Distributed Flow Calorimetry With Wide Temperature and Pressure Range Based on Scanning Radiation Thermometry

Hydrocarbon fuels play a crucial role in addressing excessive body temperatures experienced by hypersonic vehicles during high Mach number operations, serving both as propellants and coolants. Flow calorimeters measure fluid thermodynamic parameters. Traditional ones rely heavily on thermocouples for temperature measurement, leading to a black-box effect on thermodynamic parameter analysis. To solve these problems, a distributed flow calorimetry based on scanning radiation thermometry is proposed innovatively. The analysis object is transformed from the whole tube to the microelement. The heat balance equation for the microelement and the mapping relationship between tube coordinates, tube temperature, and fluid thermodynamic parameters have been established. The feasibility of the mathematical model of fluid temperature and distributed flow calorimetry is verified by numerical simulation. Experimental data from the National Institute of Standards and Technology are compared for the distributed specific heat capacities of water and n-decane over wide temperature ranges. Between temperatures of 296.43 and 564.45 K, water’s distributed specific heat capacity shows a relative error ranging from −7.42% to 8.04%, with a mean deviation of −0.72%. For temperatures spanning 298.97–601.77 K, n-decane’s distributed specific heat capacity exhibits a relative error from −5.13% to 5.57%, with a mean deviation of −0.31%. The results demonstrate that distributed flow calorimetry holds promising prospects for measuring the changes in thermodynamic parameters of fluids during heat exchange.