Investigation of Slug Calorimeter Heat Flux Measurements in the Plasmatron X Wind Tunnel

Experimental values of cold wall heat flux are crucial to characterize ground test facilities used to design and study thermal protection materials for reentry vehicles. Slug calorimeters provide a simple and reliable way to estimate cold wall heat flux by measuring the rate at which a slug of material heats up while subjected to a heat input. Heat flux measurements obtained with an in-house developed copper slug calorimeter probe inserted in the plasma jet of the Plasmatron X inductively coupled plasma (ICP) facility are investigated in this paper. Characterizations are performed under air, nitrogen, and CO2 plasma, and using two types of nozzles, a straight 100 mm diameter nozzle, and a 21.8 mm throat diameter/86.5 mm exit diameter converging-diverging nozzle. One and two-dimensional axisymmetric simulations were performed using the Porous material Analysis Toolbox based on Open-FOAM (PATO) to model the temperature profile of the slug calorimeter assembly and assess the heat losses between the slug and its housing. Experimental results at different operating conditions are provided, focusing on the effects of chamber pressure, input power, and probe position on the measured cold wall heat flux.