• Journal of the Korean Ceramic Society
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• v.32 no.3
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• pp.331-340
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• 1995

Microwave (Hybrid) Heating (MHH) was used to oxidize and sinter Al-Al2O3 powder mixture. For 25 v/o Al specimen and 35 v/o Al specimen, the total processing to produce low-shrinkage reaction bonded alumina was carried out within 1 hour even though conventional furnace process took more than 10 hours. Compared with conventional fast firing process, MHH process increased more than 40% oxidation at the same temperature, and these high oxidation rates were thought to be caused by the surface ohmic current on Al particles.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1897-1902
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• 2003

An 1/21.6 scaled experimental facility was prepared utilizing the results of a scaling analysis to simulate the APRI400 reactor and insulation system. The behaviors of the boiling-induced two-phase natural circulation flow in the insulation gap were observed, and the liquid mass flow rates driven by natural circulation loop were measured by varying the wall heat flux, upper exit slot area and configuration. And non-heating experiments have also been performed and discussed to certify the hydraulic similarity of the heating experiments by injecting air equivalent to the steam generated in the heating experimental condition.

• Journal of Powder Materials
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• v.7 no.2
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• pp.93-101
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• 2000

In order to clarify the enhanced sintering behavior of nanostructured(NS) W-Cu powder prepared by mechaincal alloying, the sintering behavior during heating stage was analysed by a dilatometry with various heating rates. The sintering of NS W-Cu powders was characterized by the densification of two stages, having two peaks in shrinkage rate curves. The temperature at which the first peak appear was much lower than Cu melting point, and dependent on heating rate. On the basis of the shrinkage rate curves and the microstructural observation, the coupling effect of nanocrystalline W-grain growth and the liquid-like behavior of Cu phase was suggested as a possible mechanism for the enhanced sintering of NS W-Cu powder in the state.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.53-54
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• 2015

This study is conducted to investigate the characteristics of cracks depending on the different mixture rates of calcium hydroxide and distilled water in high-strength concrete, which is substituted with a high percentage of blast-furnace slag, by using specimens produced under different heating temperatures: 600℃, 800℃, and 1000℃, respectively. According to the results of the study, the specimen heated under the temperature of 600℃ did not produce cracks; the specimen heated under 800℃ produced little cracks and showed no difference between calcium hydroxide and distilled water; whereas the specimen heated under 1000℃ produced cracks larger than 5mm on average in the case of calcium hydroxide, compared to distilled water.

• Nuclear Engineering and Technology
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• v.53 no.2
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• pp.474-483
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• 2021

To establish the exclusive role of hydrogen on burst behaviour of Zircaloy-4 during loss-of-coolant accident transients, an extensive single-rod burst tests were conducted on both unirradiated as-received and hydrogenated Zircaloy-4 cladding tubes at different heating rates and internal overpressures. The visual observations of cladding tubes during bursting as well as post-burst are presented in detail to understand the effect of hydrogen concentration, heating rate, and internal pressure. Impact of hydrogen on burst parameters-burst stress, burst strain, burst temperature-during loss-of-coolant accident transients are compared and discussed. Rupture at multiple locations for hydrogenated cladding at lower internal pressure and higher heating rate is reported for the very first time. A novel burst criterion accounting hydrogen concentration in nuclear fuel cladding is proposed.

• Journal of Biosystems Engineering
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• v.8 no.2
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• pp.39-48
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• 1983

This study was performed to obtain the basic data which could be used for the modification of the manual center-burner-type rice-husk furnace into a small scale automatic type for the multi-purpose use in the farm. For this purpose, first, the utilization feasibility of the rice-husk furnace in the farm was analyzed briefly in aspects of available amount of rice-husk for the fuel, annual operation time and replaceble amount of residential heating energy with rice-husk in the farm. For the experiment a prototype furnace geared with an automatic feeding device was fabricated, and feed rate, mold size and chimney height were changed to investigate the combustion efficiency of rice-husk and thermal efficiency of the furnace. Also, optimum and limiting operational factors were observed in each treatments. The results obtained are summarized as follows. 1. If the rice-husk is intensively used for residential heating in the farm for winter season, on an average 51 percent of the total heating energy can be replaced with the rice-husk. Therefore, development of a small scale automatic rice-husk furnace was recognized to be feasible. 2. The operational condition depending on husk-feed rates was very important factor for successive steady burning operation of the given furnace. When the feed-rate was 1.5 kg/hr, the top of the burning zone should be kept at the position about 55 cm from the bottom of the combustion chamber with the periodic removal of ash (termed as steady state position), which was 18 cm above the mold waist. When the feed rates were 2.4 kg/hr and 3.0 kg/hr, the steady state position was at about 4 cm above the mold waist. 3. The mold size affected inflow rate of air into the furnace and consequently CO content in the exhaust gas. The relatively bigger mold gave positive effect on the air-inflow rate. 4. When the husk-feed rates were 1.5 kg/hr, 2.4 kg/hr, 3.0 kg/hr, the combustion efficiencies of the rice-husk were 98.5%, 97.4% and 95.0%, the thermal efficiencies of the furnace were 93.4%, 93.2% and 87.6%, and CO content in the exhaust gas were 1.21%, 1.03%, and 2.43%, respectively. The air-inflow rates were decreased with the increase of feed rates. When the amount of excess air was 30-40%, the CO content in the exhaust gas was at the minimum level. 5. When the chimney height was lowered from 260 cm to 96 cm, the air-inflow rate was slightly decreased, but the average temperature in the combustion chamber, CO content in the exhaust gas and combustion and thermal efficiencies were not changed significantly. 6. The incidental problems associated with the protytype furnace were accumulation of the ash inside the mold, accumulation of the cinder between the outer-drum of the furnace and the combustion chamber wall, and accumulation of the cinder in the chimney.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.121-128
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• 2009

