On the Temperature Measurement Bias and Time Response of an Aspirated Thermocouple in Fire Environment.
On the Temperature Measurement Bias and Time Response of
an Aspirated Thermocouple in Fire Environment.
Kim, S. C.; Hamins, A.
Journal of Fire Sciences, Vol. 26, No. 6, 509-529,
thermocouples; temperature measurement; response time;
computational fluid dynamics; fire tests; simulation;
geometry; heat transfer; equations; pressure; solid
materials; temperature; flow fields; velocity fields;
To examine the uncertainty of thermocouple temperature
measurements, the present study uses numerical
simulations and analytical solutions to investigate the
heat transfer processes associated with double shield
aspirated thermocouple. This study is divided into two
parts. First, 3D CFD calculations for real geometries
are performed to understand the flow characteristics of
double shielded aspirated thermocouples. Based on
iso-thermal flow calculations for real geometry,
conjugate heat transfer calculations for a 3D simplified
geometry are performed to investigate the thermocouple
radiative exchange errors that may be important in a
fire environment. The results of the 3D heat transfer
calculation are compared with algebraic solutions from a
previously developed simple energy balance model and the
algebraic model shows acceptable results compared to the
3D CFD model, despite its many assumptions and
idealizations. A parametric study was conducted to
quantify the thermocouple errors for various gas
temperature and surrounding conditions. In this manner,
the present study improves our understanding of the
uncertainty of thermocouple temperature measurements.