Heat Transmission Coefficient Research Articles

ゲル状潜熱蓄熱材を適用した開口部の熱的・光学的挙動に関する研究

The purpose of this study is to clarify the effect of energy saving and environmental improvement of the window applying the gelled PCM with elastomer. The gelled PCM is possible to solve a technical problem because of that characteristic properties. According to the experimental results, the light transmittance in the solid and the liquid phase shows 0.1 and 0.6[-]. The heat transmission coefficient of this window is about 6[W/m2/K] at the minimum. When the PCM window installed experimental housing, temperature fluctuation was reduced about 5[K] and the average reduction rate of energy consumption is 13.4[%], and 28.7[%] in maximum.

The Issue of Including the Influence of Thermal Bonds in the Passive House

Influence of thermal bonds when evaluating the energy performance of buildings can be included in the calculation approximately by means of a surcharge on the effect of thermal bonds or precisely by using specific linear heat transmission coefficient for thermal bonds between structures. The article presents a comparison of the two options in the energy performance of a particular building, the specific amount of heat for heating the building of a brick passive house based on the foam glass.

Experimental Research on Thermal Behavior of Light Gauge Steel-Framed Composite Walls with Slotted Studs

Two thermal experiments of light gauge steel-framed composite walls with slotted studs and with external thermal insulation layer were carried out in the lab of combined energy consumption test board for components of building envelope in school of municipal and environmental engineering at Harbin Institute of Technology (HIT). The lab is one of the key laboratories of Ministry of Housing and Urban-Rural Development of the P.R.China. The method of thermocouple temperature measurement has been used. The heat transmission coefficient and the measuring point temperature of composite wall have been deeply investigated, which is finely compared with the FEA model results at the same time. Two conclusions can be drawn from the test: web slotted studs can reduce heat loss of the light gauge steel-framed composite walls obviously, thus it can weaken the thermal bridge effect of the location in stud part, so it can improve the thermal insulation properties of the composite walls significantly; the composite walls’ heat transmission coefficients of the two test schemes go to: 0.315W/(m2·K)and 0.250W/(m2·K), which can meet the residential building envelope heat transmission coefficient limit value in the cold areas of China well.

Prediction Equations for Energy Consumption Through Surveys on Energy Consumption in Apartment Buildings

This study presents energy consumption prediction equations developed by conducting multiple regression analyses of data collected in surveys of actual states of energy consumption in apartment buildings in their operational stage. Surveys of actual states of average energy consumption per unit show that 1) the largest component of energy consumption is room heating, followed by electricity, hot water supply, and gas, in that order; 2) energy consumption increases with household area; 3) among exposures, energy consumption is highest in households facing east or northeast and lowest in those facing south or southwest; 4) among height types, energy consumption is highest in super-high-rise apartment buildings (50 stories or higher), followed by semi-super-high-rises, high-rises, and medium-high-rises, in that order; and 5) among plan types, tower-type apartment buildings use approximately 17% – 20% more energy than flat types. The goodness-of-fit criterion stated in the 2009 ASHRAE Fundamentals Handbook (SI) Edition is shown to be satisfied for the equations presented in this paper for the prediction of energy consumption of apartment buildings in their operational stage. These equations were developed through multiple regression analysis using the areas and heat transmission coefficients of structures as independent variables and using energy consumption as the dependent variable.

Dynamic integrated method based on regression and averages, applied to estimate the thermal parameters of a room in an occupied office building in Madrid

A room facing north in a fully monitored office building located in Madrid (Spain) has been studied. Data corresponding to a period of more than two years, recorded while the building was regularly used, have been employed.A regression analysis method based on averages has been applied. Although the used equation is analogous to the steady state, dynamic features of the test have been considered. A dynamic energy balance equation is first stated. Then this equation is integrated for a time interval long enough to make the accumulation term much lower than the other terms. Finally averages are used to estimate integrals. The minimum integration period that allows this simplification has been identified, studying integration periods from 1 to 20 days.It is concluded that integration period and variables needed depend on test conditions and the building. Daily averages are insufficient for this analysis in these test conditions. Heat supplied by the HVAC system was modelled avoiding flow measurements. Suggested terms including occupancy and door status improve the model remarkably. A spread in the Overall Heat Transmission Coefficient (UA) estimated under 10%, was found for a 7-day integration period. This narrow interval allows to hand this parameter as intrinsic.

