Fire Safety Science Digital Archive

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 bare bead and double shield aspirated thermocouple. This study is divided into two parts. First, three dimensional CFD (Computational Fluid Dynamics) calculations for real geometry are performed to understand the flow characteristics of the double shielded aspirated thermocouple. Based on iso-thermal flow calculations for real geometry, conjugate heat transfer calculations for a 3D simplified geometry are performed to investigate the thermocouple measurement error 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. The results predicted by the algebraic model were in agreement with the CFD model over a broad temperature range despite its many assumptions and idealizations. A parametric study was conducted to quantify the thermocouple errors for various gas temperature and surrounding conditions. The transient CFD solution provides information about the time response of the thermocouple measurement. In this manner, the present study improves our understanding of the uncertainty of thermocouple temperature measurements.