• Title/Summary/Keyword: thermal flow temperature

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A study on Characteristics of Heat Flow of Low Temperature Latent Thermal Storage System (저온 잠열 축열조내의 열유동 특성에 관한 연구)

  • Lee, W.S.;Park, J.W.
    • Solar Energy
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    • v.19 no.4
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    • pp.33-43
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    • 1999
  • The study on ice thermal storage system is to improve total system performance and increase the economical efficiency in actual all-conditioning facilities. To obtain the high charging and discharging efficiencies in ice thermal storage system, the improvement of thermal stratification is essential, therefore the process flow must be piston flow in the cylindrical type. With the relation of the aspect ratio(H/D) in the storage tank, the stratification is formed better as inlet flow rate is smaller. If the inlet and the outlet port are settled at the upside and downside of the storage tank, higher storage rate could be obtainable. In case that the flow directions inside the thermal storage tank are the upward flow in charging and the downward in discharging, thermal stratification is improved because the thermocline thickness is maitained thin and the degree of stratification increases respectively. In the charging process, in case of inlet flow rate the thermal stratification has a tendency to be improved with the lower flow rate and smaller temperature gradient in case of inlet temperature, the large temperature difference between inflowing water and storage water are influenced from the thermal conduction. The effect of the reference temperature difference is seen differently in comparison with the former study for chilled and hot water. In the discharging process, the thermal stratification is improved by the effect of the thermal stratification of the charging process.

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Experimental Study on the Thermal Flow Stratification in a Horizontal Piping System (수평배관에서의 열유동 성층화현상에 대한 실험적 연구)

  • 김병주;이찬우;장원표
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.8
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    • pp.2064-2070
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    • 1995
  • Characteristics of thermal flow stratification were studied experimentally by using the small scale pressurizer-surge line model. Thermal flow stratifications in the horizontal section of surge line were analyzed by the relation between the maximum temperature difference at any cross section in surge line and the Froude number representing the boundary conditions, i.e., in/out surge flow velocity and temperature difference of system. Thermal flow stratifications in outsurge flow decreased inversely proportional to the Froude number and did not exist for Fr>1. In insurge flow thermal flow stratifications disappeared near Fr=1.5, but resulted in the higher temperature difference than the case of outsurge flow.

Identification of Thermal Flow Boundary Conditions for Three-way Catalytic Converter Using Optimization Techniques (최적화 기법을 이용한 삼원촉매변환기의 열유동 경계조건의 동정)

  • Baek, Seok-Heum;Choi, Hyun-Jin;Kim, Kwang-Hong;Cho, Seok-Swoo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.9
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    • pp.3125-3134
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    • 2010
  • Three-way catalyst durability in the Korea requires 5 years/80,000km in 1988 but require 10 years/120,000km after 2002. Domestic three-way catalyst satisfies exhaust gas conversion efficiency or pressure drop etc. but don't satisfy thermal durability. Three-way catalyst maintains high temperature in interior domain but maintain low temperature on outside surface. This study evaluated thermal durability of three-way catalyst by thermal flow and structure analysis and the procedure is as followings. Thermal flow parameters ranges were determined by vehicle test and basic thermal flow analysis. Response surface for rear catalyst temperature was constructed using the design of experiment (DOE) for thermal flow parameters. Thermal flow parameters for rear catalyst temperature in vehicles examination were predicted by desirability function. Temperature distribution of three-way catalyst was estimated by thermal flow analysis for predicted thermal flow parameters.

A study on the flow and thermal analysis of the hot gas casing of gas turbine (가스 터빈 Hot gas casing에 대한 유동 및 열응력 해석)

  • Choi, Young-Jin;Lee, Young-Shin;Kim, Jae-Hun;Park, Won-Seek;Kim, Hyun-Soo
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.557-561
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    • 2004
  • The hot gas casing of gas turbine has operated high temperature and thermal gradient. The structure safety of hot gas casing will be highly depend on the thermal stress. In this paper, flow and thermal stress analysis of hot gas casing is carried out using ANSYS program. The obtained temperature data by flow analysis of hot gas casing apply the load condition of the thermal analysis. The thermal stress analysis is carry out the elastic-plasticity analysis. The pressure, temperature and velocity of the flow and thermal stress of the hot gas casing are presented.

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Measurements of Thermal Characteristics for a Micro-Fabricated Thermal Mass Air Flow Sensor With Real-Time Controller (실시간 제어기를 이용한 마이크로 열식 질량공기 유량센서의 열특성 측정)

  • Park, Byung-Kyu;Lee, Joon-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.8
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    • pp.573-579
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    • 2009
  • A thermal mass air flow sensor, which consists of a micro-heater and thermal sensors on the silicon-nitride thin membrane structure, is micro-fabricated by MEMS processes. Three thermo-resistive sensors, one for the measurement of microheater temperature, the others for the measurement of membrane temperature upstream and downstream of the micro-heater respectively, are used. The micro-heater is operated under the constant temperature difference mode via a real time controller, based on inlet air temperature. Two design models for microfabricated flow sensor are compared with experimental results and confirmed their applicabilities and limitations. The thermal characteristics are measured to find the best flow indicator. It is found that two normalized temperature indicators can be adopted with some advantages in practice. The flow sensor with this control mode can be adopted for wide capability of high speed and sensitivity in the very low and medium velocity ranges.