During a hypothetical high-pressure accident in a nuclear power plant (NPP), molten corium can be ejected through a breach of a reactor pressure vessel (RPV) and dispersed by a following jet of a high-pressure steam in the RPV. The dispersed corium is fragmented into smaller droplets in a reactor cavity of the NPP by the steam jet and released into other compartments of the NPP by a overpressure in the cavity. The fragments of the corium transfer thermal energy to the ambient air in the containment or interact chemically with steam and generate hydrogen which may be burnt in the containment. The thermal loads from the ejected molten corium on the containment which is called direct containment heating (DCH) can threaten the integrity of the containment. DCH in a NPP containment is related to many physical phenomena such as multi-phase hydrodynamics, thermodynamics and chemical process. In the evaluation of the DCH load, the melt dispersion rates depending on the RPV pressure are the most important parameter. Mostly, DCH was evaluated by using lumped-analysis codes with some correlations obtained from experiments for the dispersion rates. In this study, MC3D code was used to evaluate the dispersion rates in the APR1400 NPP during the high-pressure accidents. MC3D is a two-phase analysis code based on Eulerian four-fields for melt jet, melt droplets, gas and water. The dispersion rates of the corium melt depending on the RPV pressure were obtained from the MC3D analyses and the values specific to the APR1400 cavity geometry were compared to a currently available correlation.

• Journal of Welding and Joining
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• v.34 no.2
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• pp.46-53
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• 2016

Effect of heating rate on microstructure of brazed joints with STS 304 Printed Circuit Heat Exchanger (PCHE),which was manufactured as large-scale($1170(L){\times}520(W)){\times}100(T)$, mm), have been studied to compare bonding phenomenon. The specimens using MBF 20 was bonded at $1080^{\circ}C$ for 1hr with $0.38^{\circ}C/min$ and $20^{\circ}C/min$ heating rate, respectively. In case of a heating rate of $20^{\circ}C/min$, overflow of filler metal was observed at the edge of a brazed joints showing the height of filler metal was decreased from $100{\mu}m$ to $68{\mu}m$. At the center of the joints, CrB and high Ni contents of ${\gamma}$-Ni was existed. For the joints brazed at a heating rate of $0.38^{\circ}C/min$, the height of filler was decreased from $100{\mu}m$ to $86{\mu}m$ showing the overflow of filler was not appeared. At the center of the joints, only ${\gamma}$-Ni was detected gradating the Ni contents from center. This phenomenon was driven from a diffusion amount of Boron in filler metal. With a fast heating rate $20^{\circ}C/min$, diffusion amount of B was so small that liquid state of filler metal and base metal were reacted. But, for a slow heating rate $0.38^{\circ}C/min$, solid state of filler metal due to low diffusion amount of B reacted with base metal as a solid diffusion bonding.

• The Journal of Advanced Prosthodontics
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• v.11 no.4
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• pp.202-208
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• 2019

PURPOSE. Fabrication of zirconia restorations with ideal mechanical properties in a short period is a great challenge for clinicians. The purpose of the study was to investigate the effect of heating rate on the mechanical and microstructural properties of monolithic zirconia. MATERIALS AND METHODS. Forty monolithic zirconia specimens were prepared from presintered monolithic zirconia blanks. All specimens were then assigned to 4 groups according to heating rate as Control, Group $15^{\circ}C$, Group $20^{\circ}C$, and Group $40^{\circ}C$. All groups were sintered according to heating rates with the sintering temperature of $1500^{\circ}C$, a holding time of 90 minutes and natural cooling. The phase composition was examined by XRD analysis, three-point bending test was conducted to examine the flexural strength, and Weibull analysis was conducted to determine weibull modulus and characteristic strength. Average grain sizes were determined by SEM analysis. One-way ANOVA test was performed at a significance level of 0.05. RESULTS. Only tetragonal phase characteristic peaks were determined on the surface of analyzed specimens. Differences among the average grain sizes of the groups were not statistically significant. The results of the three-point bending test revealed no significant differences among the flexural strength of the groups (P>.05). Weibull modulus of groups was ranging from 3.50 to 4.74. The highest and the lowest characteristic strength values were obtained in Group $20^{\circ}C$ and Control Group, respectively. CONCLUSION. Heating rate has no significant effect on the flexural strength of monolithic zirconia. Monolithic zirconia restorations can be produced in shorter sintering periods without affecting the flexural strength by modifying the heating rate.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.3
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• pp.81-90
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• 1993

Groundwater and animal wastes are typical example which are underutilized resources than their value in agriculture. This paper was to investigate the actual patterns of utilization of water curtain for greenhouses and methane gas utilization from swine wastes in a view point of promoting more efficient use of alternative energy. The results from measurements can be summarized as follows : 1.It was estimated that the maximum heating load per l0a was around 23,2804/hr and the heating load at January showed 3.93X 1064 respectively for strawberry greenhouses with insulation by the water curtain. 2.The average heating cost of the greenhouse with water curtain system amounted to about 75,000 Won per l0a. This result suggested that the greater cultivated area provides less heating cost. 3.The operating volume was about 73 percent of the optimum size of the digester. The net available methane gas rates of the produced gas remained close to 62 percent, But the conventional and small size of the digester was maintained at a lower level of around 20 to 29 percent. 4.It appeared that major problems of biogas production system were required to maintain the temperature of the fermentation above ambient temperature and the optimum volume of digester.