Applying BSRIA’s expertise

Knowing in advance that an engineered solution will work by testing a mock-up is good news for everyone involved in a project. Mock-ups can also help identify performance problems, as WILLIAM BOOTH explains.One of the key benefits of any mock-up (physical model) is the opportunity to experience the resulting environment prior to construction. This involves creating an accurate and detailed look and feel of what the end result would be. As a result, the stakeholders and end users can provide feedback, so adjustments can be made before spaces are constructed. On-site mock-ups and testing are invaluable for overcoming building-services problems prior to the main fit out. For trouble-shooting or retrofit applications, it often makes sense to construct a mock-up around an existing installation. The choice of an on-site mock-up may be made on practical or economic grounds, for example, an on-site test facility will be readily accessible at the relevant time to all stakeholders in the construction process, the design team, contractors and end users, so they do not have to travel. That can often be the best option if there are short timescales for both new-build and retrofit systems. There are five main reasons for carrying out a mock-up, either on site or in the laboratory. • Verifying a design or system concept. • Trouble-shooting an installed system. • Optimising a refit. • Rehearse installation techniques. • Independent verification of a manufacturer’s test results. The key element of any successful mock-up is thermal stability, which is ensured by adequate measurement points; calibrated, reliable and inherently accurate instrumentation; defined boundaries; in-built cross checks; and most importantly expertise and experience. Chilled beam on site mock-up One of the applications commonly mocked-up is chilled beams or ceilings to handle IT cooling loads in offices. BSRIA MicroClimate was recently called on to design an on-site mock-up to investigate an under-performing chilled-beam system. One floor of the building was between tenancies. A 6 m-wide test chamber was constructed running in from the south façade to the building centre-line. Special instrumentation was used to offset heat losses through the façade as well as simulating full design solar gain. Problems reported elsewhere in the building were replicated in the mock-up, but under controlled and known conditions. Quantitative surveys of room air movement coupled with flow visualisation and thermal imaging characterised the shortfalls in performance and enabled various contributory factors to be identified. Various potential remedial measures were also identified. It was particularly convenient for representatives of the various interested parties to experience the internal conditions. Dealer desks BSRIA has extensive experience in investigating dealer desks, both in its own laboratories and in mock-ups on site. Recently, our experts carried out on-site investigations to troubleshoot a large (150-plus workstations) dealer room which was experiencing difficulties with peak and part-load cooling. The initial tests involved setting up appropriate heat loads in buffer zones around the targeted zone. The tests were carried out over the weekend so they would not cause any disruption to the business. The IT department arranged for all systems to be in and running under typical processes. The gain from occupants was simulated with electrically heated simulators. The client was responsible for setting up the H&V plant to work at design settings. Because smoke visualisation was not an option with IT equipment operational, air-velocity and temperature surveys were carried out using a vertical and horizontal array of sensors to characterise room air movement between, under and over the dealer desks. Various factors contributing to the below-par performance were identified for the client — including excessive and non-uniform IT power densities, inconsistent slot diffuser set-up and failure to achieve design coil-off temperatures. Subsequent studies involved setting up a mock-up in an area prior to refurbishment to allow options for configuring dealer desks to be investigated. Flow visualisation using smoke was the primary tool. IT suite The explosion in IT in offices in recent years means that building operators demand reliable and effective as well as efficient cooling solutions. BSRIA was asked to investigate a large IT suite to establish, characterise and document IT equipment along with supply and extract grille location and duty. The snapshot data collection enabled the project team to develop better strategies for ongoing maintenance as well as designing upgrades and enhancements. Data collection techniques included thermal imaging, balometer surveys of supply and extract terminals and underfloor static-pressure measurements. The results and findings were presented in a database linking rack location, IT contents and measured environmental parameters. Using a computer-modelling technique BSRIA investigated the implications of the relatively poorly sited downflow units in terms of currently delivered performance as well as under potential fault conditions. BSRIA’s ‘Guide to IT equipment cooling’ that was produced in response to the increase in power densities above 1 kW per cabinet provides further insight. Downflow units — independent verification Confirmation of component or system performance before handover of installations can be completed with confidence. BSRIA MicroClimate provided independent verification of a multiple downflow installation prior to fit-out by monitoring environmental conditions, including in-duct conditions, under full simulated load (using industrial space heaters). Another project resulted from a more general investigation that pinpointed underperformance of upgraded downflow units. A ‘closed loop’ test method was devised using one of the standby units so it was isolated from the ‘live’ data suite. Although it was a complex undertaking, a clear cause of the problem was identified in a very short time of testing together with a remedial programme for the client to action. Other work has involved on-site testing of a 600 kW chiller. Benefits The benefits of fully functioning on-site mock-ups usually out-weigh the cost. Many projects involve construction of an architectural mock-up to allow lighting, finishes and the overall aesthetics to be visualised and experienced. Relatively little extra resources are required to construct a dual-purpose mock-up combining the architectural and physical representations. Add in the opportunity to optimise fixing strategies, and it can be seen that everyone in the construction process can benefit through synergetic relationships. BSRIA MicroClimate offers facilities and capabilities to verify system designs, validate control strategies and rehearse installation techniques using full-scale mock-ups (physical models). We can bring experience, expertise, appropriate instrumentation and independent opinion to any site to benefit the project or provide the service in our environmental chambers (standard or tailor made) in Bracknell. The BSRIA ‘Guide to physical modelling’ is available for download at the address below. For further information contact William Booth, head of site investigations and physical modelling at BSRIA, tel. 01344 465600
microclimate@bsria.co.uk

Related links:

• www.bsria.co.uk/microclimate