• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.404-411
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• 2011

The humidity controlling ceramic materials was developed by applying the phenomena of dew condensation in the capillary. It is said that the humidity range which human feels comfortable is from 40 to 70% in relative humidity. In this study, the ceramic tile using natural soils such as diatomite for interior wall was investigated. In particular, we had introduced novel processing routes for fabricating microcellular ceramics tile using hollow microsphere as a pore former. The microcellular pores in the humidity controlling ceramic materials showed the superior properties such as light-weight, heat insulation. The cell density was ${\sim}1.0{\times}10^9$ cells/$cm^3$ and density of sample was 0.65 g/$cm^3$ in the case of 1.71 wt% hollow microsphere content. Also, it is observed that the BET surface area and the pore volume of the sintered diatomite tile have the values of 40.92 $m^2$/g and 0.173 $cm^3$/g.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.10
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• pp.889-894
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• 2004

Infrared (IR) detectors are widely used for many applications, such as temperature measurement, intruder and fire detection, robotics and industrial equipment, thermoelstic stress analysis, medical diagnostics, and chemical analysis. Quantum detectors commonly need to be refrigerated below 80 K, and thus a cooling system should be equipped together with the detector system. The cooling load, which should be removed by the cooling system to maintain the nominal operating temperature of the detector, critically depends on the insulation efficiency of the cryochamber housing the detector. Thermal analysis of cryochamber includes the conduction heat transfer through a cold well, the gases conduction and gas outgassing, as well as radiation heat transfer, The transient cooling characteristics of an infrared detector cryochamber are investigated experimentally in the present study. The transient cooling load increases as the gas pressure is increased. Gas pressure becomes significant as the cooling process proceeds. Cool down time is also increased as the gas pressure is increased. It is also found that natural convection effects on cool down time become significant when the gas pressure is increased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.10
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• pp.960-968
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• 2004

One of the most important functions of a building is to provide thermally comfortable indoor environmental conditions for the occupants. Therefore, a great deal of energy is consumed for heating and cooling to satisfy those thermal requirements. In order to provide thermal comfort with minimum heating and cooling energy consumption, optimal design of building affecting indoor climate is required. This study used the TRNSYS for modeling and simulation of the energy flows of residential building types, and examined the energy efficient measures to reduce the thermal loads. The residential building types are classified into the detached house, apartment house and high-rise residential complex. The results of the simulation show that the heating energy consumption in the detached house is especially high, whereas the cooling load is an important determinant in the apartment house and high-rise residential complex. The measures examined are the insulation thickness, various types of glazing, infiltration, natural and controlled ventilation, solar shading, orientation and etc. Comparative evaluations and sensitivity analyses revealed the effects of these variables and identified their energy efficient building design strategies.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.122-128
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• 2019

Porcelain insulators have been used mainly for power line fixing and electrical insulation in transmission towers. Porcelain insulators have generally a 30 years desired life, but over 50% exceed their life expectancy. Since the damage to porcelain insulators is usually accompanied by enormous loss of human resource material, their efficient maintenance has emerged as an important issue. In this regard, this study applied a frequency response function (FRF) for integrity assessment of the insulator. The characteristics of the FRF according to damage types were identified and analyzed by the change in natural frequencies, curve shape, attenuation, and Nyquist diagram stability. The results showed significant differences in the FRF according to damage types, which can be used as basic data for the effective integrity assessment of porcelain insulators.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.227-228
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• 2023

A floating floor generally consists of mortar bed separated from the structural RC slab by a continuous resilient layer. It is known that the floating floors are a type of vibration-isolation system to improve the impact sound insulation performance. However, some researchers have demonstrated that the amplification of vibration response at a specific range of frequencies results in an increase in the impact sound level. This study carried out the forced vibration tests to obtain the frequency response function (FRF) of a floating floor compared with a bare RC slab. Test results shows that the additional peak occur in vibrational spectrum of the floating floor except natural vibration modes of the bare RC slab. This is because the relatively flexible resilient material and mass of the mortar bed offer an additional degree of freedom in the structural system. Therefore, it could be efficient for reduction of floor impact vibration and noise to control the additional mode frequency and response of floating floors.

