down to acceptable values, simply through the evaporation of water. The effectiveness of such systems depends significantly on local temperature-humidity conditions, nonetheless in much of continental Europe both free cooling and evaporative cooling can be exploited for most of the yea r, to the extent where some data centers are designed to use mechanical cooling as an emergency backup system only. The increasing popularity of such systems demonstrates how humidification in winter can be provided by simply adopting the same evaporative cooling system used in summer, thus reconciling humidity control with energy saving; in this case, however, demand is much lower and therefore the system must provide for modulating operation, with a built-in temperature and humidity controller that also manages air recirculation. Humidification in winter using outside air may be problematical even in data centers with a traditional layout, if AHUs are used to introduce outside air for free cooling, above all during colder winters, operating as economizers. In these cases, there is often no humidity control, as carefully-designed air recirculation systems avoid dehumidification; in winter, however the outside air, despite having a high relative humidity, has a low moisture content (absolute humidity) and therefore once mixed with the air in the data center, rapidly leads to low humidity levels.

In these cases too, one of the best solutions involves using an adiabatic humidifier; once again, control of air recirculation and modulation are necessary, as well as integration with the overall data center control system, to avoid concurrent free cooling and mechanical cooling operation.

There are several different adiabatic humidification technologies available, from so-called “wetted media” to washers and spray systems: the principle underlying all of these devices is to maximise the contact surface area between air

and water, so as to ensure effective evaporation and perfect absorption in the humidified air stream. The choice of the system depends on numerous factors, ranging from available space to required efficiency and the need for modulation; in general, the solution needs to be evaluated in terms of TCO (Total Cost of Ownership) throughout the system’s working life, also taking into consideration its resilience in terms of continuous operation as well as water consumption, which in many areas may be a critical factor: indeed, many data centers, together with the classic PUE for energy consumption also monitor WUE as regards water consumption.

Recently, atomisation systems have become quite popular; these use a system of nozzles and high pressure pumps to create minute droplets of water, thus ensuring optimum absorption. These systems can be controlled by inverters to modulate atomised water production and respond to different load conditions.

Other benefits of these systems include very low air pressure drop, no recirculation (and consequently a high level of hygiene, something that unfortunately is often neglected), and the possibility to use one pumping unit with two separate distribution systems, one for summer (evaporative cooling) and one for humidification in winter, meaning significant flexibility, even with vertical air flows.

In conclusion, the increasingly frequent adoption of adiabatic systems can help overcome the dilemma between humidity control and cost reductions, thanks to new, increasingly reliable technologies and reduced energy consumption. Fundamental for system optimisation is integration between control systems: all the devices operating in the HVAC system should feature serial communication, allowing the working set point to be adjusted based on different environmental conditions and the temperature and humidity measured in the different areas of the data center.

©2017 The Chemours Company FC, LLC. Opteon™ and any associated logos are the trademarks or copyrights of The Chemours Company FC, LLC. Chemours™ and the Chemours Logo are trademarks of The Chemours Company.

November 2017 35

Opt LG


for better

Opteon™ low global warming potential products are a small choice for a big change.

Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76