• Title/Summary/Keyword: Heat-conservation

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Correlation Analysis of the Thermal Conductivity Heat Flow Meter and MTPS (Modified Transient Plane Source) Method Using Wood Flooring and Wall Materials (목질마루바닥재와 벽체용 재료를 이용한 평판열류계법과 MTPS (Modified Transient Plane Source)법의 열전도율 상관관계 분석)

  • Cha, Jung-Hoon;Seo, Jung-Ki;Kim, Su-Min
    • Journal of the Korea Furniture Society
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    • v.22 no.2
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    • pp.118-125
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    • 2011
  • These days global warming is the most important problem and the most important factor is high emission of carbon dioxide. The 23% of carbon dioxide emission for building construction must be reduced. Thermal conductivity is the most basic factor that can decrease the energy consumption especially insulation. Therefore, an accurate and continuous thermal conductivity measurement can be a way to save energy. In this paper, there are methods about how to investigate thermal conductivity measurements and comparing two methods which are the Heat Flow Meter 436 and TCi.

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Environmental Evaluation of Sediment Quality for Small Scale Marine Ranch around the Gunsan Coastal Areas (군산해역에 있어서 소규모 바다목장화를 위한 해양저질 환경 평가)

  • Kim, Jong-Hwa;Kim, Jong-Kyu;Park, Byung-Soo
    • Journal of Fisheries and Marine Sciences Education
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    • v.20 no.3
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    • pp.508-519
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    • 2008
  • Hot air drying is a method that let moistures evaporate by heat exchange between heating air and dry target. This way is dominating more than about 70% of dryers that the use extent is wide fairly, and is established in domestic than dryer that use conduction or radiation etc. Most of research about drying had been emphasized in size of device through analysis for these dry phenomenon plain, heating topology, and aspect of form and so on by dry target's special quality, and research about device development or waste heat withdrawal technology in energy utilization efficiency side is slight real condition. Therefore, in this study, Investigated numerically about thermal efficiency elevation that is leaned against as that change the temperature of inlet and outlet in heat exchanger of the hot air drying tower.

Numerical Investigation on Smoke Behavior in Rescue Station for Tunnel Fires (철도터널 화재 시 구난역 내의 연기거동에 대한 수치해석 연구)

  • Hong, Sa-Hoon;Ryou, Hong-Sun;Lee, Seong-Hyuk
    • Proceedings of the KSR Conference
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    • 2008.06a
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    • pp.1740-1746
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    • 2008
  • The present study performed numerical investigation to analyze the smoke behavior in the rescue station by using the commercial CFD code (FLUENT Ver 6.3). The present study adopted a 10MW ultrafast mode for simulation, and it also used the MVHS(Modify Volumetric Heat Source) model modified from the original VHS(Volumetric Heat Source) model in order to treat the product generation and the oxygen consumption under the stoichiometric state. In addition, the present simulation includes the species conservation equation for the materialization of heat source and the estimation of smoke movement. From the results, the smoke flows are moving along the ceiling because of thermal buoyancy force and as time goes, the smoke gradually moves downward at the vicinity of the entrance. Moreover, without using ventilation, it is found that the smoke flows no longer spread across the cross-passages because the pressure in the non-accident tunnel is higher than that in the accident tunnel.

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Filmwise Condensation of Freon Vapor Including Air on a Horizontal Tube (공기를 함유한 프레온 증기의 수평관 외부에서의 막응축)

  • Kim, K.H.;Ko, H.J.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.7 no.1
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    • pp.20-29
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    • 1995
  • A theoretical model for film condensation of a vapor including a relatively lighter noncondensable gas on a horizontal tube has been formulated on the basis of the conservation laws and other fundamental physical principles. The model is applied to the prediction of the condensation heat transfer characteristics for the Freon vapor in the presence of air on a horizontal tube. Calculated results for the mean heat transfer coefficient, which is shown to depend strongly on the bulk concentration of air, are in good agreement with the available experimental results for a range of operating conditions. The distributions of physical quantities along the surface of tube are also calculated, such as the boundary layer thickness and local heat transfer coefficient. The present model is readily reduced to the Nusselt model as the bulk concentration of air decreases to zero. Therefore, the transition from the condensation of pure vapor to that of vapor-air mixture occurs continuously not abruptly.

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Numerical Study of Heat Transfer Associated with Droplet Impact (액적 충돌에 동반된 열전달에 관한 수치적 연구)

  • Kim, Sung-Il;Son, Gi-Hun
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.1897-1902
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    • 2004
  • Numerical analysis of the heat transfer associated with droplet impact on a hot solid surface is performed by solving the mass, momentum and energy equations for the liquid-gas region. The deformed droplet shape is tracked by a level set method which is modified to achieve volume conservation during the whole calculation procedure and to include the effect of contact angle at the wall. The numerical method is validated through test calculations for the cases reported in the literature. Based on the numerical results, the effects of advancing/receding contact angle, impact velocity and droplet size on the heat transfer during droplet impact are quantified.

