Question

We all love to have toasted bread in the morning for breakfast. When you place a slice of bread in the toaster and the toaster is activated, is the toaster in steady-state operation, non steady state operation, or both? Explain your answer.

thermo

Answer 1

An automatic toaster is a open loop control system. The steady-state heat transfers occurs within a conventionally-heated electric toaster.

Inside a toaster, rows of glowing red wires facing the bread. When electricity flows through these wires, they get hot and then fire their heat toward the bread like dozens of miniature radiators.When electricity flows through a wire, energy is transmitted from one end of the wire to another. The movement of energy is a bit like water flowing down a pipe. The electrical energy is carried down the wire by electrons, the tiny particles inside the atoms of metal that make up the wire. As the electricity flows, the electrons jostle about and collide with one another, and with the atoms in the metal wire, giving off heat in the process. The thinner the wire, and the greater the electric current, the more collisions happen and the more heat is generated.

Inside a toaster

1. Electrical energy flows into the toaster from a wire plugged into the domestic electricity supply.
2. The electric current flows through a series of thin filaments connected together but spaced widely enough apart to toast the whole bread surface.
3. The filaments are so thin that they glow red hot when the electricity flows through them.
4. Like a series of small radiators, the filaments beam heat toward the bread in the toaster.
5. The steady supply of heat rapidly cooks the bread. There are filaments on each wall of the toaster so the two sides of the bread cook at the same time.

The steady-state temperature distributions across the simulated bread/heater air space were observed (via optically-flat glass plates, which were sealed to each end of the cavity) by employing a laser-stimulated.Within a toaster, buoyancy forces created by heating cause an air current to flow through the toast compartment. At high temperatures, the absorption of radiation by carbon dioxide and water vapour present within the air, augments the convective flow, but this process is of less influence on the toasting process than the primary radiative and convective heat transfers occurring within the appliance.In the boundary layers which formed on the opposing hot and cold surfaces, the isotherms were closely packed, but in the central region of the cavity the horizontal temperature gradient was small, because the convective flow near the vertical walls tended to counteract the effect of conduction straight across the cavity.