2-D kettle reboiler circulation model

A 2-D model is developed for sections of a kettle reboiler where liquid/vapour disengagement is not severe. Using a trial set of boundary conditions it is shown that the influence of flow around the periphery of the bundle has negligible effect on flow distribution over the tubes. Uniform heat flux solutions are obtained for q = 20 and 50 kW/m² boiling pentane and R113 at 1 atm. Pronounced 2-D effects were obtained at the higher heat flux only. Use of typical superposition and asymptotic flow boiling correlations resulted in bundle average heat transfer coefficients for both heat fluxes no different from the values predicted by the 1-D model. However, it is suggested that the 2-D solution mass velocity and void fraction distribution are important for predicting the design maximum heat flux limitation.