A comparison of Convection vs. Infrared.

How is heat transfer different?

Convection can only be controlled by air temperature and airspeed. With infrared emitters a far greater flexibility in heat up rates and temperatures can be achieved using different energy densities and wavelengths.

How energy efficient are the technologies?

Convection can waste a lot of energy when switching from large to small components, Infrared emitters can target energy to areas that require heating.

How long are the reaction times of the heating systems?

It may take 30 minutes to 2 hours depending on the size of the convection oven, so an oven will be left running all-day even when there is no production. Infrared emitters can be switched on and off within seconds to suit production conditions.

How is the influence of mass change?

In convection oven the heat up rates will be influenced by mass (number) of components. Infrared is an "energy source" and is not influenced by the number of components in the oven.

How much space is required?

Convection takes up a large amount of floor space. Infrared is a lot more compact, typically 1/4 to 1/3 the space What about maintenance costs?

Convection requires frequent maintenance (fans, filters, pipes, seals, burners) and full maintenance normally makes necessary a complete strip down of the oven. Infrared systems normally only need low maintenance like a changing of emitters or filters.

How do you control temperature with changing parameters?

For convection ovens it takes a long time to reduce or raise the air temperature to suit changing line conditions. Infrared emitters can be regulated instantly to changing conditions; a closed loop control via speed or temperature is possible. A slow rate of heat transfer from air allows heat to conduct into components leading to long heat up times.Using infrared emitters with a high transfer of energy enables surfaces to be heated more rapidly overcoming conduction losses.

What about the noise?

Large convection ovens generate a lot of noise from fans and air movement or turbulence. This causes health and safety implications. Infrared ovens with low air movement cause less noise.

Can you heat in vacuum?

With convection it is not possible. Infrared emitters can be used to heat components in a vacuum chamber.

What happens in a "dirty" environment?

Combustion products, recirculation of dust etc. make convection unsuitable for "clean" applications. Infrared heat is clean, no combustion products and no need to recirculate air.

What can you say about adjustable control?

Difficult and expensive with convection (more air nozzles) at different air temperature and air speed. It is easy to achieve infinitely adjustable control with infrared emitters by selection of energy densities, wavelengths, and variable power levels.

How about holding part temperature?

Convection oven at 200 degrees C air temperature will hold part at temperature without this temperature being exceeded, but limited in maximum air temperature only. Holding with infrared employs electrical controls to prevent temperature increasing or decreasing, generally from a closed loop automatic system.

How is the flexibility with mixed batches?

Although components heat up at different rates, they never exceed temperature of convection oven. Infrared heats up components at different rates and will reach different temperatures depending on mass. Care should be taken to “group” like parts size and mass.