Fourier series solution to the heat conduction equation with an internal heat source linearly dependent on temperature: Application to chilling of fruit and vegetables

This paper proposes a separation of variables solution to the equation for heat transfer by conduction in simply-shaped, homogeneous and isotropic bodies subjected to cooling or heating processes without a phase change and with an internal heat source that is a linear function of temperature and subject to homogeneous external conditions of the third kind. The solution is given by the sum of an infinite Fourier series. Starting from this solution, the paper also proposes a simple calculation of chilling time based on an approximation to the first term of that solution (exponential zone); it further proposes a first approximation to the maximum value attained by the temperature history, and to the corresponding time. © 2008 Elsevier Ltd. All rights reserved.Peer Reviewe

Refrigeración evaporativa. Una alternativa de ahorro energético real

3 páginas, 3 fotos.-- Artículo de divulgación publicado en revista técnica sobre la construcción e ingeniería de las instalaciones.Peer reviewe

A new exact numerical series for the determination of the Biot number: Application for the inverse estimation of the surface heat transfer coefficient in food processing

10 páginas, 5 figurasAs a corollary to a previous work, a new exact numerical series is deduced for the Biot number for the case of elementary geometries. This series is rapidly converging, allowing a very accurate approximation when truncated at its first term. On the basis of this first approximation to the series, the equation is generalized and proposed to indirectly estimate the Biot number for regular geometries.CICYT. ALI96-1207-CO2-01.Peer reviewe

Graphical calculation of half-cooling times

This paper proposes a general approximate method of predicting the variation of temperature at the thermal centre and the mean temperature during cooling of bodies of any geometrical shape. The method is based on graphically determining the initial and exponential half-cooling times in simple geometric shapes. For this purpose, two diagrams have been constructed to depict these dimensionless times, plus the prime root of the Biot equation and other useful variables for the indirect approximate calculation of thermophysical parameters. © 1990.Peer Reviewe

Calculation of the minimum mean cooling/heating time of general-geometry solids

13 páginas, 13 figuras, 9 tablasPeer reviewe

Asymptotic Modelling of the Transient Regime in Heat Conduction in Solids with General Geometry

6 páginas, 1 figura, 4 tablas.This paper proposes a mathematical model for predicting the evolution of mean and thermal centre temperatures of generally convex solid bodies subjected to cooling or heating processes without a phase change. To do so, a theoretical asymptotic analysis is made under boundary conditions of the third kind of the Fourier number, valid for the aforementioned temperatures. Similar asymptotic' functions were obtained in the (Bi ~ 0 and Bi --' 00 ) limits. This enables a methodology to be established in the direct process time modelling based on its evolution as a function limited between the asymptotic values. The study is carried out in stages, starting with solids with elemental geometries up to those with general geometries. A specific, simple, easily programmed model is proposed for evahlating the said variable.The authors are grateful to the Spanish Commission for Science and Technology for funding this project (Project ALI91-0728).Peer reviewe

Dispositivo y procedimiento de regulación de temperatura y humedad

Referencia OEPM: P9601361.-- Fecha de solicitud: 18/06/1996.-- Titular: Consejo Superior de Investigaciones Científicas (CSIC).El objeto de la invención es la regulación de la temperatura y humedad en c amaras frigor íficas. Consiste en un regulador electrónico que se intercala entre los elementos habituales de control de temperatura de una planta frigor ífica, que posee un programa lógico, descriptor de un procedimiento de regulación, cuyas operaciones básicas son las siguientes: 1) Alternar y mantener dos temperaturas diferentes en el foco frío según se trate de ajustar la temperatura o la humedad relativa del recinto; 2) Controlar el caudal de aire en el foco frío en función del punto anterior; 3) Controlar la temperatura del desescarche del mencionado foco para optimizar su rendimiento. Resuelve el problema de la regulación ficiente de la humedad relativa a bajo costo.Peer reviewe

Texture analysis of fish fillets and minced fish by both sensory and instrumental methods

In an attempt to establish objective criteria for texture analysis as an effective substitute for organoleptic procedures, correlation between the results obtained by a panel of tasters and physical and chemical analyses of texture was determined. In addition, regression equations relating instrumental and sensory methods were applied to predict sensory data from those obtained during instru mental analysis.Peer Reviewe

Viscoelastic characterization of solid foods from creep compliance data: Application to potato tissues

Two software systems were developed to simplify acquisition and analysis of data describing creep behavior of viscoelastic solid foods and to determine the magnitude of instantaneous elastic compliance, viscoelastic compliances and viscosity associated with Newtonian flow. The first of these systems was used to store information on the experiment, to collect the data generated during the experiment, to present these in real time and to create files containing the experimental data for subsequent analysis. The second system was used to fit data to discrete Kelvin-Voigt models with four, six or eight constants. The systems were tested in the calculation of rheological properties of fresh and cooked potato tissues. A six-element Burgers model containing two discrete Voigt units proved the most suitable for defining tissue creep behavior, suggesting that different structural components could be related to each unit. The instantaneous elastic modulus could be associated with internal cell pressure. Gelatinization of starch andviscoelastic units appeared to reflect the viscoelastic properties of pectic substances and hemicelluloses, respectively. © Springer-Verlag 1998.Peer Reviewe