Modelling of natural-convection driven heat exchangers

Abstract: A lumped model is developed for shell-and-tube heat exchangers driven by natural convection, which is based on a one-dimensional approximation. The heat flux is driven by the logarithmic mean temperature difference. The volumetric air flow rate is driven by the buoyant force. Based on the Boussinesq aproximation, this force is characterised by an analytic expression of the inflow and outflow temperatures. The lumped model is finished by relating the buoyant force to the friction force via the drag coefficient. The model was calibrated and validated based on Computational Fluid Dynamics calculations and physical measurements