경질 폴리우레탄폼의 착화성 및 열방출특성 연구

공영건,이두형 한국화재소방학회 2003 한국화재소방학회논문지 Vol.17 No.4

본 연구에서는 Setchkin 착화성시험장치와 산소소비원리를 이용한 콘칼로리미터를 사용하여 난연처리되지 않은 경질우레탄폼의 착화특성 및 열방출특성 및 플래쉬오버 가능성에 대하여 연구하였다. 연구결과 경질폴리우레탄폼의 유도발화온도(FIT)는 <TEX>$383^{\circ}C$</TEX>∼<TEX>$390^{\circ}C$</TEX>, 자연발화온도(SIT)는 <TEX>$493^{\circ}C$</TEX>∼<TEX>$495^{\circ}C$</TEX>로 나타났으며 자연발화온도가 유도발화온도에 비해 약 <TEX>$100^{\circ}C$</TEX> 높게 나타났다. 콘칼로리미터실험에서는 착화시간은 heat flux의 크기가 증가할수록 빨라졌으며 동일한 heat flux 크기에서는 밀도가 작을수록 착화시간은 짧게 나타났다. 열방출율은 <TEX>$50 ㎾\m^2$</TEX>에서 가장 크게 나타났으며, 최대열방출율의 경우 heat flux의 크기와 밀도가 커질수록 증가하는 경향을 보였다. 착화시간과 열방출율의 관점에서 경질폴리우레탄폼의 화재성능은 가해진 heat flux의 크기와 밀도에 큰 영향을 받는 것으로 나타났으며, Petrella의 제안방법에 의해 플래쉬오버 가능성을 분류한 결과 플래쉬오버 가능성이 큰 것으로 분류되었다. In this study; the ignition and heat release rate characteristics of rigid polyurethane foam were investigated in accordance with setchkin ignition tester and cone calorimeter which is using oxygen consumption principle. In the ignition temperature study; flash-ignition temperature was <TEX>$383^{\circ}C$</TEX>-<TEX>$390^{\circ}C$</TEX>, self-ignition temperature was<TEX>$ 493^{\circ}C$</TEX>∼495<TEX>$^{\circ}C$</TEX>. The self-ignition temperature of rigid polyurethane foam was about <TEX>$100^{\circ}C$</TEX> higher than the flash-ignition temperature. In the cone calorimeter study, the time to ignition of rigid polyurethane foam was faster as the external heat flux increase. In the same heat flux level, the time to ignition was faster as the density of rigid polyurethane foam decrease. Also the heat release rate was the largest value at the heat flux of /<TEX>$50 ㎾\m^2$</TEX> and had a tendency of increase as the heat flux level and density increase. In the standpoint of time to ignition and heat release rate, the fire performance of rigid polyurethane foam was influenced by the applied heat flux level and density and the flashover propensity classified by Petrella's proposal was high.

응축기 순환수 압력에 따른 스팀 생산 히트펌프의 성능에 관한 연구

강대훈(Dae Hoon Kang),나선익(Sun-Ik Na),김민수(Min Soo Kim) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12

A steam generation heat pump cycle is an effective method for utilizing waste heat and supplying steam to industrial processes. The boiling water is fed into a plate heat exchanger and circulated to a flash tank to generate steam. Unlike conventional hot water generation heat pump, steam generation involves a large volumetric change and therefore requires a flash tank. Optimal control of flash tank affects the performance of the system and steam generation rate. In this study, the condenser outlet pressure and mass flow rate of water was controlled by a valve to compare the steam generation rate. When the same condensing pump power is used, the higher outlet pressure makes the higher condensation heat. This also increased the system COP and the steam generation rate.

