• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.764-769
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• 2001

Recently, according to increase in the requirement of electric power, a thermoelectric power plant equipped with pulverized coal combustion system is highly valued, because coal has abundant deposits and a low price compared with others. For efficient use of coal fuel, most of plant makers are studying to improve combustion performance and flame stability, and reduce pollutant emission. One of these studies is how to control the profile of particle injection and velocity dependant on coal nozzle. Basically, a mixed flow of gas and particle in coal nozzle is required to have appropriate injection and concentration distribution at exit to achieve flame stability and low pollutant, but it is very difficult to obtain that without help of a coal separating device within nozzle. In this study, each distribution of air and coal flow rate is measured for the coal nozzle with coal separator developed by us. The coal concentration at exit is various according to inlet swirl values and positions of coal separator. Also pressure drop is measured for various operating conditions of this nozzle. From these results, we can find the separation characteristic of new developed coal separator, and select proper operation range of coal nozzle. When this coal nozzle is applied to actual plant, these investigations will be very useful to confirm the shape of coal separator to have efficient particle injection.

• Nuclear Engineering and Technology
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• 제28권2호
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• pp.103-117
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• 1996

본 논문에서는 증기폭발의 전파과정을 해석하기 위한 수학적 모델을 제시하였다. 이 모델은 용융물, 용융파편, 그리고 냉각재 기상과 액상 등 4상 유체의 2차원적인 천이거동을 지배방정식 및 관련상관식의 수치적 해를 구함으로서 예측할 수 있다. 모델에 사용된 주요 상관식은 용융물 분쇄, 냉각재 상변화, 에너지 교환, 그리고 운동량 교환항으로 구성되어 있다. 그리고, 냉각재(물)의 상태방정식은 냉각재의 기상과 액상 사이의 열역학적 인 비평형을 허용할 수 있는 독특한 형태로 구성되었다. 주석 /물의 중기폭발에 대한 예제계산을 수행한 결과 본 모델이 폭발의 전파속도 및 압력 -비록 그 정량적인 값은 관련상관식의 인자들에 좌우되지마는- 등의 증기폭발 전파과정의 주요현상을 적절히 모사할 수 있음을 알 수 있었다. 또한 중요한 초기변수(중기 분율, 용융물 분율) 및 관련상관식에 대한 민감도 분석도 수행되었다.

• 한국지열·수열에너지학회논문집
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• 제2권1호
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• pp.1-7
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• 2006

This paper was studied for optimum design of the used vaporizer at a satellite station. Generally, the cold air is created by temperature drop on the vaporizer surface. In addition, the frost creates ice deposit layer, therefore, heat transfer on vaporizer decreases into the adiabatic condition. By this reason, recent vaporizer system is installed as parallel type, and it takes three times of vaporizer capacity. But this vaporizer system requires much installation costs and restricted by some space. It is very important to solve this problem. This study paper is regarding $LN_2$ vaporizer where the utilization increases recently. There are three variable conditions which are used in this study research. First, fin lengths of 4000mm, 6000mm, 8000mm and 0, 4, 8 fin types were applied rut each vaporizer. Second, we applied four season condition which consist of humidity, temperature and air velocity to the experimental environment. Finally, pressure was applied to get flow rate during experiment. This paper objective is to propose vaporizer type and length data for best performance of vaporizer through experiment.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1996년도 춘계 학술대회논문집
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• pp.58-67
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• 1996

This paper describes some computational results of various energy and environmental systems using Patankar's SIMPLE method. The specific topics handled in this study are jet bubbling reactor for flue gas desulfurization, cyclone-type afterburner for incineration, 200m tall stack for 500 MW electric power generation, double skin and heat storage systems of building energy saving for the utilization of solar heating, finally turbulent combustion systems with liquid droplet or pulverized coal particle. A control-volume based finite-difference method with the power-law scheme is employed for discretization. The pressure-velocity coupling is resolved by the use of the revised version of SIMPLE, that is, SIMPLEC. Reynolds stresses are closed using the standard $k-{\varepsilon}$ and RNG $k-{\varepsilon}$ models. Two-phase turbulent combustion of liquid drop or pulverized coal particle is modeled using locally-homogeneous, gas-phase, eddy breakup model. However simple approximate models are incorporated for the modeling of the second phase slip and retardation of ignition without consideration of any detailed particle behavior. Some important results are presented and discussed in a brief note. Especially, in order to make uniform exit flow for the jet bubbling reactor, a well-designed structure of distributor is needed. Further, the aspect ratio in the double skin system appears to be one of important factors to give rise to the visible change of the induced air flow rate. The computational tool employed in this study, in general, appears as a viable method for the design of various engineering system of interest.

