Transferência de calor
Heat moves in three distinct ways, and this simulation gives each of them a full bench of its own. Watch energy conduct along a metal bar towards its steady state, break a heated fluid layer into convection rolls once the Rayleigh number passes 1708, and radiate across an empty gap until each plate settles at the temperature where what it emits balances what it absorbs.
Como usar esta simulação
- Switch between conduction, convection and radiation
- Pick the bar's material from copper to oak, set both end temperatures, and take the lagging off to let heat leak to the air
- Choose the fluid, its depth and the temperature difference across it — or switch gravity off and watch convection stop
- Set the source temperature, move each plate along its rail and give it a different surface
- Drag the probe along the bar to read the temperature anywhere on it
O que observar
- Copper and oak reach the same steady profile, but the clock says copper takes minutes and oak takes days
- Below Ra ≈ 1708 the fluid refuses to move and Nu stays at 1.00; above it the layer folds into rolls and Nu climbs
- With gravity off the fluid is still, which is why spacecraft need fans to cool anything
- Doubling a plate's distance quarters the radiation reaching it, so its rise above room temperature drops accordingly
- A black plate and a shiny grey one end up at the same temperature — only the time they take differs
A física por trás
Conduction here is the heat equation solved along a real bar, so the profile bends towards the straight steady-state line at a rate set by the material's thermal diffusivity and the final heat flow obeys Fourier's law, Q = kAΔT/L. Convection is a two-dimensional Boussinesq flow: buoyancy fights viscosity and thermal diffusion, and the Rayleigh number decides which wins, with the Nusselt number reporting how many times more heat the moving fluid carries than conduction alone. Radiation follows Stefan–Boltzmann in both directions at once, with the irradiance falling as 1/d² and each coating's absorptivity band-averaged over the source's spectrum, which is why two grey surfaces settle at the same temperature however shiny they are while white paint stays cool and polished metal runs hot.