AIR MOVEMENT
Understanding air handling units
We fi nd HVAC systems in buildings and industrial processes frequently nowadays. Such systems move air around and the technical term for this is air handling unit (AHU). Martin Altenbokum business development manager Europe of Petra explores the technical intricacies of AHUs.
V
entilation and air conditioning systems keep the condition of room air, or air to be supplied to processes, constant within
certain limits of purity, temperature, and humidity. AHUs consist of a series of sections through which air is moved. In each of these sections the air is treated and leaves it in a diff erent state than when it entered. Depending on the section, air is moved, heated or cooled, mixed, humidifi ed or dehumidifi ed, fi ltered, soundproofed or diverted. There are also sections that care for heat recovery. The sections are each self-contained in function but are connected to preceding or succeeding sections in the air fl ow. Each of the sections usually has openings for cleaning and maintenance. Sections usually consist of metal frame structures and thermally insulated panels, ideally without thermal bridges between inside and outside. AHUs, either installed outdoor or indoor,
condition outside air, move used air to the outside again, or mix part of the air inside rooms with outside air or just condition air in rooms without any outside air.
The vast majority of AHUs relate to these
applications: for commercial and residential buildings (offi ce buildings, hotels, shopping malls, houses); these units comply with standard requirements
for service areas with high humidity where spe- cifi c requirements apply
for use in medical fi elds (hospitals, laboratories), universities and industrial areas; hygienic units pose stringent requirements on design and build
for data centre applications, special control re- quirements may apply for ensuring safe operation in areas of sensitive equipment
for use in hazardous environments e.g. for service areas of oil and gas industry where special certifi - cates like ATEX apply.
Structure of an AHU The mostly cuboid sections with square sections are arranged in a frame system which gives the AHU also its static structure. The frame structure is made of a penta-post construction and is reinforced with panels side by side or perpendicularly. Doors or other inspection openings are provided in to allow easy maintenance. Panels are made of double-skinned sheet metal,
the inside and outside of which are thermally separated by insertion of thermal insulation made of PU foam, rock- or glass-wool suitable for this purpose. The metal is galvanized and electrostatically powder coated. AHUs may contain many sections and may be several meters long. To support the sectional manner and for strength and rigidity welded base rails are provided to form an integrated base on the full perimeter under the unit.
18 July 2021 •
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