Development of Thermal Mass Flow Meter (열전달 질량유량계 개발)

  • Chi, Daesung
    • 유체기계공업학회:학술대회논문집
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    • 1999.12a
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    • pp.118-122
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    • 1999
  • Thermal mass flow meter was developed using principle of convective heat transfer. The advantage of thermal mass flow meter is measuring mass flow directly, therefore, it is not required to use densitometer or temperature/pressure and DP gages. The final accuracy of this thermal mass flow meter is $\pm1.0{\%}$ or better, reproducibility is $\pm0.2{\%}$, and the response time is 600 ms. The thermal mass flow meter was developed from a single point to multi-points (maximum is 9 points), and the number of points is determined according to desired accuracy and size of piping/duct. Since this thermal mass flow meter adopted microprocessor based design, it is intrinsically accurate, self-error detectable, and has self-diagnosis function. The applications of this thermal mass flow meter are for measurement and control of HVAC air flow, other gas flow, and liquid flow.

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Experimental Study on Thermal Sensation Evaluation in Heating(part I: Emotion & Sensibility Image Evaluation by Indoor Temperature Change in Heating) (실내 난방시 온열쾌적성 평가에 관한 연구(part I;실내 난방시 실온변화에 따른 감성이미지 평가))

  • 한남규;금종수;김형철;김동규;김창연
    • Proceedings of the Korean Society for Emotion and Sensibility Conference
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    • 2003.05a
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    • pp.41-46
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    • 2003
  • In recently, Is inhabiting more than 70% indoors during a day in case of company employee and ordinary people which is looking at usual business. Therefore Thermal comfort of human body about indoor temperature and air flow acting very heftily. When intestine temperature is fallen for external low temperature and air flow in winter in case enter into heated room feel comfort by effect of temperature and feel comfort or discomfort by room heating condition gradually. Therefore it is important that grasp thermal comfort about temperature and air flow in heating to keep continuous comfort in indoor dwelling. Temperature and thermal comfort factor of emotion & sensitivity image exert fair effect since heating middle although thermal comfort change greatly effect on sensation about temperature at actuality heating early. Need much study yet in vantage point of emotion & sensitivity although much study were held about thermal and comfort sensibility and when heat in existing research until now. Therefore this study is targeting that evaluate thermal comfort through introduction of estimation method by emotion & sensibility image real and synthetic sensibility about thermal environment that is becoming winter heating.

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Temperature Rise Prediction of GIS Bus Bar Considering Thermal Flow (열유동을 고려한 GIS 모선의 온도상승 예측)

  • Kim, Joong-Kyoung;Oh, Yeon-Ho;Lee, Ji-Yeon;Hahn, Sung-Chin
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.4
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    • pp.742-747
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    • 2009
  • Many works on the temperature distribution of power apparatus have usually done by coupled magneto-thermal analysis. Such a method can not consider the internal gas or oil flow in the power apparatus such as gas insulated switchgear, GIS bus bar, and power transformer. Moreover it can not show the internal temperature distribution of the power apparatus exactly. This paper proposes a coupled magneto-thermal-flow analysis considering Navier-Stokes equations. The convection heat transfer coefficient is calculated analytically by applying Nusselt number for natural convection and is applied to the boundary condition of proposed method. Temperature distribution of the GIS bus bar model considering thermal flow is obtained by the proposed method and shows good agreement with the experimental data.

Prediction of Thermal Load Distribution and Temperature of the Superheater in a Tangentially Fired Boiler (접선 연소식 보일러의 최종 과열기 열부하 분포 및 튜브 온도 예측에 관한 연구)

  • Park, Ho-Young;Sea, Sang-Il
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.7
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    • pp.478-485
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    • 2008
  • The extreme steam temperature deviation experienced in the superheater of a tangentially fired boiler can seriously affect its economic and safe operation. This temperature deviation is one of the main causes of boiler tube failures. The steam temperature deviation is mainly due to the thermal load deviation in the lateral direction of the superheater. The thermal load deviation consists of several causes. One of the causes is the non-uniform heat flow distribution of burnt gas on the superheater tube system. This distribution is very difficult to measure in situ using direct experimental techniques. So, we need thermal load model to estimate the tube temperature. In this paper, we propose a thermal load distribution model by using CFD analysis and plant data. We successfully predict the tube temperature and the steam flow rate in a final superheater system from the thermal load model and one dimensional heat-flow system analysis. The proposed model and analysis method would be valuable in preventing the frequent tube failure of the final superheater tubes.

Conjugate Heat Transfer Analysis of High Pressure Turbine with Secondary Flow Path and Thermal Barrier Coating (2차유로 및 열차폐 코팅을 고려한 고압터빈의 열유동 복합해석)

  • Kang, Young-Seok;Rhee, Dong Ho;Cha, Bong Jun
    • The KSFM Journal of Fluid Machinery
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    • v.18 no.6
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    • pp.37-44
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    • 2015
  • Conjugate heat analysis on a high pressure turbine stage including secondary flow paths has been carried out. The secondary flow paths were designed to be located in front of the nozzle and between the nozzle and rotor domains. Thermal boundary conditions such as empirical based temperature or heat transfer coefficient were specified at nozzle and rotor solid domains. To create heat transfer interface between the nozzle solid domain and the rotor fluid domain, frozen rotor with automatic pitch control was used assuming that there is little temperature variation along the circumferential direction at the nozzle solid and rotor fluid domain interface. The simulation results showed that secondary flow injected from the secondary flow path not only prevents main flow from penetrating into the secondary flow path, but also effectively cools down the nozzle and rotor surfaces. Also thermal barrier coating with different thickness was numerically implemented on the nozzle surface. The thermal barrier coating further reduces temperature gradient over the entire nozzle surface as well as the overall temperature level.