Comparison of Heat Flux Gages for High Enthalpy Flows - NASA Ames and IRS

Abstract

This article is a companion to a paper on heat flux measurements as initiated under a Space Act Agreement in 2011. The current focus of this collaboration between the Institute of Space Systems (IRS) of the University of Stuttgart and NASA Ames Research Center is the comparison and refinement of diagnostic measurements. A first experimental campaign to test different heat flux gages in the NASA Interaction Heating Facility (IHF) and the Plasmawindkanäle (PWK) at IRS was established. This paper focuses on the results of the measurements conducted at IRS. The tested gages included a flat face and hemispherical probe head, a 4" hemispherical slug calorimeter, a nullpoint calorimeter from Ames and a nullpoint calorimeter developed for this purpose at IRS. The Ames nullpoint calorimeter was unfortunately defective upon arrival. The measured heat fluxes agree fairly well with each other. The reason for discrepancies can be attributed to signal-to-noise levels and the probe geometry.

Review of Heat Flux Measurements for High Enthalpy Flows

“…During testing in pure oxygen it was found that the maximum heat flux is measured with an oxidized surface. 34 Heat flux analysis at NASA Ames concluded similarly and measurements at IPM observed the same heat flux increase during CO 2 plasma flow testing. 20, 35 Figure 2 shows the polished copper and the oxidized state.…”

“…34,58 Here, the condition was defined by measuring heat flux and total pressure with one of the sensors and comparing all other sensors against this first data set. The advantage of this procedure is that a shear facility effect is excluded with respect to the heat flux data acquisition.…”

Testing a Transpiration Cooled Zirconium-Di-Boride sample in the Plasma Tunnel at IRS

“…This seems to suggest that the better normalisation factor is the heat flux incident on the uncooled ZrB 2 sample. In fact, since the catalytic effects are extremely dependent on the surface material composition, 24 it is sensible to use a normalising heat flux obtained by the same probe geometry and material characteristics. If the heat flux incident on the uncooled sample is chosen, the heat flux reduction of the probes exposed to condition 3 is larger for both samples compared to the transient cases.…”

Surface Heat Flux Measurement in Transpiration-Cooled Porous Materials using Plenum Pressure Data

“…This probe was used because its head has the same shape as the sensor heads investigated within this work. Furthermore it can be seen as a reference heat flux probe [16,17]. A stagnation point heat flux of 2 MW/m 2 was measured, which equals the uncooled case for the investigations in this paper.…”