A leading auto manufacturer in Pune was setting up a 222,812 sq ft office building. This space was a former press shop with a floor thickness of 350 mm. Our challenge was to recommend an HVAC system for this single, high volume space.
We decided to use the floor thickness to our advantage as it was an effective component to store energy and proposed a radiant cooling system. We envisaged that the floor cooling system would operate for longer hours than the occupation hours of the building to take advantage of the storage effect in the structure.
For areas assumed to be air-conditioned, the peak coincident load operating simultaneously works out to 514 TR, considering storage effect. We met this demand and added on a fresh air cooling system as well.
We achieved the optimal indoor temperatures by cooling the floors and ceilings by embedding PEX piping in the RCC and circulating chilled water of 15°C inlet temperature and 18°C outlet temperature. This cools the RCC mass and reduces the radiant surface temperature of the floor and ceiling below the mezzanine. No false ceilings have been used in the occupied areas to take advantage of the radiant ceilings.
By operating the system for longer hours to take advantage of lower ambient temperatures, we can store the cooling effect in the concrete mass and use the flywheel effect of the large mass at lower than room temperature. The shared load of air conditioning is met by air drawn into a special air handling unit for precooling with chilled water of 15°C inlet and 18°C outlet temperature, thereby providing adequate dehumidification to cater to the internal latent load.
Air is distributed in occupied areas at around 180 C, and low absolute humidity and is directed directly on to occupants to achieve adequate movement. Masonry ducting from below the basement connects to the conditioned zone. The air circulates in the conditioned area and is exhausted from the roof or used for recovery.
We solved a complex problem by addressing the total cooling loads in two parts: the bulk of the sensible cooling load was addressed via a radiant floor, and a small part of the sensible load and the entire latent load was met by cold and dry air.
April 28, 2020
