• 대한토목학회논문집
• /
• 제29권1B호
• /
• pp.47-62
• /
• 2009

지구가 온난화됨에 따라서 발생되는 기후변화는 증발과 같은 수문순환과정에 직접적인 영향을 주는 것으로 보고된 바 있다(IPCC, 2001). 또한 지역특성에 따른 기후변화가 증발에 미치는 영향을 파악하는 것은 필요하다. 본 연구에서는 지리지형적 특성을 고려하면서, 연별 pan 증발량을 모의하기 위한 6개 증발식들의 적용성을 비교 검토하였다. 이를 위하여, 전국 56개 연구지역을 지리지형적 특성(도시화율, 해안근접성, 지역 평균경사, 수역면적)에 따라서 분류하고, 기존에 제안된 증발식(Penman, Kohler-Nordenson-Fox(KNF), DeBruin-Keijman, Priestley-Taylor, Hargreaves, Rohwer)을 적용하여 pan 증발량과 비교 검토하였다. 또한 Penman 증발식의 풍속함수를 보정하고 보정된 식의 적용성을 검증하였다. 연구결과에서 KNF식은 가장 pan 증발량과 유사한 결과를 보여서 8.72%의 상대오차를 보였고, 그 다음으로 Penman 식은 8.75%의 상대오차를 보였으며, 반면에 질량이동에 근거한 Rohwer 식이 기장 큰 상대오차(33.47%)를 보였다. 그리고 풍속함수와 풍속과의 상관관계가 높게 나타나는 경우 Penman 식의 풍속함수 보정을 통하여 증발량 산정의 정확도를 높일 수 있었다.

• 한국지구과학회지
• /
• 제24권1호
• /
• pp.22-29
• /
• 2003

Temporal and spatial variability of precipitation (P), evaporation (E), and moisture balance (P-E; precipitation minus evaporation) has been investigated over the tropical ocean during the period from January 1998 to July 2001. Our data were analyzed by the EOF method using the satellite P and E observations made by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and the Special Sensor Microwave/Imager (SSM/I). This analysis has been performed for two three-year periods as follow; The first period which includes the El Ni${\tilde{n}}$o in early 1998 ranges from January 1998 to December 2000, and the second period which includes the La Ni${\tilde{n}}$o events in the early 1999 and 2000 (without El Ni${\tilde{n}}$o) ranges from August 1998 to July 2001. The areas of maxima and high variability in the precipitation and in the P-E were displaced from the tropical western Pacific and the ITCZ during the La Ni${\tilde{n}}$o to the tropical middle Pacific during the El Ni${\tilde{n}}$o, consistent with those in previous P studies. Their variations near the Korean Peninsula seem to exhibit a weakly positive correlation with that in the tropical Pacific during the El Ni${\tilde{n}}$o. The evaporation, out of phase with the precipitation, was reduced in the tropical western Pacific due to humid condition in boreal summer, but intensified in the Kuroshio and Gulf currents due to windy condition in winter. The P-E variability was determined mainly by the precipitation of which the variability was more localized but higher by 2-3 times than that of evaporation. Except for the ITCZ (0-10$^{\circ}$N), evaporation was found to dominate precipitation by ${\sim}$2 mm/day over the tropical Pacific. Annual and seasonal variations of P, E, and P-E were discussed.

• 자원환경지질
• /
• 제36권2호
• /
• pp.103-109
• /
• 2003

동해탄광 지역의 산성광산배수에는 Ca, SO$_4$, Mg, Al의 함량이 높게 나타난다. 이 일대의 산성광산배수를 증발시켰을 때 생성된 증발잔류물에서는 주로 석고(CaSO$_4$${\cdot}$2$H_2O$)가 생성되었으며 그 외에 소량의 알루노겐(Al$_2$(SO$_4$)$_4$${\circ}$17$H_2O$) 과 헥사하이드라이트(MgSO$_4$${\circ}$6$H_2O$)가 형성되었다. 석고를 형성하는 Ca는 주변의 모암속에 포함된 방해석에서, SO$_4$ 는 폐석에 포함된 황철석에서 기원한 것으로 생각된다. 함수 알루미늄황산염광물인 알루노겐은 침상의 결정으로 나타난다. 하천수의 Al은 모암이나 폐석에 포함된 엽납석, 일라이트, 녹니석과 같은 층상규산염광물의 화학적 용해작용에 의해 부과된 것으로 추정된다. 함수 마그네슘황산염광물인 헥사하이드라이트는 침상이나 섬유상의 결정으로 생성되었으며 Mg의 기원은 모암내의 돌로마이트와 광산폐셔의 주 구성광물인 녹니석으로 판단된다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
• /
• pp.18-19
• /
• 2005

