Numerical investigation of tube bundle arrangement effect on falling film fluid flow and heat transfer

Falling film heat transfer, an advanced technology, has been widely applied in the refrigeration and desalination system and beyond. Numerical simulations are conducted aiming to investigate the impacts of liquid flow rate, distributor height, tube pitch and tube bundle arrangement on the falling film hydrodynamics and heat transfer performance in the tube bundles. The liquid film thickness (LFT), heat transfer coefficient (HTC) and bundle effect are obtained under various conditions. The results indicated that: (1) the calculation results are in good consistent with the previous studies in both LFT and HTC; (2) various inter-column flow patterns, solitary wave, droplet and liquid bridge are widely observed; (3) the velocity fluctuation due to the pulsatile droplet impacting or liquid column impingement is one of the fundamental causes of bundle effect; (4) bundle effect universally exists in the falling film tube bundle, and varies with the liquid flow rate, distributor height, tube pitch and tube bundle arrangement; (5) the triangular and square tube bundles behave the best and the worst in the average HTC of the tube bundle, respectively, while the square tube bundle and rotated square tube bundle provide the largest and the smallest bundle effect, respectively.