Thermocouple Response in Fires, Part 1: Considerations in Flame Temperature Measurements by a Thermocouple

Abstract

This PIRT exercise identifies a number of factors which can influence thermocouple readings made in fires. Identified factors are: (a) the fuel/oxidizer equivalence ratio and its effect on readings, (b) the influence of the state of oxidation and variation with time for the thermocouple sheath, (c) the convection coefficient models and how experimental readings are influenced by thermocouple diameter and yaw angle, (d) response time of a MIMS thermocouple, and (e) thermocouple end effects.

Thermocouple Response in Fires, Part 2: Validation of Virtual Thermocouple Model for Fire Codes

“…These results are reflective of the modeling intent -to compare the output of the thermocouple model, to experiment and to achieve a large region of uniform temperature surrounding the thermocouple There is remarkable agreement between the thermocouple temperature prediction and observed thermocouple response, as demonstrated in Validation of Virtual Thermocouple Model for Fire Codes simulation values represented by the red triangles in Figure 8 (and the results shown in Figure 5) were calculated using the temperaturedependent emissivity [7]. The actual diameters of the thermocouple probes were not measured, and the uncertainty in diameter is also propagated through the numerical results.…”

Experimental and numerical investigation on combustion characteristics of premixed hydrogen/air flame in a micro-combustor with a bluff body

“…For the sake of safety, a flash arrester was used between the mixer and the flow meter of hydrogen. Moreover, a K-type thermocouple with a bead diameter of 0.5 mm was used to measure the exhaust gas temperature, and the temperature presented in this paper has been corrected considering the heat losses to the ambient [32]. A digital camera was used to take flame pictures from the top viewpoint.…”

Effect of thermocouple insertion depth in multiple directions on temperature measurements

“…Previously, CARS measurements also showed that Hencken burners are nearly adiabatic. 3,4 The grid was generated using polyhedral cell elements to create a conformal multiregion to allow heat transfer between solids and fluids. Figure 3 shows the grid and the detailed thermocouple surrounded by boundary-layer prism cells.…”

“…The virtual thermocouple model in Vulcan and experimental validation based on well-established flame experiments, using a Hencken burner, various sizes of thermocouples, and Coherent Anti-Stokes Raman Spectroscopy (CARS), are discussed in detail for MIMS thermocouples. 3,4 To supplement these earlier research investigations, detailed multiphysics modeling 5 was performed using a commercial code STAR-CCM + . 6 Although Vulcan and STAR-CCM + have similar physical modeling capabilities, the commercial code has more versatile meshing capabilities, which is an advantage when complex, multiregion grids are needed.…”