EDDC(Evaporation using Drum in Dual Chamber) deposition system was manufactured for 100m long superconducting coated conductor. It is composed of reaction chamber, evaporation chamber and differential chamber. The drum is located across the differential and exposed to both of the evaporation chamber and the reaction chamber, and the tape is wound on the drum. The elements of superconducting material are co-evaporated from respective element boats in the evaporation chamber and deposited on the drum and reacted with oxygen in the reaction chamber. This process repeats by rotating the drum. When the total pressure of the reaction chamber was 5 mTorr, that of the evaporation chamber was $5{\sim}10^{-5}$Torr. This atmosphere can be achieved by means of differential pumping. There are four evaporator in the evaporation chamber. One is the radiation heating evaporator and the others are the high frequency induction evaporator. EDDC is one of promising methods for commercialization of superconducting coated conductor.

• 한국산학기술학회논문지
• /
• 제9권2호
• /
• pp.264-269
• /
• 2008

본 논문은 수평 이중관식 열교환기 내 프레온계 냉매의 대체냉매인 탄화수소계 냉매(R-290과 R-600a)의 증발 열전달 계수에 대한 실험적 결과를 나타내었다. 증발기의 내관 내경은 각각 10.07 mm와 6.54 mm의 2가지를 사용하였다. 증발실험은 질량유속 $35.5{\sim}210.4\;kg/m^2s$이고, 냉각용량 $0.95{\sim}10.1\;kW$인 조건에서 수행하였다. 실험결과를 요약하면, 탄화수소계 냉매 R-290과 R-600a의 증발 열전달 계수가 프레온계 냉매 R-22보다 높았다. 즉, R-22의 증발 열전달 계수에 비해, R-290와 R600a는 각각 $56.7{\sim}70.1%$와 $46.9{\sim}59.7%$ 정도 높았다. 실험데이터와 종래의 상관식을 비교한 결과, 모든 냉매와 관경에 대해서 Kandlikar상관식이 가장 좋은 일치를 보였다.

• 설비공학논문집
• /
• 제16권9호
• /
• pp.845-854
• /
• 2004

The evaporation heat transfer coefficient for R-l34a, R-407C (a mixture of 23wt% R-32, 25 wt% R-125, and 52 wt% R-l34a) and R-410A (a mixture of 50 wt% R-32 and 50 wt% R-125) flowing in the oblong shell and plate heat exchanger were investigated experimentally in this study. Four vertical counterflow channels were formed in the exchanger by four plates of commercial geometry with a corrugated sinusoid shape of a chevron angle of 45 degree. The effects of the mean vapor quality, mass flux, heat flux, and saturation temperature of different refrigerants on the evaporation heat transfer were explored in detail. Similar to the case of a Plate heat exchanger, even at a very low Reynolds number, the flow in the oblong shell and plate heat exchanger remains turbulent. It is found that the evaporation heat transfer coefficient in the plates is much higher than that in circular pipes. The present data show that the evaporation heat transfer coefficients of all refrigerants increase with the vapor quality. At a higher mass flux h, is higher than for the entire range of the vapor quality. Raising the imposed wall heat flux was found to slightly improve h$_{r}$, while h$_{r}$ is found to be lower at a higher refrigerant saturation temperature. A comparison of the performance of the various refrigerants reveals that R-410A has the highest heat transfer performance followed by R-l34a, and R-407C had the lowest performance of the refrigerants tested. Based on the present data, empirical correlations of the evaporation heat transfer coefficient were proposed.sed.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2005년도 동계학술발표대회 논문집
• /
• pp.262-267
• /
• 2005

