cucumber. Increasing rate of root respiration in tomato with increase in root-zone temperature was greater than those in lettuce and cucumber. The lowest dry weight and leaf area of the crops studied were obtained at $10^{\circ}C$ of root-zone temperature, but they were not different between 20 and $30^{\circ}C$. Increase in root-zone temperature generally resulted in increase in T/R ratio and net assimilation rate. At the low root-zone temperature, root growth and leaf area of tomato and cucumber were severely affected. Relative growth rates of lettuce and cucumber were also greatly reduced by the low root-zone temperature. Contents of N, P, K, Ca, and Mg in the crops increased as root-zone temperature increased from 10 to $20^{\circ}C$, whereas only Ca content in tomato and cucumber increased with increase in root-zone temperature to $30^{\circ}C$. Remarkably low contents of P and Mg in the crops were found at the low root-zone temperature. Inhibition of plant growth and nutrient uptake due to low root-zone temperature was much greater in cucumber than in lettuce and tomato.

• Journal of People, Plants, and Environment
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• v.24 no.5
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• pp.519-527
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• 2021

Background and objective: This study was conducted to establish a Plant Hardiness Zone (PHZ) map, investigate the effect of global warming on changes in PHZ, and elucidate the difference in the distribution of evergreen trees between the central and southern region within hardiness Zone 7b in Korea. Methods: Mean annual extreme minimum temperature (EMT) and related temperature fluctuation data for 40 years (1981 to 2020) in each of the meteorological observation points were extracted from the Open MET Data Portal of the Korea Meteorological Administration. Using EMT data from 60 meteorological observation points, PHZs were classified according to temperature range in the USDA Plant Hardiness Zone Map. Changes in PHZs for each decade related to the effects of global warming were analyzed. Temperature fluctuation before and after the day of EMT were analyzed for 4 areas of Seoul, Suwon, Suncheon, and Jinju falling under Zone 7b. For statistical analysis, descriptive statistics and ANOVA were performed using the IBM SPSS 22 Statistics software package. Results: Plant hardiness zones in Korea ranged from 6a to 9b. Over four decades, changes to warmer PHZ occurred in 10 areas, especially in colder ones. Based on the analysis of daily temperature fluctuation, the duration of sub-zero temperatures was at least 2 days in Seoul and Suwon, while daily maximum temperatures were above zero in Suncheon and Jinju before and after EMT day. Conclusion: It was found that the duration of sub-zero temperatures in a given area is an important factor affecting the distribution of evergreen trees in PHZ 7b.

• Journal of the Korean Society of Combustion
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• v.12 no.3
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• pp.24-32
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• 2007

A theoretical model was developed for rotary kiln and computational study was conducted to find the effect of feeding characteristics. One dimensional model with the variations of heating distribution, length of heating zone, excess air ratio and revolution was considered. The comparison of parallel-flow rotary kiln with that of counter-flow was conducted. For parallel-flow type, it is found that the variation of temperature of solid is not great for the zone that is following flame-heating zone. This zone is good to take the special treatment because thermal deviation is small and contacting time is enough for another treatment. Increase of excess air ratio have the effect of decreasing solid temperature. But this effect of decreasing solid temperature goes small for the great excess air ratio. The heating is efficient for the flame which has the maximum heating at the central region of the full length.

• Journal of the Korean Society of Tobacco Science
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• v.26 no.1
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• pp.50-56
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• 2004

The quality of burley leaf tobacco was affected by various toasting conditions. In this study, we determined main factor to influence the quality of burley tobacco on toasting and established proper toasting condition to improve the quality of toasted tobacco. Our results indicated that the main factor to influence the quality of burley tobacco was the amount of treatment and 3rd drying zone temperature. We also found that the proper toasting conditions to improve the quality of toasted tobacco and reduce the smoking irritation were moisture content (34 %), amount of treatment (1,520kg/hr), 1st drying zone temperature (135$^{\circ}C$), 2nd zone drying temperature(145$^{\circ}C$) and 3rd zone drying temperature (147$^{\circ}C$).

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1997.11a
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• pp.43-48
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• 1997

The smoke filling process for the atrium space containing a fire source is simulated using two types of deterministic fire modus: Zone model and Field model. The zone mode used is the CFAST(version 1.6) mode developed at the Building and Fire Research laboratories, NIST in the USA. The lied model is a self-developed fire field model based on Computational Fluid Dynamics(CFD) theories. This article is focused on finding out the smoke movement and temperature distribution in atrium space which is cubic in shape. A computational procedure for predicting velocity and temperature distribution in fro-induced flow is based on the solution, in finite volume method and non-staggered grid system, of 3-dimensional equations for the conservation of mass, momentum, energy, species and so forth. The fire model i. e. Zone model and Field model predicted similar results for Ire clear height and the smoke layer temperature.