Application of Flash Lamp Annealing on Nitrogen-Doped Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistors

Kim, Yoonsuk,Kim, Jinsoo,Kim, Byungkuk,Kim, Hyoung June,Kim, Seok,Choi, Eunsoo,Hwang, Jin-Ha,Park, Seungho Electrochemical Society 2017 ECS journal of solid state science and technology Vol.6 No.12

<P>Amorphous nitrogenated indium-gallium-zinc oxide (a-IGZO:N) thin films were deposited on highly doped silicon (n+Si) wafer substrates and heat-treated by millisecond flash lamp annealing (FLA) at different preheating temperatures to enhance the electrical characteristics of oxynitride thin film transistors (TFTs). A one-dimensional conduction/radiation heat transfer simulation was conducted to predict the temperature fields in the Si substrate, which indicated that the film temperatures during FLA instantaneously rose above 700°C. The electrical characteristics of the a-IGZO:N TFTs were compared with those produced by conventional furnace annealing of one hour. As a result of the FLA process, a remarkable improvement in the TFT device performance was observed in terms of the electrical output characteristics and transfer curves of the a-IGZO:N TFTs. Morphological analyses were conducted using X-ray diffraction, atomic force microscopy, and field emission scanning electron microscopy, indicating the possibility of partial crystallization of the a-IGZO:N channel layers under high-temperature annealing conditions, but the best TFT performance was found for the amorphous phase of IGZO:N.</P>

An Experimental Study on Atomization Characteristics of Flash-boiling Swirl Spray Injected into Heated Convective Cross-flow for Urea-SCR system application

Hao Han,Woong Sup Yoon,Kwang Min Chun 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11

Urea-SCR, the selective catalytic reduction using urea as reducing agent, has been the most promising way to diminish NOx emissions originating from heavy duty vehicles. However, one of the shortcomings of Urea-SCR is NOx reduction performance degradation at low exhaust gas temperatures on account of ammonia slip and ammonia deposition. Therefore, in the present study, a new type of injection method is suggested which overcomes the shortcoming. The flashboiling atomization is one of the best means that improve the spray characteristics as finer droplets, shorter spray breakup length, and better distribution for enhancing the mixing of urea with exhaust gases. When liquid sheet is subjected to sufficient superheating (boiling) or pressure reduction (cavitation), it becomes formed bubbles. The subsequent growth of the bubbles drives the atomization process. In this experiment study, the injection temperature (dimensionless superheat degree) and crossflow temperature were varied. A high-speed photography technique and a laser-based optical technique (GSV, TSI Inc.) were used to characterize the breakup pattern and spray quality at the downstream of injection position. The spray breakup length and SMD distributions were measured as function of operating conditions. The experiment result proved that the atomization performance improved by flash-boiling swirl spray without being affected by exhaust gas temperatures.

Cu-Al-Ni계 SMA합금 리본의 안정화 및 열처리

장우양,양권승,강조원 조선대학교 생산기술연구소 2003 生産技術硏究 Vol.25 No.2

In order to clarify the effect of the composition and wheel speed on the phase stability of parent phase, the Cu-AI-Ni based alloy ribbons with different Al content were manufactured by rapid solidification process at various wheel speed. The effect of heat treatment on the microstructure and transformation characteristics of the ribbons with fiber structure have been studied by using OM, SEM, TEM, XRD and DSC. The parent phase was retained in the ribbon fabricated at a faster wheel speed even the same composition or in the ribbon contained higher Al content even at the same wheel speed. As flash-heating temperature increased from 750℃ to 850℃, the retained parent phase disappeared and peak of martensite phase only appeared. When ribbon A5 was aged at 60℃ for 10, 24, 48 and 72 hour, no remarkable changes was observed with increasing in aging time. Transformation temperatures in ribbon AS aged at 60℃ for 10, 24, 48 and 72 hour were lower than those in ribbon A5 in as-spun ribbon. When the ribbon A5 was aged at 100℃ for 10, 24, 48 and 72 hour, both retained parent phase and martensite were observed in the ribbon A5 aged for 10 and 24 hour observed. Microstructure of cross-sectional surface of ribbon aged at 100℃ for 72 hour was changed to columnar structure and transformation temperature rose only ribbon A5 aged for 72 hour.

