Experimental Study of Novel Bi-Metal Slug Calorimeter for Hypersonic Applications

This study presents the development and experimental validation of a novel bi-metallic slug calorimeter composed of explosively bonded copper and stainless steel layers. The sensor was tested under controlled radiative heat loads using a 1.5 kW continuous-wave laser. The heat flux was reconstructed from temperature data acquired with two thermocouples embedded in both layers of the sensor using a finite difference algorithm by assuming one-dimensional heat transfer. Two insulation materials, Macor and Microsil, were employed to evaluate their effect on suppressing heat loss in the radial direction. The results showed that Microsil, due to its low thermal conductivity, significantly reduced conductive losses in the radial direction and improved reconstruction fidelity. Additional tests using a back-side water cooling demonstrated an improved aptitude for tolerating higher heat fluxes and thus allowed for longer test durations without overheating. The reconstructed heat flux showed close agreement with the applied input, with errors lower than 5% in all cases, validating the effectiveness of both the bi-metallic design and the reconstruction method for heat flux measurement in high-enthalpy environments.