• 설비공학논문집
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• 제17권4호
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• pp.370-376
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• 2005

For the purpose of investigating the effective removal of heating/cooling load from light-weighted building envelope, two air-conditioning systems, conventional parameter air-conditioning system and air-barrier system, are evaluated and compared by both experiment and simulation with six different cases during heating and cooling season. In addition, the characteristics of window-side building thermal load are assessed by varying supply air velocity in order to seek the optimal system operation condition. The results are as follows. 1) Air-barrier system is more effective to remove heating/cooling load at perimeter zone than conventional parameter air-conditioning system. Moreover, the better effectiveness appears during cooling season than during heating season. 2) The experiment during cooling season provides that indoor temperature of air-barrier system shows $1^{\circ}C$ less than that of the conventional system with similar outdoor air temperature profile, and indoor temperature distribution is more uniform throughout the experimented model space. It concludes that air-barrier system can achieve energy saving comparing to the conventional system. 3) The capturing efficiency of air-barrier system is 0.47 on heating season and 0.2 on cooling season with the same supply air volume. It results that the system performs effectively to remove building thermal load, moreover demonstrates high efficiency during cooling season. 4) The simulation results provide that capturing efficiency to evaluate the effective removal of building load from perimeter zone shows high value when supply air velocity is 1 m/s.

• 수산해양교육연구
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• 제19권1호
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• pp.84-90
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• 2007

This paper was studied on the electrochemical corrosion characteristics of weld zone for refrigerating and heating systems pipe. Austenitic stainless steel is widely applied to various fields of industry, because it is good to corrosion resistance and mechanical properties. But STS 304 is reliable to sensitization by heat cycle on welding. Therefore, in this study, electrochemical polarization test of STS 304 steel pipe manufactured by arc welding in tap water was carried out. And then polarization resistance behavior, uniform and local corrosion behaviors of base metal(BM), weld metal(WM) and heat affected zone(HAZ) for STS 304 pipe were investigated. The corrosion current density of STS 304 steel pipe is high in order of BM(153nA/cm2) < WM(614nA/cm2) < HAZ ($1.675{\mu}A/cm2$). The pitting potential of HAZ(238mV/SCE) for STS 304 is lower than BM(1206mV/SCE) and WM(369mV/SCE). Therefore, the local corrosion like pitting corrosion, galvanic corrosion and crevice corrosion of HAZ for STS 304 is more sensitive than BM and WM.

• International Journal of Air-Conditioning and Refrigeration
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• 제12권2호
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• pp.108-112
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• 2004

The purpose of this study is to investigate the characteristics of thermal comfort index and to present the thermal comfort range through regression analyses and experiment in a radiant floor heating system laboratory. The results were compared to the comfort zone of ISO-7730, and the applicability of the thermal comfort index to a radiant floor heating system was studied. On comparing the sedentary posture on the floor to sitting on the chair, the comfort zone and the neutral point of comfort index showed different values. It is considered that the influence of conduction from floor to the human is sufficient. Moreover, we could find a correlation between the thermal sensation votes of subjects, and the comfort indexes were lower than those by calculation.

• 원예과학기술지
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• 제28권5호
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• pp.783-789
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• 2010

저온기 토마토 펄라이트 자루재배에서 근권의 가온이 작물의 생육과 수확량, 경제성에 미치는 영향을 알아보고, 효과적인 저온기 근권온도 조절방법을 구명하고자 본 연구를 수행하였다. 저온기 동안에 근권의 가온시각과 가온기간 처리를 각각 저온기 일출시간(7시 30분)을 기준으로 일출 전후 1시간씩 2시간 가온처리, 일출 전후 2시간씩 4시간씩 4시간 가온처리, 일몰 후부터 15시간 가온처리 및 무가온 처리를 두어 실험하였다. 근권온도 처리 간에는 무가온 처리(NON)에서 근권온도가 실험기간 동안 주간과 야간 모두 가장 낮았고, 야간의 온도 하강이 주간의 온도에까지 영향을 미침을 알 수 있었다. 일출 전후 2시간씩 4시간 가온처리에서 근권온도가 일출 전후 1시간씩 2시간 가온처리보다 1시간 먼저 상승하고, 하강도 늦었으며 전체 실험기간 동안의 평균 온도도 약간 높게 유지되었다. 처리구 중에서 가장 가온시간이 길었던 일몰 후부터 15시간 가온처리에서는 전 실험기간동안 $19-23^{\circ}C$ 정도에서 가장 높은 근권온도로 유지되었다. 지상부 생육조사에서는 처리간 차이가 미미하여 통계적 유의성이 없었으나, 뿌리생육은 근권온도가 높게 지속될수록 뿌리 량이 많았고, 뿌리의 분포는 전실험구에서 균일하였다. 식물생육지표에 의해 실험기간 동안 작물의 화방별 수확과 생장양상의 변화 사이에 상관관계가 있음을 알수 있었다. 일몰 후부터 15시간 가온처리와 일출 전후 2시간씩 4시간 가온처리가 동일하게 토마토의 생육 및 수확량에서 가장 좋았기 때문에 가온을 위한 비용을 고려한다면 일출 전후 2시간씩 4시간 가온처리가 가장 좋을 것으로 사료된다.

