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On-site calibration of flow meters in district heating

EnEff:Wärme - Forschung für energieeffiziente Wärme- und Kältenetze

LDV meter for on-site calibration of flow measurements

© TÜV Rheinland/ILA/Optolution

Settlement summary

Project status Projektstatus: Phase 3Realisation
Location Berlin district heating network
Project plan The project’s goal is to increase the efficiency of district heat generation and transport. For this, more precise balancing of transmission losses is required, which can be achieved by reducing measurement uncertainties when measuring heat quantities, among other measures. This goal is to be reached by further developing a laser optical on-site calibration method for large-scale flow meters for perturbed inflow conditions which commonly occur in practice. After researching the typical flow perturbations in the Berlin district heating network, a test rig will be set up at TU Berlin for flow analyses of perturbations. In cooperation with TU Berlin, PTB Berlin, ILA GmbH and Optolution Messtechnik GmbH a method for laser optical on-site calibration even under problematic inflow conditions by combining laser optical and numerical methods will be developed. In cooperation with PTB Berlin, the measurement uncertainty of this new method will be studied in detail via comparison measurements based on the national standard. This will be followed by testing whether it is possible to trace the method back to the national standard. At the same time, the method will be tested at typical measurement points in the Berlin district heating network together with the partner Vattenfall Europe Wärme AG.
Developer, organizer ILA GmbH
Project themes

Project description

The overall goal of the project is to contribute to energy optimisation of district heating networks. For this, more precise balancing of transmission losses is required, which can be achieved by reducing measurement uncertainties when measuring heat quantities, among other measures. By combining laser optical and numerical methods, a practical and, where possible, traceable method is to be developed which permits on-site calibration of existing flow sensors (hereinafter FS) with a diameter of approx. 150 to approx. 1,000 mm in the district heating network while it is running. Reducing measurement deviations and uncertainties at the most important flow measurement points permits more precise network balancing. Only these measures permit efficient distribution and use of the thermal energy converted in the cogeneration process. That will significantly increase the efficiency in the entire energy generation and distribution process, and, as a result of this, significantly reduce the use of resources.

Concept, work programme

The research project subject of the application is intended to develop a process which will permit determination and reduction of measurement uncertainties in on-site calibration even for typically perturbed inflow conditions by combining numerical and technical measurement methods. That will extend the scope of application of the currently available laser optical method for on-site calibration of flow meters from rotationally symmetrical flows to typical perturbed inflow conditions, thus adapting it to the practical requirements. In order to permit a laser optical on-site calibration of large-scale flow meters, even in perturbed inflow conditions, the velocity profile measured using LDV (laser Doppler velocimetry) is to be combined with the velocity distribution determined based on the CFD calculations (computational fluid dynamics), which can be deformed by installations. The CFD data provides a basis for determining the previously unknown contribution to the measurement uncertainty due to flow perturbation effects.

The planned procedure can be broken down into the following steps:

  • Improvement of laser optical measurement technology
  • Reduction of systematic measurement uncertainties of LDV measurement
  • Simulation of practically relevant flow perturbations on the test rig
  • Measurement of perturbed velocity distributions on the test rig
  • CFD calculation of the perturbed velocity distributions on the test rig
  • Development of a process to calibrate the CFD results with measured velocity distributions
  • Development of a process to determine measurement uncertainties based on CFD velocity fields
  • Development of a measurement uncertainty budget for the overall method
  • Upscaling comparison via measurements in PTB Berlin
  • Tracing the overall method on the large-scale thermal test rig of PTB Berlin
  • Field testing the overall method in the Berlin district heating network
  • Studying options to increase the efficiency via optimised operation of the network and the generators