• Nuclear Engineering and Technology
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• v.56 no.8
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• pp.3043-3066
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• 2024

In various small modular reactor (SMR) designs currently under development, the conventional concrete containment building has been replaced by a metal containment vessel (MCV). In these systems, the gap between the MCV and the reactor pressure vessel is filled with gas or vacuumed weakly, effectively suppressing conduction and convection heat transfer. However, thermal radiation remains the major mode of heat transfer during normal operation. The objective of this study was to investigate the heat-transfer mechanisms in integral pressurized water reactor (IPWR)-type SMRs under various gas-filled conditions using computational fluid dynamics. The use of thermal radiation shielding (TRS) with a much lower emissivity material than the MCV surface was also evaluated. The results showed that thermal radiation was always the dominant contributor to heat loss (48-97%), while the conjugated effects of the gas candidates on natural convection and thermal radiation varied depending on their thermal and radiative properties, including absorption coefficient. The TRS showed an excellent insulation performance, with a reduction in the total heat loss of 56-70% under the relatively low temperatures of the IPWR system, except for carbon dioxide (13%). Consequently, TRS can be utilized to enhance the thermal efficiency of SMR designs by suppressing the heat loss through the MCV.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.501-507
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• 2011

To develop environmental-friendly insulating composite materials, natural cellulose and porous ceramic balls were used as core materials and activated Hwangtoh was used as a binder. Various specimens were prepared with different water/binder ratios and core material/binder ratios. The physical properties of these specimens were then investigated through compressive strengths, flexural strengths, absorption test, hot water resistance test, pore analysis, thermal conductivity, and observation of micro-structures using scanning electron microscope. Results showed that the maximum compressive strength varied appreciably with the water/binder ratios and core material/binder ratios, but the flexural strength increased with the core material/binder ratios regardless of water/binder ratios. The compressive strength and the flexural strength measured after the hot water resistance test decreased remarkably compared to those measured before test. The pore analysis measured after the hot water resistance test showed that total pore volume, porosity and average pore diameter decreased, while bulk density increased by the acceleration of hydration reaction of binder in the hot water. The thermal conductivity decreased gradually with an increase of core material/binder ratios. It can be evaluated that the composite insulation materials having good insulating properties and mechanical strengths can be used in the field.

• Magazine of the Korean Society of Agricultural Engineers
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• v.22 no.1
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• pp.53-66
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• 1980

The research work is concerned with the analytical and experimental studies on the heat transfer phenomenon around the underground concrete digester used for biogas production Systems. A mathematical and computational method was developed to estimate heat losses from underground cylindrical concrete digester used for biogas production systems. To test its feasibility and to evaluate thermal parameters of materials related, the method was applied to six physical model digesters. The cylindrical concrete digester was taken as a physical model, to which the model,atical model of heat balance can be applied. The mathematical model was transformed by means of finite element method and used to analyze temperature distribution with respect to several boundary conditions and design parameters. The design parameters of experimental digesters were selected as; three different sizes 40cm by 80cm, 80cm by 160cm and l00cm by 200cm in diameter and height; two different levels of insulation materials-plain concrete and vermiculite mixing in concrete; and two different types of installation-underground and half-exposed. In order to carry out a particular aim of this study, the liquid within the digester was substituted by water, and its temperature was controlled in five levels-35。 C, 30。 C, 25。 C, 20。C and 15。C; and the ambient air temperature and ground temperature were checked out of the system under natural winter climate conditions. The following results were drawn from the study. 1.The analytical method, by which the estimated values of temperature distribution around a cylindrical digester were obtained, was able to be generally accepted from the comparison of the estimated values with the measured. However, the difference between the estimated and measured temperature had a trend to be considerably increased when the ambient temperature was relatively low. This was mainly related variations of input parameters including the thermal conductivity of soil, applied to the numerical analysis. Consequently, the improvement of these input data for the simulated operation of the numerical analysis is expected as an approach to obtain better refined estimation. 2.The difference between estimated and measured heat losses was shown to have the similar trend to that of temperature distribution discussed above. 3.It was found that a map of isothermal lines drawn from the estimated temperature distribution was very useful for a general observation of the direction and rate of heat transfer within the boundary. From this analysis, it was interpreted that most of heat losses is passed through the triangular section bounded within 45 degrees toward the wall at the bottom edge of the digesten Therefore, any effective insulation should be considered within this region. 4.It was verified by experiment that heat loss per unit volume of liquid was reduced as the size of the digester became larger For instance, at the liquid temperature of 35˚ C, the heat loss per unit volume from the 0. 1m$^3$ digester was 1, 050 Kcal/hr m$^3$, while at for 1. 57m$^3$ digester was 150 Kcal/hr m$^3$. 5.In the light of insulation, the vermiculite concrete was consistently shown to be superior to the plain concrete. At the liquid temperature ranging from 15。 C to 350 C, the reduction of heat loss was ranged from 5% to 25% for the half-exposed digester, while from 10% to 28% for the fully underground digester. 6.In the comparison of heat loss between the half-exposed and underground digesters, the heat loss from the former was fr6m 1,6 to 2, 6 times as much as that from the latter. This leads to the evidence that the underground digester takes advantage of heat conservation during winter.

