Adiabatic cooling isn’t so great

But the writer failed to point out any of the deficiencies with the adiabatic cooling system that are exacerbated by the UK climate.

The system works on the principle of increasing moisture content of air to achieve a reduction in dry bulb temperature. The adiabatic element (either water spray or saturated material) is situated in either the supply or the exhaust stream and both have disadvantages: supply air RH is too high or energy is lost through plate heat exchanger efficiency when energy is transferred between exhaust and supply air stream. Even so, return air will have already absorbed the latent gain from the space so there is even less scope for dry bulb reduction.

The system is proven in arid climates where air onto the humidifier would typically be 40°C db/ 20% RH, but in the UK, when air is already around 45% RH at peak summer, it would be difficult to achieve even close to the 10°C db reductions claimed in the article, not forgetting that the closer we get to the saturation line the more difficult it is for air to absorb moisture.

We haven’t even discussed water treatment issues, higher AHU specifications to avoid corrosion and the potential for legionella.

Has Fulcrum Consulting (the designers behind the system in the report) proposed the adiabatic cooling system as part of the CIBSE Carbon 60 CIBSE Headquarters regeneration project they won? If so, there may be another article outlining the drawbacks of the system in 2010 when the completed building is in operation.

Alex Maguire MCIBSE