This is a listed building that was experiencing severe overheating problems in certain areas where there are no HVAC systems in place. Indeed, internal temperatures as
high as 36C were being recorded in some consulting rooms, and this when the average external temperature was monitored at around 20C to 21C. Given the unusually high heat
gains, Datum decided to incorporate a honeycomb tile to give more cooling capability. This is an aluminium tray with an aluminium honeycomb insert filled with the RACUS PCM compound. The benefit of this particular tile
format is that it can incorporate a greater concentration of PCM within each honeycomb cell, thus improving the heat transfer rate through the matrix of the RACUS PCM compound. At Great Ormond Street, two adjacent
and identical consulting rooms were selected, and again both rooms were monitored using heat flux sensors and data loggers for a period of two months. The monitoring results identified that the RACUS ceiling tile was able to reduce the room temperature to 4C below that of the adjacent room without RACUS, maintaining temperatures at a more comfortable 25C to 26C. ‘We strongly believe that the RACUS
ceiling tile is a fantastic innovation that is easily installed in new and retrofit projects where there is a demand for space cooling and thermal mass requirements utilising a passive system,’ says Mike Berry. Indeed, the company has just won a £3m
order for a company headquarters building in Barcelona. The future looks very healthy for soya. CJ
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Temperature difference of 4.33˚C
TIME (hh:mm:ss)
Figure 2: The Ofcom head office trial took place in two identical, adjacent meeting rooms, with each room making use of fan coil units to provide comfort cooling. Temperature sensors and data loggers were installed by MITIE, which also recorded the occupancy rates in each room
Room with RACUS®
Room with RACUS®
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Temperature difference of 3.67˚C
Whilst outside temperature
remains low during early hours of the morning, internal
temperatures remain above 21˚C
Temperature in the room with RACUS® stabilises between 22˚C – 24˚C
TIME (hh:mm:ss) Room A (without RACUS® ) Room B (with RACUS® ) Outside Temperature
Figure 3: At Great Ormond Street Hospital, two adjacent and identical consulting rooms were monitored using heat flux sensors and data loggers for a period of two months. The monitoring results identified that the RACUS ceiling tile was able to reduce the room temperature to almost 4C below that of the adjacent room without RACUS
Fatty acids: The basis of Datum’s organic phase change material
Phase change materials have several forms such as organics, inorganics, or eutectics (a combination of both). The RACUS ceiling tile uses an organic microencapsulated phase change material (PCM), derived from soya oils and fatty acids that, according to Datum, has twice the heat storage capacity of alternative organic PCMs, such as petroleum- based PCM or inorganic salt hydrates. Datum claims its bio-PCM is the only organic PCM on the market today that is biodegradable within 12 months, compared to more than 100 years
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these processes are desirable in a narrow temperature range close to the human comfort temperature, with large amounts of heat being absorbed and released.
for petroleum-based PCMs. PCMs store energy in a latent form. They undergo an endothermic process of phase change to store heat energy when ambient temperature rises, and an exothermic process to release this energy when the temperature drops. In building applications,
During the transition phases, the core of the microcapsule will melt as the room temperature reaches this temperature, and in doing so will absorb latent heat, where it will be stored until such time as the room temperature cools to around 20C. At this point the PCM core has started to solidify and emit the stored latent heat.
The RACUS ceiling tile is available in two formats. The
first is a preformed mineral tile incorporating various abundant minerals that encapsulate the bio- PCM microcapsules. This tile has a latent heat storage capacity of up to 75Wh/ sq m, and can easily replace a standard mineral fibre tile using the existing suspended ceiling grid.
The second is a metal ceiling tile that is predominantly used in commercial buildings, and is a composite panel assembly comprising a solid or acoustic metal tile with a RACUS insert, having a higher latent heat storage capacity of up to 224Wh/sq m.
July 2012 CIBSE Journal 41
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