Displacement activity

A new approach to the integrated design and function of air diffusion systems has been introduced at Heathrow

The ventilation and air-conditioning of large airport terminals often create considerable problems for design engineers and architects. In the majority of buildings, air-conditioning using a fresh and room air mixing system is typically applied, but in airport terminals there are often great distances between the air outlet and the occupied zone, which can lead to high room-air velocities and draughts caused by the usually restricted location of the diffusers.

There are a limited number of standard products on the market that meet the requirements of air supply appropriate to large airport passenger spaces. However, these difficulties may be overcome by the application of displacement ventilation systems.

The main problem with displacement systems is positioning the large low-velocity front faces of the diffusers and integrating them into the visual and spatial design. Even the integration of displacement diffusers into a concourse is difficult using standard products. To achieve high environmental air quality with an air-conditioning system that also fits into the architectural concept, special solutions are required. Here the design engineer is responsible for the most suitable function and the architect for an integrated aesthetic design. To solve this problem at Heathrow’s Terminal 5, a new approach has been taken.

Design process

At a very early stage of the project’s production design phase, a team was assembled to include the selected supplier of the air diffusion systems, the design engineers and the architects, with input from BAA at key stages. This approach meant the supplier, Germany-based Strulik, had to find solutions that cooperated with design engineers, architects and other trade contractors.

The role was to define the requirements and develop a design for the particular product, and to test manufacture and supply it with a warranty as to function. This required the presence of the supplier’s project engineer on site to a large extent.

The installation of these integrated air diffusion systems interacts with other elements and products within the building. To achieve full integration, the supplier was authorised to cooperate and have direct contact with the interfacing suppliers involved in the integration and installation of the diffusion systems.

Integration challenges

The principal air diffusion system chosen in Terminal 5 for the front-of-house areas is a displacement system. To fulfil the design criteria, the front faces of the diffusers not only had to be integrated into the space, but also meet all the functional requirements.

To ventilate the 6m-wide passenger arrivals corridors, diffusers with 2m high front panels were initially proposed. These panels had to be protected from potential damage by heavy grilles. However, BAA required that the glass lining should not be interrupted with perforated steel grilles to enable it to achieve its operational requirements. As a result, this concept was replaced by a system of wall-lining diffusers with integrated swirls, which were mounted in the space between the primary wall and the front-of-house glass wall lining. An added benefit of this design was that the air distribution was even better than with normal displacement diffusers.

On the apron and arrivals levels at Terminal 5, a large number of displacement diffusers needed to be installed as casings around the structural steel columns. The diffuser was built of two semi-round sections made of special LSE stainless steel material with internal air distribution ducts. The column casing is 918mm in diameter, 4.2m in height and supplies air at a rate of 830 litres/sec.

Another system was installed where a quarter-round diffuser was integrated into the web of the structural steel columns and the casing that was supplied by the wall linings contractor.

The gate level and departures level concourses are very large spaces that require an obstruction-free floor area for good passenger flow. Supplying air from walls or columns is not possible because of the excessive distances and lack of suitable wall surfaces. In this situation, the air is supplied by freestanding diffusers integrated with other passenger information and safety systems. Strulik integrated the air distribution ducts and the fixing frames to which the face panels of the diffuser were fixed into the steel profile frame construction.

The comfort ‘near zone’ and floor air velocity from the diffuser are set by the individual diffuser design for each face, so that comfortable conditions, especially in the seating areas, were guaranteed. In addition, a heavy stainless steel LSE front grille was installed in front of the diffuser face plates to protect against damage.

Across the four above-ground levels of Terminal 5 Concourse A, more than 20 different types of non-standard diffusers work to achieve comfortable environmental conditions, having been designed to be as functional as possible. Special solutions from Strulik are also used in other areas of Terminal 5, including T5B and the tracked transit system.

By integrating the specialist supplier Strulik into the design team and using its know-how in air diffusion systems, solutions were found and implemented that could never have been realised through the traditional method of working.

Passenger Terminal World | Annual Review 2012 (passengerterminaltoday.com)