Valerio Nalini's presentation on adiabatic technologies and evaporative cooling effect, at HVAC/R Expo Saudi 2016 Jeddah.

1. Adiabatic technologies and
evaporative cooling effect
Energy saving opportunities in humidity and
temperature control
Valerio Nalini
HVAC/R Expo Saudi 2016
Jeddah

2. CAREL is one of the world leaders in control solutions
for air-conditioning, refrigeration and heating, and systems for
humidification and evaporative cooling.
Our products are designed to bring energy savings and reduce
the environmental impact of machinery and systems.

3. 1100+
Employees
6,200
Part numbers
182 Mln€
Turnover (2014)
7 Mln
Pcs per year
6
Production facilities
CAREL in snapshot
18
Subsidiaries
3,700+
Customers

4. Agenda
Why humidify?
Isothermal and adiabatic humidification
Evaporative cooling
• Direct Evaporative Cooling
• Indirect Evaporative Cooling
• Evaporative Cooling for chillers and drycoolers
Adiabatic technologies overview

5. Why humidify?

6. Relative humidity is, with temperature, one of the fundamental ambient
parameters in a wide range of applications:
• for personal comfort in residential and commercial environments
• in industrial processes, to ensure process stability and product quality
Why humidify?
• in datacenters to prevent electrostatic
discharges from damaging the electronic
components
• in hospitals and operating thaters,
precise humidity control is required by law

7. Precise and accurate control of relative humidity is required as it influences the main
factors that affect the performance of most processes:
• risk of electrostatic discharges
• processing and conservation of food and material
• proliferation of biological contaminants
• speed of chemical reactions
• painting quality
• quantity of dust in the air
• people comfort and health
Why humidify?

8. Psychrometric chart
• Dry bulb temperature is the one we normally
perceive. It is a measure of sensible heat.
• Air contains another form of energy other than
sensible heat: it is called latent heat and we do
not directly feel it.
• Enthalpy is the total amount of energy contained
in the air and is the sum of sensible and latent
heat.

9. Psychrometric chart
• Absolute humidity is the total mass of water
vapor present in a given volume of air.
• The capacity of air to contain
humidity increases with
temperature.
• Relative humidity is the value that indicates
how far the air is from saturation. When air is
100% saturated condensate starts forming.

10. Isothermal humidification
• Isothermal humidification is achieved by
introducing steam into the air
• Energy for the water to steam change of
state (≈700W/l) is provided externally.
Enthalpy increases.
• Air temperature does not change (hence
isothermal)

11. Adiabatic humidification
• Adiabatic humidification is achieved by
spraying fine water droplets
• Water spontaneously evaporates
• Energy for the change of state is provided
by air. The total amount of energy does
not change (hence adiabatic)
• Sensible heat is converted into latent heat
Air is cooled

12. Adiabatic humidification
10µ droplets 600m2
1µ droplets 6000m2
VOLUME SURFACE
1 liter <0.1m2
If 1 liter of water is atomized in:
QUICK, SPONTANEOUS
EVAPORATION
Why does water evaporate?

13. MAXIMUM CAPACITY (kg/hr)
Adiabatic vs Isothermal
ELECTRIC CONSUMPTION (W/kg)
0 100 200 300 400 500 600 700 800 900 1000
Adiabatic
Isothermal
0 100 200 300 400 500 600 700 800
Isothermal
Ultrasonic
Pressurized water

15. Direct Evaporative Cooling
Supply air is humidified and cooled down
Ideal in hot and dry climates, where the needs for
humidification and cooling coexist

16. Direct Evaporative Cooling
Supply air before
humidification
30°C
30% RH
Supply air after
humidification
25°C
50% RH
Assumptions
Air flow rate: 30000 m3/h
Atomized water: 74 kg/h
Cooling system EER: 2,8
We can calculate the heat removed:
qsens ≈
qsens = sensible heat, in kW
Ga = air flow-rate, in kg/s
Cpa = specific heat of dry air at constant pressure
= 30000 m3/h × 1.225 kg/m3 = 10.2 kg/s
= 1.005 kJ/(kg × K)
Ga × cpa × (t1 – t2)

17. Direct Evaporative Cooling
qsens ≈ 10.2 × 1.005 × (30-25) ≈ 51.3 kW
Supply air before
humidification
30°C
30% RH
Supply air after
humidification
25°C
50% RH
We can calculate the heat removed:
Assumptions
Air flow rate: 30000 m3/h
Atomized water: 74 kg/h
Cooling system EER: 2,8
qsens = sensible heat, in kW
Ga = air flow-rate, in kg/s
Cpa = specific heat of dry air at constant pressure
= 30000 m3/h × 1.225 kg/m3 = 10.2 kg/s
= 1.005 kJ/(kg × K)

18. Direct Evaporative Cooling
Cooling capacity: 51.3 kW
Electric consumption: 1 kW
Energy saving: (51.3 kW – 1 kW) / 2.8 = 18 kWAssumptions
Air flow rate: 30000 m3/h
Atomized water: 74 kg/h
Cooling system EER: 2,8
Supply air after
humidification
25°C
50% RH
Supply air before
humidification
30°C
30% RH

19. Indirect Evaporative Cooling
Return air is humidified and cooled down before entering the heat recovery
system
Supply air is not humidified, but only sensibly cooled
Smaller coil and smaller chiller: lower investment and running costs

20. Indirect Evaporative Cooling
Outside air
35°C
40% RH
Return air
25°C
50% RH
Exhaust air
31°C
36% RH
Cooled outside air
29°C
56% RH
Assumptions
Air flow rate: 30.000 m3/h
Heat recovery efficiency: 58%
Cooling system EER: 2,8
Cooling capacity: 58 kW

