Low-order dynamic model of a domestic electric oven Part II: parameter identification and model validation for the static heating mode

Abstract

Appliances are responsible for almost the 25% of the overall environmental impact of buildings, and, among these, electric domestic ovens represent a low-efficiency category when considering flats, with an energy efficiency between 10% and 12%, thus stimulating the development of more efficient technologies. The energy performance of such an appliance is determined through a test according to the EN 60350-1 European standard, which, among others, requires suitable control of the oven centre temperature. Since the development of reliable dynamic models represents a high-potential tool to design better control strategies, the aim of this work is to create a model simulating the transient thermal behaviour during the static, i.e. non-ventilated, heating mode of an electric domestic oven within the cabinet adopted for energy consumption tests; the model must be able to predict the main temperatures within the cavity, with particular attention to the oven centre. A lumped parameter approach based on the thermoelectric analogy was chosen, in order to obtain a low-order dynamic model suitable for control design purposes. Since the model strives to reproduce the transient behaviour of the oven centre temperature, a single lumped parameter simulating the thermal behaviour of the whole oven cavity was unsuitable and a certain level of macroscopic discretization had therefore to be introduced. Thus, the oven cavity was modelled with eight parameters, representing its main parts like the walls, the glass door and the air in the cavity; also, the temperature probe, a Pt500 as is customary for such devices, was included in the model, since this is the only temperature feedback during operation and its presence in the model could lead to an easier implementation of efficient control logics. Three lumped parameters simulating the thermal behaviour of the heaters were also considered, leading to an 11 ^th order model.