Transient response of circular foil heat-flux gauges to radiative fluxes

Keltner, N.R.; Wildin, M. W.

doi:10.1063/1.1134435

Cited by 29 publications

(9 citation statements)

References 3 publications

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“…Commercial Gardon gauges are available with metal bodies, blackbody sensor foils and water cooling designs for high heat flux measurements with long lifespan in harsh environments [33][34][35][36][37][38]. Gardon gauges were first introduced to measurement of heat flux for radiation and are usually only calibrated for radiation.…”

Section: Introductionmentioning

confidence: 99%

A method to measure heat flux in convection using Gardon gauge

Fu¹,

Zong²,

Zhang³

et al. 2016

Applied Thermal Engineering

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Heat flux measurements are widely used in thermal environment analyses. The Gardon gauge is an excellent heat flux sensor with a wide measurement range and long lifespan in harsh environments. However, the Gardon gauge is usually calibrated for radiation heat transfer and is not good for convective heat transfer. This paper introduces a method to measure heat flux for convective heat transfer using the Gardon gauge by relating the measurement sensitivity for convection to that for radiation. The heat flux and convective heat-transfer coefficient can then be simultaneously determined by the standard thermo-electromotive voltage output of the Gardon gauge. The method was demonstrated for convective heat-transfer coefficient ranging from 200 to 3000 W/(m 2 K). The analysis illustrates that the measurement sensitivity for convection decreases with increasing convective heat-transfer coefficient. A correction is necessary especially for higher convective heat-transfer coefficient. The corrected convective heat-transfer coefficients and heat fluxes agree well with the actual values. The relative uncertainty in heat flux is within 0.64%. The method not only greatly improves the measurement accuracy of the Gardon gauge for convection applications, but also provides a reference for evaluating convective heat transfer coefficients in convection environments.

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Section: Introductionmentioning

confidence: 99%

A method to measure heat flux in convection using Gardon gauge

Fu¹,

Zong²,

Zhang³

et al. 2016

Applied Thermal Engineering

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“…These simulated "measurements" were input into Eqs. (8) and (11), and the dimensionless irradiation was calculated using both the approximate and linearized models.…”

Section: Measurement Of the Incident Radiative Flux Using The Linear mentioning

confidence: 99%

“…Circular foil heat flux gauges have been studied extensively, and the effects of phenomena such as heat loss down the center wire [3,4], convective heat transfer [3,5,6], 2-D conduction in the foil [7], and the effects due to property variations have been studied [4]. The transient response of this type of gauge has also been studied [4,8]. However, the nonlinear emission from the foil has not previously been included in a thermal model of a circular foil heat flux gauge.…”

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confidence: 99%

Nonlinear Thermal Model of Circular Foil Heat Flux Gauges

Liechty

Clark

Jones

et al. 2007

Journal of Thermophysics and Heat Transfer

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This paper presents the solution to a nonlinear model of a circular foil heat flux gauge that is exposed to a blackbody source in a vacuum environment. This is the scenario typically used to calibrate a circular foil heat flux gauge. The nonlinear model is solved using a Green's function approach. This approach results in an integral equation for the steady-state temperature profile in the gauge, which is solved using the method of successive approximations. A relationship between the incident radiative heat flux and the temperature profile is developed using this model. This relationship is compared to relationships that were derived using linear models. The first and simplest linear model neglects emission from the foil. The second linear model is obtained by linearizing the emissive power of the gauge. It is shown that these linear models only produce accurate results when the gauge design and operating conditions result in a nearly uniform foil temperature. A procedure based on the nonlinear model is proposed for optimizing the design of a circular foil heat flux gauge. A calibration procedure based on the nonlinear model is also proposed. NomenclatureH=T 4 R c = calibration function constants d = calibration function constants f = calibration functions depending on A G = Green's function H = irradiation, W=m 2 h r = radiation heat transfer coefficient, W=m 2 K I o = modified Bessel function k = thermal conductivity of the constantan foil, W=m K N c = conduction-to-radiation parameter, kt=R 2 T 3 R n = calibration function constant R = radius of the constantan foil, m r = radial coordinate, m T = temperature, K t = thickness of the constantan foil, m = relaxation factor = dimensionless temperature difference = Dirac delta function " = emittance = dimensionless temperature, T=T R = dimensionless radial coordinate, r=R = Stefan-Boltzmann constant, 5:67e-8, W=m 2 K 4 Subscripts a = approximate L = linear o = temperature at center of heat flux gauge, K R = temperature of the copper heat sink, K 1-7 = index for calibration functions and constants Superscript i = iteration number

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“…Some disadvantages are that it has a fairly slow frequency response, and some caution is required in calibration to ensure that the mode of heat transfer is similar to that anticipated in the actual field situation. Reference [7] gives extensive details regarding the transient response of the circular foil calorimeter. Typical time constants are about l/lOth of a second.…”

Section: Heat Flux Measurementsmentioning

confidence: 99%