Study on temperature distribution of vertical liquid falling film heat transfer with Al2O3 nanofluid

Abstract

This study presents a laminar smooth 2-D theoretical model of the falling liquid film using an in-house code and validated with experimental results. The numerical model considers thermophysical property enhancements with nanoparticles Al2O3 to different liquids such as water, ethylene glycol (EG), and LiBr-H2O. An experimental setup has been developed to validate the pure heat transfer process in the falling liquid film, using the measurement of the falling film interface temperature. The simulation results agreed well with the experimental results for various liquids at low flow rates. The discrepancy increases as the flow rate increases due to the limitations of the laminar smooth film model in the numerical simulation. With a volumetric concentration of ϕ=4% nanoparticle Al2O3, the heat transfer coefficient of nanofluid water, EG, LiBr-H2O increased around 15%–20% compared with the baseline fluid. A new correlation was obtained to predict the average heat transfer coefficient based on experimental data. The experimental results have an uncertainty at 9.3% for the surface temperature and 5.5% for the falling film bulk temperature. The maximum deviation between the calculated heat transfer coefficient by the model and experimental data is around 25%, at Re<1000. The average error has decreased by 23% when comparing the new correlation considering Ka and the conventional form.