Simulation of an Electric Oven

An oven is a device for cooking all kinds of cakes, foods such as pizza, chicken, lasagna, etc. in a closed compartment and the cooking temperature can be adjusted in it. Uniform cooking of these foods is very important and determines their quality.

Electric ovens use one or more heating elements to provide heat and cook food. The bigger the oven compartment, the more elements there are. Elements may be placed at the bottom of the oven or elements may be used both at the top and at the bottom of the oven. The thermostat measures the temperature inside the oven and adjusts the temperature inside the oven to the desired temperature by turning the elements on and off.

Also, fans are installed in the oven that circulate the hot air produced by the elements and transfer it to the cooler area inside the oven. Therefore, the heat reaches all parts of the food equally and the food is cooked uniformly in less time and temperature.

A metal cover with special specifications separates the fan area from the cooking area in the form of a partition. This separator is used to direct the circulation of the current inside the oven.

Physical phenomena

Inside the oven, heat is transferred through three heat transfer processes:

  • Convection: the fan at the back of the oven blows hot air into the oven in this way.
  • Conduction: heat is transferred from the edges to the middle of the food. It is also a process during which heat is exchanged between air and food at their interface.
  • Radiation: the hot element emits heat to the walls of the oven and to the food.

Design evaluation parameters by simulation

There are restrictions that must be observed in transferring the hot flow caused by the elements into the oven chamber in order to prepare the oven chamber for a favorable cooking; Also, the life of the parts inside the oven increases due to not overheating. In fact, the user’s satisfaction with the product depends on the careful examination of these conditions and the appropriateness of their related parameter values.

By using simulation, the status of these parameters in the completed design is checked and evaluated.

Some of these adverbs are:

  1. The temperature of the current should not exceed its tolerance limit in the area of the front glass of the oven.
  2. The flow speed within the area of the food tray should not exceed 0.7-0.9 m/s.
  3. The flow around the food area should flow uniformly and be sucked cyclically to the area where the elements and fans are placed.
  4. The flow must be able to pass through obstacles such as the tray, flow guiders on the chamber wall, punches on the separating metal cover in a continuous and uniform manner in all areas of the oven, especially food place, and do not suffer local vorticity and return to the initial domain of fans to complete this cycle.

Description of the simulation model

This simulation is done with the aim of evaluating the design of the metal cover of the fan. For this geometry, modeling coupled fluid flow and heat transfer produces an extensive model with high computational volume.

Since the design of the fan cover mainly affects the flow pattern and its circulation inside the oven and does not affect the temperature directly, and also since the forced convection of the flow dominates the natural displacement, in this analysis we can model the transfer Ignore the heat and the natural movement of the flow; and create a cold incompressible flow model.

These cases are simplifications of the model and reduce the calculation time; While their results are acceptable for design evaluation with proper accuracy.

For this purpose, in this simulation, the analysis of the cold flow inside the oven chamber has been done with the k-e turbulent flow model, and the rotation of the fan has been modeled with its frame motion. The number of 8919071 mesh cells was created for this analysis and the solution was performed in a steady state.

In this phase, changes were made in the geometry of the cover and the effect of the number of punches, import or export of the separator was investigated. The optimal geometric combination of these changes was obtained after simulation and analysis of different modes and the results were applied in product development.

The function of the simulation model

This simulation predicts the behavior of the flow inside the oven chamber and shows the changes in the flow due to the changes in the fan cover plate with an overview and display of the flow pattern. It is possible to evaluate the design in the physical laboratory by making a prototype and changing it or making multiple samples, which leads to spending money; Also, unlike simulation, the flow velocity in the laboratory can only be measured at limited points and the flow pattern is not determined.

Based on the simulation results that have a good approximation of the laboratory results, the design is modified and improved.