CONSTRUÇÃO DE UMA CÉLULA DE ARNOLD PARA DETERMINAÇÃO DA DIFUSIVIDADE MÁSSICA EM SISTEMAS GÁS-LÍQUIDO

Abstract

Molecular diffusion plays a fundamental role in several unit operations in Food Engineering, and the binary diffusion coefficient DAB is a key parameter for quantifying mass transfer by molecular diffusion. This study describes the development of a low-cost Arnold diffusion cell constructed from readily available materials, including PVC pipes and fittings, a test tube, and a hair dryer, for the experimental determination of the binary diffusivity of the ethanol–air system under pseudo-steady-state conditions. The proposed apparatus was designed as an affordable experimental platform to support the teaching of Transport Phenomena. Experiments were performed at 40.1 °C for 60 min, and the variation in the liquid column height was measured at 10 min intervals using a digital caliper. The mathematical model was derived from the continuity equation and Fick’s first law, assuming steady-state diffusion in the gas phase, one-dimensional mass transfer, an inert medium, and stagnant air. The experimental data were fitted by linear regression, resulting in a binary diffusion coefficient of DAB= 0.1783 cm² s⁻¹, with an excellent coefficient of determination R² = 0.9883. The measured diffusivity differed by 16.51% and 8.96% from two literature values reported for the ethanol–air system. These results demonstrate that the proposed Arnold cell provides reliable experimental data while offering a simple, inexpensive, and effective laboratory apparatus for integrating theoretical concepts with hands-on experimentation and quantitative analysis in mass transfer education.