• Journal of Korea Foundry Society
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• v.20 no.3
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• pp.197-207
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• 2000

Al-Si alloys were solidified in a rotating cylindrical mold by a vertical centrifugal casting process. Under a certain casting condition, there are four distinct zones such as the chill zone, the primary fine columnar zone, the equiaxed zone, and the secondary coarse columnar zone from the mold wall. The columnar-equiaxed transition (CET) and the equiaxed-columnar transition (ECT) were measured as functions of solute content, flow rate (mold velocity), pouring temperature and mold temperature. Within the critical value of solute content, as the flow rate increases, the columnar-equiaxed transition were found, but not the equiaxed-columnar transition. The aspect ratio of the primary columnar zone was more affected by the solute content than the flow rate. However the aspect ratio of the equiaxed zone was more affected by the flow rate than the solute content. The aspect ratio of the secondary columnar zone was affected by both the flow rate and the solute content.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05a
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• pp.6-8
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• 2004

The NdBaCuO superconductor samples were zone-melted in low oxygen partial pressure (1 % $O_2$＋99%Ar). The zone-melting temperature was decreased about 12$0^{\circ}C$ from 1, 06$0^{\circ}C$, the zone-melting temperature in air. Thus the loss of liquid phase (BaCu $O_2$and CuO) was reduced during the zone-melting process. The content of non-superconducting phase Nd422 in zone-melted NdBaCuO samples was clearly decreased and, therefore, the substitution of Nd for Ba was occurred. The superconductivity of zone-melted N $d_{1＋x}$B $a_{2－x}$C $u_3$ $O_{y}$prepared under low oxygen partial pressure was distinctively improved.d.d.d.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.146-153
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• 1997

An experimental study was performed of natural-convection downward smolder spread across a sawdust bed peripherally enclosed with an insulating container, to examine the effect of the open- ing condition at the top end on downward smolder spread. Experiments were conducted by using relatively coarse sawdust and 25-cm-long cylindrical container The variations of temperature profiles along the bed axis with time were determined far different opening conditions and were com-pared with those in smolder spread from open top to open bottom. It was shown that the smolder zone initiated from open top toward closed bottom penetrates the bed with keeping high peak temperature like the case of open top to open bottom spread, although mean spread rate is smaller. This indicates that the downward smolder zone can be sustained stably if sufficient air or oxygen Is supplied from the back of it by natural convection even if upward draft entering from the bottom of the bed is absent. When the top end was partially closed by mounting a cover after stable smolder spread had begun from open top toward open bottom, the temperature at the peak decreased more than 200 K and the smolder zone became to spread with thickening residue. In this case, the shape of temperature profiles continuously changed or decayed until end-effect at the open bottom end enhanced the reaction. The temperature at the shrunk peak, free from the end-effect, was almost identical with the temperature at the exothermic oxidative-degradation zone in smolder spread from open top to open bottom. from these results, it can be inferred for natural-convection downward smolder spread that the oxidation reaction of the char is very sensitive to the oxygen supply by natural convection in the space above the smolder zone, and that the top end opening condition strongly alters the completeness of reactions, structure, and behavior of the smolder zone.

• Polymer(Korea)
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• v.29 no.6
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• pp.549-556
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• 2005

Effects of the dimensionless variables on the heat transport phenomena in the extrusion process of a single screw extruder have been studied numerically. Based on the understanding of the solids conveying related to the geometrical structure and characteristics of the screw, the heat balance equation for the solids conveying zone was established and normalized. The finite volume method and power-law scheme were applied to derive a discretized equation and the equation was solved using the alternating direction iterative method with relaxation. Effects of the dimensionless parameters, Biot and Peclet numbers, that define the heat transfer characteristics of the solids conveying zone have been investigated with respect to the temperature of the feeding zone and the length of the solids conveying zone. As the Biot number is increased, the heat loss by cooling dominates to decrease the temperature of the barrel but it has little effects on the temperature of the solids bed and the length of the solids conveying zone. On the other hand, if the Peclet number is increased, the convection term dominates to decrease the temperature of the solids bed and it results in an increase in the length of the solids conveying zone.