Multi-level simulation of cooking processes in a domestic oven

According to Eurostat 2020 household appliances are responsible for more than 50% of household electricity consumption in the UE. In particular, the electricity used for cooking is 12.15% of the total. Therefore, they have a relevant impact on energy consumption in the residential sector. Electric ovens, compared to surface or microwave cooking, consume more energy for the same cooking processes. The average cooking efficiency on stoves is about 40%, microwaves nearly 55%, and electric ovens are less than 14%, so there is a great deal of potential for their improvement. There is a wide range of numerical models implemented in the literature to analyse the thermal behaviour of the oven. Many numerical models aim to predict the results of the test regulated by the EN60350 standard, which evaluates the energy class of the oven in the UE at a rate between A+++ and D. This project aims to determine the key parameters that influence the energy consumption of a domestic electrical oven. A combination of theoretical approach and Computational Fluid Dynamics (CFD) is employed. Obtained the oven model, the velocity and temperature distribution within the cavity are analysed under certain boundary conditions, typical of the cooking processes, using steady-state numerical simulations. The numerical approach has been verified through the comparison with the experimental outcome. The studies focus on cooking uniformity as the primary condition to improve the energy performance of the oven. For this purpose, two heat transfer coefficients, radiative and convective, are analysed and the results will be discussed. This analysis forms the foundation for a multi-level approach that provides a dynamic analysis of the energy and mass exchange processes within a cooking cavity. The variables used as input in the dynamic model are integrated with the results obtained by steady-state numerical simulations. In this paper, the first step of this analysis is shown, where the heat transfer coefficients are obtained by CFD simulations made on steady state conditions. By this analysis it is possible to optimise some characteristics of the internal geometry of the oven, such as the air inlets, to achieve a uniform temperature on the internal surfaces and then the best quality of the cooking process. The best indicators for this optimal procedure are evidenced and discussed. These indicators, the convective and radiation heat transfer coefficients, are the starting point for the multi-level methodology for the detection of the optimal cooking process.