• Journal of the Korea Furniture Society
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• v.24 no.1
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• pp.60-69
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• 2013

Timber is an eco-friendly material that is suitable for low carbon and green growth, and recently, studies on utilization and manufacture of timber are increasing. Thus, we need a stable supply of wood working materials for the formative element and widespread function of timber. It is necessary to develop the use of timber because it enhances the added value of this material by making the most of it. In this way, skin-timber is an appropriate material for life articles because skin-timber has a variety of functions including the ability for storage use, the beauty of structure, the ability to maintain heat and insulation, and the capability to control humidity. In this study, I developed household items using skin-timbers that are made up of circular columns and square columns of pine, larch, and yellow popular. The circular and square columns have an inner hole that is approximately 90% of the external structure's width. I intended for the concept of these designs to display creativity considering functionality and productivity. These items are life articles and furniture for modern people. They are eco-friendly products that are varnished with traditional lacquer and natural oil. According to the result of this study, skin-timbers are made of domestic pine, larch, and yellow popular and are resource of furniture, household items, and woodcraft. I believe skin-timber is not only a useful material for processability and design applicability, but it also has the capability to be a multifunctional and high value-added material. Also, if the standards, such as cortex thickness, outside diameter, and length, of skin-timber are producted diversely, I believe skin-timber can be have more the possibility of industrial products' development.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.416-421
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• 2005

Most of solar system dissemination has been focused on domestic hot water system of which utilization to a building is relatively simple and safe than solar heating system. Through the survey on a cause of solar house dissemination failure in Korea, we conclude that design integration and systematic approach method for technology application are the most important element for a successful solar house. KIER(Korea Institute of Energy Research) and Hanbat National University have started new project on a development of Zero energy Solar House, called ZeSH which can be sustained just by natural energy without the support of existing fossil fuel. This is the 1st phase research of 10 years long-term ZeSH plan which develops a low-cost and $100\%$ self sufficient ZeSH. The goal of 1st phase ZeSH research is to get a $70\%$ self sufficiency only in thermal loads. Actual demonstration house, named KIER ZeSH I was designed and constructed as a result of 1st phase research work in the end of 2002. Various innovative technologies such as super insulation, high performance window, passive and active solar systems, ventilation heat recovery system are applied and evaluated to the KIER ZeSH I. A lot of computer simulations had been conducted for the optimal design and system integration in every design steps. Considering all the results from detailed hourly computer simulation, it is expected that at least $70\%$ self-sufficiency in thermal loads which is 1st phase target value can be excessively achieved in actual demonstration house. Besides, many valuable findings from the design and analysis to construction could be established such as collaboration method among the participants, practical design and construction techniques for system integration and the others. The purpose of this paper is to introduce the main findings through the development of KIER ZeSH I project. Practical guidelines in every design step for new low- or zero- energy solar house is proposed as result.