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Development of a General Analytical Model for Desiccant Wheels (로터리 제습기의 일반 해석 모델)

  • Kim, Dong-Seon;Lee, Dae-Young
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.25 no.2
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    • pp.109-118
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    • 2013
  • The absence of a simple and general analytical model has been a problem in the design and analysis of desiccant-assisted air-conditioning systems. In this study, such an analytical model has been developed based on the approximate integral solution of the coupled transient ordinary differential equations for the heat and mass transfer processes in a desiccant wheel. It turned out that the initial conditions should be determined by the solution of four linear algebraic equations including the heat and mass transfer equations for the air flow as well as the energy and mass conservation equations for the desiccant bed. It is also shown that time-averaged exit air temperature and humidity relations could be given in terms of the heat and mass transfer effectiveness.

The Influence of Variable Thermophysical Properties for Filmwise Condensation of Superheated Vapor on a Vertical Wall (수직 벽에서 과열증기의 막응축에 대한 열물성의 영향)

  • 김경훈;성현찬
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.3
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    • pp.235-243
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    • 2000
  • A theoretical model for laminar filmwise condensation along an isothermal vertical wall at constant pressure has been formulated on the basis of conservation laws and other fundamental physical principles. The model was applied to the prediction of the influences of variable thermophysical properties of liquid and vapor layers in the filmwise condensation of superheated vapor of Rl2, R134a, R142b and R152a. The dimensionless velocity component method was employed in the transformation of the governing equations and their boundary conditions, and the polynomial method was used for treating variable thermophysical properties of liquid and vapor. Physical quantities, such as the dimensionless thickness of the liquid layer, local heat transfer rate and mean heat transfer coefficient, were investigated for different values of the superheated temperature of the stagnant vapor far from the wall. It was found that the value of mean heat transfer coefficient of R134a was higher than other refrigerants for the change of the superheated temperature.

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The Performance of a Heat Pump with a Variation of Expansion Valve at Various Charging Conditions (냉매 충전량과 팽창장치 변화에 따른 열펌프 시스템의 성능특성에 관한 연구)

  • 최종민;김용찬
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.8
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    • pp.661-666
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    • 2003
  • Constant area expansion devices such as capillary tubes, short tube orifices are being gradually replaced with electronic expansion valves (EEVs) because of increasing focus on comfort and energy conservation. In this study, the performance of a water-to-water heat pump as a function of refrigerant charge is investigated in steady state, cooling mode operation with expansion devices of a capillary tube and an EEV. The performance of the capillary tube system varies drastically according to the change of refrigerant charge amount and inlet temperature of the secondary fluid in the condenser. Cooling capacity and COP of the EEV system show little dependence on the refrigerant charge, while those are strongly dependent on the secondary fluid temperature at the condenser inlet. In general, for a wide range of operating conditions the EEV system shows much higher performance as compared with the capillary tube system. The performance of the EEV system can be optimized by adjusting EEV opening to maintain a constant superheat at all test conditions.

Plane wave propagation in transversely isotropic magneto-thermoelastic rotating medium with fractional order generalized heat transfer

  • Lata, Parveen;Kaur, Iqbal
    • Structural Monitoring and Maintenance
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    • v.6 no.3
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    • pp.191-218
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    • 2019
  • The aim of the present investigation is to examine the propagation of plane waves in transversely isotropic homogeneous magneto thermoelastic rotating medium with fractional order heat transfer. It is found that, for two dimensional assumed model, there exist three types of coupled longitudinal waves (quasi-longitudinal, quasi-transverse and quasi-thermal waves). The wave characteristics such as phase velocity, attenuation coefficients, specific loss, penetration depths, energy ratios and amplitude ratios of various reflected and transmitted waves are computed and depicted graphically. The conservation of energy at the free surface is verified. The effects of rotation and fractional order parameter by varying different values are represented graphically.

Comparision of Heat Exchanging Performance Depending on Different Arrangement of Heat Exchanging Pipe (II) (열회수장치의 열교환 파이프배치형식별 열교환 성능 비교(II))

  • Suh, Won-Myung;Kang, Jong-Guk;Yoon, Yong-Cheol;Kim, Jung-Sub
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 2001.10a
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    • pp.281-285
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    • 2001
  • This study was carried out to improve the performance of heat recovery device attached to exhaust gas flue connected to combustion chamber of greenhouse heating system. Three different units were prepared for the comparison of heat recovery performance; AB-type(control unit) is exactly the same with the typical one fabricated for previous study of analyzing heat recovery performance in greenhouse heating system, other two types(C-type and D-type) modified from the control unit are different in the aspects of airflow direction(U-turn airflow) and pipe arrangement. The results are summarized as follows; 1. In the case of Type-AB, when considering the initial cost and current electricity fee required for system operation, it is expected that one or two years at most would be enough to return the whole cost invested. 2. Type-C and Type-D, basically different with Type-AB in the aspect of airflow pattern, are not sensitive to the change of blower capacity with higher than $25\;m^{3}/min$. Therefore, heat recovery performance was not improved so significantly with the increment of blower capacity. This is assumed to be that air flow resistance in high air capacity reduces the heat exchange rate as well. Never the less, compared with control unit, resultant heat recovery rate in Type-C and Type-D were improved by about 5% and 13%, respectively. 3. Desirable blower capacity for these heat recovery units experimented are expected to be about $25\;m^{3}/min$, and at the proper blower capacity, U-turn airflow units showed better heat recovery performance than control unit. But, without regard to the type of heat recovery unit, it is recommended that comprehensive consideration of system's physical factors such as pipe arrangement density, unit pipe length and pipe thickness, etc., are required for the optimization of heat recovery system in the aspects of not only energy conservation but economic system design.

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