Development and application of the Thermal Bridge Breaker for Preventing the Thermal Bridge Effect on the Apartment Buildings

When there are parts happened high-conductivity or non-insulation at the connection structures of walls, slabs and roofs in apartments, these parts are became thermal weak points. For this reason, the lost of many quantities of heat and energy is occurred. It is called the thermal bridge. This study is to investigate the use of Thermal Breaker that is preventing Thermal Bridge in foreign countries and to evaluate through the comparison of the environmental thermal performance with three different condition; “applying of thermal breaker that is a representative device of foreign country”, “applying of thermal breaker that has been developing” and “Non-applying of thermal breaker”. For this study, Physibel that is a program to analyze the interpretation of heat transfer is used and the temperature condition of indoor and outdoor is applied to each 25oC and -15oC proposed by “Design Criteria for Apartment to Prevent Condensation”. Simulations with thermal breaker and without it are conducted to compare the heat transmission coefficient based on the heat flow and area of a wall. As a result, Thermal performance decline is founded approximately 56.5% through the simulation result without thermal breaker; the heat transmission coefficient of inner wall is 0.471W/m2K and outer wall is 0.301W/m2K. In contrast, the thermal performance decline is showed approximately 3.6%~12.3% through the simulation result with thermal breaker; the heat transmission of inner wall and outer wall is around 0.311W/m2K~0.338W/m2K. Thus, installing the thermal breaker at the connection structure of apartment can reduce the thermal bridge and prevent condensation.

Wood moisture monitoring during log house thermal insulation mounting

The current designs of thermal insulation for buildings concentrate on the achievement of the required heat transmission coefficient. However, another factor that cannot be neglected is the assessment of the possible water vapour condensation inside the construction. The aim of the study was to find out whether the designed modification of the cladding structure of an existing log house will or will not lead to a risk of possible water vapour condensation in the walls after an additional thermal insulation mounting. The condensation could result in the increase in moisture of the walls and consequently the constructional timber, which would lead to the reduction of the timber construction strength, wood degradation by biotic factors – wood-destroying insects, mildew or wood-destroying fungi. The main task was to compare the theoretically established values of moisture of the constructional timber with the values measured inside the construction using a specific example of a thermal insulated log house. Three versions of thermal insulation were explored to find the solution of a log house reconstruction which would be the optimum for living purposes. Two versions deal with the cladding structure with the insulation from the interior, the third version deals with an external insulation.In a calculation model the results can be affected to a great degree by input values (boundary conditions). This especially concerns the factor of vapour barrier diffusion resistance, which is entered in accordance with the producer’s specifications; however, its real value can be lower as it depends on the perfectness and correctness of the technological procedure. That is why the study also includes thermal technical calculations of all designed insulation versions in the most unfavourable situation, which includes the degradation of the vapour barrier down to 10% efficiency, i.e. the reduction of the diffusion resistance factor to 10% of the original value. Moreover, the dependence of the weight moisture of timber inside the insulated cladding on temperature-moisture changes in the internal and external ambient environment was examined.

Heat Transfer in Film Boiling from Electrically Heated Nichrome Wire to Boiling Water at Different Pressure-II

Values of film thickness in film boiling have been computed for three different sizes of nichrome wires at five different sub-atmospheric pressures. The values of alpha , total heat transmission co-efficient, ac heat transmission co-efficient due to conduction through the vapour film and alpha R, heat transmission co-efficient due to radiation, have been calculated. The values of film thickness were found to decrease with external pressure, but were found to increase slightly with the radius of the wire. alpha & alpha c both increase with rise of pressure but decrease with the radius of the radius of the heated wire. Alpha R shows a minimum value at a pressure of 15 cm. of Hg. in the case of all the wire sizes. The radiation loss alpha R is much smaller than conduction loss alpha.

