The total enthalpy of a gas stream is evaluated directly using a calorimetric probe, the complete probe assembly is composed of a water-cooled-stainless steel probe, a closed-loop cooling water circuit, a gas sampling line and a data acquisition and control unit.
Each measurement was accomplished in two successive steps; the first step is a ‘tare’ measurement of the heat load to the probe in the absence of gas sampling, during this phase is possible to measure the impact gas pressure also; the second is a measurement of the heat load under ‘flow’ or gas sampling conditions. By means of a combined energy balance, accounting for the cooling water flowthrough the probe and the gas sample extracted from the plasma, the local specific enthalpy at the probe tip canbe calculated on the basis of a simple equation.
Also it is possible to analyse the gas composition, collecting the gas sample in a dedicated instrument,i.e a mass spectrometer. The showed probe was AISI 316 stainless-steel made, with a tip curved to right angle to protect the remaining probe parts from the hot gas, outer diameter is 4 mm.