Heat Transfer Study in 3-Pass Fire-Tube Boiler During a Cold Start-up

In this work, we are interested to simulate the transient thermal-hydraulic behaviour of 3-pass fire-tube boiler during a cold start-up. A transient thermal model has been developed based upon energy balance equations of the main components of the boiler and the relevant correlations describing heat transfer phenomena taking place. The variation of the main thermal parameters describing the boiler dynamic behaviour, namely: temperatures of combustion gas, tube walls and water as well as heat transfer rates are also studied. The model validation has been performed by comparing the simulation results against experimental data obtained during the boiler start-up. The comparative study shows a good agreement between the simulation and the boiler operating data. Indeed, the maximum error in predicting the main parameters of the boiler was found to be acceptable and the deviations are mainly due to simplifications introduced in the model. The agreement between the simulation and experimental data reveals the accuracy and the suitability of the proposed model to estimate the dynamic behaviour of the studied boiler and other similar designs.