The estimation of a concentration-dependent diffusion coefficient in a drying process is known as an inverse coefficient problem. The solution is sought wherein the space-average concentration is known as function of time (mass loss monitoring). The problem is stated as the minimization of a functional and gradient-based algorithms are used to solve it. Many numerical and experimental examples that demonstrate the effectiveness of the proposed approach are presented. Thin slab drying was carried out in an isothermal drying chamber built in our laboratory. The diffusion coefficients of fructose obtained with the present method are compared with existing literature results. (c) 2006 Elsevier Ltd. All rights reserved.
Inverse design techniques in the area of fluid mechanics are normally conducted for continuous flow turbomachines rather than positive displacement devices. However, the work in this article is concerned with a class of rotary positive displacement device referred to as the limaçon-to-limaçon machine. The rotors and housings of these machines are manufactured of limaçon profiles, and are likely to suffer from interference if the rotors are not carefully profiled. Published literature indicates that solutions proposed to tackle the interference problem in these machines will adversely affect their efficiency figures. This notion motivated the work presented in this article, which first introduces the relevant mathematical models of the limaçon-to-limaçon machine and then uses these models to construct an inverse geometric design problem formulation. The proposed model has been coded in a computer program that utilises a Marquardt-Levenberg technique to converge to the required geometric parameters. Case studies are presented at the end of the article to verify the validity of the proposed inverse design model.