Microstructure Evolution and Mechanical Properties of Lean Duplex Stainless Steel Bars Prepared by a Short Process

Xinghai Zhang,Qingdi Gong,Jiaqi Li,Chunting Liu,Jingyuan Li 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.9

The effect of cold deformation and annealing temperature on the microstructure evolution and mechanical properties isshown in this research together with a unique short strategy for manufacturing lean duplex stainless steel bars. Furthermore,the effects of post-weld heat treatment (PWHT) and cooling treatments on the microstructure and mechanical properties ofLDX 2101 bars are being investigated. The results demonstrate that the austenite produces a large number of deformationtwins and strain-induced martensite (SIM) as cold deformation increases, and the SIM and austenite follow the traditionalK–S and N–W orientation relationships. The best mechanical properties overall are achieved in LDX 2101 bars that havebeen annealed at 1020 °C. Moreover, short-time PWHT improves the austenite proportion in the heat-affected zone andweld metal, and PWHT can greatly enhance the overall mechanical properties of the welded joints. Additionally, the optimalheat treatment temperature of the welded joints is 1050–1080 ℃. Furthermore, compared to those treated with air cooling,the mechanical properties of the welded joints treated with water quenching following flash butt welding are superior. As aresult, it is recommended that following flash butt welding, the welded joints are given a water-quenching treatment.

나노탄소섬유 적외선등 난방이 절화장미의 생육과 수명 및 난방비에 미치는 영향

임미영(Lim Mi Young),고충호(Chung Ho Ko),손문숙(Moon Sook Son),이상복(Sang Bok Lee),김길주(Gil Ju Kim),김병수(Byung Soo Kim),김영복(Young Bok Kim),정병룡(Byoung Ryong Jeong) (사)한국생물환경조절학회 2009 생물환경조절학회지 Vol.18 No.1

장미 생산농가의 대부분은 겨울철 난방비가 생산비의 가장 큰 몫을 차지한다. 요즘과 같은 고유가 시대에 농가의 부담을 줄이기 위하여 난방비 절감율이 높은 난방시스템에 대한 연구를 수행하였다. 복사열을 이용한 적외선등 난방의 경우 식물체와 같은 물체를 먼저 가열하여 주변의 기온이 올리는 방식으로 빠르게 온도를 높일 수 있고 경유를 이용한 난방방식에 비해 비용이 절감되는 장점이 있다. 농가에 설치된 나노탄소 섬유 적외선등 난방시스템의 현지조사를 실시하여 난방효과 및 난방비 절감율을 분석하고, 나노탄소섬유 적외선등 난방시스템과 전기히터 난방시스템에서 생산된 ‘오렌지 플레쉬’ 장미의 생육과 절화수명을 조사하였다. 나노탄소섬유 적외선등의 경우 온실 내부 공기 설정온도가 20℃인 경우 식물체 온도는 1~2℃ 정도 더 높게 나타났을 뿐만 아니라 베드와 근권부 온도는 17~19℃ 정도로 유지하는 등 우수한 난방의 효과를 알 수 있었고, 전기히터 난방시스템과 온수보일러 난방 시스템의 추정 난방비를 비교한 결과 난방비 절감 효과가 아주 높게 나타났다. 장미의 생육을 조사한 결과 전기히터 난방시템에서 생육한 장미와 차이가 없었으며 화색이나 엽색의 발현이 더 좋았다. 절회수명에서는 나노탄소섬유 적외선등에서 생육한 장미가 생체중과 수분 흡수량이 높아 다소 더 길어진 절회수명을 뒷받침해 주었다. The greatest and major cost for cut rose production during winter seasons in Korea is cost of heating the greenhouse. A study was conducted on a cost-efficient heating system to reduce expenses of cut rose growers in times of high energy prices. An infrared heating system utilizing radiant energy has an obvious advantage over other heating methods in that the energy is first used to raise temperatures of plants and other objects and subsequently that of the atmosphere, resulting in faster reaching to desired plant temperatures at a reduced heating cost. In this study the heating effect and heating cost saving of a nano-carbon fiber infrared heating system (NCFIHS) installed in cut rose greenhouses in Gimhae, Gyeongnam Province were analyzed comparatively. In addition growth, quality, and vase life of 'Orange Fresh' roses grown in greenhouses heated by NCFIHS against those grown in greenhouses heated by so called an electrical heating system. In greenhouses with a NCFIHS with a set point ail" temperature of 20℃, plant temperature was maintained at 1~2℃ higher than the air temperature, and temperatures of growing bed surface and root zone were maintained at 17~19℃ throughout cold winter nights. The cost for heating in NCFIHS was about 25 and 51 % of that of an electrical heating system and a hot water heating system heated by petroleum, respectively. Growth of roses harvested in greenhouses with a NCFIHS was similar to those grown in greenhouses with an electrical heating system. However, cut roses with more intense petal and leaf colors and a longer vase life (fresh weight and amount of water uptake) were harvested in greenhouses with a NCFIHS as compared to those harvested in greenhouses with an electrical heating system.

