• 제목/요약/키워드: Heat Transfer Control

검색결과 549건 처리시간 0.037초

통신해양기상위성의 전이궤도 열해석 (TRANSFER ORBIT THERMAL ANALYSIS FOR COMS)

  • 전형열;김정훈;김성훈;양군호
    • 한국전산유체공학회지
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    • 제13권2호
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    • pp.48-54
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    • 2008
  • COMS (Communication, Ocean and Meteorological Satellite) is a geostationary satellite and has been developing by KARI for communication, ocean and meteorological observations. It will be launched by ARIANE 5. Ka-band components are installed on South panel, where single solar array wing is mounted. Radiators, embedded heat pipes, external heat pipe, insulation blankets and heaters are utilized for the thermal control of the satellite. The Ka-band payload section is divided several areas based on unit operating temperature in order to optimize radiator area and maximize heat rejection capability. Other equipment for sensors and bus are installed on North panel. The ocean and meteorological sensors are installed on optical benches on the top floor to decouple thermally from the satellite. During the transfer orbit operation, satellite will be under severe thermal environments due to low dissipation of components, satellite attitudes and LAE(Liquid Apogee Engine) firing. This paper presents temperature and heater power prediction and validation of thermal control design during transfer orbit operation.

위성의 전이궤도 열해석 (TRANSFER ORBIT THERMAL ANALYSIS FOR SATELLITE)

  • 전형열;김정훈;김성훈;양군호
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2007년도 추계 학술대회논문집
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    • pp.227-231
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    • 2007
  • COMS (Communication, Ocean and Meteorological Satellite) is a geostationary satellite and has been developing by KARI for communication and ocean and meteorological observations. It will be launched by ARIANE 5. Ka-band components are installed on South panel, where single solar array wing is mounted. Radiators, embedded heat pipes, external heat pipe, insulation blankets and heaters are utilized for the thermal control of the satellite. The Ka-band payload section is divided several areas based on unit operating temperature in order to optimize radiator area and maximize heat rejection capability. Other equipment for sensors and bus are installed on North panel. The ocean and meteorological sensors are installed on optical benches on the top floor to decouple thermally from the satellite. During the transfer orbit operation, satellite will be under severe thermal environments due to low dissipation of components, satellite attitudes and LAE(Liquid Apogee Engine) firing. This paper presents temperature and heater power prediction and validation of thermal control design during transfer orbit operation.

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사각 공동구의 벽면 가진에 의한 자연 대류 유동의 공진 현상 및 열전달에 관한 연구 (Resonance of Natural Convection and Heat Transfer inside a Square Cavity due to a Vibrating Wall)

  • 허남건;김영규;강병하
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집D
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    • pp.483-488
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    • 2001
  • In the present study a numerical simulation is performed on a natural convection inside a square cavity with a vibrating wall. The study has been conducted varying the heat transfer rate, wall excitation frequency and also the orientation of the cavity. The temperature and velocities inside the cavity was observed and also, the heat transfer coefficients on the heating wall was seen. From the results, it can be seen that the temperature inside the cavity decreases when excited with the proper frequency and the heat transfer coefficient increased with cavity inclination angle, ${\theta}$. It is also found from the results that flow resonance is occurred near the inclination angle ${\theta}=90^{\circ}$.

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발전용 보일러 전열 튜브 유로내 온도분포 불균일 개선기법 (The improvement method for power plant boiler temperature nonuniformity of heat transfer tube bank flow path)

  • 정훈;김범신;장석원;안연식;박건복;황정보
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 추계학술대회논문집B
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    • pp.837-841
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    • 2001
  • Almost all power plant boiler has temperature distribution nonuniformity problem in heat transfer tube flow path. It can cause hot spot damage of superheated or reheated heat transfer section and reduce maintenance schedule when nonuniformity is severe. There are two solutions for improvement temperature nonuniformity. one is change of gas flow distribution of gas path and the other is contorl steam flow in tube bank. Of course, first method is very difficulty to apply but second method is'nt. In this paper, control steam flow is used to solve temperature nonuniformity of power plant boiler.

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분기 가진을 통한 충돌제트 능동 제어 연구 (Active Control of Impinging Jets Using Bifurcating Excitations)

  • 김정우
    • 한국생산제조학회지
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    • 제22권3_1spc호
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    • pp.525-530
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    • 2013
  • The objective of the present study is to investigate the heat transfer characteristics of turbulent impinging jets with bifurcating excitations. Bifurcating excitations use the dual mode, dual frequency forcing, where an axial forcing frequency is equal to double the helical forcing frequency. Under the bifurcating excitation, the heat transfer significantly increases in one plane (bifurcating plane), while nearly no heat transfer occurs in the perpendicular plane (bisecting plane). This result is closely associated with the change in the vortical structures caused by the excitation.

