• Journal of Environmental Science International
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• v.16 no.5
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• pp.583-591
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• 2007

In this study, meteorological characteristics concerning the occurrence of fog are analyzed using 4-years (2000-2003) data at Chuncheon. From the analysis of meteorological characteristics, the fog at Chuncheon occurred before sunrise time and disappeared after that time and lasted for 2-4 hours. When fog occurred, on the whole, wind direction was blew the northerly and wind speed was below 2.1 m/s. Especially, about 42 % of foggy day fell on the calm($0{\sim}0.2m/s$) conditions. The difference between air temperature and dew point temperature near the surface were mainly less than $2^{\circ}C$. For the lack of water surface temperature, the water sur-face temperature was calculated by using Water Quality River Reservoir System (WQRRS). In Chuncheon, there is close correlation between the frequency of fog day and outflow from Soyang reservoir and high frequency of occurrence due to the difference between air and cold outlet water temperature.

• Journal of ILASS-Korea
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• v.28 no.2
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• pp.89-96
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• 2023

This study presents a numerical simulation investigating hydrodynamic characteristics of high-temperature hydrocarbon aviation fuel injected through a plain orifice injector. The analysis encompassed the temperature range up to the critical point, and the obtained results were compared with prior experimental observations. The analysis unveiled that the injector's exit pressure remains equivalent to the ambient pressure when the fuel injection temperature is below the boiling point. However, when the fuel temperature surpasses the boiling point, the exit pressure of the injector transitions to the saturated vapor pressure corresponding to the fuel injection temperature. Consequently, the exit pressure of the injector increases in tandem with the rapid increase of the saturation vapor pressure due to escalating fuel temperatures. This rise in the exit pressure necessitates a proportional increase in fuel injection pressure to ensure a fixed fuel mass flow rate. Furthermore, the investigation revealed that the discharge coefficient obtained by applying the exit pressure instead of the ambient pressure did exhibit no decrease, but rather was maintained at a nearly constant value, comparable to its level below the boiling point.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.1
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• pp.51-60
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• 2012

Optimization procedures of performance analysis for ORC(Organic Rankine Cycle) system are established to the characteristics of low temperature heat sources such as open-type and closed-type. Effective heat recovery and heat extraction related to maximum power of the cycle as well as heat quality and thermal efficiency must be considered in the case of the open-type low temperature heat source. On the other hand, in the case of the closed-type low temperature heat source, only thermal efficiency is important due to constant heat input. In this study, thermal efficiency and exergy efficiency representing a level of close to Carnot cycle are studied, as useful index for the optimization of the ORC system. To validate the results of cycle analysis, those are compared with appropriate experimental data of ORC system as a thermal efficiency point of view.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.8
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• pp.1154-1160
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• 2015

This paper describes the thermal characteristics of underground power cable system terminations according to the change of ambient temperature as well as operating temperature. Recently, the failure has been gradually increasing in outdoor termination during winter season because the power demand was increased by electricity heating system. The power demand and outdoor temperature is difference between day time and night time. The temperature difference has an influence on conductor extension and shrinkage due to conductor force as well as thermal mechanical characteristics. These phenomena have daily repeated during heating and cooling period of conductors. In these cases, the insulation of outdoor terminations might be degraded by the reduced interface pressure surrounding stress relief cone. Therefore, in this paper, the thermal characteristics are variously analysed by simulation considering power demand and ambient temperature condition during winter season at epoxy type termination as well as slip-on type termination

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.713-718
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• 2006

In this study, temperature sensors were adhered to transformer that is used in KHST(Korean High-Speed Train) to verify variation of temperature characteristics about transformer synthetically and efficiently. In the case that temperature of transformer exceeds reference temperature for running of KHST, overheating of transformer may cause a fatal accident of vehicle. Characteristics and main specifications of transformer in KHST were described in this paper. Also, measuring system for temperature measurement of transformer was explained in brief. Temperature data of transformer was acquired using measuring system, KRRI(Korea Railroad Research Institute) analyzed characteristic in contrast with comparing with temperature of transformer about month, running speed and running time.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.131-132
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• 2018

The world market for BESS (Battery Energy Storage System) is growing rapidly, and battery technology is also developing. It is important to understand the battery characteristics and develop a control strategy to develop the optimal BMS (Battery Management System). In this paper, we compare and analyze the parameter characteristics of NCM LIB (Lithium Ion Battery) according to the temperature change.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.17 no.4
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• pp.36-45
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• 2021

In this study, to improve the indoor thermal environment of the radiant floor heating system, a study was conducted on the temperature change characteristics and energy consumption according to the change of the indoor air set temperature, the supply hot water temperature and the outdoor temperature. As for the control method, the on/off control and the thermal difference proportional control method proposed through previous studies were applied. In addition, in consideration of field applicability, numerical analysis was performed for the case where the indoor air temperature sensor was affected by the wall temperature. As a result, it was found that the temperature difference proportional control method is more effective for thermal comfort and energy saving than on/off control.

• Journal of the Korean Solar Energy Society
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• v.32 no.5
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• pp.83-93
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• 2012

This study is to perform the effect of urbanization in urban and suburban districts, and to identify regional characters of climate according to the analysis of slope at rise, and descent of temperature and globe temperature, correlation between seasonal temperature analysis, and calculation of degree hour. According to this study, the result is summarized as follows. (1) The average temperature, rated from high to low, consists of residential area, Daegu weather station, intracity, green belt, water-front green belt, and suburban. (2) At the rise and descent of temperature, the result of the slope change of in each point may be one of the useful indexes to be able to perform the regional unique thermal characteristic, including the seasonal urbanization. (3) Although there is a difference between the surface of the earth and ambient environment. The result of the correlation of temperature between summer and winter is that temperature slope in urban districts was higher than in suburban districts, and the difference of slope was unvaried among the four observations in the same city region. (4) To show objectively, regional thermal characteristics in urban and suburban districts, the exponentiation of winter degree hour and summer degree hours were checked. The result of the exponentiation is that the more artificial a region, the lower index.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3
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• pp.380-387
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• 2013

In this study, two finite element (FE) models were developed to evaluate the thermal characteristics of a feeding axis of a CNC lathe. One was used for analysis of heat transfer to identify the temperature distribution of the feeding axis and then, the other was used for analysis of thermal deformation to evaluate its structural behavior based on the temperature distribution. The FE models were based on the test standard for the axial thermal displacement. The feeding velocity was composed of three steps: the ascending, constant, and descending velocities. Therefore, the heat generation and convection coefficient were calculated for each velocity and applied to the thermal FE model. The convection coefficient for the ball screw rotation was based on an experimental equation. The result of the analytical thermal displacement was compared with that of the experimental displacement to verify the finite element models.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1420-1425
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• 2012

Nowadays, Interior permanent magnet synchronous motor(IPMSM) which having high power density is much used for the vehicles. However, IPMSM causes a lot of losses because of high-speed driving and high current density, and temperature rising by iron loss and copper loss could reduce torque characteristics and durability of IPMSM. Therefore, analysis about thermal characteristics of IPMSM is required at design stage. In this paper, temperature characteristics according to current vector control method were analyzed through calculate thermal equivalent circuit. And calculated results were verified through comparing with the experiments.