Evaporative cooling:
Why evaporative cooling doesn’t work in pharmaceutical warehouses in the UK
There is a lot of misinformation within the industry surrounding the use of evaporative cooling within pharmaceutical warehouses.
Because of the UK climatic conditions evaporative cooling cannot keep pharmaceutical warehouses sufficiently cool to comply with the MHRA and manufacturer’s requirements during the summer months.
Using the manufactures performance data evaporative cooling units during hot dry weather will deliver an 8°C-10°C reduction in supply air temperature.
This sounds pretty impressive until you realise that this temperature reduction is from the outside air temperature and not the room temperature.
During the summer of 2006 we had outside air temperatures reaching 36°C with an evaporative cooler working in such conditions the best they can hope to supply air to the warehouse is at 26°C, this supply temperature is already above the recommended maximum room temperature if 25°C
The manufacturer’s literature also states warehouses can be typically 5°C warmer inside then the outside ambient temperature (which is correct) due to all the gains created by solar, lighting, MHE and people this means that the internal temperature in such operating conditions even with evaporative cooling will be around 31°C, a massive 6°C above the manufacturer’s recommendation of 25°C.
The literature also state what the coolers performance will be during peak conditions (8°C-10°C reduction) what they fail to point out is that during a more typical summer day when the external humidity level is around 60%-65% their performance is reduced significantly to a temperature reduction of only 2°C- 4°C as their performance is dependant on the wet bulb temperature being low which isn’t usually the case with the UK’s climatic conditions.
You may think that is drastic reduction in performance is OK as with a lower outside temperature not so much cooling is required however most the cooling load in a typical pharmaceutical warehouse isn’t dependant on external air temperatures in fact only 33% of the load is attributed to this, the remainder are a combination of lighting and MHE (which are fixed) and solar which is reliant on sun altitude and orientation (not temperature).
So typically an evaporative cooling solution which has been sized for peak conditions will struggle to cope during supposedly less demanding external temperatures.
An important factor in achieving even temperature control in warehouses is good air distribution as this ensures all stored products are maintained at a constant temperature. With an evaporative cooling system this is often compromised as the system is reliant on individual coolers providing large amounts of air in one location and relying on natural air circulation to do the rest. As a typical warehouse is usually full with products stored on racking all these barriers impedes air circulation so good air distribution isn’t achieved with this type of system.
As one size of cooler is generally used what this means that on a typical project multiple units will have to be employed to achieve a required cooling load this along with an equal number of extract fans to provide a balanced ventilation will mean that many roof penetrations have to be provided with the associated risk of leaks. In addition to this an extensive water supply system has to be installed to serve each cooler this again adds to the potential of loss of stock as a result of water damage.
Very little seems to be written with regards to maintenance of these systems however the require twice annual servicing to clean and replace the pads, on the face of it this sounds fairly straightforward however when you consider both the number and locations of the units (at high level in warehouses or roof mounted) specialist equipment will be required to get to these units to carry out works safely all this adds considerably to the annual running cost of the system. In addition to this if the units are installed internally in a busy area, sections of the warehouse will have to be cordoned off to enable the serving to take place.
Legionnaires disease is also a potential risk when you have the combination of air blowing over wetted surfaces Although the manufacturers state there is no risk of contracting Legionnaires’ disease from evaporative coolers and that there has been no cases of people contracting this disease from this type of equipment, the risk still exists.
If there is no risk then why does a risk assessment have to be completed for each installation?
If a fault occurs within the unit, or else the maintenance isn’t carried out or carried out incorrectly then your warehouse operatives could be at risk.
Although manufacturers state their systems are suited to pharmaceutical applications in the UK we believe the only example of one of these systems in a pharmaceutical warehouse is in the South of France where the climate is more suited to their operation i.e. ambient conditions (warm and dry) as opposed to the UK’s temperate climate (cool and wet) this is borne out by the images and case studies shown on various web sites.
• Go back:
