The third kind of thermal transfer is thermal radiation in the form of electromagnetic waves that are emitted by every object. The higher the temperature, the more intensive the thermal radiation, the darker the surface of a body, the greater its capacity to absorb and emit heat.
A conventional temperature control chamber has a cube-shaped interior. Ideally, an equally heated cube radiates heat in the same intensity from all six sides. The less surface area that is heated inside a temperature control chamber, as is the case for example with ring heaters radiating from a point source, the greater the risk that dark chamber loads are heated up too strongly (thermal transfer from hot to cold), or that on the other hand the chamber load that is shaded will not take up any heat.
Picture credit: Memmert GmbH + Co. KG