DOI: 10.1615/ICHMT.2008.CHT
ISBN Print: 978-1-56700-253-9
ISSN: 2578-5486
MODELLING FLUID FLOW, HEAT TRANSFER AND WATER CONDENSATION IN A PRESSURE COOKER
SINOPSIS
Pressure cooker allows rapid and energy saving cooking of various food products. But both thermal phenomena and bio-chemical transformation of food during pressure cooking are very poorly understood. The aim of this study was to simulate with a CFD approach the thermal phenomena inside a pressure cooker in order to predict the temperature evolution in the food product and its heterogeneity. Different difficulties appear because of geometric complexity and many coupled phenomena: evaporation and condensation of vapour in presence of non-condensable gas (air) is of major importance, natural convection occurs in an unstable configuration (bottom horizontal hot wall), pressure increases with time, density depends on composition, temperature and pressure. Coupled unsteady equations for fluid flow, heat transfer and mass transfer (air and water vapour) were solved using the finite volume method for a 3-dimensional geometry. Liquid water fluid flow was not represented but water evaporation from the bottom and condensation on the lateral walls and on the food product surface were taken into account. The numerical results are coherent with the orders of magnitude obtained with empirical correlations in similar configurations and with some global measurements. Numerical simulation allowed better understanding of some phenomena which are very difficult to characterise experimentally (fluid flow, stagnation zones of air, zone of condensation...) which can explain the heterogeneity of heat treatment (difference of cooking degree) sometime observed. After validation, this approach could help for the equipment design (geometry of the vessel, lid and basket) in order to improve cooking homogeneity.