RADIATIVE HEAT TRANSFER

Thermal radiation is a form of electromagnetic radiation similar to X rays, light waves, gamma rays, and so on, differing only in the wavelength. It is an important mode of heat transfer and is especially important where large temperature differences occur. In other words, radiation is the transfer of energy through space by means of electromagnetic waves in much the same way as electromagnetic light waves transfer light. The same laws that govern the transfer of light govern the radiant transfer of heat. Solids and liquids tend to absorb the radiation being transferred through them so that radiation is important primarily in transfer through space or gases.

DAILY LIFE EXAMPLE

1. Accidents due to thermal radiation
2. Firewood in a fireplace
3.  Black ice formation

ACCIDENTS DUE TO THERMAL RADIATION

In 1999, after the Istanbul-Kocaeli earthquake disaster, a fire broke out at the biggest petroleum refinery in Turkey. Once a storage tank started to burn and reached extremely high temperatures, one of the nearby tanks also caught fire due to the radiative heat transfer from the hot tank. In order to prevent heat transfer between tanks, the surrounding environment was tried to be cooled by spraying water.

FIREWOOD IN A FIREPLACE

When single firewood is started to burn in a fireplace, the pyrolysis takes place and the produced heat is lost to the environment by the radiation. In this case, pyrolysis cannot continue. But if a stack of firewood is burnt, the radiative heat lost by one firewood is absorbed by the others, and consequently, pyrolysis continues.

BLACK ICE FORMATION

Black ice or frost, a thin layer of glazed ice formed on the roadways, is one of the leading causes of accidents due to its invisibility in unexpected weather conditions. Even at temperatures above zero, frost formation can cause drivers to have accidents especially mornings of clear nights. On these nights, the sky behaves like a black body and absorbs radiative heat from the roads. For highways, lost heat is gained from the soil via conduction and from the air via convection. On the contrary, for bridges or viaducts, lost heat results in a thin layer of frost formation on the surface.