Aluminium encyclopaedia

Air conditioning technology

The high reflectance of bright-finish aluminium alloys for light and heat radiation (which is equivalent to low radiation of heat), coupled with good thermal conductivity and corrosion resistance make aluminium a preferred material in air conditioning technology. Additional benefits include the fact that aluminium neither releases dust (like various insulating materials) nor does it rot or go mouldy. These properties are used for numerous different applications.

When exposed to solar radiation, coating materials with a high aluminium pigment content lead to the temperatures under roofs and in storage tanks containing temperature-sensitive substances being lower than with other coatings.

For damp-proof layers on roofs, strip coated on one side with bitumen is laid with several layers on top of each other whereby the aluminium side is always on top, to reflect the sunrays and to protect the bitumen.

With underfloor and ceiling heating, aluminium sheet helps distribute the heat from the heating tubes to the brickwork or into the room.

Radiators of hot water heating systems made of extruded profiles and die-castings are significantly smaller in design (and lighter) than ones made of steel thanks to their better conduction of heat.

For air-conditioning ducts (pipework for heating, cooling and exhaust air) profiles with a round or rectangular cross section are mainly used in aircraft construction, building construction, and rail and road vehicles.

In many cases strip and foil are used for thermal insulation, whereby the actual insulation is due to air or a vacuum. The bare aluminium surfaces have the job of reflecting heat radiation.

With sheet insulation, foil or strip is fixed along its edges between spacers which should be as poor heat conductors as possible in order to avoid cold bridges.

For super insulation (for example of containers containing very cold liquids such as liquid hydrogen at -253 °C) aluminium foil is laid between the evacuated double wall of the container as reflection layers. In this way, a double-wall spacing some three centimetres thick can produce the same insulating effect as a conventional insulating layer some five metres thick.

Thermally insulated composite profiles prevent condensation forming on the inside of window, door and façade frames. The intermediate layer between the inside and outside of the aluminium consists of plastic, is thermally insulating and avoids cold bridges. Heat exchangers serve to utilise heat and waste heat from the most varied processes.