• Ecology and Resilient Infrastructure
• /
• v.3 no.1
• /
• pp.46-53
• /
• 2016

This study was conducted to analyze the effect of the different land covers of an urban park (Hyowon park) in downtown Suwon on the urban thermal variations during a hot summer. The effect of the air temperature reduction in the urban park was 4.4%-4.5% for the downtown residence (Maetan-dong). This value was about 0.8% lower than that of the outskirts residence (Sanggwanggyo-dong). The daily mean temperature, daily maximum temperature, summer day and heat wave frequency were measured under the different land covers (cement-block, grass, pine-grass, shading area and mixed forest) showed these values generally decreased under natural land cover types. Daily minimum temperature and tropical night frequency didn't seem to correlate with the land cover types. Means of thermal comfort indices (wet bulb globe temperature, heat index and discomfort index) in the shading area, mixed forest and the pine-grass types were lower than those of cement block and grass types. However the levels of those indices were equal to 'very high' or 'caution' levels in the afternoon (13:00-15:00). In the morning (06:00-08:00), thermal comfort indices of the urban park didn't correlate with land cover types. Therefore, to reduce heat stress and to improve the thermal comfort in urban parks, an increase in the area of natural land cover such as grass, forest and open spaces is required.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2006.05a
• /
• pp.31-35
• /
• 2006

Degradation characteristics of filament-winded composites due to accelerated environmental aging have been evaluated under high temperature, water immersion and thermal impact conditions. Two kinds of laminated composites coated by an urethane resin have been used: carbon-fiber reinforced epoxy(T700/Epon-826, CFRP) and glass-fiber reinforced phenolic (E-glass/phenolic, GFRP). For tensile strength of $0^{\circ}$ composites, CFRP did high reduction by 25% under the influence of high temperature and water while CFRP showed little degradation. However for water-immersed $90^{\circ}$ composites both CFRP and GFRP showed high reduction in tensile strength. Bending strength and modulus of $90^{\circ}$ composites were largely reduced in water-immersion as well as high temperature environment. Urethane coating on the composite surface improved the bending properties by 20%, however hardly showed such improvement for water-immersed $90^{\circ}$ composites.

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10b
• /
• pp.636-639
• /
• 1996

We have developed a part of hydraulic stroke sensing cylinder using magnetic sensor that can detect each position under severe construction fields. In this paper, for evaluating the developed cylinder under various environment condition, thermal control systems and two hydraulic systems to be coupled consist of. The former is composed of an heater case, temperature sensor, and interface circuits which include SCR(silicon controlled rectifier) for the control of the voltage's phase. The latter is composed of an hydraulic cylinder for position control with solenoid valve (ON/OFF motion) and a load cylinder with proportional reducing valve. To obtain the various performance evaluation, it is carried out under high temperature condition in thermal system controlled by using Ziegler-Nichols PID tuning method and artificial disturbances such as impulse or constant force. The results show that the developed cylinder has good performance under the various environment condition.

• Journal of the Korean Solar Energy Society
• /
• v.40 no.2
• /
• pp.25-36
• /
• 2020

The Korean government has a plan to mandate zero-energy buildings in 2020 for public and 2025 for private buildings. In order to design a zero-energy building, insulation and airtightness, which are the most basic elements of passive house technology, are required, and the government has been accomplished this through step-by-step strengthening of related standards. In passive house with high thermal insulation and airtightness performance, the heat introduced into the building through solar radiation can be stored for a long time to keep the inside warm during winter. On the other hand, during summer, heat introduced into the building cannot be easily released to outside, so it is necessary to actively block solar radiation and high temperature outdoor air to prevent an increase of indoor temperature. Therefore, this study aims to derive an appropriate operation condition of passive house to maintain the indoor temperature at an suitable level according to the ventilation methods and solar shading conditions. As a result, under the conditions that the outdoor temperature was 28℃ or less, the ventilation using a heat recovery ventilation system at daytime and natural ventilation at nighttime were selected for the most appropriate operation method. In addition, in the case of solar shading, it was found that blocking solar radiation at daytime using the blind and open the blind at nighttime to ensure natural ventilation were selected for the most appropriate solar shading condition.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.23 no.5
• /
• pp.450-455
• /
• 2014

Domestic power plants have consistently been developed over the years in industrially developed nations with high standards of living. Considering the power plant development strategy, design efficiency is of upmost importance. Therefore, an improper design directly affects the power plant's risk management plan and the potential risks of the piping system. Therefore, in this study, research is intended to be carried out to allow efficient power plant operation, through optimization of the design of the piping system. The purpose of the study is to confirm economic feasibility by changing the piping loop design, expanding the length of pipe loops, and to investigate the thermal stress influence on the piping system through simulations of systems similar in condition to those currently used in existing plants in Korea.