실험계획법을 이용한 진공유리 패널 모서리 용융 접합 강도실험 분석

건축물 에너지 효율등급제도, 건축물 에너지 소비증명제 등 건축물 에너지 관련 법 제도가 지속적으로 강화되면서, 이에 대응하기 위한 고성능 단열재, 기능성 유리를 적용한 창호의 개발이 활발히 진행되고 있다. 에너지 절약을 위한 기능성 유리의 중요성이 크게 부각되고 있음에 따라 진공유리에 대한 관심이 높아지고 있다. 진공유리의 핵심공정 중 모서리 접합공정은 진공유리의 기밀성, 강도, 형상에 있어 매우 중요한 공정이다. 본 논문에서는 수소혼합가스를 이용하여 전기로 내부에서 두 장의 유리를 접합하였다. 공정변수에 따른 접합유리의 강도와 형상을 측정 및 분석 하였으며, 다구치 실험계획법을 이용하여 접합유리의 강도를 예측하였다. 추가실험을 통해 예측 값과의 오차율을 확인함으로서 실험의 타당성을 검증하였다. The vacuum-glazing panel is a panel that keeps two glasses completely sealed in a vacuum condition. It is the high function insulation material of having the wall level minimizing the heat loss by the conduction and convection heat transmission coefficient. The edge sealing is a very important process of vacuum glass on the strength, thickness and air tightness. In this study, by using the hydrogen mixture gas torch, two sheets of glass was sealing in the furnace. The thickness and strength of the glass according to the process parameters is measurement and analysis, and predicting the edge sealing strength of glass by using taguchi method of experiment. We verified the validity of the experiment by checking the error rate through additional experiment.

건물 외장재로서의 PV 시스템의 경제성 및 보조금 정책 분석

The purpose of this study is to analyze cost effective applications of a building integrated photovoltaic system and to suggest vigorous applications of a PV system as a building material for wall cladding. The PV system, which produces electricity by solar energy among new and renewable energies, has merits to be applied to in cities with relative ease although it has not been favored broadly due to its low efficiency and the high first cost. Therefore, the solution has been searched by the heat transmission coefficient calculation and the cost effective analysis of a PV system in this paper when the PV system replaces a building material for wall cladding such as a brick and a marble. To have better performance of the PV system, it is necessary to vent the heat that is generated from the system and is trapped between the wall and the system. When the PV system is used as a building material for wall cladding, more than 2cm of air gap is required for the regional heat transmission coefficient in Korea. Internal insulation for the construction method is expected to minimize the risk of fire than external insulation. The higher the price of the building materials is, the shorter the payback period is. Under the current subsidy policy on the PV system, the replacement of cheap building materials cause the longer payback period. Consequently, the subsidies are needed to be revised for the application of a PV system as a building material for wall cladding.

Building Physical, Energetical and Hygrothermal Analysis of Earth-Sheltered Building Constructions

Covering soil layer significantly reduces the heat loss of earth-sheltered building elements. Quantity of heat loss is highly influenced by the thickness of soil on examined building constructions. Based on the above mentioned facts an earth-sheltered sample building was designed. Ecological designing principles (recycled building materials and passive solar designing rules) were taken into consideration during planning of examined residential house. The building structures are general solutions, the earth-sheltered characteristic manifested by soil-covered elevations and green roof. The detailed energetic calculations are based on the linear heat transmission coefficient, which serves as a numerical definition of the heat bridge effect. Linear heat transmission coefficients were calculated as simulational results that can be derived from the finite element modelling of structural intersections. Detailed building simulations represent the advantages of soil covering. Hygrothermal analysis of building constructions based on their thermal simulations is essential. Due to the intensified waterproofing of earth-sheltered structures vapour diffusion is considerably reduced. At the same time environmentally conscious design prefers diffusion open orders of layers. Hygrothermal calculations of different waterproofing materials can categorise the environmental friendly solution of the protection.

