• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
• /
• pp.351-353
• /
• 2003

We present a retrieval scheme for the remote sensing of evapotranspiration (ET) over rice paddy. To perform the retrieval, high-resolution airborne imagery of multi-spectral visible and thermal infrared data, and ground-based meteorological measurements are utilized. Our ET retrieval scheme is based on the basic principal of surface energy budget, which is a result of balance in longwave and shortwave radiation, latent heat, sensible heat, and energy flux into the ground. To partition the latent and sensible heat fluxes of interest from the energy balance equation, three basic parameters are of most concern, including albedo, surface temperature, and normalized difference vegetation index (NDVI). The NDVI and albedo can be easily derived from the visible and near infrared spectral data, while the surface tem-perature can be determined through the analysis of the infrared data with the Stefan Boltzmann law. From the airborne imagery taken on 28 April 2003, we observe very good dry and wet pixels that can be easily corre-sponded to the radiation and evaporation controlled crite-ria, respectively, and, hence, for the further use in defin-ing the evaporative fraction needed to partition sensible and latent heat fluxes from the net energy flux. The de-rived ET is compared with the in situ measurements.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제9권4호
• /
• pp.17-26
• /
• 2001

Simulation was conducted using TRNSYS to evaluate the thermal performance of a facility. This facility has a condensing-type heat exchanger which is able to recover the latent energy for the purpose of reducing the heating energy in winter. The boiler and chiller are selected based on the annual peak loads and controlled to maintain the facility at the set temperature of 14~$17^\circ{C}$. Supplied energy by the boiler and recovered energy by the heat exchanger were calculated as a function of number of pass through heat exchanger, kind of fuel and hot water velocity. Simulation results show that about 20% of the total heating load can be recovered by the heat exchanger and the amount of latent heat is increasing with the number of pass. This means that the efficiency of the waste energy recovery system can be increased by using a condensing-type heat exchanger rather than a traditional sensible heat exchanger.

• 한국지구과학회지
• /
• 제23권8호
• /
• pp.676-682
• /
• 2002

겨울철 체감온도는 온도와 바람에 의해 느끼는 추위의 정도를 정량화한 것이다. Siple-Passel은 최초로 바람에 의한 냉각효과를 이용하여 바람냉각상당온도를 제시하였으나 일반인에게 적합하지 않기 때문에 많은 문제점이 지적되어 왔으므로 이 논문에서 결점들을 비교 분석하였다. Steadman 모델은 열평형(thermal equilibrium) 이론에 근거하여 보다 현실적이지만 추위의 정도를 구분하여 설명하지 못하였다. 최근 캐나다와 미국에서 개발한 JAG/TI-모델은 보다 정확하고 이해하기 쉬우며 인체실험을 반영하였으나 태양복사, 습도, 개인의 신체적 차이 등은 고려하지 않았다. 나이, 사람의 활동, 건강, 신진대사 등이 다르기 때문에 어느 모델이 사람에게 적합한지는 실험 비교가 필요하다. 따라서 우리의 야전환경에 적합한 체감온도모델의 개발이 요구된다.

• 대한기계학회논문집B
• /
• 제39권1호
• /
• pp.37-43
• /
• 2015

현열 뿐만 아니라 잠열을 이용하는 증발냉각은 배기열 회수에 매우 유용하게 사용될 수 있다. 본 연구의 목적은 증발냉각을 이용한 배기열 회수장치의 성능을 실험적으로 규명하는 것이다. 성능실험장치는 플라스틱 열교환기, 물 분무 노즐, 공기유동용 홴, 물 순환용 펌프, 수조, 온도 습도 유량 측정 센서 등으로 구성되었다. 증발이 없는 현열 회수에서의 유용도와 증발을 수반하는 전열 회수에서의 유용도를 여러가지 작동조건에서 측정하여 비교하였다. 현열냉각과 증발냉각의 유용도는 공기의 유량이 증가함에 따라 감소하고, 대향류에서의 유용도가 평행류에서의 유용도 보다 휠씬 높다. 증발냉각의 경우 물 유량이 증가함에 따라 유용도는 증가하고, 평행류가 대향류보다 물 유량에 더 민감함을 알 수 있다.

