In this presentation are shown the fundamental concepts, industrial applications and recent scientific progresses of Humidification.

1. HUMIDIFIER: FOUNDATIONS, APPLICATIONS
AND SCIENTIFIC PROGRESS
1
UNIT OPERATIONS LAB II
UNITOPERATION:HUMIDIFICATION

2. HUMIDIFIER
CARLOS MAURICIO ARRIETA HURTADO*
IRIS BUSTAMANTE PÁJARO*
ANGIE CASTILLO GUEVARA*
ALVARO JOSE GARCÍA PADILLA *
ROSAANA MARTÍNEZ REVUELTA*
KARIANA ANDREA MORENO SADDER*
LUZ MARINA RAMOS TORRES*
9th SEMESTER
CHEMICAL ENGINEERING PROGRAM
UNIVERSITY OF CARTAGENA
2
UNIT OPERATIONS LAB II
UNITOPERATION:HUMIDIFICATION

3. 3
OUTLINE
1. Introduction
2. Theoretical foundations
3. Applications
4. Limitations
5. Current researches
6. Objectives & Methodology
7. Calculus
8. Conclusion
Acknowledgements
DISTILLATION COLUMN: FOUNDATIONS, APPLICATIONS AND
SCIENTIFIC PROGRESS
"Good, better, best. Never let it rest. 'Til your good is better and your better is best." - St. Jerome
UNITOPERATION:HUMIDIFICATION

4. INTRODUCTION
UNIT OPERATION
HUMIDIFICATION
Method used to increase the
moisture content of air or a carrier
gas.
Importance:
Prevent static electricity buildup in industries
Preserve material properties
Ensure a comfortable with air conditioning
Chemical engineer, job duties:
Design, simulate, develop & operate humidification unit, where mass and
heat transfer phenomena take place.
Sharqawy et al., 2017; El-Agouz & Abugderah, 2008
UNITOPERATION:HUMIDIFICATION
4

5. THEORETICAL FOUNDATIOS
UNITOPERATION:HUMIDIFICATION
5
Dry air Humid air
ADIABATIC HUMIDIFIER
Air with low
humidity is loaded.
By resistances the
air is preheated.
Air-water contact to
mass and heat
transfer.

6. THEORETICAL FOUNDATIOS
PRINCIPLE OF HUMIDIFICATION
UNITOPERATION:HUMIDIFICATION
Packed-bed humidifier:
Hot liquid
Air is loaded from the bottom of the column.
Humidified air
Air 6
Non-saturated
gas
Liquid with a low
temperature.
The water is sprayed from the top of the
column.
Through the column both substances have
heat and mass transfer.

7. THEORETICAL FOUNDATIOS
Schlesch et al, 1996
UNITOPERATION:HUMIDIFICATION
Steam humidifier:
7
Used in industries where the water is
heated and boiled.
Release stream for raising the humidity
and moisture level in the air.
Comprises a manifold for receiving steam
and at least one steam dispersion.
Steam emitting nozzles on the dispersion
tube into an air flow to be humidified.

8. THEORETICAL FOUNDATIOS
UNITOPERATION:HUMIDIFICATION
8
Basic concepts
Molar humidity
𝑌 𝑚 =
𝑛 𝑣
𝑛 𝑔
=
𝑝 𝑣
𝑝 𝑔
=
𝑝 𝑣
𝑃 − 𝑝 𝑣
Absolute humidity
𝑌 =
𝑀𝑣
𝑀𝑔
𝑌 𝑚 =
𝑀𝑣
𝑀𝑔
𝑝 𝑣
𝑃 − 𝑝 𝑣
Relative humidity
𝜑 =
𝑝 𝑣
𝑝 𝑣
∗
Porcentual humidity
𝜑 𝑝 =
𝑌
𝑌∗ =
𝑝 𝑣
𝑝 𝑣
∗
𝑃 − 𝑝 𝑣
∗
𝑃 − 𝑝 𝑣
Specific volume of humid gas
𝑉 =
1
𝑀𝑔
+
𝑌
𝑀𝑣
𝑅𝑇
𝑃
Specific heat of humid gas
𝑐 = 𝑐 𝑝 𝑔
+ 𝑐 𝑝 𝑣
𝑌

