In recent years the market for closed-circuit air conditioning units is increasingly coming up with models where the fan unit is housed underneath the A/C unit in a raised floor. What is behind this trend? Installation is undoubtedly more complex, and the units are generally taller – and probably more costly as well. So there must be benefits that prompt customers to opt for such equipment. What are they then?
There are two main benefits here: Such systems offer a marked improvement in efficiency, in addition to a higher cooling capacity in relation to their footprint. So customers not only get a unit that is more efficient, but also one that requires less space to attain a specific cooling capacity.
That's easier said than done. See below for an explanation how these two benefits are achieved. A conventional precision air conditioning unit is generally approx. 2 m tall and stands on a raised floor. The raised floor under the unit does not normally contain anything more than cold air. In other words, wasted space. The designers have now taken advantage of this fact, removing the fans from the conventional precision air conditioning unit, installing them in a separate fan unit and positioning them under in a raised floor. The space gained this way in the A/C unit has been used to install a more powerful heat exchanger and larger filters. Above the raised floor the A/C units don't look any different and are still around 2 m in height. The fan unit contained inside the underfloor section then makes up the overall height to 2.5 m or so.
Positioning the fan unit under the A/C unit in an underfloor section means that the flow of air from the fans to the raised floor is now directly horizontal. In conventional precision air conditioning units with integrated fans – i.e. where the fans are above the raised floor – the air exiting the fan has to change direction twice before entering the raised floor horizontally (see figure). The associated turbulence and impact losses affecting efficiency are eliminated by positioning the fans under the raised floor. Fan power consumption falls, and efficiency improves.