• Title/Summary/Keyword: heat-wave data

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Comparison of Performance Characteristics in the Chevron Type Plate Heat Exchanger with Performance Correlation (성능 예측 상관식에 따른 쉐브론 형태 판형 열교환기 성능 특성 비교)

  • Bae, Kyung-Jin;An, Sung-Kuk;Cho, Hyun-Uk;Nam, Sang-Chul;Cho, Hong-Hyun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.23 no.8
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    • pp.535-542
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    • 2011
  • The performance of a plate heat exchanger for using liquid solution in the absorption chiller-heater was analyzed. The model was developed by using the various performance prediction correlations. The performance characteristics of the plate heat exchanger with the mass flow rate ratio was verified by using experimental data. To investigate performance of plate heat exchanger with geometry variables, the chevron angle, corrugated wave length, and corrugation depth were changed. As a result, the capacity of Kim and Martin correlation models was similar with the experimental data, and the capacity difference was less than 2%. Besides, the pressure drop of Marin correlation model showed a similar variation with experimental data, and the difference of pressure drop was less than 1.5 kPa.

An Experimental Study on the Heat Exchangers in the Pulse Tube Refrigerator (맥동관 냉동기 열교환기에 관한 실험적 연구)

  • 남관우;정상권;정은수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.3
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    • pp.284-291
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    • 2000
  • A basic pulse tube refrigerator has been constructed with extensive instrumentation to study the characteristics of the heat exchanger experimentally under the oscillating pressure and the oscillating flow. This paper describes the sequential experiments with the basic pulse tube refrigerator. The experiments were performed for various cycle frequencies under the square pressure wave forms. First, the heat flux was measured through the cycle at the both cold and warm end heat exchangers without the regenerator. In order to enhance the thermal communication capability of the heat exchanger with the gas at low operating frequencies, a unique design of the triangular shape radial fin concept was applied to the heat exchangers. For the fin heat exchanger, the measured heat flux and the calculated heat flux from the two well-known oscillating heat transfer correlations were compared and discussed. Second, the regenerator was added to the pulse tube to make a basic pulse tube refrigerator configuration. The experiment showed the great impact of the regenerator on the temperature and the heat flux profiles. At the warm-end, the cyclic averaged heat flux had its maximum value at the specific operating frequency. The paper presents the explanation of the surface heat pumping effect as well as the experimental data.

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Daily Variation of Heat Budget Balance in the Gangjeong-Goryung Reservoir for Summertime - Concerning around the Rate of Heat Storage - (낙동강 강정고령보의 여름철 열수지 일변화 - 열 저장량 변동을 중심으로 -)

  • Kim, Seong-Rak;Cho, Chang-Bum;Kim, Hae-Dong
    • Journal of Environmental Science International
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    • v.24 no.6
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    • pp.721-729
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    • 2015
  • Surface heat balance of the Gangjeong-Goryung Reservoir is analyzed for 12-17 August 2013. Each flux elements at the water surface is derived from the special field observations with application of an aerodynamical bulk method for the turbulent heat fluxes and empirical formulae for the radiation heat fluxes. The rate of heat storage in the reservoir is estimated by using estimated by surface heating rate and the vertical water temperature data. The flux divergence of heat transport is estimated as a residual. The features of the surface heat balance are almost decided by the latent heat flux and the solar radiation flux. On average for 12-17 August 2014 in the Gangjeong- Goryung Reservoir, if one defines the insolation at the water surface as 100 %, 94 % is absorbed in the reservoir; thereafter the reservoir loses about 30~50% by sensible heat, latent heat and net long-wave radiation. The residue of 50~80 % raises the water temperature in the reservoir or transported away by the river flow during the daytime.

Characteristics on Big Data of the Meteorology and Climate Reported in the Media in Korea

  • Choi, Jae-Won;Kim, Hae-Dong
    • Quantitative Bio-Science
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    • v.37 no.2
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    • pp.91-101
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    • 2018
  • This study has analyzed applicable characteristics on big data of the meteorology and climate depending on press releases in the media. As a result, more than half of them were conducted by governmental departments and institutions (26.9%) and meteorological administration (25.0%). Most articles were written by journalists, especially the highest portion stems from straight articles focusing on delivering simple information. For each field, the number of cases had listed in order of rank to be exposed to the media; information service, business management, farming, livestock, and fishing industries, and disaster management, but others did rank far behind; insurance, construction, hydrology and energy. Application of big data about meteorology and climate differed depending on the seasonal change, it was directly related to temperature information during spring, to weather phenomenon such as monsoon and heat wave during summer, to meteorology and climate information during fall, and to weather phenomenon such as cold wave and heavy snow during winter.