9. THEORETICAL FOUNDATIOS
UNITOPERATION:HUMIDIFICATION
9
Basic concepts
Humid temperature
𝑝 𝑤
∗
− 𝑝 𝑣 =
ℎ 𝑐
𝑘 𝐺 𝑀𝑣 𝜆 𝑤
𝑡 − 𝑡 𝑤
Adiabatic saturation temperature
𝑌𝑠 − 𝑌 =
𝑐
𝜆 𝑠
𝑡 − 𝑡 𝑠
Specific enthalpy
𝑖 = 𝑐 𝑡 − 𝑡0 + 𝜆0 𝑌

10. THEORETICAL FOUNDATIOS
UNITOPERATION:HUMIDIFICATION
10
Psicrometric diagram
Fuente: www.procesosbio.wikispaces.com

11. THEORETICAL FOUNDATIOS
UNITOPERATION:HUMIDIFICATION
11
Psicrometric diagram
Dry bulb
temperature
Humid bulb
temperature
Dew point
temperature
Relative
humidity

12. THEORETICAL FOUNDATIOS
UNITOPERATION:HUMIDIFICATION
12
Psicrometric diagram
Absolute humidity
Saturation
enthalpy
Specific volume

13. APPLICATIONS
UNITOPERATION:HUMIDIFICATION
Fonseca et al., 2008
Where:
a: Initial state (supply humidifier)
b: Real final State (exhaust
humidifier).
c: Theoretical final state (ideal
procedure)
X*W: Air humidity ratio (Kg water
vapor/ Kg dry air)
Fig. 10 a) Functional scheme of atomizing humidifier, b) Functional scheme and
pictures of the wetted media humidifier
Negligible air enthalpy and wet bulb
temperature variations
HUMIDIFIER EFFECTIVENESS
Refrigeration and air conditioning systems
a)
13
𝜀ℎ𝑢𝑚,𝑤 =
(𝑋 ∗ 𝑊) 𝑏−(𝑋 ∗ 𝑊) 𝑎
(𝑋 ∗ 𝑊) 𝑐−(𝑋 ∗ 𝑊) 𝑎
b)

14. APPLICATIONS
UNITOPERATION:HUMIDIFICATION
Amara et al., 2003
Fig. 11. Solar desalination technique
using multiple-effect humidification.
SPRAY HUMIDIFIER AND DEHUMIDIFIER SYSTEM
Solar desalination
14
Warm unsaturated air
Warm saline water under specified
conditions
Certain desired air humidity
Advantages:
• Simplicity.
• Low cost of fresh water
production.
• Renewable energy sources.

15. APPLICATIONS
UNITOPERATION:HUMIDIFICATION
Perera et al., 1997
HEAT PUMP DEHUMIDIFIER
Drying of food
15
Total electrical energy input
Advantages:
• High energy efficiencies
• Carried out at relatively low
temperatures.
• Microbial safety.
• Quality of dried food products
improvements.
Fig. 12 a) Heat pump dehumidifier, b) Functional scheme of heat pump dehumidifier
Energy absorbed at the evaporator
Drying efficiency
a)
b)

16. APPLICATIONS
UNITOPERATION:HUMIDIFICATION
Alix et al., 2011
ABSORBER
Storage of CO2
16
Proper performance of packing
in capture with 30 wt% MEA
Advantages:
• Low pressure drop.
• High interfacial area.
• Reduce of electric consumption,
operating costs and efficiency
lostFig. 13 Experimental setup for post-
combustion CO2 capture
Proper control of hydrodynamics
and mass transfer variables

17. APPLICATIONS
UNITOPERATION:HUMIDIFICATION
Pang et al., 2013
DEHUMIDIFIER
Automotive industry
17
Remove the water vapor in the
atmosphere
Fig. 14 scheme of vertical gas atomizer
Recover low-grade heat
Reduce the moisture level
Advantages:
• Reduce the heat pollution to
the environment.
• minimize the consumption of
fossil energy to drive the
absorption and adsorption
system
Utilization of clean solar energy

18. APPLICATIONS
UNITOPERATION:HUMIDIFICATION
Banks et al., 1986
ULTRASONIC HUMIDIFIER
Conservation of library, archive and museum colletions
18
Monitoring of humidity levels
Useful source of moisture when there
is a reduction of the relative humidity
Computation of the quantity of
moisture required
a)
b)
Advantages:
• Conservation of objects.
Disadvantages:
• Severely limited reservoir
capacities.
Fig. 15 a) Schematic section of a typical
ultrasonic humidifier, b) ultrasonic
humidifier