• 열처리공학회지
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• 제25권3호
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• pp.126-133
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• 2012

Semi-solid forming of the high melting point alloys such as steel is a promising near-net shape forming process for decreasing manufacturing costs and increasing the quality of the final products. This paper presents the microstructure characteristics of SKH51 (high speed tool steel) during heating and holding in the mushy zone between $1233^{\circ}C$ and $1453^{\circ}C$, which has been measured by differential scanning calorimetry (DSC). The results of heating/holding experiments showed that the grain size and the liquid fraction increased gradually with temperature up to $1350^{\circ}C$. The drastic grain growth occurred at heating above $1380^{\circ}C$. The strain-induced melt-activated (SIMA) process has been applied to obtain globular grains in the billet materials. Working by mechanical upsetting and successive heating of SKH51 into the temperatures in the mushy zone resulted in globular grains due to recrystallization and partial melting.

• 한국농공학회지
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• 제19권3호
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• pp.4483-4491
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• 1977

The results obtained are as follows; 1. The variation of the temperature in a vinyl house without heating system is similar to that of air temperature in a day. The difference of maximum temperature and minimum one in a day is 27$^{\circ}C$ which is two times greater than the daily difference of air temperature. 2. When the length of the duct is increased, the high temperature zone is built up in the direction of warm air discharge from the duct, and the low temperature zone is built up in the opposite direction of warm air discharge. But, in case of the duct length is short (0.05 L), the temperature distrubution in a vinyl house become uniform. It is concluded that the shorter length of the duct, the better the distribution of the temperature in a vinyl house is. 3. When the duct is installed at high position, the high temperature zone is built up in the upper zone of the vinyl house and the low temperature zone is built up in the lower zone. And when the position of the duct is low, the rate of temperature variation along the vertical direction become high, and the direct contact of warm air with the plant in the house is occured. It is concluded that the duct should be installed at the position of slightly higher than the plant height. 4. When the fuel consumption rate is fixed at the 101/hr, the lowest temperature warming rate in the vinyl house is 5$^{\circ}C$ without regard to the air temperature.

• 한국연초학회지
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• 제3권2호
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• pp.89-93
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• 1981

Some or the parameters affecting the thermal analysis of different types of ground tobacco have been discussed. The sample, Korean flue- cured and burley and Greek orient tobacco leaves were run in air at heating rate of $10^{\circ}$ and 20^{\circ}C$ per minute. The thermograms obtained were divided into four temperature zones. The effect of different heating rates on thermal degradation has been discussed At the lower heating rate the maxima of DTA curves in zone 3 and 4 were 25-$40^{\circ}C$ lower than that of the higher heating rate.

• 설비공학논문집
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• 제22권3호
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• pp.123-129
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• 2010

The district heating users can be generally classified into two groups such as apartments and buildings. In consideration that the time zone of the maximum heat load for apartments is different from those of buildings during a day, the maximum heat supply range is presented. In case of the investigated area, the maximum heat supply is occurred at the ratio between apartments and buildings that is 65%：35%. Thus the heat supply range is increased as much as 15% if the time zone when the maximum heat load is occurred is considered.

• 한국정밀공학회지
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• 제11권2호
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• pp.173-181
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• 1994

A Cold spot temperature control system for the batch annealing furnace has been estabilished in order to reduce energy consumption to improve productivity and stabilize the propertics of products. Therefore we confirmed a relation between annealing cycle time and atmospheric gas, variation of coil cold spot temperature with time during heating and actual temperature measurements at mid-width of each coil during heating and actual temperature measurements at mid-width of each coil during soaking. The results of the tempaeature variation effect on the batch annealing are as follows. 1) Heating time is reduced to one half with increasing atmospheric gas flow rate and changing of atmospheric gas component from HNx to Ax gas, and annealing cycle time is reduced to 2.7 times. 2) In case of short time healing, the slowest heating part is the center of B coil, in case of long time heating, the low temperature point moves from the center of coil to inside coil. And the temperature in this part is higher than other parts when cooling. When finished heating, the cold spot is located 1/3 of coil inside in case of HNx atmospheric gas. But center of coil in case of Ax atmospheric gas. 3) The outside of top coil is the highest temperature point when heating, which becomes the lowest temperature point when cooling. So, this point becomes high temperature zone at heating and low temperature zone at cooling, It has relation according to atmospheric gas component and flow rate. 4) Soaking time at batch annealing cycle determination is made a decision by the input coil width, and soaking time for quality homogenization of 1214mm width coil must be 2.5 hours longer than that of 914mm width coil for the same ciol weight. 5) Annealing cycle time with Ax atmospheric gas is extended 1 hour in of slow cooling during 5 hours in order to avoid rapid cooling.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.213-216
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• 2006

During the last decade several different methods have been proposed for the estimation of thermal deformations in the line heating process. These are mainly based on the assumption of residual strains in the heat-affected zone or simulated relations between heating conditions and residual deformations. However these results were restricted in the application from the too simplified heating conditions or the shortage of the data. The purpose of this paper is to develop a simulator of thermal deformation in the line heating using the artificial neural network. Two neural network predicting the maximum temperature and deformations at the heating line are studied. Deformation data from the line heating experiments are used for learning data for the network. It was observed that thermal deformation predicted by the neural network correlate well with the experimental result.