Dynamic model of a waste heat boiler

Abstract

The paper discusses the experience of developing and identifying a model of a waste heat boiler as a distributed parameters plant. The waste heat boiler is considered as a heat exchanger with cross flows of interacting media. The first order hyperbolic equation acts as a mathematical model of water flow heating with a variable rate. Using the spectral method of distributed systems, a representation of the problem is obtained in the form of an expansion into a series in an orthonormalized basis, which makes it possible to represent the solution in the form of a vector-matrix model of the state space. The state-space representation is used to implement the model in a dynamic systems simulation package. The heater temperature calculation is based on the energy balance equation. The temperature of the media separator wall is determined by the heat fluxes between the exhaust gas, the wall, and the heated water. The wall temperature is assumed to be constant along the entire length of the heat exchanger. The paper presents a block diagram of the model, which takes into account the mutual influence of the wall temperatures and the heated water flow. The heat flux from the exhaust gas is calculated directly from the known parameters of the exhaust gas at the inlet and outlet of the waste heat boiler. Based on the design parameters of the heat exchanger, the dynamic characteristics of the heat transfer process are determined. The data obtained during the operation of the waste heat boiler are used to identify the heat transfer coefficient between the walls of the heat exchanger and the water flow. The result of the heat transfer coefficient identification agrees with the reference data. The article presents graphs of the original data, simulation results. It is shown that the maximum mismatch between the model and real data does not exceed two degrees, and the mean absolute error is less than 0.2 degrees.