19. CURRENT RESEARCHES
CONVENTIONAL
HUMIDIFIER
Liu & Sharqawy, 2016
UNITOPERATION:HUMIDIFICATION
Very low heat and mass transfer coefficients
Large volume & high capital cost
Packed-bed humidifier:
Surface-area-to-volume ratio
Depends on
Type of the fill
Large packing due to low specific superface
Humidified air
Air
Problems?
19

20. CURRENT RESEARCHES
Liu & Sharqawy, 2016
UNITOPERATION:HUMIDIFICATION
Steam humidifier:
Air Steam
directly
Heat to evaporate
supplied water
Consume large energy from gas, fossil
fuel or electricity
Problems?
Spray humidifier:
Type of atomizing mechanism:
Ultrasonic Centrifugal Pneumatic
Production white dust as a by-product
Problems?
20

21. CURRENT RESEARCHES
Liu & Sharqawy, 2016
UNITOPERATION:HUMIDIFICATION
Desalination process PEM fuel cells
Small-scale humidifier
PEM= Proton Exchange Membrane
Type of humidifier for these recent applications?
Enhance heat and mass transfer processes hence small
equipment volume
Bubble columns Membrane humidifier Cross flow humidifier
21

22. CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Sea water
Abd-ur-Rehman et al., 2015
Application:
Solar humidification-
dehumidification (HDH)
Decentralized small
scale water desalination
system
- =
Novel solar heated multi-stage
bubble column humidifier
Salt
Potable water
Simple
functionality
Moderate
investment
Usage of low grade
heat sources
Advantages:
22

23. CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Abd-ur-Rehman et al., 2015
Fig. 1 Schematic illustration of the humidifier design
Note: Cross section in bubble column 300 x 300 mm
Design of humidifier
Perforated
plates features
Water column
height
Air superficial
velocity
Inlet water
temperature
Inlet air
humidity
23

24. CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Abd-ur-Rehman et al., 2015
Three perforated
plate design
D 1 >D 3 > D 2
Fig. 2 Pressure drop under different design considerations
of the perforated plate and air superficial velocity
NO leakage
LESS pressure
drop
Open ratio of designs
Design 3
Air superficial
velocity
Pressure drop
24

25. Air is not able to
propagate
effectively
CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Abd-ur-Rehman et al., 2015
Fig. 3 Influence of water column height on the absolute
humidity of the moist air at the exit of humidifier under
varying air superficial velocities.
NO significant influence on absolute humidityWater column height
Height 1 cm
25 cm/s
30 cm/s has higher
pressure drop than
25 cm/s
25

26. CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Behnam et al., 2015
Air bubble column
humidifier
Evacuated tube
collector
Heat pipe
High interface area
and effective mixing
Lower rate of
heat loss
High performance
in heat transfer
Fig. 4 Experimental setup 26

27. CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Behnam et al., 2015
Height 7.5 cm
High interface area and
effective mixing
Why?
Condensers of the heat pipes
completely submerged in the
water.
Maximum rate of heat transfer
Fig. 4 Production for different initial water depths in the humidifier.
27

28. CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Behnam et al., 2015
Inlet air flow rate
In the morning decrease
productivity with air flow rate
Enhanced convective heat transfer
Fig. 4 Production for different inlet air flow rate.
Daily fresh water
production
Inlet air flow rate=8 L/min
28

29. CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Behnam et al., 2015
24.6%
Increase of heat transfer rate
Effect of adding fluid to the space between the heat pipes and ETCs
Oil, best fluid to add
40.6%
74.3%
Aluminum foil
Water
Oil
Fig. 5 Efficiency changes for the system for adding fluid to the space between the
heat pipes and ETCs. 29

30. CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Liu et al., 2015
Fig. 6 Photo of the laboratory scale test-rig without showing the compressor and
vacuum pump
Bubble column
humidifier
Bubble column
dehumidifier
Sub-atmospheric
pressures
Elevated
pressures
30

31. CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Liu et al., 2015
Bubble column humidifier
Fig. 7 a) Effect of static water column height on the total heat transfer rate, b) Outlet
temperatures of air at different pressures and superficial velocity
a) b)
Superficial
velocity
Heat transfer
rate
Effectiveness 10.7% up from
15 psia to 7 psia.
No significant changes
31

32. CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Liu et al., 2015
Bubble column dehumidifier
Fig. 7 a) Effect of static water column height on the total heat transfer rate, b) Outlet
temperatures of air at different pressures and superficial velocity
a) b)
Superficial
velocity
Heat transfer
rate
Effectiveness 2.4 % down
from 15 psia to 30 psia.
32

33. CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Solsona et al., 2017 Membrane humidifier for fuel cell applications
Fuel cells Convert chemical energy into electricity
Moisture TemperatureOptimal
Humidification
systems
Internal External
More
proper
Fig. 8 Scheme of PEM fuel cell 33

34. CURRENT RESEARCHES
UNITOPERATION:HUMIDIFICATION
Solsona et al., 2017
Model experimentally validated
under both static and dynamic
conditions
Fig. 9 a) Power: 123 W; air mass flow: 5 slpm, b) Relative humidity under control
system
Proper control of varibles
Suitable manipulation of the power
related to the warming temperature
Efficiency of PEMFC process
Control oriented fourth-order non-linear model
a)
b)
34

35. OBJECTIVES & METHODOLOGY
35
UNITOPERATION:HUMIDIFICATION
Adiabatic Humidification
Objectives
Study the basic principles of the air
humidification process by identifying the
components of an adiabatic humidifier
Observe the behavior of the coefficient
of matter Ky, convection coefficient
when varying the conditions of mass
flow and temperature of the air
Calculate the efficiency of the adiabatic
saturation chamber
Generally
To study the behavior of an adiabatic humidifier,
as well as the equilibrium behavior of the air-
water system

36. OBJECTIVES & METHODOLOGY
36
UNITOPERATION:HUMIDIFICATION
Materials and
equipment
Fig. 10 Laboratory equipment
The adiabatic humidifier is
composed of:
 Bomb  Blower
 Spray chambrer  Electrical
controls
 Wet and dry
temperature meters  Sprinklers
 Heating system and
heating duct
The materials to be used are:
 Water  Air

37. OBJECTIVES & METHODOLOGY
37
UNITOPERATION:HUMIDIFICATION
Identification of variables
Variable Type Definition unit
Air velocity Independent Distance in time m/s
Air
temperature
independent
Magnitude that
measures the
thermal level
°C
Weather Intervener
Determined period
during which an
action is taken
s
Air humidity dependent
Amount of water
present in the air
%
Table 1. Main variables of experimental procedure

38. OBJECTIVES & METHODOLOGY
38
UNITOPERATION:HUMIDIFICATION
Determination of the behavior of 𝐊 𝐘 and 𝐡 𝐜 with variable temperature
Connect the equipment to the power supply and the board lights up
The blower is started by
selecting the desired speed
(Maximum or minimum)
The resistors are turned on by
selecting the desired
temperature
The pump turns on
For a constant mass flow at
the entrance of the spray
chamber, the temperature is
varied controlling the
resistances
Collect Data

39. CALCULUS
39
UNITOPERATION:HUMIDIFICATION
It is important to collect the data indicated in the following table
Resistance
Air Flow velocity
High Low
T1(°C) Hr1 T2(°C) Hr2 T1(°C) Hr1 T2(°C) Hr2
Low
Medium
High
We use these data in the
psychrometric chart
Table 2. Experimental data gathering

40. CALCULUS
40
UNITOPERATION:HUMIDIFICATION
With the help of temperature and humidity we locate the points of input
and output of the humidifier in the psychrometric chart and determined the
other properties

41. CALCULUS
41
UNITOPERATION:HUMIDIFICATION
Mass transfer coefficient
𝐾 𝑦 =
𝑚
𝑎 𝑉𝑡
ln
𝐻𝑠 − 𝐻 𝑎
𝐻𝑠 − 𝐻 𝑏
Hs is the air humidity in saturated
conditions.
Ha and Hb is the input air humidity
and the output air humidity of the
saturation chamber respectively.
ts is the air temperature in
saturated conditions.
t1 is the input air temperature of
the humidification chamber
tb is the input air temperature of
the saturation chamber
ℎ 𝑐 =
𝑚 𝑐
𝑎 𝑉𝑡
ln
𝑡 𝑠 − 𝑡1
𝑡 𝑠 − 𝑡 𝑏
Convection coefficient air/water
Efficiency
𝜀 = 1 − 𝑒
−𝐾 𝑦 𝑎 𝑉𝑡
𝑚
Plot 𝐾 𝑌 vs dry bulb temperature and
ℎ 𝐶 vs mass flow

42. CONCLUSION
42
UNITOPERATION:HUMIDIFICATION
Humidification is the method used to
increase the moisture content of a
carrier gas.
A small scale humidifiers are used
for PEM fuel cells and desalination
process
the psychrometric chart It is a widely
used tool that has facilitated the
calculation of the properties of the
vapor and air mixtures used in
industry

43. THANKS !
43