An empiric equation for the latent heat of vaporization of moisture in bananas during its isothermal drying

Abstract

In order to determine the energy needed to artificially dry a product, the latent heat of vaporization of moisture in the product, hfg, must be known. Generally, the expressions for hfg reported in the literature are of the form hfg = h(T)f(M), where h(T) is the latent heat of vaporization of free water, and f(M) is a function of the equilibrium moisture content, M. But expressions of this type contain a simplification because, in this case, the ratio hfg/h would only depend to the moisture content. In this article a more general expression for the latent heat of vaporization, namely hfg = g(M,T), is used to determine hfg for banana. To this end, a computer program was developed which fits automatically about 500 functions, with one or two independent variables, imbedded in its library to experimental data. The program uses nonlinear regression, and classifies the best functions according to the least reduced chi-square. A set of executed statistical tests shows that the generalized expression used in this work given by hfg = g(M,T) produces better results of hfg for bananas than other equations found in the literature.