N2 - Under steady-state conditions when fluid temperature is constant, temperature measurement can be accomplished with high degree of accuracy owing to the absence of damping and time lag. However, when fluid temperature varies rapidly, for example, during start-up, appreciable differences occur between the actual and measured fluid temperature. These differences occur because it takes time for heat to transfer through the heavy thermometer pocket to the thermocouple. In this paper, a method for determinig transient fluid temperature based on the first-order thermometer model is presented. Fluid temperature is determined using a thermometer, which is suddenly immersed into boiling water. Next, the time constant is defined as a function of fluid velocity for four sheated thermocouples with different diameters. To demonstrate the applicability of the presented method to actual data where air velocity varies, the temperature of air is estimated based on measurements carried out by three thermocouples with different outer diameters. Lastly, the time constant is presented as a function of fluid velocity and outer diameter of thermocouple.
L1 - http://so.czasopisma.pan.pl/Content/94284/PDF/04_paper.pdf
L2 - http://so.czasopisma.pan.pl/Content/94284
PY - 2011
IS - No 4 December
EP - 55-66
KW - Temperature measurement
KW - Transient conditions
KW - First-order model
KW - Time constant
KW - Uncertainty analysis
A1 - Jaremkiewicz, Magdalena
PB - The Committee of Thermodynamics and Combustion of the Polish Academy of Sciences and The Institute of Fluid-Flow Machinery Polish Academy of Sciences
T1 - Reduction of dynamic error in measurements of transient fluid temperature
SP - 55-66
DA - 2011
UR - http://so.czasopisma.pan.pl/dlibra/publication/edition/94284
T2 - Archives of Thermodynamics
DOI - 10.2478/v10173-011-0031-3