설비공학 분야의 최근 연구 동향 : 2016년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2016)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제29권6호
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    • pp.327-340
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    • 2017
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.

CFD를 이용한 폐쇄생태계 내 토양표면의 열전달계수 분석 (An Analysis of Heat Transfer Coefficient of Soil Surface in Closed Ecosystems Using CFD)

  • 노상목;남상운
    • 농업과학연구
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    • 제33권1호
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    • pp.85-95
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    • 2006
  • A model experiment has been performed to get the heat transfer coefficient on the soil surface in the closed ecosystem. The heat flux on the soil surface was measured and the heat transfer coefficient was derived in the following two cases with 5-stepped control of inside air current speed. One case was that heat flowed from air to soil and the other case was that heat flowed from soil to air. Three dimensional CFD model has been set to simulate thermal environment in the closed ecosystem including soil layers. The standard $k-{\varepsilon}$ model of the CFD program was chosen for turbulence model and heating wire buried in the soil layers was set as heat source option to simulate the case when the temperature of soil surface was higher than that of inside air in the closed ecosystem. Between one case that heat flowed from air to soil and the other case that heat flowed from soil to air, there were big differences in the temperature distribution of soil layers and the heat transfer coefficient of the soil surface. The increasing rate of heat transfer coefficient on each case according to the increase of inside air current speed was similar to each other and it respectively increased linearly. But the heat transfer coefficient on the case that heat flowed from soil to air was much bigger than that of the other case. The model was validated by comparing simulated values of CFD model with measured values of the model experiment. Simulated and measured temperature of inside air and soil layers, and heat transfer coefficient of the soil surface were well accorded and the range of corrected $R^2$ was 0.664 to 0.875. The developed CFD model was well simulated in parts of the temperature of inside air and soil layers, the distribution of the inside air current speed, and heat transfer coefficient of the soil surface were able to be quantitatively analyzed by using this model. Therefore, the model would be applied and used for analysis of heat transfer coefficient between air and surface in various agricultural facilities.

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배기열 회수용 종이 열교환기의 성능예측에 관한 연구 (A Study on the Performance Prediction of Paper Heat Exchanger for Exhaust Heat Recovery)

  • 유성연;김진혁;정민호;지명석
    • 설비공학논문집
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    • 제20권6호
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    • pp.372-380
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    • 2008
  • In order to control indoor air quality and save energy, it is needed to install a suitable ventilation system equipped with heat exchanger for heat recovery. Paper heat exchanger can recover $50{\sim}70%$ of the enthalpy difference between supply and exhaust air. The purpose of this research is to obtain the experimental correlations for the friction factor, heat transfer coefficient, mass transfer coefficient and permeance of paper heat exchanger, which can be used to predict the performance of the paper heat exchanger. Pressure drops at various velocities, and sensible and latent heat transfer rates at various dry-bulb temperatures, relative humidities and specific humidities are measured to derive experimental correlations. The results of prediction using correlations show fairly good agreement with the experimental data obtained in the actual operating conditions.

설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제26권12호
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

상변화물질의 대류유동 및 열전달 현상에 관한 연구 (Study of Convective Flow and Heat Transfer Phenomena in the Phase Change Material)

  • 손상석;이채문;이재헌;임장순
    • 태양에너지
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    • 제6권2호
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    • pp.43-53
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    • 1986
  • The objective of this study is to report on the characterics of convective flow and heat transfer during metling process in order to provide design information for thermal energy storage systems which use phase change material. In present study, flow and heat transfer characteristics of the Phase Change Material in the Open Top Model (O.T.M) and in the Closed Top Model (C.T.M) were studied numerically by the control volume formulation using the algebraic non-orthogonal coordinate transformation. For the calculation procedure, the physical properties of fluid are assumed to be constant except density which is linely dependent on temperature in the bouyancy term of momentum equations. At start of melting process, the thickness of melting layer is assumed from the Stefan Problem assumption. The heat transfer results of Open Top Model and Closed Top Model are compared with the parameters of Grashof number and aspect ratio. It was found that heat transfer phenomena in melted region was greatly affected by buoyancy-driven natural convection and the melting distance of Open Top Model at the upper region is greater than that of Closed Top Model.

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