A General Evaluation on Double Skin Facades

This study examines the literature of double-skin facade systems over the last decade, and, with the help of tables and graphics, investigates their advantages and disadvantages. Moreover, a detailed comparison is made between double skin facade systems. The results of the study show that the greatest advantage (95%) of double skin facade systems is their provision of natural ventilation. Other advantages are highlighted according to their percentage as follows: An increase in interaction between user and environment because of the high proportion of transparency, support of heat and sound insulation, reduction in heat transmission and solar heat gain coefficient, an increase in thermal comfort, allowance of solar control elements between the two facade spaces, and protection of these elements from external environment conditions. The most commonly accepted disadvantage (72%) is overheating in the air space of the two facades. Other disadvantages are highlighted according to their percentage as follows: Problems related to a decrease in the amount of daylight entering the building, high investment costs, additional maintenance and repair costs, fire, and acoustic problems. In our country, architectural design decisions related to overheating must be taken so as to provide a positive contribution to energy performance and the applicability of these systems.

모듈러 건축의 MC 설계 적용에 관한 연구 불연속 모듈격자를 활용한 MC 설계를 중심으로

This study attempted to explore the MC design methods of modular construction using discontinuous double module grids and further, the design methods of walls. Modular construction is generally characterized with multiple units called modules with a module dimension of 3M(300mm) appearing in the form of double grids. The discontinuous double grids including correction values and gap values occurs inevitably in the modular construction where units are joined horizontally. Therefore, it is desirable to carry out the MC design taking into account these discontinuous double grids. In this study, the MC design was applied to the plane of wooden houses in modular construction, going through a process of setting the size of pillars and inside dimensions, of determining the dimension of discontinuous double grids that occur during the assembly of units, and of setting the dimension of outer walls in conjunction with the derived dimensions. The dimension of outer walls was applied differently depending on the range of regional use by analyzing the energy performance with the materials used. Consequently, the materials and components of factory-produced buildings can be used directly without processing, and the suitability of the outer wall design can be pre-determined by previewing the calculation of the cross-sectional configuration and heat transmission coefficients of outer walls in modular construction, allowing to be used as a decision-making tool of design.

Energy demand analysis according to window size and performance for Korean multi-family buildings

Special attention is required for the design of windows due to their high thermal vulnerability. This paper examines the problems that might arise in the application of the u-value, by reflecting the changes in the u-value of the window, depending on the window-to-wall ratio obtained in an energy demand analysis. Research indicates that the u-value of a window increases with an increase in the difference between the u-values of the frames and the glass. Relative to the changes in the u-value of the windows, the energy demand varied from 1.3% to 9.3%. Windows with a g-value of 0.3 or 0.5 displayed a higher energy demand than windows with a g-value of 0.7. Therefore, when the difference between the performance of the glass and the frame is significant, especially when the g-value is small, a modified heat transmission coefficient should be applied to the window size during the evaluation of the building energy demand.

Improvement of window thermal performance using aerogel insulation film for building energy saving

In buildings, windows have a major influence on space heating demand and indoor environment both with respect to climate and daylight. To reduce the window coefficient of the overall heat transmission, we use aerogel. Aerogels have a high surface area, low density, open pore structure, and excellent insulation properties. We mixed pressure sensitive adhesive and aerogel (10, 15, and 20 mass%) using a homogenizer. A mixture of the adhesives and silica aerogels attached film can reduce thermal conductivity. Silica aerogels are characterized by a surface area analyzer (BET), a Fourier transform infrared spectrometer, a thermogravimetry (TG) analyzer, and probe tack method. Thermal conductivity was measured by a TCi thermal conductivity analyzer.

Heat Transmission Coefficient Measurements in Buildings Utilizing a Heat Loss Measuring Device

Global energy efficiency can be obtained in two ordinary ways. One way is to improve the energy production and supply side, and the other way is, in general, to reduce the consumption of energy in society. This paper has focus on the latter and especially the consumption of energy for heating and cooling our houses. There is a huge energy-saving potential in this area for reducing both the global climate problems as well as economy challenges. Heating of buildings in Denmark accounts for approximately 40% of the entire national energy consumption. For this reason, a reduction of heat losses from building envelopes are of great importance in order to reach the Bologna CO2 emission reduction targets. Upgrading of the energy performance of buildings is a topic of huge global interest these years. Not only heating in the temperate and arctic regions are important, but also air conditioning and mechanical ventilation in the “warm countries” contribute to an enormous energy consumption and corresponding CO2 emission. In order to establish the best basis for upgrading the energy performance, it is important to make measurements of the heat losses at different places on a building facade, in order to optimize the energy performance. This paper presents a method for measuring the heat loss by utilizing a U-value meter. The U-value meter measures the heat transfer in the unit W/Km2 and has been used in several projects to upgrade the energy performance in temperate regions. The U-value meter was also utilized in an EUDP (Energy Technological Development and Demonstration Program) focusing on renovation of houses from the 1960s and 1970s.

