A Mixed Radiative-Convective Technique for the Calibration of Heat Flux Sensors in Hypersonic Flow

Abstract

The ability to measure the very high heat fluxes that typically occur during the hypersonic re-entry phase of space vehicles is generally considered a subject of great importance in the aerospace field. Most of the sensors used for these measurements need to be checked periodically and re-calibrated accordingly. Another bottleneck relates to the need to procure thermal sources that are able to generate reliable reference heat fluxes in the range between 100 and 1000 kW/m 2 (as order of magnitude). In the present study, a method is presented by which, starting from a calibration system with a capacity of approximately 500 kW/m 2 only, heat fluxes in the range of interest for hypersonic applications are generated. The related procedure takes advantage of established standards for the characterization of a radiative heat flux. It also builds on the hybrid radiative-convective nature of typical hypersonic heat fluxes and the yet poorly explored possibility to use convective sources of heat to produce high-intensity fluxes. The reliability of such a strategy has been tested using a high enthalpy supersonic flow facility relying on an electric arc-heater and pure Nitrogen as work gas. Stagnation-point heat fluxes have been successfully measured (with reasonable accuracy) in the range between 600 and 1500 kW/m 2 for values of the centerline enthalpy spanning the interval from to 6 to 24 MJ/kg.

Theoretical and Experimental Analysis of Heat Transfer and Condensation in Micro-Ribbed Tubes

“…From one point of view, the studies performed on pipes can be classified into two categories of experiments performed on large-scale and small-scale pipes. Esposito et al [10] investigated the effect of flow maldistribution in cross-flow heat exchangers. In recent years, the use of compact heat exchangers for single and two-phase applications has increased in the process industry [11].…”