• Title/Summary/Keyword: Constant heat flux

Search Result 223, Processing Time 0.03 seconds

Simulated Distribution Characteristics of Surface Temperature on Irradiating of a Laser

  • Lee, Young-Wook;Yeon, Sang-Ho
    • International Journal of Contents
    • /
    • v.5 no.2
    • /
    • pp.16-19
    • /
    • 2009
  • In this paper, we concern about the distribution characteristics of surface temperature by the increment of time, diffusivity and heat flux on irradiating of a laser. The penetration depth corresponding to the induced constant heat flux or irradiated laser, is simulated by a computer algorithm. The distribution of temperature versus penetration depth for the variation of time and diffusivity is characterized at the constant heat flux and on irradiating of a laser. The temperature of constant heat flux at the fixed diffusivity or time, is decreased by the pattern of exponential function as the time t or diffusivity a is increased (a=10, 100, 1000). The temperature of constant heat flux is not changed but exponentially fixed with the increasing diffusivity and the fixed time. On the other hand, the temperature of laser at the fixed diffusivity or time is decreased linearly. Our results show that the characteristics of the simulated surface temperature in a semi-infinite solid are similar to the graphs on theoretical consideration.

A Study on Calibration of Heat Flux Sensor by using Convective Heat Transfer (대류방식을 이용한 열유속센서의 검정에 관한 연구)

  • Yang, Hoon-Cheul;Song, Chul-Hwa;Kim, Moo-Hwan
    • Proceedings of the KSME Conference
    • /
    • 2004.04a
    • /
    • pp.1358-1363
    • /
    • 2004
  • The objective of this work is to propose calibration facility in which a thin film type heat flux sensor can be calibrated under convective flow condition by using a small wind tunnel with the constant temperature plate condition. A small wind tunnel has been built to produce a boundary layer shear flow above a constant temperature copper plate. 12-independent copper blocks, thin film heaters, insulators and temperature controllers were used to keep the temperature of flat plate constant at a specified temperature. Three commercial thin film-type heat flux sensors were tested. Convective calibrations of these gages were performed over the available heat flux range of $1.4{\sim}2.5kW/m^2$. The uncertainty in the heat flux measurements in the convective-type heat flux calibration facility was ${\pm}2.07%$. Non-dimensional sensitivity is proposed to compare the sensitivity calibrated by manufacturer and that of experiment conducted in this study.

  • PDF

Measurement Bias of Heat Flux Gauge based on Calibration Constant supported by Manufacturer (제조사 보정상수에 기인한 열유속계의 측정 오차)

  • Kim, Sung-Chan;Hamins, Anthony
    • Fire Science and Engineering
    • /
    • v.32 no.4
    • /
    • pp.1-6
    • /
    • 2018
  • As a preliminary study to quantify the measurement uncertainty of the Schmidt-Boelter type heat flux gauge, the present study has been conducted to evaluate the measurement error due to the calibration constant supported by manufacturer. Calibrations of heat flux gauges are performed at NIST Fire Research Division using a calibration facility with heat source of a 2000 W halogen-tungsten filament lamp and the calibration constant is obtained by comparing the response of the reference and a standard heat flux gauge at the same irradiance conditions. Calibration for heat flux gauges made by three different manufacturers is compared with their factory calibration constant. Relative error due to fluctuation of output signal from heat flux gauges does not exceed 1% of the mean value and the relative error between calibration of this study and factory calibration constant ranged from 1.5% to 14.3%. The present study shows that a continuous and periodic calibration is necessary for accurate heat flux measurement.

A Low-Reynolds Number Second Moment Closure for Turbulent Heat Fluxes (저레이놀즈수 2차 모멘트 난류 열유속모형 개발에 관한 연구)

  • 신종근;최영돈;이건휘
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.17 no.12
    • /
    • pp.3196-3207
    • /
    • 1993
  • A second moment turbulent closure for the turbulent heat flux near a wall is developed by modification of model constants in pressure interaction term as the variables of the turbulent Reynolds number using the universal properties of turbulent heat flux near the wall. The present model shows that model constant for the wall reflection term in pressure interaction is most important in modelling of the near wall heat flux. Fully developed pipe flows with constant wall heat flux are tested to validate the proposed model. In most of calculation region, the predicted turbulent properties agree better with the experimetal data than the results from standard algebraic heat flux model which use the uniform model constants.

Study on the Heat Flux Using Instantaneous Temperature as Height of Probe in the Combustion Chamber (연손실 순간온도 측저에 있어서 돌출높이에 따른 실험적 연구)

  • 이치우;김지훈;김시범
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.25 no.2
    • /
    • pp.395-402
    • /
    • 2001
  • The gasoline engine tends to high performance, fuel economy, small-sized. Therefore, it is necessary to solve the problems on thermal load, abnormal combustion, etc, in the engine, Thine film instantaneous temperature measurement probe was made. And the manufactural method of probe was established. The instantaneous surface temperatures in the constant volume combustion chamber were measured by this probe and the heat flux was obtained by Fourier analysis. The authors measured the wall temperature of combustion chamber and computed the heat flux through the cylinder wall in order to understand the combustion characteristics depending on height of probe. For achieving this goal, the thin film instantaneous temperature probe was developed for analyzing the instantaneous surface wall temperature and unsteady heat flux on the constant volume combustion chamber.

