• Title, Summary, Keyword: Wall temperature

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Heat transfer of green timber wall panels (그린팀버월 패널의 열전달 특성)

  • Kim, Yun-Hui;Jang, Sang-Sik;Shin, Il-Joong
    • Korean Journal of Agricultural Science
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    • v.38 no.1
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    • pp.115-120
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    • 2011
  • 20% of total energy use to sustain temperature of building inside. In this reasons, researchers effort to improve the thermal insulation capacity with new wall system. Using appropriate materials and consisting new wall system should considered in energy saving design. OSB(Oriented strand board), Larch lining board used to consist wall system. $2{\sim}6$ Larch lining board has tongue & groove shape for preventing moisture. Comparing with gypsum board and green timber lining board as interior sheathing material, temperature difference of Green timber wall system was bigger than temperature difference of gypsum board wall system. This aspects indicate that Green timber wall system was revealed higher thermal insulation property than gypsum board wall system. Gypsum board portion transfer heat easily because temperature difference gradient of gypsum board wall system was smaller than OSB wall system. Total temperature variation shape of G-4-S and G-6-S show similar model but, temperature variation shape in green timber wall portion assume a new aspect. The purpose of this study was that possibility of thermal insulation variation and new composition of wall system identify to improve thermal insulation performance. In the temperature case, this study shows possibility of improving thermal insulation performance. Humidity, sunshine and wind etc. should considered to determine building adiabatic properties.

Fluid heating in a nano-scale Poiseuille flow: A non-equilibrium molecular dynamics study

  • Faraji, Fahim;Rajabpour, Ali
    • Current Applied Physics
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    • v.17 no.12
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    • pp.1646-1654
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    • 2017
  • In this paper we develop a non-equilibrium molecular dynamics computer simulation to study the fluid heating in a nano scale Poiseuille flow system and discuss the effects of the fluid-wall interaction strength and wall temperature on the fluid heating. We calculate the fluid temperature distribution, as well as the heat flux from the fluid towards the walls and the interfacial thermal resistance and discuss the variations of the fluid heating caused by the viscous and surface frictions as the fluid-wall interaction strength and wall temperature vary. It is found that as the fluid-wall interactions strengthen, the fluid heating diminishes. In weak interactions, the heat flux from the fluid to the wall is almost independent of the wall temperature while the interfacial thermal resistance decreases with increased wall temperature and the surface friction is the major contribution to the fluid heating; in contrast, in large interactions, both the heat flux and thermal resistance increase with increased wall temperature and the viscous friction is the major contribution to the fluid heating.

Behavior of UHPC-RW-RC wall panel under various temperature and humidity conditions

  • Wu, Xiangguo;Yu, Shiyuan;Tao, Xiaokun;Chen, Baochun;Liu, Hui;Yang, Ming;Kang, Thomas H.K.
    • Advances in concrete construction
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    • v.9 no.5
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    • pp.459-467
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    • 2020
  • Mechanical and thermal properties of composite sandwich wall panels are affected by changes in their external environment. Humidity and temperature changes induce stress on wall panels and their core connectors. Under the action of ambient temperature, temperature on the outer layer of the wall panel changes greatly, while that on the inner layer only changes slightly. As a result, stress concentration exists at the intersection of the connector and the wall blade. In this paper, temperature field and stress field distribution of UHPC-RW-RC (Ultra-High Performance Concrete - Rock Wool - Reinforced Concrete) wall panel under high temperature-sprinkling and heating-freezing conditions were investigated by using the general finite element software ABAQUS. Additionally, design of the connection between the wall panel and the main structure is proposed. Findings may serve as a scientific reference for design of high performance composite sandwich wall panels.