• 한국지구과학회지
• /
• 제22권1호
• /
• pp.40-46
• /
• 2001

기상청에서 덕적도와 칠발도에 설치한 해양기상 관측부이 자료를 이용하여 해양 및 대기 특성과 해양-대기간의 열교환을 살펴보았다. 각 관측지점에서의 일평균 현열속 및 잠열속은 벌크공기역학법을 적용하여 계산하였다. 표층수온은 기온과 같이 뚜렷한 연주기를 보이지만, 1달 정도 시간지연을 가진다. 해면기압은 7월에 가장 낮았고 겨울에 가장 높았으며, 습도는 5-8월 사이 비교적 높았다. 풍속은 가을과 겨울에 평균 5m/s 이상으로 강한 편이었다. 현열속 분석결과 가을부터 겨울에 걸처 해양의 열손실이 두드러졌으며, 봄과 여름에는 반대로 대기에서 해양으로의 약한 열전달이 이루어져 연중 순현열속은 해양에서 대기로의 열전달을 보여주었다. 잠열속 분석결과 봄에서 여름까지 대기의 열손실이 나타나지만, 그 외 기간에는 해양의 열손실이 월등히 크게 나타났다. 현열속과 잠열속의 크기를 비교해 볼 때,1-2월을 제외하고는 전반적으로 현열속보다 잠열속에 의한 해양의 열손실이 우세함을 알 수 있었다. 관측지점별로 분석한 열속의 크기와 변동폭은 대체적으로 덕적도에서 더 크게 나타났다. 일정 기간을 선정한 사례연구에서, 1998년 5월사례의 경우 현열속과 잠열속 모두 칠발도에서 더 크고, 1996년 11월 사례의 경우에는 덕적도에서 훨씬 크게 나타났다.

• 한국환경과학회지
• /
• 제19권3호
• /
• pp.281-293
• /
• 2010

The present study explores time and spatial thermal environment for Daegu, which is a city built on a basin area, according to varying land cover conditions of the earth's surface by analyzing data derived from meteorological observation and satellite images. The study has classified land use by utilizing MODIS satellite images and analyzed land surface temperature. Also, by using data acquired from automatic weather system, the study has evaluated the effects of atmospheric heating caused by city pavements by analyzing the sensible heat flux between the city's land surface and the atmosphere. The results are as follows. 1) Classification of land use in the Daegu area shows 46.64% of urban and built-up area, 1.39% of watersides, 35.19% of forest, 11.43% of crops, and 5.37% grasslands. 2) During the weekdays throughout the year, the land surface temperature was high for Dalseogu, Bukgu, and Seogu regions where industrial complexes could be found. Comparatively, lower temperature could be observed in the woodlands. 3) While the land surface temperature displayed the effects of pushing air upwards during the weekdays in urban areas, the reverse was true for forest regions. During the night, the temperature did not exert any significant influence on air movement.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 추계학술대회
• /
• pp.1317-1322
• /
• 2004

In this report, the heat transfer model of spray cooling on hot surface was developed by focusing on the effect of rebound motion of droplets. In the model, it was assumed that droplets rebound repeatedly on the hot surface and heat transfer upon droplet impact is proportional to sensible heat which heats up the droplets to the saturation temperature. In addition, to take account of the contribution of th heat flux upon impact of rebound droplets, it was assumed that the rebound droplets are distributed following the Gaussian distribution from 0 to L, which distance L is determined by maximum flight distance $L_{max}$. Also the calculated results were compared with existing experimental results.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제6권
• /
• pp.168-176
• /
• 1998

A simulation study was conducted to use city-water which is thermally regulated by unused energy as a heat source for urban dwellings. This study utilized multiple heat pump system using the city-water as a heat source and suggested a method of reducing the heat load of hot water supply. The simulation was done to calculate the energy savings at a dwelling for a year. The relation between the controlled temperature of city-water. and electric energy in all seasons was also investigated. Furthermore, it has been found that the controlled water system can lead to considerable energy savings and decrease environmental load such as sensible waste heat which otherwise would form heat islands.

• 한국해양공학회지
• /
• 제2권1호
• /
• pp.176-182
• /
• 1988

The exergy analysis on the heat storage performance of the senible heat storage unit which consists of the heat storage material in the concentric annulus and the hot fluid flowing through the inner tube is performed. Heat transfer characteristics which are necessary for the performance of the exergy analysis is obtained from the energy balance equations and the second law of thermodynamics. As the index of heat storage performance, the exergy lossnumber $N_{s}$, and exergy storage ratio from the concepts of the second law of thermodynamics are defined. Results are ovtained for the grometry of the storage unit, the Biot number Bi, ambient temperature $T_{o}$ as parameters. From these results the exergy storage ratio can be considered as the efficiency of the hat storage unit and is introduced as a guide to design.

• 전기학회논문지
• /
• 제67권10호
• /
• pp.1257-1264
• /
• 2018

This paper proposes Autoregressive Integrated Moving Average (ARIMA)-based forecasting algorithms using meteorological indices to predict seasonal peak load. First of all, this paper observes a seasonal pattern of the peak load that appears intensively in winter and summer, and generates ARIMA models to predict the peak load of summer and winter. In addition, this paper also proposes hybrid ARIMA-based models (ARIMA-Hybrid) using a discomfort index and a sensible temperature to enhance the conventional ARIMA model. To verify the proposed algorithm, both ARIMA and ARIMA-Hybrid models are developed based on peak load data obtained from 2006 to 2015 and their forecasting results are compared by using the peak load in 2016. The simulation result indicates that the proposed ARIMA-Hybrid models shows the relatively improved performance than the conventional ARIMA model.