Do you remember the modes of heat transfer?
Heat has three transfer methods: conduction, convection, and radiation. Heat always moves from warmer to colder, which is why heat is transferred practically every time there is a temperature difference between objects. The greater the temperature difference, the more heat is transferred.
A sauna is a good illustration environment for both heat transfer and the importance of insulation. The insulation keeps the heat produced by the stove inside the walls of the sauna. If you cool down for too long, the heat of the sauna evaporates from your skin, and especially in cooler weather, you may suddenly miss the wool socks knitted by your grandma.
During the sauna trip, it is also desirable that the cold drink stays cold and the sausage stays hot – you can influence these with, for example, a cool bag and foil. In the video below, Einari experiences all three ways heat transfer during his sauna trip.
Heat radiation is electromagnetic wave motion that does not need a medium – radiation also occurs in a vacuum. When the radiation hits the surface, some of it is absorbed by the object, some is reflected away and some can pass through the surface. The absorption capacity of the surface affects how much of the radiation is converted into heat, and this capacity is expressed by the absorption coefficient. When heating the sauna, Einari gets to feel the radiation of heat for the first time from the hearth of the stove before the sauna has even had time to heat up.
In heat convection, heat is transferred in a moving medium, such as gas or liquid. From the perspective of insulation, convection occurs when air flows through the insulation due to air movement caused by wind or height difference. During Einari’s sauna trip, convection occurs, for example, when water hits the stove and releases water vapor into the air.
Conduction of heat always takes place through a medium – conduction can occur in a solid substance as well as in a gas or liquid. Einari feels the effect of conduction on his skin when he grabs his foil-wrapped sausages from the stove or when he accidentally sits on a hot bench without a sauna cloth. In the world of insulation, we talk about cold or
thermal bridges. They refer to a body that penetrates the insulation layer and has better thermal conductivity than the insulation layer.
Test whether you remember the most common insulation purposes
The ultimate purpose of insulation is to limit heat and cold losses to minimize energy costs. Of course, this is self-evident for an insulation professional, but can you name the most common purposes of thermal and cold insulation? Here’s a recap of that:
The most common thermal insulation purposes
- Economical thermal insulation, dimensioned based on the optimization of energy and insulation costs caused by heat losses.
- Protective insulation, i.e. insulation measured based on occupational safety requirements. The highest possible surface temperature under normal operating conditions is usually +70 °C.
- Freeze protection insulation, which is dimensioned according to the insulation object, such as the prevention of freezing of the contents of the pipeline.
- Process-technical thermal insulation, i.e. insulation dimensioned to maintain the temperature of the contents of the insulation object within the limits required by the process.
The most common cold insulation purposes
- Economical cold insulation, where the insulation is dimensioned based on the optimization of energy and insulation costs caused by cold losses.
- Dew or sweat insulation, where the dimensioning basis is to maintain the surface temperature of the insulation higher than the dew point of the environment.
- Process-technical cold insulation, i.e. insulation dimensioned to maintain the temperature of the contents of the insulation object within the limits required by the process.
Getting to know insulation – to be continued
Maybe after reading this article, the next time you sit on the bench of the sauna, you will think about heat from completely new perspectives. That’s not a bad thing at all, because the better we understand the benefits of insulation in our everyday lives, the easier it is to spread the joyous message of insulation.
Stay tuned for the following articles as well!