• 수산해양기술연구
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• 제58권4호
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• pp.359-366
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• 2022

In this study, the load fluctuation of the main engine is considered to be a disturbance for the jacket coolant temperature control system of the low-speed two-stroke main diesel engine on the ships. A nonlinear PID temperature control system with satisfactory disturbance rejection performance was designed by rapidly transmitting the load change value to the controller for following the reference set value. The feed-forwarded load fluctuation is considered the set points of the dual loop control system to be changed. Real-coded genetic algorithms were used as an optimization tool to tune the gains for the nonlinear PID controller. ITAE was used as an evaluation function for optimization. For the evaluation function, the engine jacket coolant outlet temperature was considered. As a result of simulating the proposed cascade nonlinear PID control system, it was confirmed that the disturbance caused by the load fluctuation was eliminated with satisfactory performance and that the changed set value was followed.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.1255-1260
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• 2006

This present study analyzed temperature depreciation ratio of window inside surface by KS F 2295 'Procedure for determining fenestration product condensation resistance values'. it estimated window indoor surface condensation due to variable environmental condition. Performance of condensation resistance by using temperature depreciation ratio until applied Low-e and Ar glazing improved about 45% from 24 mm clear. Temperature depreciation ratio by KS F 2295 considers analytic index of window condensation due to variable boundary condition.

• 설비공학논문집
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• 제15권11호
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• pp.937-942
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• 2003

In the present study, low-temperature low-pressure refrigerant storage method is proposed to achieve higher cooling capacity during a short period of time than that of a compressor in steady operation. Experimental apparatus was designed and set up to analyze the performance of the new-conceptual cooling system. Two reservoirs for sequential storage of refrigerant were used in the cooling system. Several on/off solenoid valves were installed for control of refrigerant flow. From the experimental results, the initial rapid cooling by low temperature low-pressure refrigerant storage method was ascertained for successful operation. This rapid cooling methodology shall be useful for other low-capacity refrigeration system.

• 전기전자학회논문지
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• 제18권3호
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• pp.383-391
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• 2014

본 논문에서는 겨울철 저온환경에서 디젤 엔진의 연료필터를 검사하기 위한 온도, 압력 및 유량 분석 시스템을 제안하였다. 디젤엔진의 연료인 경유는 특정 온도 이하로 내려가면 파라핀과 같은 반고체 상태인 왁싱(Waxing)물질을 형성하여 유동성이 낮아지기 때문에 엔진 시동이 원활하지 않다. 그래서 이러한 문제점을 해결하기 위해서 블록 히터를 내장하게 된다. 그리고 연료필터의 성능을 측정하기 위해서는 극저온 하에서 엔진 시동 시부터 온도, 압력 및 유량을 분석할 수 있는 시스템이 요구된다. 본 논문에서는 제작된 시스템을 이용하여 연료필터 주변의 성능에 관계된 물리량을 측정하였으며 이를 분석하였다. 또한 측정된 데이터는 임베디드 시스템의 웹서버를 이용하여 원격 네트워크로 전송하였고 원격에서 사용자들이 웹브라우저를 이용하여 운전 상태를 용이하게 파악할 수 있게 설계하였다. 설계된 시스템을 검증하기 위하여 제작된 소형 실험 챔버에 설치하고 상온 및 극저온 상황에서 실험하여 연료필터 입출력 측 연료의 온도, 압력, 유량 데이터를 얻을 수 있었으며, 연료히터의 동작 시 연료의 흐름이 개선되는 것을 알 수 있었다.

• 한국세라믹학회지
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• 제44권12호
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• pp.727-732
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• 2007

In order to fabricate a highly performing cathode for low-temperature type solid oxide fuel cells working at below $700^{\circ}C$, electrode microstructure control and electrode polarization measurement were performed with an electronic conductor, $La_{0.8}Sr_{0.2}MnO_3$ (LSM) and a mixed conductor, $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3$(LSCF). For both cathode materials, when $Sm_{0.2}Ce_{0.8}O_2$ (SDC) buffer layer was formed between the cathode and yttria-stabilized zirconia (YSZ) electrolyte, interfacial reaction products were effectively prevented at the high temperature of cathode sintering and the electrode polarization was also reduced. Moreover, cathode polarization was greatly reduced by applying the SDC sol-gel coating on the cathode pore surface, which can increase triple phase boundary from the electrolyte interface to the electrode surface. For the LSCF cathode with the SDC buffer layer and modified by the SDC sol-gel coating on the cathode pore surface, the cathode resistance was as low as 0.11 ${\Omega}{\cdot}cm^2$ measured at $700^{\circ}C$ in air atmosphere.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.381-381
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• 2011

In this study, a TiO2 colloidal sol was synthesized by sol-gel process, which was used as a "glue" agent to enhance interconnection of TiO2 particles in low temperature process for plastic dye sensitized solar cell. The crystalline phase of this TiO2 glue is pure anatase with average particles size of 5 nm, which was characterized by powder X-ray diffraction and high revolution-TEM. The viscous alcoholic paste without any organic binder was prepared from the mixture of commercial P25 powder and glue. Paste composition and sintering process parameters were optimized for high photovoltaic performance based on low temperature process. The electrochemical impedance spectroscopy and photocurrent-photovoltage transient spectroscopy were also employed to investigate the mechanism of electron transport in this binder free TiO2 film system.

• 설비공학논문집
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• 제15권7호
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• pp.551-556
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• 2003

The present study concerns an experiment on the heating characteristics of a system air-conditioner (A/C) using PWM method or inverter method at low temperature con-ditions. The compressors used are digital scroll type and BLDC inverter type. Under the low outside temperature condition, -5$^{\circ}C$, -1$0^{\circ}C$, -15$^{\circ}C$, heating capacities and COPs are mea-sured by the psychometric calorimeter using air enthalpy method. Also, outlet air temperatures at heating operation mode are measured at -5$^{\circ}C$, -1$0^{\circ}C$ and -15$^{\circ}C$. Experimental results show that COPs of the system A/C using a PWM method are more effective than those of the inverter method at heating operation mode. Although the heater is on, COPs of PWM method are similar to those of BLDC inverter method. Moreover, the heating capacities of PWM method at -5$^{\circ}C$, -1$0^{\circ}C$ and -15$^{\circ}C$ are larger about 10~20% and outlet air tempe-rature at -15$^{\circ}C$ is larger about 10%, compared to the inverter method.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.367-372
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• 2005

This study primarily is concerned with a new device which has been developed following the international standards to measure the ventilation performance at elevated temperature. This device can measure duration of ventilation, performance of electricity, static pressure at elevated temperature and also it is having provision to measure reversible performances during fire hazards. Invented device is closed circuit type system which is best suited for korean industrial environment with low cost and high efficiency. International standards has been compared and performance testing has been major using BS 7346 which is tested by Warrington Fire Research Centre.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.66-70
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• 2001

The combustion characteristics have been investigated to develop the low $NO_{x}$ gas turbine combustor. The lean premixed combustion technology was applied to reduce the $NO_{x}$ emission. Also, the conventional combustor was designed and tested for the baseline of low $NO_{x}$ combustor performance. The test was conducted at the condition of high temperature and ambient pressure. The combustion air which has the temperature of 500K were supplied to the combustor through the air preheater. The temperature and emissions of $NO_{x}$ and CO were measured at the exit of combustor. The premixing chamber can be operated very lean condition of equivalence ratio around 0.35. The $NO_{x}$ was decreased with decreasing the equivalence ration. The CO was decreased with decreasing the equivalence ratio, but the CO was increased with decreasing the equivalence ratio below 0.45. But, at the very lean condition of equivalence ratio below 0.35 both NOx and CO were increased because of the flame unstability. The $NO_{x}$ was decreased slightly and CO was increased with increasing inlet air flowrate. This results can be used to determine the size of combustor. The low $NO_{x}$ combustor has lower values of $NO_{x}$ and CO compared with conventional one. Consequently the performance of combustor shows the possibility of the application to the gas turbine system.

• Journal of Animal Science and Technology
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• 제61권6호
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• pp.305-312
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• 2019

This study was carried out to investigate the effects of dietary energy levels on growth performance, blood parameter, and intestinal morphology of Pekin ducks in low temperature. A total of 500, 21-d-old Pekin ducks (initial BW = 1,089 ± 5.21 g) were evenly assigned to five dietary treatments (2,950, 3,000, 3,050, 3,100, or 3,150 kcal AME/kg, calculated on an as-is basis) with four replicates (pens) for each treatment (25 ducks per pen). During the experiment, hens were provided with feed and water ad libitum. Overall, increasing dietary energy levels corresponded to an increase of final body weight and body weight gain (linear, p < 0.01). Feed intake decreased (linear, p < 0.01) and feed conversion ratio increased (linear, p < 0.01) with increasing levels of energy. There were no significant differences (p < 0.05) in the level of leukocytes between groups. However, heterophils decreased (quadratic, p < 0.05) and lymphocytes increased (linear, p < 0.01) as inclusion of dietary energy levels increased. The H/L ratio increased (linear, p < 0.01) with increasing dietary energy levels while serum corticosterone levels decreased at overall experimental periods. Triglycerides increased (linear and quadratic, p < 0.05) with increasing dietary energy levels. There were no significant changes in villus height or crypt depth of the jejunum at overall experimental. In conclusion, increasing concentrations of dietary energy levels up to 2,950-3,150 kcal/kg in diet. Additionally, 3,150 kcal/kg dietary energy had been revealed more beneficial and could be practiced as protective management for the Pekin ducks reared under low ambient temperature (8℃ to 10℃).