위성영상 토양수분 기반 FDII를 활용한 돌발가뭄의 메커니즘 분석

이희진,남원호,서찬양,Jason A. Otkin,Yafang Zhong,Mark D. Svoboda 한국농공학회 2023 한국농공학회논문집 Vol.65 No.3

A flash drought is a rapid-onset drought that develops over a short period of time as weather and environmental factors change rapidly, unlike generaldroughts, due to meteorological abnormalities. Abnormally high evapotranspiration rates and rapid declines in soil moisture increase vegetation stress. In addition, crop yields may decrease due to flash droughts during crop growth and may damage agricultural and economic ecosystems. In this study,Flash Drought Intensity Index (FDII) based on soil moisture data from Gravity Recovery Climate Experiment (GRACE) was used to analyze flashdrought. FDII, which is calculated using soil moisture percentile, is expressed by multiplying two factors: the rate of intensification and the droughtseverity. FDII was developed for domestic flash drought events from 2014 to 2018. The flash drought that occurred in 2018, Chungcheongbuk-doshowed the highest FDII. FDII was higher in heat wave flash drought than in precipitation deficit flash drought. The results of this study show thatFDII is reliable flash drought analysis tool and can be applied to quantitatively analyze the characteristics of flash drought in South Korea.

Heat transfer and flow characteristics of a cooling thimble in a molten salt reactor residual heat removal system

Zonghao Yang,Zhaoming Meng,Changqi Yan,Kailun Chen 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.8

In the passive residual heat removal system of a molten salt reactor, one of the residual heat removalmethods is to use the thimble-type heat transfer elements of the drain salt tank to remove the residualheat of fuel salts. An experimental loop is designed and built with a single heat transfer element toanalyze the heat transfer and flow characteristics. In this research, the influence of the size of a threelayerthimble-type heat transfer element on the heat transfer rate is analyzed. Two methods are usedto obtain the heat transfer rate, and a difference of results between methods is approximately 5%. The gasgap width between the thimble and the bayonet has a large effect on the heat transfer rate. As the gasgap width increases from 1.0 mm to 11.0 mm, the heat transfer rate decreases from 5.2 kW to 1.6 kW. Inaddition, a natural circulation startup process is described in this paper. Finally, flashing natural circulationinstability has been observed in this thimble-type heat transfer element.

기액분리기를 적용한 가스 인젝션 히트펌프의 성능 향상에 관한 실험적 연구

손길수(Kilsoo Son),김동우(Dongwoo Kim),최성경(Sungkyung Choi),김용찬(Yongchan Kim) 대한설비공학회 2017 설비공학 논문집 Vol.29 No.6

Air-source heat pumps are widely used in residential heating systems. However, the decrease in the capacity of the heat pump is unavoidable when operating at very low and high ambient temperatures. The vapor injection technique is considered a promising technology to overcome this problem. Recent research on vapor injection cycles have mainly adopted a scroll compressor with an internal heat exchanger at severe operating conditions. This study measured the COP and EER of a gas injection heat pump using a flash tank with an inverter-driven rotary compressor at severe operating conditions. Compared to non-injection heat pumps, the heating capacity and COP of the gas injection heat pump improved up to 15% and 2.9%, respectively, at outdoor temperatures of -10℃ to 7℃. The cooling capacity of the gas injection heat pump was 11% higher than the non-injection heat pump at an outdoor temperature of 35℃. At the same time, the EER of the gas injection heat pump was similar to that of the non-injection heat pump.