Browsing by Author "Matolla, Jacques"

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    Thermal design of a helically coiled boiler
    (Stellenbosch : Stellenbosch University, 2016-12) Matolla, Jacques; Meyer, Chris J.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: This thesis describes the thermal design of a once-through forced circulation helically coiled boiler. The formulation of the one-dimensional steady state thermal model used for sizing the boiler was based on the empirical correlation of Gnielinski and John Thompson best practices. The magnitude and location of the critical heat flux (CHF) in the helical coil was initially quantified using the empirical correlation of Ünal. Due to the onedimensionality of the Ünal model and the complexity of the helical coil geometry CFD was used to predict the exact location of the CHF. A single-phase numerical simulation followed by a two-phase flow analysis using the Rensselaer Polytechnic Institute (RPI) wall heat flux partitioning model was used to establish the location and magnitude of the CHF and the results compared to that obtained using the Ünal model. It was found that the Ünal model underestimated the location of the CHF by approximately 37%.