• Journal of the Korean Solar Energy Society
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• v.32 no.2
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• pp.113-119
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• 2012

This study aims to examine the effect of the combined application of green roof and PV system on the PV efficiency by measuring the temperature and performance of PV module in order to reduce the temperature on the roof using roof planting system and determine the potential of efficient increase in solar-light power generation. In the experimental methodology, either monocrystalline or polycrystalline PV module was installed in green roof or non-green roof, and then the surface temperature of PV was measured by TR-71U thermometer and again the performance, module body temperature, and conversion efficiency were measured by MP-160, TC selector MI-540, and PV selector MI-520, respectively. As a result, the average body temperature of monocrystalline module was lower by $6.5^{\circ}C$ in green roof than in non-green roof; that of polycrystalline module was lower by $8.8^{\circ}C$ in green roof than in non-green roof. In the difference of generation, the electricity generation of monocrystalline module in green roof was 46.13W, but that of polycrystalline module was 68.82 W, which indicated that the latter produced 22.69W more than the former.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.26-31
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• 2009

This study was analysed influence of urban higher temperature in Busan about time series analysis of AWS data. The results are as follows. (1) The temperature of Busan show min $13.2^{\circ}C$ ~max $15.8^{\circ}C$ by 50 years, it is on the rise. (2) The seasonal adjustment series, summer appeared min $17.5^{\circ}C$ ~max $28.9^{\circ}C$ with primitive series similarly. The winter was min $-11.4^{\circ}C$ ~max $17.9^{\circ}C$, the minimum temperature was more lowly than primitive series and maximum temperature was more higher than primitive series. The results, seasonal adjustment series is guessed with influence difference urban structural element beside seasonal factor. (3) Regional analytical result, January appeared with range of min 28% ~max 196% of the seasonal factor and August appeared min 90% ~ max 106%. One of the case which is of 100% or more of the seasonal factor January 12nd~17th, August appears at the 15~17th.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.6
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• pp.540-548
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• 2019

This study was conducted to develop insulation for solid oxide fuel cell (SOFC). The developed insulation is based on the lamination technology and the radiation shielding technology of the satellite insulation. The insulation material is consisting of insulation material for conduction resistance, spacer, and radiation shielding material. The experimental apparatus consisting vacuum bell jar, pump, heater and temperature recording device has developed to verify the performance of the insulation. The experimental values were used as reference data for the modeling development. In this paper, heat transfer is assumed to be one- dimensional phenomena for the prediction of insulation performance and internal temperature distribution in high temperature region of SOFC. The developed model was used to compare the performance difference of insulation types according to composition materials. The analysis result shows that the insulation including spacer and radiation shielding has better heat insulation performance than other cases. In this study, the thickness reduction effect of about 20% was shown compared to the insulation including only conductive material. It is noted that the radiant shielding material should be carefully selected for durability, because SOFC insulation should be used for a long time at high temperature.

• Journal of the Korean Institute of Landscape Architecture
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• v.34 no.5 s.118
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• pp.70-75
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• 2006

The purpose of this study is to explore the effects of difference in urban tree plantings on microclimate amelioration, and to suggest essential information for quantifying urban energy budgets and energy savings. This study was focused on measuring and analyzing air temperature and relative humidity in summer. Daytime air temperatures at places with 8%, 24%, 44%, 79%, and 100% cover of woody plants were, respectively, $0.6^{\circ}C,\;1.3^{\circ}C,\;2.4^{\circ}C,\;3.5^{\circ}C,\;and\;4.8^{\circ}C$ cooler, compared to a place with 0% cover. A 10% increase of woody plant cover was estimated to reduce the temperature by approximately $0.55^{\circ}C$. The temperature reduction effects were relatively greater between places with lower cover of woody plants than between those with higher cover. Woody plant cover and crown volume were the appropriate indicators which quantified the effects of tree plantings on air temperatures, based on the correlation analysis. Regression equations to estimate temperature change ($Y:^{\circ}C$) using woody plant cover ($X_1:%$) or crown volume ($X_2:m^3$) as independent variables are as follows: $$1nY=3.3233-0.0018X_1\;(r^2=0.99,\;p<0.0001)\;Y=27.5297-0.0019X_2\;(r^2=0.96,\;p=0.0007)$$

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.171.2-171.2
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• 2010

Geothermal effects on the underground water conveyance pipe system have been investigated through the multiregional water supply system from Paldang water intake station. To make an investigation of raw water thermal energy, temperature sensors are installed the surface of the pipes of metropolitan area water supply system. In 2009 winter and early spring seasons, the monthly averaged temperatures at Paldang 2 intake stations are $1.94^{\circ}C$ in February, $4.96^{\circ}C$ in March, and $10.56^{\circ}C$ in April. After the transfer in 26.0 km distance of tunnel and buried pipe, the raw water temperatures are raised to $3.13^{\circ}C$, $6.04^{\circ}C$, and $11.39^{\circ}C$ respectively. As the temperature difference between the raw water and the air reduces, the temperature increasement is reduced by $1.19^{\circ}C$ in Feb., $1.08^{\circ}C$ in Mar., and $0.83^{\circ}C$ in Apr. Since the flowrate is over 1,150,000 $m^3$/day, it is estimated that the water exchanges a huge amount of heat over 1.0 Tcal a day with the ground.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.31-36
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• 2004

