Stagnation point heat flux measurements in a plasma wind tunnel using a diamond heat transfer gauge

A Diamond Heat Transfer Gauge has been used to measure the stagnation point heat flux at three flow conditions in an arc heated plasma wind tunnel. The gauge was coated with a thin layer of copper to provide a known surface catalycity and reflectivity. The temperature dependent impulse response of the probe was determined from a finite element model of the probe, and from the result of a laser-based calibration experiment using the Non-Integer System Identification method. The two sets of impulse responses were used to calculate heat flux from a measured temperature rise in the wind tunnel. Differences between the impulse responses from the two methods, particularly at higher initial temperatures, led to differences in measured heat fluxes of up to 55 %. A measurement taken using a steady state calorimeter gauge did not conclusively agree with heat flux measurements calculated using impulse responses from either method

Stagnation point heat flux measurements in a plasma wind tunnel using a diamond heat transfer gauge

A Diamond Heat Transfer Gauge has been used to measure the stagnation point heat flux at three flow conditions in an arc heated plasma wind tunnel. The gauge was coated with a thin layer of copper to provide a known surface catalycity and reflectivity. The temperature dependent impulse response of the probe was determined from a finite element model of the probe, and from the result of a laser-based calibration experiment using the Non-Integer System Identification method. The two sets of impulse responses were used to calculate heat flux from a measured temperature rise in the wind tunnel. Differences between the impulse responses from the two methods, particularly at higher initial temperatures, led to differences in measured heat fluxes of up to 55 %. A measurement taken using a steady state calorimeter gauge did not conclusively agree with heat flux measurements calculated using impulse responses from either method

Thermal impulse response in porous media for transpiration cooling systems

A solution of the coupled differential equations for fluid and solid phases in a one-dimensional porous medium in thermal nonequilibrium is presented using the concept of analyzing the impulse response. The impulse response is shown to be sensitive to the volumetric heat transfer coefficient and the coolant mass flux. Experimental data obtained from surface heating of transpiration-cooled porous zirconium di-boride (ZrB2) samples are compared to a newly developed theoretical model. The surface and backside temperatures of the solid are measured using thermographic imaging and thermocouple instrumentation. The noninteger system identification approach is used to experimentally obtain the thermal impulse response, which is then compared to the model prediction. Good agreement is found between the simulated and experimental data with average deviations below 10%. The developed model provides the basis for inverse heat transfer measurements and further analysis of transpiration-cooled materials

Fluid-solid heat exchange in porous media for transpiration cooling systems

This paper presents a semi-analytical solution of the coupled differential equations for fluid and solid phase in a one-dimensional porous medium in thermal non-equilibrium. The thermal impulse response of the fluid and solid phases is used to determine the pressure loss over the thickness of the material. Experimental data obtained from surface heating of porous ZrB2 samples is compared to the theoretical model. The plenum pressure, surface temperature and backside temperature are measured using pressure sensors, thermographic imaging and thermocouple instrumentation The non-integer system identification (NISI) approach is used to obtain the thermal impulse response which is then compared with the model prediction. Plenum pressure rise and thermal impulse response of the heating experiments are used to assess the volumetric heat transfer coefficient of the sample. Good agreement is found between the simulated and experimental data for the temperature and pressure measurements. The obtained heat transfer coefficients are between 2.1 · 104 and 6.8 · 104 W m−3 K−1 for mass fluxes of 10 to 244 g m−2 s −1

Thermal impulse response in porous media for transpiration cooling systems

A solution of the coupled differential equations for fluid and solid phases in a one-dimensional porous medium in thermal nonequilibrium is presented using the concept of analyzing the impulse response. The impulse response is shown to be sensitive to the volumetric heat transfer coefficient and the coolant mass flux. Experimental data obtained from surface heating of transpiration-cooled porous zirconium di-boride (ZrB2) samples are compared to a newly developed theoretical model. The surface and backside temperatures of the solid are measured using thermographic imaging and thermocouple instrumentation. The noninteger system identification approach is used to experimentally obtain the thermal impulse response, which is then compared to the model prediction. Good agreement is found between the simulated and experimental data with average deviations below 10%. The developed model provides the basis for inverse heat transfer measurements and further analysis of transpiration-cooled materials

Thermal Impulse Response in Porous Media for Transpiration Cooling Systems - Dataset

According to linked publication: Thermal Impulse Response in Porous Media for Transpiration Cooling System

Plenum pressure behavior in transiently heat loaded transpiration cooling system

In this paper, the behavior of the plenum pressure behind a transpiration-cooled porous material sample after an incident surface heat flux to the sample is analyzed in experiment and theory. Two porous materials, zirconium diboride and carbon/carbon, were characterized using the pressure-based noninteger system identification method. The resulting impulse responses are analyzed based on two numerical models. One model calculates a plenum pressure impulse response by modeling the porous sample’s heat conduction. A second model considers an additional plenum behind the sample and allows a changing mass flow rate through the sample. The experimentally obtained impulse responses show a stronger response for increasing coolant mass flow rates. Both models cover this trend, essentially depending on the volumetric heat transfer coefficient. However, only the second model allows the entire rebuilding of the experimental data. The plenum pressure impulse response for a transpiration-cooled system depends not only on the material parameters of the porous sample, but also on the volume of the plenum. The reason is that the flow rate changes through the porous sample although the mass flow rate at the controller always stays constant