• Journal of Surface Science and Engineering
• /
• v.27 no.2
• /
• pp.91-98
• /
• 1994

For the plasma sprayed as well as the EB-PVD thermal barrier coatings, the fracture paths within the oxidation products developed at the interface between the partially stabilized zirconia ceramic coating and NiCoCrAlY bond coat during cyclic thermal oxidation has been investigated. It was observed that the fracture in the oxidation products primarily took place within the oxide such as $Ni_{1-x}Co_3(Al_,Cr)_2O_4$ or at the interface between the oxide and $Al_2O_3$. It was found that Al2O3 developed first, followed by the Ni/Co/Cr rich oxides such as ,,$Ni_{1-x}Co_x(Al_,Cr)_2O_4$ $Cr_2O_3$and NiO at the interface between the ceramic coating and the bond coat in a cyclic high temperature environment. It was therfore concluded that the formation of the oxide containing Ni, Cr and Co was a life-limiting event for thermal barrier coatings during cyclic thermal oxidation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.20 no.4
• /
• pp.287-293
• /
• 2008

The purpose of this study was to clarify the effects of air and ceiling temperatures on a type of ceiling cooling system that involves cool water circulation. The experiment is conducted in summer. The subjects (11 young females) are exposed to the following conditions: combinations of air temperatures $(27^{\circ}C,\;29^{\circ}C,\;31^{\circ}C)$ and ceiling temperature of $(22.7^{\circ}C,\;23.7^{\circ}C,\;24.7^{\circ}C)$ in still air and RH 50%. The following results were obtained; the thermal sensation vote is neutral at a mean skin temperature of $34.5^{\circ}C$. The ceiling temperature affected different parts of the body. For example, the forehead, scapula and abdomen produced different skin temperatures. Thermal comfort vote was rated as comfortable at high temperature environment. The satisfaction from the ceiling temperature was valued comfortable zone in this experiment. Mean skin temperature showing higher thermal neutrality temperature than existing studies for floor and wall radiation cooling results.

• Advances in materials Research
• /
• v.8 no.4
• /
• pp.275-293
• /
• 2019

The engine parts material used in gas turbines (GTs) should be resistant to high-temperature variations. Thermal barrier coatings (TBCs) for gas turbine blades are found to have a significant effect on prolonging the life cycle of turbine blades by providing additional heat resistance. This work is to study the performance of TBCs on the high-temperature environment of the turbine blades. It is understood that this coating will increase the lifecycles of blade parts and decrease maintainence and repair costs. Experiments were performed on the gas turbine blade to see the effect of TBCs in different combinations of materials through the air plasma method. Three-layered coatings using materials INCONEL 718 as base coating, NiCoCrAIY as middle coating, and La₂Ce₂O₇ as the top coating was applied. Finite element analysis was performed using a two-dimensional method to optimize the suitable formulation of coatings on the blade. Temperature distributions for different combinations of coatings layers with different materials and thickness were studied. Additionally, three-dimensional thermal stress analysis was performed on the blade with a commercial code. Results on the effect of TBCs shows a significant improvement in thermal resistance compared to the uncoated gas turbine blade.

• 한국태양에너지학회:학술대회논문집
• /
• 2012.03a
• /
• pp.475-479
• /
• 2012

Thermal energy storage (TES) systems using Microencapsulated phase change material (MPCM) have been recognized as one of the most advanced energy technologies in enhancing the energy efficiency and sustainability of buildings. We examined a way to incorporate MPCMs with building materials through application for wood-based flooring. Wood-based flooring is commonly used for floor finish materials of residential buildings in Korea. However, wood-based flooring has not performed the characteristic of heat storage. This study is aimed at manufacturing high thermal efficiency wood flooring by increasing its heat storage using MPCM. As a result, this study confirmed that MPCM is dispersed well in adhesive through the scanning electron microscopy analysis. From the differential scanning calorimetry analysis, it can be confirmed that this composite has the characteristic of a thermal energy storage material. Also, we analyzed how this composition was formed by physical combination through the Fourier transform infrared analysis. Also, we confirmed the bonding strength of the material by using the universal testing machine.

• International Journal of High-Rise Buildings
• /
• v.2 no.4
• /
• pp.293-314
• /
• 2013

Double-Skin Façade (DSF), which is a kind of passive indoor environmental control technique, is effective way to control environmental loads while maintaining the transparency especially in perimeter zone and hence the adoption example of DSF keep increasing recently. The objective of this study was to perform a field survey of air quality environment with natural ventilation through DSF and thermal environment within office building with six stories during a mild climate period in Japan. Moreover, to understand the comprehensive environmental performance of the target building, questionnaire survey was conducted to subjectively evaluate the productivity and satisfaction with the environmental factors in office space. In this field measurement, there was a positive correlation between the DSF internal ventilation flow and the amount of solar radiation on the DSF normal surface; the primary driving force for ventilation in the DSF was considered to be the buoyancy force caused by solar radiation. The results of questionnaire survey with regard to productivity level indicated the need for improvement in the thermal (temperature) and spatial environment (room size and furniture placement).