  • PDF

A Study of Heat Flux According to the Initial Temperature of Combustion Chamber and Blight of Probe in a Constant Volume Combustion Chamber (돌출높이와 초기온도 변화에 따른 연소실 벽면에서의 열유속에 관한 연구)

  • Lee Chi-Woo
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.28 no.7
    • /
    • pp.1055-1062
    • /
    • 2004
  • As for the Production of internal combustion engines there has been further movement toward development of high Performance engines with improved fuel efficiency as well as a lightweight and a small size. These tendencies help to solve the problems in engines for example, such as thermal load. abnormal combustion and so on. In order to investigate these Problems, a thin film-type probe for measuring instantaneous temperature has been suggested. A method for manufacturing such a probe was established in this study The instantaneous surface temperature of a constant volume combustion chamber was measured by using this probe and the heat flux was obtained through Fourier analysis In order to thoroughly understand the characteristics of combustion. authors measured wall temperature of combustion chamber and calculated heat flux through a cylinder wall while varying the protrusion height of probe. For these Purposes, the instantaneous surface temperature probe was developed. thereby making possible the analysis of instantaneous temperature of wall surface and the detection of unsteady heat flux in the constant volume combustion chamber.

Entropy Generation Analysis for Various Cross-sectional Ducts in Fully Developed Laminar Convection with Constant Wall Heat Flux

  • Haghgooyan, M.S.;Aghanajafi, C.
    • Korean Chemical Engineering Research
    • /
    • v.52 no.3
    • /
    • pp.294-301
    • /
    • 2014
  • This study focuses on analysis and comparison of entropy generation in various cross-sectional ducts along with fully developed laminar flow and constant uniform wall heat flux. The obtained results were compared in ducts with circular, semicircular, and rectangular with semicircular ends, equilateral triangular, and square and symmetrical hexagonal cross-sectional areas. These results were separately studied for aspect ratio of different rectangular shapes. Characteristics of fluid were considered at average temperature between outlet and inlet ducts. Results showed that factors such as Reynolds number, cross section, hydraulic diameter, heat flux and aspect ratio were effective on entropy generation, and these effects are more evident than heat flux and occur more in high heat fluxes. Considering the performed comparisons, it seems that semicircular and circular cross section generates less entropy than other cross sections.

A Study of Hear Flux and Instantaneous Temperature According to the Initial Tamperature of Combustion Chamber in a Constant Volume Combustion Chamber (연소실 초기온도 변화에 따른 순간열유속에 관한 연구)

  • Lee, Chi-Woo
    • Journal of the Korean Society of Industry Convergence
    • /
    • v.6 no.3
    • /
    • pp.193-200
    • /
    • 2003
  • In the production of internal combustion engines, there has been a move towards the development of high performance engines with improved fuel efficiency, lighter weight and smaller sizes. These trends help to answer problems in engines related to thermal load and abnormal combustion. In order to investigate these problems, a thin film-type probe for instantaneously measuring temperatures has been suggested. A method for manufacturing such a probe was established in this study. The instantaneous surface temperature of a constant volume combustion chamber was measured by this probe and the heat flux was obtained through Fourier analysis. In order to thoroughly understand the characteristics of combustion, the authors measured the wall temperature of the combustion chamber and computed heat flux through a cylinder wall while varying the protrusion height of the probe. For achieving the above goals, a instantaneous temperature probe was developed, thereby making possible the analysis of the instantaneous temperature of wall surface and the detection of unsteady heat flux in the constant volume combustion chamber.

  • PDF

A Study of Heat Flux on the Height of an Instantaneous Temperature Probe in a Constant Volume Combustion Chamber (정적 연소기에서 순간온도 프로브의 돌출높이에 따른 열유속에 관한 연구)

  • Lee, C.W.
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.16 no.4
    • /
    • pp.216-223
    • /
    • 2003
  • In the production of internal combustion engines, there have been trends to develop the high performance engines with improved fuel efficiency, lighter weights and smaller sizes. This trends help to answer problems related to thermal load and abnormal combustion, etc. in these engines. In order to investigate these problems, a thin film-type probe and its manufacturing method for instantaneously measuring surface-temperatures have been proposed in this study, Instantaneous surface temperature of a constant volume combustion chamber was measured by this probe and heat flux was obtained by Fourier analysis. In order to thoroughly understand the characteristics of combustion, the authors measured the wall temperature of the combustion chamber and computed heat flux through a cylinder wall while varying the protrusion height of the probe have been measured. To achieve the above goals, a instantaneous temperature probe was developed, thereby making possible the analysis of the instantaneous temperature of wall surface and the detection of unsteady heat flux in the constant volume combustion chamber.

Heat Transfer Characteristics under Saturated Nucleate Pool Boiling for Various Heating Surface Angles using Heater with Artificial Cavity (인공 캐비티를 가진 히터를 이용한 가열면 경사각에 따른 포화상태 풀 핵비등 열전달 기초연구)

  • Kim, Jeong-Bae
    • Journal of the Korean Solar Energy Society
    • /
    • v.29 no.4
    • /
    • pp.7-14
    • /
    • 2009
  • Nucleate pool boiling experiments with constant heat flux condition were performed using pure R11 and R113 for various surface angles under saturated pool condition. A circular heater of 1 mm diameter, with artificial cavity in the center, fabricated using MEMS technique and the high-speed controller were used to maintain the constant heat flux. Images of bubble growth were taken at 5,000 frames per second using a high-speed CCD camera. The bubble geometry was obtained from the captured bubble images. The effects of surface angles on the bubble growth behaviors were analyzed as dimensional scales for the initial and thermal growth regions. The parameters for the bubble growth behaviors were bubble radius, bubble growth rate, sliding velocity, bubble shape and advancing and receding contact angles. These phenomena require further analysis for various surface angles, but this study will provide good experimental data with constant heat flux boundary condition for such works.