An infrared heater is produces radiating heat; whereas, convection is produced by hot air. When a heater or product is heated by an infrared source, the heater requires a direct line of sight to the product. The distance or space between the part or product and the heater will decide the rate with which the product is heated.
A lesser-known factor in infrared heating is how the products’ or color affects the heating rate. Emissivity is the measure of the part’s capability to absorb or emit energy when compared to that of a black object. The emissivity of the product must be measured to determine its heat-up rate.
Infrared energy heating could be the most efficient and effective source to heat products. However, proper temperature control must be used to ensure that the product is not overheated. Similar to how a black car can be hotter than the air around it on a sunny day, an object heated by infrared can be hotter than the air around it. To correct for this, ensure that you are measuring the temperature of the object itself and not the air around it.
In hot air or convection heating, the position and shape of the product are less important due to the distribution of heat by the air’s movement. Hot air is circulated from various angles encircling the product at the same rate, like an oven set to a consistent temperature with highly accelerated heat passing around the parts. In this scenario, the parts absorb the heat uniformly reducing the chance of overheating in spots.
A frequent argument against convection heat is depending on the mass or size of the object to be heated it is oftentimes slower than other methods. Another factor with gas convection is the dissipation or exhausting of combustion by-products to prevent unsafe conditions in the heated chamber.
When the length of time to heat a part or product has not been established previously, a heat profile must be conducted on the part or product. Data loggers and thermocouples can be used in this process. Thermocouples are mounted onto the parts in critical locations and record temperature data during heating.
To determine which is the more efficient heating method, data must be logged for each respective heater. Temperatures and times may vary for convection heaters during curing, whereas infrared heating will show a higher temperature on the surface throughout the heating cycle.
Another important note is that maximum temperatures of the parts or products during heating will never exceed the maximum temperature setting of the oven. As you will see below, this is not the case with infrared heaters.
In comparison, the profile of a product heated by infrared shows a substantially higher surface temperature, as well as on the interior thermocouples.
· An infrared heated cure may reach a higher temperature during the post-heat stage, which could be appropriate for some processes. However, in some other processes that uneven heat could damage certain products being heated.
· A convection heated product or part might take a longer time to arrive at the necessary temperature dependent on its mass, yet it is known that temperature will never be exceeded in any portion of the product heated and all parts will be thoroughly heated given appropriate time.