21. Indirect Evaporative Cooling
Outside air
35°C
40% RH
Return air
25°C
50% RH
Cooling capacity: 58 kW
Humidified air
18°C
100% RH
Cooled outside air
25°C
70% RH
Exhaust air
28°C
55% RH
Cooling capacity with IEC: 100 kW
Capacity increase: 42 kw
Assumptions
Air flow rate: 30.000 m3/h
Heat recovery efficiency: 58%
Cooling system EER: 2,8

22. Indirect Evaporative Cooling
100 kg/h
atomized water
58%
heat exchanger efficiency+ +1kW
electric consumption
= 42kW
extra cooling capacity
= smaller
cooling coil and chiller
≈ 15kW
electric energy saving
Quick recap…

23. DEC + IEC
According to the season and the geographic region, it is possible to use a combination
of both systems to maximize energy saving:
• DEC for winter humidification
• IEC during the summertime to support the cooling system

24. Energy saving and ROI estimation
State City Koppen climatic classification
USA Denver Cold semi-arid
USA Los Angeles Warm Summer Mediterranean
Spain Madrid Hot Summer Mediterranean
France Paris Oceanic
Italy Rome Hot Summer Mediterranean
China Shanghai Humid subtropical
China Beijing Humid continental
Feasibility and results of evaporative cooling depend on the starting temperature-
humidity conditions.

25. Energy saving and ROI estimation
Break-even occurs in less than 2 years in most climatic conditions.

26. EC for chillers and drycoolers
Most chiller and drycooler installations are oversized, designed according
to the maximum outdoor temperature.
More pollution
Higher noise levels
Higher investments in unproductive capacity
Evaporative cooling of the outside air can also be exploited.

27. • The airflow is cooled
by the droplets
evaporation
• The air enters
deeply in the coil
• Some droplets wet
the coil: water
evaporates giving an
additional cooling
power
EC for chillers and drycoolers

28. EC for chillers and drycoolers
The pumping unit is activated based on outdoor temperature or condensing
pressure, or a combination of the two.
2 possible working logics:
• Temperature and load peaks (~200 h/yr)
Highest specific effect
• Full summertime operation (~1000 h/yr)
Highest overall efficiency

29. EC for chillers and drycoolers
Without EC With Evaporative Cooling
Outdoor T
(°C @ 50% RH)
Dry capacity
(kW)
Wet capacity
(kW)
Capacity
increase
Water
(l/h)
Equivalent T
(°C)
15 823.6 860.9 5% 50 14.2
20 597.3 649.9 9% 50 18.8
25 385.5 420.6 9% 50 24.2
30 161.2 365.9 127% 300 25.4
35 (*) 339.3 ∞ 600 25.9
(*) Dry coolers cannot dissipate heat because the outdoor temperature is higher than the
temperature of the liquid refrigerant.
Calculations for a unit designed for a capacity of 340.3 kW at 26°C, power consumption
21.3 kW, outdoor humidity 50%RH. Full design data in the appendix.

30. EC for chillers and drycoolers
Advantages of evaporative cooling:
Increased cooling capacity (at least 20-30%) and reduced running costs
Longer working life
Less compressor maintenance and greater system reliability
Reduced environmental impact
Easy to install: simple assembly on existing (retrofit) and new units
Lower investment costs in oversized units
Assuming inverter-controlled variable speed fans are available, low temperature systems
can achieve even higher efficiency.

31. Preserving water
Every 1 gallon we use
for evaporative cooling
2 gallons are not used at
power plant
=
Source: Google Data Center Efficiency Best Practices.
Water is a precious good and it should be preserved.
If you think evaporative cooling is wasting water, remember:

32. Adiabatic technologies

33. Pressurized water atomizers
Working principle
Water is pressurized by an inverter pump
and atomized into minuscule droplets (10-
20µ)
Low energy consumption (<4 W/kg)
High precision (±2% RH)
With demineralized water
maintenance is minimized
One unit can be used for DEC + IEC
High absorption ratio (up to 95%)
No recirculating water: certified
hygiene
Adiabatic technologies

34. Ultrasonic humidifiers
Working principle
Immersed piezoelectric transducers
vibrate at ultrasonic frequency: very fine
droplets of water (1-5µ) are released
Maximum precision (±1% RH)
With demineralized water
maintenance is minimized
10000 working hours guaranteed:
reliability
High absorption ratio (up to 98%)
No recirculating water and automatic
washing cycles: maximum hygiene
Adiabatic technologies

35. Wet media humidifiers
Working principle
Air flows through a large surface made up
of corrugated wet pads and water is
absorbed.
Low investment cost
Pads degrade and must be periodically
replaced: high maintenance cost
Low absorption ratio (<10%)
Water recirculates. Requires chemical
biocides and periodic water analysis
High pressure drop in the duct: every
lost pa costs 2.5 $/yr
Adiabatic technologies

36. Experience proves that the best results often derive from solutions that are
initially less convenient, above all due to:
The efficiency of the air-conditioning system
The accuracy of the control system
The quality and the frequency of routine maintenance
Adiabatic technologies

37. eBooks – Climate tools
Unless specified, all information comes from the Air humidification and Evaporative
cooling publications. You can request them in e-book format:
• at carel.com
• via the climate tools app

39. Appendix 1
Design data
Cooling water supply temperature 36 °C
Cooling water outlet temperature 31.3 °C
Outdoor temperature 26 °C
Outdoor humidity 50% RH
Power consumption 21.3 kW
Coil area 1608.6 m2
Fin thickness 1 mm
Fin material Aluminium
Air flow-rate 186600 m3/h
Heat dissipated (capacity) @ 26°C 340.3 kW