Analysis of pressure fluctuations during water evaporation in spouted bed

Authors

  • R.N. Marreto,

    1. Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Via do Café s/n, Campus USP, Ribeirão Preto, 14040-903 SP, Brazil
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  • M.P.G. Peixoto,

    1. Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Via do Café s/n, Campus USP, Ribeirão Preto, 14040-903 SP, Brazil
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  • C.C.C. Teixeira,

    1. Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Via do Café s/n, Campus USP, Ribeirão Preto, 14040-903 SP, Brazil
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  • L.A.P. Freitas

    Corresponding author
    1. Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Via do Café s/n, Campus USP, Ribeirão Preto, 14040-903 SP, Brazil
    • Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Via do Café s/n, Campus USP, Ribeirão Preto, 14040-903 SP, Brazil.
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  • This article is a contribution to the special issue on Spouted Beds that was produced recently in honour of Prof. N. Epstein.

Abstract

The aim of this work was to study the behaviour of conventional spouted beds during water evaporation and to analyze the pressure fluctuations at the maximum water evaporative capacity for different bed heights and air flow rates. The results showed that spout pressure drop could not indicate the proximity of maximum evaporative capacity; however this condition is denoted by a minimum in fountain height. The standard deviation and amplitude of the pressure fluctuations also showed a minimum point at the maximum water evaporation capacity. The frequency domain analysis of pressure fluctuations revealed that the dry bed has a dominant frequency varying from 6 to 8.2 Hz and that the peak of dominant frequency tends to disappear with the increase in water feed rate.

Abstract

L'objectif de ce travail était d'étudier le comportement des lits jaillissants traditionnels pendant l'évaporation d'eau et d'analyser les fluctuations de pression au moment où la capacité d'évaporation d'eau est maximale pour différents débits d'air et hauteurs de lit. Les résultats ont montré que la chute de pression en trombe ne pouvait pas indiquer la proximité de la capacité d'évaporation maximale; cependant, cette condition est dénotée par une hauteur minimale de l'effet de fontaine. L'écart et l'amplitude standard des fluctuations de la pression ont également montré un point minimal situé à la capacité d'évaporation d'eau maximale. L'analyse du domaine fréquentiel des fluctuations de pression a révélé que le lit sec a une fréquence dominante qui varie entre 6 et 8,2 Hz et que le sommet de la fréquence dominante a tendance à disparaître avec l'augmentation du débit d'eau.

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