Simulations of Thermal Stratification of Daecheong Reservoir using Three-dimensional ELCOM Model (3차원 ELCOM 모형을 이용한 대청호 수온성층 모의)

  • Chung, Se Woong;Lee, Heung Soo;Choi, Jung Kyu;Ryu, In Gu
    • Journal of Korean Society on Water Environment
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    • v.25 no.6
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    • pp.922-934
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    • 2009
  • The transport of contaminants and spatial variation in a deep reservoir are certainly governed by the thermal structure of the reservoir. There has been continuous efforts to utilize three-dimensional (3D) hydrodynamic and water quality models for supporting reservoir management, but the efforts to validate the models performance using extensive field data were rare. The study was aimed to evaluate a 3D hydrodynamic model, ELCOM, in Daecheong Reservoir for simulating heat fluxes and stratification processes under hydrological years of 2001, 2006, 2008, and to assess the impact of internal wave on the reservoir mixing. The model showed satisfactory performance in simulating the water temperature profiles: the absolute mean errors at R3 (Hoenam) and R4 (Dam) sites were in the range of $1.38{\sim}1.682^{\circ}C$. The evaporative and sensible heat losses through the reservoir surface were maximum during August and January, respectively. The net heat flux ($H_n$) was positive from February to September, while the stratification formed from May and continued until September. Instant vertical mixing was observed in the reservoir during strong wind events at R4, and the model reasonably reproduced the mixing events. A digital low-pass filter and zero crossing method was used to evaluate the potential impact of wind-driven internal wave on the reservoir mixing. The results indicated that most of the wind events occurred in 2001, 2006, 2008 were not enough to develop persistent internal wave and effective mixing in the reservoir. ELCOM is a suitable 3D model for supporting water quality management of the deep and stratified reservoirs.

A Study on the Impulse Voltage Breakdown Characteristics of Heat-Deteriorated Polyethylene Cables ( I ) (열렬화된 폴리에틸렌 케이블의 충격전압에 의한 파괴특성에 관한 연구 I)

  • 곽영순
    • 전기의세계
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    • v.24 no.1
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    • pp.63-69
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    • 1975
  • This study investigated the characteristics of fatigue breakdown caused by the impulse voltage of heat treated polyethylene cables through fault currents. This study attempted to obtain the badic data on the insulation design by the repeated load of impulse voltage wave zone (1*40.mu.s) on heat treated polyethylene cables. Besides this study also analysed the data involving their durability by means of the Weibull distribution. An analysis of the breakdown characteristics based upon the repeated load of impulse voltage has revealed that worn out deteriorative breakdown existed at a high voltage near the initial breakdown voltage, and that random breakdown was discovered at a voltage somewhat lower than the initial breakdown voltage. These phenomena were more remarkable especially in the case of the higher temperature treated cables.

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Analysis of Passive Cooling Effect of Membrane Shading Structure and the Tree by Field Observations in the Summer (하절기 복사환경 관측을 통한 수목과 일사차폐 막 구조물의 자연냉각효과)

  • Choi, Dong-Ho;Lee, Bu-Yong
    • Journal of the Korean Solar Energy Society
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    • v.27 no.4
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    • pp.137-146
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    • 2007
  • This study is about the passive cooling effects of three outdoor solar shading facilities as trees, pergola with wistaria vine and membrane shading structure, which are expected to provide cool spots in the summer. Field observations of measuring thermal environment of selected facilities is executed. Thermal environment measuring was categorized as short wave radiation, long wave radiation, net radiation, globe temperature, surface temperature measured by infrared camera. Heat transfer mechanism is analyzed with overall data from field measurement. Results from this study are as below; 1) Radiation balance measured on shaded surface under membrane shading structure was 17%($86W/m^2$) of the unshaded surface radiation balance($511W/m^2$). 2) Surface temperature comparison between vegetation and membrane of the shading structure is performed at 3 o'clock in the afternoon. Surface temperature of vegetation was same as air temperature and that of membrane was $5^{\circ}C$ higher than air temperature. Vegetation transpiration is considered as the causing factor which make those differences. 3) Results from this study could be used as fundamental data for reducing heat island phenomena and continuos research on this subject would be needed.