공동주택 연도별 단열기준 강화에 따른 에너지소요량 비교 연구

에너지사용은 우리생활과 밀접한 관계성을 유지하고 있다. 사계절이 뚜렷한 우리나라로서는 건물분야에 냉,난방이 필수품처럼 여겨지는 세대에 살고있어 에너지 사용과 유지에 새로운 트렌드를 요구하고 있다. 이에따라 정부는 신축 및 기존건축물의 에너지효율 개선을 위해서 단열기준을 지속적으로 강화하여 에너지절감을 꾀하고 있다. 공동주택의 에너지효율 분석중 가장 중요한 요소가 열관류율이며 그값은 외피면적비에 대한 창면적비에 따라 난방에너지 요구량이 큰차이를 보여주고 있다. 그러므로 지속적인 효율개선 정책과 외피면적에 대한 창면적비의 규제가 필요한 시점이라 생각한다. Energy consumption is closely related to our lives. As Korea has four seasons, heating and cooling system is considered as essential facilities for the residential buildings. Accordingly, the government has continuously strengthened the design criteria to improve energy for new and existing building to save energy. The most important factor in the energy efficiency analysis for apartment is the heat transmission coefficient, and the value is significantly different as the heating energy amount is greatly different according to the window area ratio versus facade area ratio. Therefore, it is time to conduct continuous set-up for goal to enhance efficiency and restriction on window area ratio versus facade area ratio.

수치해석을 통한 진공유리 제작 및 성능실험에 관한 연구

For air-tight modern buildings, secondary damage is likely to occur due to condensation in the relatively high heat-transmission windows since water vapor is not easy to discharge. Therefore, in this study, condensation performance of vacuum glazing was numerically analysed, compared with that of ordinary glass and confirmed experimentally by three sheets of vacuum glazing manufactured. The results show that the heat transmission coefficient of the vacuum glazing whose internal pressure is <TEX>$10^{-3}$</TEX> torr was as low as about <TEX>$5.7W/m^2{\cdot}K$</TEX>. Thus, the condensation performance as well as the adiabatic performance was greatly improved compared to that of the ordinary glass.

BIM기반 건축물 설계 과정에서 실시간 에너지 성능 분석을 위한 기술 개발에 관한 연구 - 열관류율 분석을 중심으로

This study intended to introduce the method of designing an eco-friendly building based on BIM(Building Information Modeling) and BIM-based application. The proposed application aimed to generate the environmental performance of the designed alternative automatically in real-time manner in the process of architectural design. We focused on the feasibility of BIM-based eco-friendly design process and the applicability of the developed application for the architectural design practice. In this manner, in the end of paper, we proposed the so-call EcoBIM which is the performance evaluation module for the designed alternative using BIM in the real-time manner and the new design process with it. EcoBIM generate the coefficient of overall heat transmission of wall, roof and slab of the designed alternative with their physical characteristics such as thickness, thermal resistance and so on.

진공챔버 내 프리트 이용 진공유리 봉지공정 최적화에 관한 연구

In houses that use heating and cooling system, most of heat loss occurs through the windows, so that low-E glass, double-layered glass, and vacuum glazing are used to minimize the heat loss. In this paper, an encapsulating process that is a final process in manufacturing the vacuum glazing has been studied, and bonding in a vacuum chamber rather than atmospheric bonding was considered. For the efficiency of the encapsulating process, frit-melting temperature and bonding time were optimized with heater temperature, and the glass preheating temperature was optimized to prevent glass breakage due to thermal stress. Thus the vacuum glass was successfully manufactured based on these results and heat transmission coefficient measured was about 5.7W/m 2 K which indicates that the internal pressure of the vacuum glazing is 10 -2 torr.