Abbilden des instationären Betriebs eines Pelletkessel durch Messung und Simulation

Published 2012

Citation: Schnetzinger, R. Abbilden des instationären Betriebs eines Pelletkessel durch Messung und Simulation, Diploma Thesis, FH Oberösterreich, Wels, Austria, 2012.

Abstract

This thesis focuses on portraying the thermal behavior of a biomass pellet boiler through measurement and simulation. During operation the power of a pellet boiler changes depending on the heat demand. Detailed measurements were conducted to record this changing behavior of some boilers and estimate their levels of efficiencies. Subsequently a mathematical model was created to emulate boilers and their thermal performance without such measurements. The first part of this thesis deals with the description of the simulation model and the measurements which were carried out. Secondly, the verification of the model is discussed. For this verification simulation results of three different boilers are compared to measurement data and pictured in various diagrams. The last part of this thesis is about further simulations of these three boilers where the control units were emulated too. The model was built in the MATLAB/Simulink® environment and is generally based on
thermodynamic relationships and heat balances in a boiler. However, through constant comparison of the simulation results with the measurement data some parameters were adapted to fit the simulation to reality. Therefore this model is “semi-empirical” as physical correlations are included but some parameters were deduced from measurement. Following, the verification of the model is discussed through the comparison of measurement data and simulation results. For the verifications the boiler power, fuel mass flow as well as
the heat consumption were taken from the measurement data and set as input for the simulation. The calculated results show that the boiler model enables to portray the thermal behavior of the three boilers tested with only small divergences. At the end of this thesis it was attempted to model the control unit of the three boilers by analyzing the measurement data. Having a model for the control unit, the inputs from the measurement data are reduced to just two variables, the water inlet temperature and the water volume flow (heat consumption). The comparison of the calculated values to the measurement data shows slightly higher divergences than during the validation, especially where the simulated control unit does not behave like the real one. Through the simulation of further boilers the model could be continuously enhanced. In the future this “virtual boiler” should be used to test control algorithms of boiler control units to enhance their efficiencies.