• Environmental Engineering Research
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• 제11권1호
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• pp.1-13
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• 2006

In this study, conventional biofilters packed with flexible synthetic polyurethane (PU) foam carriers were operated to remove toluene from a contaminated air stream. PU foams containing various adsorbents (e.g., zeolite, sepiolite, dolomite and barite) were synthesized for the biofilter media and their adsorption characteristics of toluene were determined. Adsorption capacity of PU-adsorbent foam was in the order of PU-dolomite ${\approx}$ PU-zeolite > PU-sepiolite > PU-barite. During the biofiltration experiment, influent toluene concentration was in the range of 0-160 ppm and EBRT (i.e., empty bed residence time) was 45 seconds. Pressure drop of the biofilter bed was 4-5 mm $H_2O/m$ column height. The maximum removal capacity was in the order of PU-dolomite > PU-zeolite > PU-sepiolite > PU-barite, while the complete removal capacity was in the order of PU-dolomite > PU-sepiolite > PU-zeolite > PU-barite. The better biofiltration performance in PU-dolomite foam was because PU-dolomite foam had lower density and higher porosity than the others providing favorable conditions for microbial growth. The results of biodegradation kinetic analysis showed that PU-dolomite foam had higher maximum removal rate ($V_m\;=\;11.04\;g$ toluene/kg dry material/day) and saturation constant ($K_s\;=\;26.57\;ppm$) than the other PU foams. This supports that PU-dolomite foam was better than the others for biofilteration of toluene.

• Journal of Biosystems Engineering
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• 제27권6호
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• pp.529-536
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• 2002

The performance of stilting engine, in particular, its energy conversion efficiencies are critically influenced by the regenerator characteristics. The regenerator characteristics are influenced by effectiveness, void fraction. heat transfer loss and fluid friction loss in the regenerator matrix. These factors were influenced by the surface geometry and material properties of the regenerator matrix. The regenerator design goals arc good heat transfer and low pressure drop of working Bas across the regenerator. Various data for designing a wire screen matrix have been given by Kays and London(1984). The mesh number of their experiment. however, was confined below the No. 60. which seems rather small for the Stirling engine applications. In this paper. in order to provide a basic data for the design of regenerator matrix, characteristics of heat transfer and flow friction loss were investigated by a packed mettled of matrix in oscillating flow as the same condition of operation in a Stirling engine. Seven kinds of sing1e wire screen meshes were used as the regenerator matrices. The results are summarized as follows; 1. While the working fluid flew slowly in the regenerator. the temperature difference was great at the both hot-blow(the working fluid flows from healer to cooler) and cold-blow(the working fluid flows from cooler to healer). On the other hand. while the working fluid flew fast. the temperature difference was not distinguished. 2. The No.150 wire screen used as the regenerator matrix showed excellent performance than tile others. 3. Phase angle variation and filling rate affected heat transfer or regenerator matrices. 4. Temperature difference between the inlet and outlet of the regenerator is very hish in degree of 120 phase angle.

• 한국의류학회지
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• 제9권3호
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• pp.45-51
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• 1985