Thermal Performance Evaluation Monitoring Study of Transparent Insulation Wall System (투명단열 축열벽 시스템의 열성능 평가 실험 연구)

  • Kim, B.S.;Yoon, J.H.;Yoon, Y.J.;Baek, N.C.;Lee, J.S.
    • Journal of the Korean Solar Energy Society
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    • v.23 no.1
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    • pp.1-8
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    • 2003
  • Various efforts to combine new high-tech materials with solar system have been progressed nowadays in order to improve the performance of the existing passive solar system. TIM(Transparent Insulation Material) replacing the conventional outer building envelope glazing as well as the wall is good example for this trend. TI integrated wall is a thermal mass wall with a special shaped TIM instead of using typical envelope materials The tested TIM type is a small(diameter 4mm and thickness 50mm) capillary tube of Okalux model and cement brick(density 1500kg/m3). The purpose of this study was to analyze the thermal performance through the actual measurements performed in a test cell. This study was carried out to justify the following issues. 1) the impact of Tl-wall over the temperature variations 2) the impact of mass wall surface absorptance over the transient thermal behavior and 3) the impact of thermal mass wall thickness over the temperature variations. Finally, as results indicated that the peak time of room temperature was shifted about one hour early when absorptance of thermal mass wall changed from 60% to 95% for the 190mm thickness thermal mass wall test case. the temperature difference of both surfaces of thermal mass wall surface showed about $23^{\circ}C$ during a day of March for the 380mm thickness thermal mass wall case. However, the thermal mass wall was over-heated by outside temperature and solar radiation in a day of May the temperature difference of both surfaces of thermal mass wall surface was indicated $10^{\circ}C$ and inside temperature was observed more than average 22C.

Direct Numerical Simulation of Turbulent Scalar Transport in a Channel with Wall Injection

  • Na, Yang
    • Journal of Mechanical Science and Technology
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    • v.18 no.4
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    • pp.597-605
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    • 2004
  • Turbulent temperature field in a channel subject to strong wall injection has been investigated via direct numerical simulation technique. These flows are pertinent to internal flows inside hybrid rocket motors. A simplified model problem where a regression process at the propellant surface is idealized by wall injection has been investigated to understand how the temperature field is modified. The effect of strong wall injection displaces thermal boundary layer away from the wall and this causes a sharp drop of friction temperature. Turbulent diffusivity and dissipation time scale for temperature field are found to show large variations in the streamwise direction under application of wall blowing. It is, thus, expected that more sophisticated turbulence models would be required to predict the disturbed temperature field accurately.

Measurement of local wall temperature and heat flux using the two-thermocouple method for a heat transfer tube

  • Ahn, Taehwan;Kang, Jinhoon;Jeong, Jae Jun;Yun, Byongjo
    • Nuclear Engineering and Technology
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    • v.51 no.7
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    • pp.1853-1859
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    • 2019
  • The two-thermocouple method was investigated experimentally to evaluate its accuracy for the measurement of local wall temperature and heat flux on a heat transfer tube with an electric heater rod installed in an annulus channel. This work revealed that a thermocouple flush-mounted in a surface groove serves as a good reference method for the accurate measurement of the wall temperature, whereas two thermocouples installed at different depths in the tube wall yield large bias errors in the calculation of local heat flux and wall temperature. These errors result from conductive and convective changes due to the fin effect of the thermocouple sheath. To eliminate the bias errors, we proposed a calibration method based on both the local heat flux and Reynolds number of the cooling water. The calibration method was validated with the measurement of local heat flux and wall temperature against experimental data obtained for single-phase convection and two-phase condensation flows inside the tube. In the manuscript, Section 1 introduces the importance of local heat flux and wall temperature measurement, Section 2 explains the experimental setup, and Section 3 provides the measured data, causes of measurement errors, and the developed calibration method.

Analysis on the Modification of Near-wall Turbulent Characteristics of Temperature Field in a Channel imposed with Linearly Increasing Wall Disturbance (선형적으로 증가하는 벽면교란이 벽 근처 난류 온도장의 특성 변화에 미치는 영향 해석)

  • Park, Soo Hyung;Byun, Yung-Hwan;Na, Yang
    • Journal of the Korean Society of Propulsion Engineers
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    • v.17 no.5
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    • pp.101-112
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    • 2013
  • Large eddy simulation was performed to investigate the effect of linearly increasing wall disturbance on the modification of turbulent characteristics of temperature field in the vicinity of the wall. It was noted that temperature variance increased monotonically whereas temperature dissipation decreased significantly, resulting in a noticeable reduction in both time and length-scales. A sudden drop in turbulent Prandtl number down to around 0.25 in the near-wall region indicated that the similarity between velocity and temperature fields decreases near the wall as a result of linear wall disturbance.

