Two-Dimensional Conduction Effects in Estimating Radiative Heat Flux from a Plasma Jet

Abstract

It is quite common to employ thin metallic films for the determination of heat transfer rates at a fluid -solid interface. Depending on the duration of the event and gage design, it may be important to account for multi -dimensional heat conduction within the substrate of the thin film. The objective of this work is to assess the effects of two -dimensional heat conduction on the deduced radiative heat fluxes using a conjugate -gradient based inverse algorithm. For comparison, a previously developed one -dimensional inverse technique is also used. The high heat fluxes are produced by an electrothermal -chemical plasma jet. The plasma, initiated within a 3.2 mm diameter and 26 mm long polyethylene capillary by exploding a 3.6 mg thin copper wire, emerges into an open -air atmosphere as a high temperature, high -pressure, underexpanded sup ersonic jet. The jet impinges over a stagnation plate equipped with thin -film sputtered platinum heat -flux gages, whose temperature history serves as an input to the heat -flux estimation algorithm. Four different charging voltage levels are investigated, r anging from 2.5 to 7.5kV. While both algorithms capture the temporal variations of the radiative heat fluxes, two -dimensional heat conduction model reveals the discrepancies between the two techniques as well as the range of applicability of the one -dimens ional model.