Selected Problems of the Uncertainty Determination of Measurements and Computational Value in Thermal Processes

Thermal measurements in energy engineering are a rather complex matter. Many physical quantities cannot be measured directly. They must be calculated making use of algorithms basing on the results of direct measurements. Any measurement is always an inaccurate operation. A measure of the inaccuracy of measurements is the uncertainty of this measurement defined as a parameter characterizing the scatter of values of the measured quantity. The paper deals with some selected problems connected with the determination of the uncertainty of measurements and calculated values in compliance with DIN and ISO standard. The calculations of the uncertainty of the specific enthalpy, difference of enthalpy, the fluid flux and the energy efficiency of the steam boiler determination have been presented, as well as exemplary results of calculation of the uncertainty of the thermal efficiency of a steam boiler fired with pulverized coal.