CASE STUDY MARY ROSE MUSEUM
spraying to continue, uninterrupted, 24 hours a day, seven days a week. The wood- clad building’s low, elliptical form was dictated partly by the parabolic geometry of its roof and partly by the need to minimise the space around the hull to make it easier to maintain the strict environmental conditions necessary for its preservation. The designers set out to evoke the dark claustrophobic atmosphere on board the medieval ship. The salvaged hull, still cocooned within the hot box, is located on one side of the museum. Facing it, a virtual port side has been created, containing three decks of galleries housing the original artefacts in a mirror image of where they would have been found on the starboard side. Walkways divide the hull from its recreated twin, while galleries at the prow and stern of the museum provide a theatre and further displays on the ship’s crew – the cook, the carpenter, the surgeon – containing personal possessions and professional tools. Heat from the artificial lighting is minimal because the galleries are dimly lit; what light there is has been focused on the cabinets housing the salvaged artefacts of everyday Tudor life. These require tight environmental control and are housed in highly controlled display cases (see box opposite). And through windows in the hot box, visitors can glimpse the 500-year-old hull itself.
Gently does it PEG spraying finished earlier this year and the hull is currently wrapped in a series of textile ducts while its timbers are being dried. Conservationists estimate that between 110 and 130 tonnes of water were trapped in the timbers following the years of PEG spraying. The task was to start drying the timbers as quickly as possible to prevent mould growth. It is expected that most moisture will be drawn out during the first year, but it will take up to four years before the wood is fully dry. Unless the environment around the
ship is controlled to ensure the timbers dry evenly, they could crack and deteriorate. With the hot box now contained within the museum, its heat losses are small. ‘If you designed a ventilation system to meet the actual heating load, the volume of air needed would only be around 1-2m3
conditions needed inside the 40m long, 16m wide, 13m high space.
30 CIBSE Journal September 2013
Ramboll’s solution has been to significantly increase the volume of the air supply to the box, but to target it onto the hull. Conditions required for
successful drying are 19°C +/-1°C, with 54% relative humidity +/-4%. To design the air distribution, the remnants of the ship and its enclosure were laser-scanned to create a precise model. Engineers then used this to test various ventilation and cooling techniques, and to check air velocities, dwell times and shear stresses created by the air movement to find the most effective. ‘Using computational fluid dynamics (CFD), we found that the minimum volume of supply air we could use that would maintain the
correct conditions around the ship was 25m3
/s,’ Lloyd explains. /s’, says
Lloyd. However, this quantity of air would be insufficient to maintain the close control
The precise location of the ducts and position and number of holes in the ducts were also arrived at using CFD analysis. The designers were aiming to cloak the ship in conditioned air that had a maximum velocity of 0.25m/s adjacent to the hull. ‘The boundary conditions are absolutely critical if
CFD analysis determined the position of the ductwork and the number of holes necessary to dry the timber evenly
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