Even if you're familiar with the principles of technical insulation, sometimes it's good to repeat the basics. This is the first article in a series we have called the ABCs of insulation. In this article, you get the opportunity to check if you have the basics under control.
Do you remember the main forms of heat transfer?
Heat has three methods of transfer: conduction, flow (convection) and radiation. Heat always moves from warmer to colder, and therefore heat is transferred whenever there is a temperature difference between objects. The greater the temperature difference, the more heat is transferred.
A sauna is a good example of both heat transfer and the importance of insulation. The insulation keeps the heat from the stove inside the sauna walls. If you cool down for too long, the heat from the sauna evaporates from your skin, and if the weather is chilly, you'll quickly miss the woollen socks your grandmother knitted for you.
During your sauna trip, you'll also want to make sure your cola stays cold and your hot dog stays hot - you can help with a cooler bag and aluminium foil. In the video below, our colleague at Kespet in Finland, Einari, experiences all three main forms of heat transfer during a sauna trip.
Thermal radiation is electromagnetic radiation that does not need a medium - and the radiation 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 absorbency of the surface affects how much of the radiation is converted into heat, and this property is expressed by the absorption coefficient. When Einari heats the sauna, he feels the heat radiation for the first time from the wood-burning stove before the sauna has even had time to heat up.
In thermal convection, heat is transferred in a moving medium, such as a gas or liquid. From an insulation perspective, convection occurs when air flows through the insulation due to air movement caused by wind or height differences. During Einari's sauna trip, convection occurs when water hits the heater and releases water vapour into the air.
Heat conduction always occurs through a medium - solid, gas or liquid. Einari feels the effect of heat conduction on his skin when he takes the foil-wrapped sausages from the oven or when he happens to sit on a hot bench without a towel. These are what we in the insulation industry call thermal bridges - a building part or object that penetrates the insulation layer and has better thermal conductivity than the insulation layer.
Do you remember the most common insulation purposes?
The ultimate purpose of insulation is to limit heat and cold losses in order to minimise energy costs. This goes without saying for a skilled insulator, but can you remember the most common purposes of heating and cooling insulation? Here's a summary:
The most common purposes of thermal insulation
- Cost-saving thermal insulation, dimensioned based on optimising energy and insulation costs caused by heat loss.
- Protective insulation, i.e. insulation measured based on occupational safety requirements. The highest surface temperature under normal operating conditions is usually +70°C.
- Antifreeze insulation, dimensioned according to the object to be insulated, such as preventing freezing of water or other liquid in the pipe.
- Process-technical thermal insulation, i.e. insulation dimensioned to keep the temperature of the contents of the insulation object within the limits required by the process.
The ABC of insulation continues
Perhaps after reading this article, you'll think about warmth in a whole new perspective the next time you sit in a sauna. Then we've achieved what we set out to do, because the better we understand the benefits of insulation in everyday life, the easier it is to spread the good news about insulation.
Stay tuned for upcoming articles!
This article was originally published by our Finnish sister company, Kespet Oy, and has been translated into Norwegian. Original title: Back to basics: Do you still remember the basics of technical insulation?