The purpose of this study is to research into the thermal condition and the weight of clothes suitable for the officers engagged in light works in an air-conditioned room in summer. The Major findings are as follows: 1. Thermal conditions of the working environment are $24.5^{\circ}C$ (Dry bulb temp.), $68\%$ (Relative humidity) and 2.6m/sec (Air Velocity). 2. Total clothing weights are 416.6 g/$m^2$ (male) and 340.9 g/$m^2$ (female). Underwear weights are 96.8g/$m^2$ (male) and 85.1g/$m^2$ (female). The latter turned out to be statistically significant in Sexual difference. 3. Means of the thermal sensation are 3.0 (comfortable; male) 2.7 ('Slightly cool' -'Comfortable'; female) and the relationship between clothing weights and thermal sensation proves to be significantly correlated in the case of female. 4. $66.7\%$ of the women and $37.1\%$ of the men feel sensation of coldness at the body's specific area and $79.5\%$ of the women and $54.3\%$ of the men reveals air-conditioning disturbance. 5. As the thermal sensation is close to 'cool-cold', sensation of coldness or air conditioning disturbance are showed up more frequently which is reversely related with weight of under-wear. It is also proved that air conditioning disturbances are influenced by sexual difference in addition to sensation of coldness and thermal sensation. 6. According to the result of experiment, we can have the idea that at condition $X_1$, the drop of limbs' skin temp. is remarkable. At condition $X_2$ skin temp. for distal limbs and mean skin temp. are raised and the falling degree is similar. At condition $X_3$, mean skin temp. and distal skin temp. are remarkably raised, and the falling degree decreases and the beats of pulse rate increase and diastoric blood pressure is lowered.

• 한국추진공학회지
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• 제18권4호
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• pp.74-80
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• 2014

본 논문은 무유도 로켓탄의 명중률을 향상시키기 위해 개발한 이중추력형 비행모터에 관하여 기술하였다. 고연소속도 특성을 지닌 더블베이스 추진제의 형상 조절을 통해 이중추력형 비행모터를 설계하였으며, 실제 지상연소시험을 통해 이중추력 성능을 확인하였다. 연소시험 결과 서스테이닝 단계와 부스팅 단계의 추력비는 약 1:7.6으로 정상적인 이중추력 특성을 보였으며, 압력강하에 의한 추진제 소화현상은 나타나지 않았다.

• 대한의용생체공학회:의공학회지
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• 제13권3호
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• pp.225-234
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• 1992

In order to use a low cost polymer valve in our total artificial heart and ventricular assist device, we have developed a slit-type bileaflet polymer valve[BPV 1. The aim of this study is to determine the hydrodynamic effectiveness of the newly-designed BPV and its feasibility for temporary use in the blood pumps. For hydrodynamic comparison, we investigated in-vitro the pressure drop across the valve, the leakage volume, the flow rate and the flow pattern of the BPV, two mechanical valves and a trileaflet polymer valve. We employed the ventriculo-pulmonary bypassing method for in-vivo tests of the BPV's together vilh our electrohydraulic left venIn ricular assist device in mongrel dogs. The BPV showed adquate gydrodynamic performances and in the preliminary animal bests, there was no xvi dence of thrombus formation on the valve leaflets and around the struts. Detailed results obtained from the animal tests will be separately reported. This report involves the design criteria, fabrication and hydrodynamic charateristics of she BPV, and the basic merits and demerits of the valve are dis- cussed from the hydrodynamic point of view.

• 대한환경공학회지
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• 제22권4호
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• pp.713-722
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• 2000

본 연구는 입자크기를 분석하기 위한 장치인 레이저회절 분광계의 측정오차 및 재현성을 분석한 것이다. 레이저회절 spectrometers는 입자크기를 분석하기 위한 장치 중에서 가장 대표적이고 중요성을 가진다. 이 측정장치는 운전이 간단하며, 입자분석에 있어서 재현성이 우수하고, 빠른 속도로 분석이 가능한 형태이다. 입자크기를 분석하는 과정에 있어서 공급되는 분산형태와 흐름율에 따라서 측정오차가 미세하게 발생되었고, 흐름율은 분산형태가 건식인 경우 0.1~23 g/min로 공급하였고, 습식인 경우는 분산되는 용매에 따라서 1.4~35 %가 되도록 조절하여 측정결과에 따라서 발생되는 측정오차를 분석하였다. 흐름을 변화에 따라서 발생되는 측정 오차는 측정 cell 내의 입자에 입사되는 레이저 회절패턴이 변화함으로서 측정오차가 다양하게 발생하였다. 본 연구에서 측정오차를 분석하기 위해서는 입자모양, 크기, 분산형태와 용매, 흐름율과 농도의 변화에 따라서 실험을 실행하였고, 분석장치의 시스템에 따른 측정오차를 나타내기 위해서는 장치내의 역학적인 공정, 측정시간, 초점거리, 주입압력, 전처리과정인 ultrasonic이나 혼합에 의한 분산효과에 따라 측정오차 및 재현성을 분석하였다.