The evaporation heat transfer coefficient of $CO_2$ in a horizontal round tube was investigated experimentally. The experiments were conducted without oil in a closed refrigerant loop which was driven by a magnetic gear pump. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and evaporator(test section). The test section was made of a horizontal stainless steel tube with the inner diameter of 7.75 mm, and length of 5 m. The experiments were conducted at mass flux of 200 to 500 $kg/m^2s$, saturation temperature of $-5^{\circ}C$ to $5^{\circ}C$, and heat flux of 10 to 40 $kW/m^2$. The test results showed the evaporation heat transfer of $CO_2$ has great effect on more nucleate boiling than convective boiling. The evaporation heat transfer coefficients of $CO_2$ are highly dependent on the vapor quality, heat flux and saturation temperature. In comparison with teat results and existing correlations, correlations failed to predict the evaporation heat transfer coefficient of $CO_2$, therefore, it is necessary to develop reliable and accurate predictions determining the evaporation heat transfer coefficient of $CO_2$ in a horizontal tube.

• Transactions on Electrical and Electronic Materials
• /
• 제9권3호
• /
• pp.105-109
• /
• 2008

Electrical characteristics of organic light-emitting diodes were investigated by varying a hole-size in evaporation boat in the device structure of ITO/tris(8-hydroxyquinoline) aluminum$(Alq_3)$/Al. The device was manufactured using a thermal evaporation under a base pressure of $5{\times}10^{-6}$ Torr. The $Alq_3$ emitting organics were evaporated to be a thickness of 100 nm at a deposition rate of $1.5{\AA}/s$. A cylindrical-shaped evaporation boat was made out of stainless steel with a small size of hole on top of the boat. Several evaporation boats were made having a different hole size on top; 0.8 mm, 1.0 mm, 1.5 mm, and 3.0 mm. We found that when the hole size on top of the evaporation boat is 1.0 mm, the average roughness is rather smoother compared to the other ones. Also, luminance and external quantum efficiency are superior to the others. Compared to the ones from the devices made with the hole-size of 0.8 mm boat. The luminance and external quantum efficiency of the device made with the hole-size of 1.0 mm boat were improved by a factor of seventy and thirty three, respectively. Also operating voltage is reduced to 2 V.

• 대한기계학회논문집B
• /
• 제38권3호
• /
• pp.255-262
• /
• 2014

판형열교환기의 증발과정에서 오일에 위한 영향을 알아보기 위해 마이크로 기어 펌프를 이용한 냉매-R134a 순환 성능실험 장치를 구성하여, 증발열전달 실험을 수행하였다. POE 오일을 펌프를 이용하여 냉매 질량 유량에 비례하도록 0~5%를 첨가하여, 오일순환량에 따른 열전달계수 변화를 측정하였다. 오일순환율이 증가할수록 R134a 증발 열전달계수는 감소하며, 압력손실은 증가한다. 질량유량 80 g/s, 증발 온도 $30^{\circ}C$ 일 때, 오일 순환율 2%조건에서 무오일 대비 약 10%의 열전달계수가 감소하였고, 압력손실은 약 10% 증가하였다.

• 한국농공학회논문집
• /
• 제61권5호
• /
• pp.101-108
• /
• 2019

The domestic duck industry is the sixth-largest among the livestock industries. However, 34.3% of duck houses were the duck houses arbitrarily converted from plastic greenhouses. This type of duck house was difficult to properly manage internal air temperature and humidity environment. Humidity environment inside duck houses is an important factor that directly affects the productivity and disease occurrence of the duck. Although the humidity environments of litters (bedding materials) affect directly the inside environment of duck houses, there are only few studies related to humidity environment of litters. In this study, evaporation rates from litters were evaluated according to air temperature, relative humidity, water contents of litters, and wind speed. The experimental chamber was made to measure evaporation rates from litters. Temperature and humidity controlled chamber was utilized during the conduct of the laboratory experiments. Using the measured data, a multi linear regression analysis was carried out to derive the calculation formula of evaporation rates from litters. In order to improve the accuracy of the multi linear regression model, the partial vapor pressure directly related to evaporation was also considered. Variance inflation factors of air temperature, relative humidity, partial vapor pressure, water contents of litters, and wind speed were calculated to identify multicollinearity problem. The Multiple $R^2$ and adjusted-$R^2$ of regression model were calculated at 0.76 and 0.71, respectively. Therefore, the regression models were developed in this study can be used to estimate evaporation rates from the litter of duck houses.