In this paper, fretting wear tests were conducted in air at room temperature (RT) and in water at high temperature and high pressure (HTHP) environment to analyze the wear characteristic. As for the supporting condition between the tube and spring/dimple, the gap of 0.2 mm in air at RT and the normal force of 10 N and the slip of $50\;{\mu}\;m$ in water at HTHP were applied. Four different shapes of spring/dimple specimen (type A, B, C, D) were used. Detail eaxamination of wear scar was also performed using SEM micrographs. As a result, in the case of the spring of truncated wedge, severer wear occurs than the others. Protrusion part was found and larger in air at RT. It is thought that the difference in the wear volume and the protrusion is caused by the different wear mechanism corresponding to the different environment.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.2
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• pp.45-53
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• 2018

Demand for essential resources including water, energy and food is rapidly increasing due to climate change, population growth and urbanization. To solve this problem, the concept of water-energy-food nexus has been introduced, and many countries have been trying to acquire the Nexus technology that can maximize the efficiency by analyzing the interconnection between resources. In this regard, this study attempted to estimate the probable maximum water thermal energy in the dam based on the water-energy nexus concept. The estimation of the probable maximum water thermal energy was implemented to monthly water storage of the largest dams in the four major river systems. As a result of analyzing the estimated monthly water thermal energy from 2000 to 2016, Soyang River dam has the largest probable maximum water thermal energy, and Sumjin River dam has the smallest. However, the probable maximum water thermal energy was small in common between March and April, between September and October due to the small temperature difference between the ambient air and the dam water. Also, according to the characteristics of the dam, Daecheong dam and Soyang River dam were beneficial for supplying water thermal energy for heating, and Sumjin River dam and Andong dam were advantageous for supplying water thermal energy for cooling. Our findings can be useful to realize the water-energy-food nexus by increasing the utilization and value of water resources as well as expanding the roles and functions of dams as a starting point to use dam water thermal energy.

• Design & Manufacturing
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• v.15 no.1
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• pp.26-31
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• 2021

As the aging ages, the disease also increases, and the development of AI technology and X-ray equipment used to treat patients' diseases is also progressing a lot. X-ray tube converts only 1% of electron energy into X-ray and 99% into thermal energy. Therefore, when the cooling time of the anode and the X-ray tube are frequently used in large hospitals, the amount of X-ray emission increases due to temperature rise, the image quality deteriorates due to the difference in X-ray dose, and the lifespan of the overheated X-ray tube may be shortened. Therefore, in this study, temperature rise and cooling time of 60kW, 75kW, and 90kW of X-ray tube anode input power were studied. In the X-ray Tube One shot 0.1s, the section where the temperature rises fastest is 0.03s from 0s, and it is judged that the temperature has risen by more than 50%. The section in which the temperature drop changes most rapidly at 20 seconds of cooling time for the X-ray tube is 0.1 seconds to 0.2 seconds, and it is judged that a high temperature drop of about 65% or more has occurred. After 20 seconds of cooling time from 0 seconds to 0.1 seconds of the X-ray tube, the temperature is expected to rise by more than 3.7% from the beginning. In particular, since 90kW can be damaged by thermal shock at high temperatures, it is necessary to increase the surface area of the anode or to require an efficient cooling system.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1027-1031
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• 2014

Free cooling system is used to reduce energy consumption of cooling system. Free cooling system is consisted of cooling group and dry-cooler in which heat exchange of chilled water and out air is conducted. Although this system has an excellent energy saving effect in place having cooling load regularly, data or material of design for free cooling system is lacked. In this study, characteristics analysis of free cooling system is conducted through software HYSYS with changing some facts. The main result is following as : Dry-cooler capacity is influenced by out air temperature, required chilled water temperature and LMTD(Logarithmic Mean Temperature Difference) of heat exchanger. As out air temperature is more low, dry-cooler capacity become increased. in addition, as required chilled water temperature is more high and LMTD is more low, the out air temperature range is widened for using dry-cooler. If out air temperature is below $0^{\circ}C$, antifreeze need to be used because freeze and burst can be occurred. In case of South Korea, antifreeze of 34% of ethylene glycol concentration is proper. When compressor load of R22, R134a and R407C is compared, considering environmental regulation and energy consumption, R134a is best working fluid.

• Journal of the Korean Solar Energy Society
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• v.34 no.6
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• pp.19-25
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• 2014

Alternative sources of energy take a higher interest in order to reduce the greenhouse gas under the Climate Change Convention, fossil fuel consumption, and lower social anxiety about nuclear power such as crisis involving the Fukushima plant, problem of obsolete equipment. The energy consumption of agriculture, forestry and fisheries in South Korea is 3,082,000toe by 2011, reliance on electrical energy(35%) and oil(57.2%) is very high with 92.2%. In this study, we examined reserves and available capacity of temperature difference energy for thermal discharge from plant, treated sewage, river water, dam, and agricultural reservoir in rural community. Reserves of unutilized energy are 455,735Tcal/yr in rural community, these accounts for 78% of total reserves 582,385Tcal/y. Thermal discharge from plant has the most reserves of unutilized energy in rural community, it is estimated that it has the reserves of 277,410Tcal/y. Available capacity of unutilized energy in rural community is total 134,147Tcal/y, thermal discharge from plant available for heating is the most 128,035Tcal/y, and it shows in the order of treated sewage 4,318Tcal/y, river water 1,653Tcal/y, and reservoir 141Tcal/y. Elevating temperature area of green house by 2012 is 21,208ha. The amount of energy required for heating the greenhouse a year is dbout 11,365Tcal/y with 8.5% of the total available capacity of unutilized energy.