An Experimental Study on the Cylinder Wall Temperature Characteristics for Load Variations in a Gasoline Engine (가솔린엔진의 부하(負荷)에 따른 실린더 벽면 온도특성(溫度特性)에 관(關)한 연구(硏究))

  • Kwon, K.R.;Ko, J.K.;Hong, S.C.
    • Journal of the Korea Society For Power System Engineering
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    • v.3 no.1
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    • pp.16-22
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    • 1999
  • The purpose of this study is to prevent the stick, scuffing, scratch between piston and cylinder, is to contribute the piston design such as piston profile, clearance by calculating reaction force by over-lap of piston skirt, as measuring the temperature distributions of cylinder wall. The experiment has been peformed to obtain data during actual engine operation. Temperature gradient in peripheral and axial distributions of cylinder wall according to torque and speed of engine were measured by use of an 800cc class gasoline engine. The results obtained are summarized as follows ; 1) The temperature of cylinder wall at TDC was about $50{\sim}75^{\circ}C$ higher than temperature of cooling water. 2) The rear side temperature of top dead center was $141^{\circ}C$(1/4 load) in axial distribution, whereas the rear side of midway position temperature was $98^{\circ}C$. 3) The temperature of cylinder wall increased in according to rising temperature of cooling water. 4) The thrust side temperature of cylinder wall was about $15^{\circ}C$ in all load test. 5) The rear side temperature of top dead center was $159^{\circ}C$ (1/2 load) in peripheral distribution, it was about $39^{\circ}C$ higher than thrust side temperature.

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Transient cooling experiments with a cooper block in a subcooled flow boiling system (과냉비등류에 있어서 동블록을 이용한 과도적 냉각실험)

  • 정대인;김경근;김명환
    • Journal of the Korean Society of Marine Engineering
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    • v.11 no.1
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    • pp.72-79
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    • 1987
  • When the wall temperature is very high, a stable vapor film covers the heat transfer surface. The vapor film creates a strong thermal resistance when heat is transferred to the liquid though it. This phenomenon, called "film boiling" is very important in the heat treatment of metals, the design of cryogenic heat exchangers, and the emergency cooling of nuclear reactors. In the practical engineering problems of the transient cooling process of a high temperature wall, the wall temperature history, the variation of the heat transfer coefficients, and the wall superheat at the rewetting points, are the main areas of concern. These three areas are influenced in a complex fashion such factors as the initial wall temperature, the physical properties of both the wall and the coolant, the fluid temperature, and the flow state. Therefore many kinds of specialized experiments are necessary in the creation of precise thermal design. The object of this study is to investigate the heat transfer characteristics in the transient cooling process of a high temperature wall. The slow transient cooling experiment was carried out with a copper block of high thermal capacity. The block was 240 mm high and 79 mm O.D.. The coolant flowed throuogh the center of a 10 mm diameter channel in the copper block. In the copper block, three sheathed thermocouples were placed in a line perpendicular to the flow. These thermocouples were used to take measurements of the temperature histories of the copper block.

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A Study on the Responsibility of Thin film instantaneous surface temperature probe of a Dual-pipe structure (이중관 구조 박막형 순간온도 프로브의 응답성에 관한 연구)

  • Choi, Seok-Ryeol;Park, Kyoung-Suk
    • 한국연소학회:학술대회논문집
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    • pp.237-242
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    • 2003
  • The measurement study of instantaneous temperature at combustion chamber wall and the temperature of combustion gas has been under lots of research and development to conclude the temperature process in internal combustion engine for combustion characteristics analysis. The measurement with fast responsibility should be used for temperature measurement inside combustion chamber wall since temperature of wall changes, due to the various gas temperature, irregularly during the combustion. Therefore, thin film instantaneous surface temperature probe, which characterizes the fastest and the most accurate responsibility among contact typed temperature measurement, was used for the experiments. This new thin film instantaneous surface temperature probe improved the problems of noise and durability. The optimal coating thickness of thin film instantaneous surface temperature probe was proven to be $10{\mu}m$ for the best responsibility and durability. It also allowed the stable temperature measurement be taken up to $1,200^{\circ}C$ and proven to be read possibly from the combustion chamber wall.

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