Technique for Evaluating the Uncertainty of Enthalpy of Water and Steam for Thermal Energy Metering Systems

: pp. 79 – 86
Received: October 18, 2018
Revised: December 06, 2018
Accepted: December 12, 2018
Lviv Polytechnic National University
Lviv Polytechnic National University
Lviv Polytechnic National University
Lviv Polytechnic National University

The paper presents an analysis of existing techniques for calculating the enthalpy of water (steam). Based on the analysis the techniques were defined that should be applied for computer-aided design of thermal energy metering systems. Equations for calculating relative expanded uncertainty of water (steam) enthalpy are developed taking into account methodical uncertainty of enthalpy calculation and uncertainties of metering temperature and pressure of water (steam). Simplified dependencies are developed for calculating the relative sensitivity coefficients of the enthalpy uncertainty to the uncertainties of water pressure and temperature. These dependencies make it possible to calculate the values of the sensitivity coefficients for a range of pressure from 0 to 5 MPa and temperature from 300 to 550 K. The relative deviations of the sensitivity coefficients obtained by the simplified dependencies from the values obtained by the equations of International Association for the Properties of Water and Steam (IAPWS) are 0.48% (for the sensitivity coefficient of uncertainty of enthalpy to uncertainty of pressure) and 0.56% (for the sensitivity coefficient of uncertainty of enthalpy to uncertainty of temperature) for the above pressure and temperature ranges. The developed simplified technique for evaluating uncertainty of water (steam) enthalpy can be applied to determine the metrological characteristic of thermal energy metering systems and also for their computer-aided design.

  1. GOST 8.728-2010 State system for ensuring the uniformity of measurements. Estimation of errors of measurements of thermal energy and weight of the heat-carrier of water systems of the heat supply. D.I. Mendeleyev Institute for Metrology.  (in Russian)
  2. Celenza, L., Dell'Isola, M., Ficco, G., Vigo, P., Pauletti, L. (2015) Metrological characterization of a new direct heat accounting device. AISEM Annual Conference, XVIII.
  3. Release on the IAPWS Industrial Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use. International Association for the Properties of Water and Steam,
  4. Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam. International Association for the Properties of Water and Steam,
  5. Aleksandrov A.A., Grygoriev B.A. GSSSD 187-99. Tables of Standard Reference Data. Ordinary water specific volume and enthalpy in the temperature range 0 to 1000 °C and the pressure range 0.001 to 1000 MPa. (in Russian)
  6. MI 2412-97 Recommended Practice - National Measurement Standards - Piped Hot Water Heat Supply Systems - Equations for Measurement of Thermal Energy and Quantity of Heat Transfer Agent.  D.I. Mendeleyev Institute for Metrology. (in Russian)
  7. Matiko, F. D., Slabyk, O. M., Hutnyk, M. B. (2018) Analysis of normative base for systems of measuring the amount of thermal energy. Scientific Bulletin of UNFU, Vol. 28, No 3, 105-110, (in Ukrainian)
  8. JCGM 100:2008, GUM 1995 with minor corrections Evaluation of measurement data — Guide to the expression of uncertainty in measurement.
  9. Lesovoy L. V. (2011) Calculation of the flowrate of the humid water steam by method of the differential pressure with standard primary device. Quality Control Tools and Techniques, Vol. 1, No. 26, 71-76. (in Ukrainian)
F. Matiko, O. Slabyk, L. Lesovoy, H. Matiko. Technique for evaluating the uncertainty of enthalpy of water and steam for thermal energy metering systems. Energy Eng. Control Syst., 2018, Vol. 4, No. 2, pp. 79 – 86.