CASE STUDY MARY ROSE MUSEUM
Unless the environment around the ship is controlled to ensure the timbers dry evenly, they could crack and deteriorate
Walkways separate the hull from the galleries, which house precious artefacts salvaged from the seabed
the hull is to dry evenly,’ says Lloyd. Ordinary textile ductwork, which allows
the air to permeate the walls of the duct, would not provide sufficient control of the supply air. Instead, impermeable ductwork was used, with laser cut holes to control and direct the air supply. The textile ducts are attached to a stainless steel and titanium suspension system, which was installed while the hull was still being sprayed. The ducts were then attached to the suspension system during the switchover phase and plugged into pre- installed ventilation plant. ‘It was important that, as far as practicable, everything was ready for the changeover from spraying to drying to ensure it happened in the shortest possible time.’ Three air-handling units (AHUs), hidden in the dry dock, supply 8.3m3
/s of air each.
The air is distributed via two 1,200mm- diameter ducts that run the length of the hull; these drop down to supply 14 smaller ducts that weave in and out of the timbers like giant worms. The air system
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is fully recirculating, with extract air dried and returned to the hot box at boundary conditions. Lloyd describes these AHUs as ‘a bit of
a work of art’. To build in robustness, the AHUs make use of fan wall technology, so instead of a single fan there is a wall containing six inverter speed-controlled fans. Each unit will operate at 80% peak demand so that, if one fan fails, the speed of the other five can be ramped up to make good the loss. In addition, each heating and cooling coil is split into three sections, with two of the sections capable of supplying the duty required. The three AHUs feed a common air supply header. Heating and cooling plant is located in
a plant room at the north of the building. There is no gas supply so the two heating boilers are oil-fired. There is, however, a dock steam main so the plant room includes a heat exchanger, which is the primary source of heat for the building in winter. Cooling is from three packaged air- cooled chillers, which circulate water
A CASE-BY-CASE BASIS
Many of the display cases manufactured by Reier feature a micro-air conditioning system to help preserve the delicate leather and wooden artefacts on display. Conventional museum cases usually control only the humidity of the cabinet; they do not have temperature control but instead rely on the temperature of the room in which they are housed to be kept constant. However, the small size of the galleries and the large numbers of expected visitors meant that this was not possible at the museum. Instead units are fitted with a thermoelectric Peltier heat pump unit, to filter and humidify the air and provide heating, cooling and dehumidification. Each cabinet has its own electrical supply and chilled water connections.
September 2013 CIBSE Journal 31
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