Good morning my name is Enrico Boscaro and I am application manager for Computer Room Air Conditioning @ Carel. Today I’m giving a short presentation about our ultrasonic humidifier , with special reference to compact (or modular) datacenters where the In row cooling system is used.
Since many years now we assist to a continuous improvement of cooling systems for datacenters with the purpose of reducing the energy consumption. Many of the new datacenter are made now using the extended conditions indicated by ASHRAE TC 9.9 , with a wider range of temperature and humidity; on one side this, combined with hot aisle and cold aisle segregation allows to perform cooling, staying above the dew point of the air thus avoiding de-humidification. As a consequence nowadays often CRAC units are not provided with a humidifier. On the other side the use of fresh air for free-cooling is often emphasizing the need for humidity control as in winter time ambient air can be very dry and it is not rare to have low humidity problems after installing direct airside economizers.
This latest statement is particularly evident in the following example that introduces the main subject of this presentation. This is a case of a system with in row units total recirculation and no dehumidification. (leggere i punti) What was noticed is that humidity was low even if units are not dehumidifying. The problem is that datacenter is not sealed so fresh air infiltration and diffusion phenomena through the walls might reduce the moisture content.
In the end the issue might be how to dimension the humidifiers for the installation: something that is interesting to consider for recirculation system is the total moisture content this is the real amount of moisture ithe the air contained in the room...normally the humidifier is dimensioned basing on the cooling power in the hypothesis of dehumidification. In this example with that cooling power normally there would be something like 18 kg/h humidifiers that actuallu are not necessary as the moisture content reduction is maily performed by air infiltration, mnoreover the ashrae specs suggest that transitory low humidity conditions can be allowable . A different way of dimensioning is necessary: the total moisture content. (leggi i punti) In this hypothesis 1could be enough to compensate this effect. Experimental data show then that this phenomenon is normally slow and takes hours to reduce humidity so the small humidifier can bring quickly the humidity to de minimum level. Even considering an over dimensioning for the worst possible case is one fourth of the traditional humidifiers.
A perfect solution could be an ultra-sonic humidifier: this is using the Piezoelectric Transducers Technology: the transducers vibrate in resonance frequency (high speed, 1.650.000 vibration per second) generating pressure waves elevating to water surface. The pressure waves alternate very rapidly to depression instants: because of its inertial mass, water can not follow the oscillator movement, some voids are generated, so some bubbles rise up to the water surface, conveying very fine droplets of water. The ventilator will move the droplets away. The humiSonic comes from the experience in fancoil humidification for comfort and so it is very compact ; it is adiabatic so it is efficient, through the modulation of the transducers it is possible to control precisely and then neing designed for comfort it is hygenic (silver ions in the plastic of the tank and specific drain cicles to avoid stagnant water.
Here are some technical features of this humidifier that you could see operating in the Technology park (leggere i punti eventualmente con breve commento) 100 W instead of 735 W of an isothermal humidifier and there is also a cooling side effect. The modulation is very precise and the production is immediate.
The characteristics of this humidifier makes it suitable for the installation in in row coolng systems which usually are very compact. The warm air allow a quick absorption in very few centimeters ths making it possible to put it before the cooling coil without the risk of increasing de-humidification (actually we are bringing back te return air to design conditions so no de-humid). The coling coils so is a drop eliminator and re-evaporating surface; with actual technologies like the variable speed compressors then it is possible to control the cooling coil temperature to avoid de-humidification (for example stop humidifier in transitory conditions during whichc coil temperature is very low).
Very often though the in row cooling unit has not enough space to fit an humidifier inside or it is not convenient or recommended to connect water pipes; some other times a humidifier might be necessary to solve a humidity problem in an existing site This is an example of installation on the walls ..being so compact (see the dimensions) It can be installed in a box or in wall niches, using the conveyor and diffuser. Here we are showing 4 kg but 1 is enough and diffusion is helping to have quickly a good level of humidity.
Finally I would like to conclude showing that the product you’ve seen is part of a whole family of ultrasonic humidifiers that we are launching both for duct mounting and room installation as you see in this picture; a system to be installed on the wall provided with fans for the distribution of moisture. The range of these humidifiers reaches 18 kg/h making them a good solution for humidity problems of bigger datacentres included the ones, and there are many, in which ambient air is introduced…for the design obviously a total moisture content approach should be used…visit us to receive copy of our white papers on humidification and evaporative cooling.
Carel ultrasonic humidifier for In-row cooling and Compact Datacenter
Carel ultrasonic humidifier
for In row cooling and Compact Datacenter
New specs and new needs for humidification
• Wider allowable humidity range
• Use of fresh air
Focus on a small datacenter with In row cooling
Low humidity for ambient conditions
Installation in Scandinavia
100 kW cooling power
Temperature in cold aisle 24°C
Design temperature in hot aisle 34°C
4 units with full recirculation: water
temperature 15°C (higher than dew
point). No dehumidification
No humidifiers installed: traditional
dimensioning would be 15-18 kg/h
Minimum humidity in cold aisle: 32%
(@24°C it is 5,5 g/kg ASHRAE
Humidity measured: 14,5% with 24°C
this is 2,5 g/kg
A new approach for dimensioning : Total Moisture Content
Volume of the room: 200 m3
Total Moisture Content in minimum-desired conditions:
0,6 vs 0,92 kg.
Max moisture using recommended limit (60%r.h.) is
Hypothesis: dehumidification performed by AC units in
transitory conditions but mainly by the infiltration of
fresh air with low humidity and diffusion phenomena
Hypothesis for calculation: high infiltration 0,5 vol/h
(to keep into account diffusion and door open
The equivalent is a reduction of 850 g/h. In 0,5 h the
humidity goes down from acceptable to minimum
value. Experimental data show slower reduction.
With 4 kg/h humidifier the Total Moisture Content can
be brought from minimum to maximum in 15 minutes 100m3/h@-20°C
humiSonic: the compact ultra-sonic humidifier
humiSonic is an adiabatic humidifier that
utilises the ultrasonic vibrations technology.
humiSonic: technical features
Nebulizer: very fine drops (Ø = 5 µm)
Low energy consumption (100 W for 1 l/h)
Water flow: 0,5 – 1 l/h (230 V)
Modulation according to request (1-100%)
Up to 3 slaves managed
RO water not mandatory but recommended for datacenter
Example of Installation of humiSonic
in In row cooling unit
• Warmer and dry air in inlet
allows quick absorption
• Coil used as re-evaporation
• Possible evaporating
temperature control in case
of variable speed
• Installation in the corners for a
quick distribution but 1 point is
enough for diffusion
• Use of diffuser and conveyor to
install in a box or niche
• RO water treatment is
recommended to avoid the diffusion
of dust and minerals and to reduce
An whole range to solve your humidity issues
• Duct and Room
• Up to 18 kg/h