A Study of Improving Combustion Stability with Sonic Wave Radiation (음파를 이용한 연소 안정성 개선에 관한 연구)

  • Min, Sun-ki
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.8
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    • pp.401-406
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    • 2020
  • NOx (nitrogen oxide) in the exhaust gas engines causes severe air pollution. NOx is produced under high-temperature combustion conditions. EGR (exhaust gas recirculation) is normally used to reduce the combustion temperature and NOx production. As the EGR ratio increases, the NOx level becomes low. On the other hand, an excessively high EGR ratio makes the combustion unstable resulting in other air pollution problems, such as unburned hydrocarbon and higher CO levels. In this study, the improvement of fuel droplets moving by the radiation of sonic waves was studied for the stable combustion using analytic and experimental methods. For the analytical study, the effects of the radiation of a sonic wave on the fuel droplet velocity were studied using Fluent software. The results showed that the small droplet velocity increased more under high-frequency sonic wave conditions, and the large droplet velocity increased more under low-frequency sonic wave conditions. For the experimental study, the combustion chamber was made to measure the combustion pressure under the sonic wave effect. The measured pressure was used to calculate the heat release rate in the combustion chamber. With the heat release rate data, the heat release rate increased during the initial combustion process under low-frequency sonic wave conditions.

A Study on Identification of the Heat Vulnerability Area - Case Study in Chungcheongnamdo - (폭염 취약지역 도출에 관한 연구 - 충청남도를 대상으로 -)

  • Lee, Gyeongjin;Cha, Jungwoo
    • Journal of Korean Society of Rural Planning
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    • v.25 no.1
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    • pp.67-74
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    • 2019
  • This study is to identify the heat vulnerability area as represented by heat risk factors which could be attributable to heat-related deaths. The heat risk factors were temperature, Older Adults(OA), Economic Disadvantage(ED), Accessibility of Medical Services(AMS), The population Single Person Households(SPH). The factors are follow as; the temperature means to the number of days for decades average daily maximum temperature above $31^{\circ}C$, the Older Adults means to population ages 65 and above, furthermore, the Economic Disadvantage means to the population of Basic Livelihood Security Recipients(BLSR), the Accessibility of Medical Services(AMS) means to 5 minutes away from emergency medical services. The results of the analysis are showed that the top-level of temperature vulnerability areas is Dong, the top-level of vulnerability OA areas is Eup, the top-level of AMS vulnerability is Eup. Moreover, the top-level of vulnerability ED area appears in the Eup and Dong. The result of analysing relative importance to each element, most of the Eup were vulnerable to heat. Since, there are many vulnerable groups such as Economic Disadvantage, Older Adults in the Eup. We can be figured out estimated the number of heat-related deaths was high in the Eup and Dong by the data of emergency activation in the Chungcheongnam-do Fire Department. Therefore, the result of this study could be reasonable.

Smart Helmet for Vital Sign-Based Heatstroke Detection Using Support Vector Machine (SVM 이용한 다중 생체신호기반 온열질환 감지 스마트 안전모 개발)

  • Jaemin, Jang;Kang-Ho, Lee;Subin, Joo;Ohwon, Kwon;Hak, Yi;Dongkyu, Lee
    • Journal of Sensor Science and Technology
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    • v.31 no.6
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    • pp.433-440
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    • 2022
  • Recently, owing to global warming, average summer temperatures are increasing and the number of hot days is increasing is increasing, which leads to an increase in heat stroke. In particular, outdoor workers directly exposed to the heat are at higher risk of heat stroke; therefore, preventing heat-related illnesses and managing safety have become important. Although various wearable devices have been developed to prevent heat stroke for outdoor workers, applying various sensors to the safety helmets that workers must wear is an excellent alternative. In this study, we developed a smart helmet that measures various vital signs of the wearer such as body temperature, heart rate, and sweat rate; external environmental signals such as temperature and humidity; and movement signals of the wearer such as roll and pitch angles. The smart helmet can acquire the various data by connecting with a smartphone application. Environmental data can check the status of heat wave advisory, and the individual vital signs can monitor the health of workers. In addition, we developed an algorithm that classifies the risk of heat-related illness as normal and abnormal by inputting a set of vital signs of the wearer using a support vector machine technique, which is a machine learning technique that allows for rapid binary classification with high reliability. Furthermore, the classified results suggest that the safety manager can supervise the prevention of heat stroke by receiving feedback from the control system.