46
Evaporative Air-Conditioning: Applicationsfor
Environmentally Friendly
Cooling
Commercial
Kitchen Evaporative
Air-Conditioning
Makeup air, or exhaust
air replacement, is typically
needed in food service facilities-by
building and health
codes,
if for no other reason-and
EAC can be used to good effect
in meeting these requirements.
Proper
kitchen
ventilation in particular has safety implications
and requires a well-designed makeup
air system. In
concert, EAC and makeup
air systems can improve
the comfort, safety, and efficiency
of commercial kitch-
ens while
affording energy savings, improving worker morale, and providing customers better
comfort.
Cooling Comfort
Heating/cooling rooftop makeup air units provide summertime
cooling to commercial kitchens through
direct evaporative air-conditioning.

These systems are
ideally suited to commercial
kitchens because
they provide
100 percent fresh air ventilation
and cooling, requiring
exhaust for proper application,
rather
than recirculation
of air. With its large
summer cooling potential of 15°C
or more, this system can
increase
employee
comfort substantially. In many
areas of the world, direct
evaporatively conditioned air
can be
introduced through
a makeup air unit into the kitchen
at between 5 and 10°C
below outdoor dry-bulb
temperatures
or lower depending
on ambient conditions.
Cost Savings
Although
VAC in kitchens is relatively common, it is certainly not
the most efficient approach to comfort,
because most of

the air introduced through
the VAC system is immediately
exhausted by the stove hood
before it can recirculate.
Thus, constantly running
fresh air through a VAC
substantially increases the
load on the unit and requires purchasing refrigerated air-conditioning capacity
well beyond what would
be required for the same
internal load with a recirculating
system. In addition,
a typical rooftop refriger-
ated-heated makeup
air unit would be oversized
on the heat mode as well and
would increase the initial
capital
cost. By contrast, an EAC
unit could supply kitchens
with makeup air without water
circulation
through the pads when cooling was
not needed.
Sizing
Engineers generally
size the makeup air unit
to match a predetermined amount
of air being exhausted
by

the hood ventilator
selected. Proper selection
of a makeup air unit of the
correct size (the quantity of
air
that can be delivered by a
given unit at the necessary introduction
temperature) is
the key decision pa-
rameter. Temperature
rise and air delivery performance
vary with different units.
The amount of permis-
sible temperature rise
necessary in a given application
is determined by the winter
design conditions for
the
area in question and by the
desired indoor temperature
level.
Laundry and Dry Cleaning
Evaporative air-conditioning in
laundry and dry-cleaning operations
cross a variety of ambient air-condi-
tions. Evaporative
air-conditioning systems perform
important cooling and
ventilating functions. Evapora-
tive air-conditioning

may provide features that give
the laundry operator greater
cost-effective versatility
in the interior
environment as compared to
vapor compression air-conditioning
and ventilation alone.
Extreme
Heat Conditions
The heat levels of laundry
and dry-cleaning plants are high.
ln addition to the solar gain and human
heat
load
occurring in a typical (140 to 900 square
meter) facility, the equipment
used generates a large amount
of heat. Heat levels
can become unbearably
high for finishing (ironing) personnel
in particular. Workers
Commercial Evaporative Air-Conditioning
47
are exposed to heated areas from steam above 80°C. Every plant has a boiler to provide steam for finish-
ing textiles. These units in larger plants are rated as high as 5.3 to 10.5 million KJ/hour (5 to 10 million
BTUh). Although boilers are walled off, at least part of their heat is added directly to the heat load of the
plant. Other equipment that contributes to the heat environment includes washers and tumblers, and in
dry cleaning plants some of the
solvent reclamation equipment.
EACs can introduce air approximating the ambient wet-bulb

temperature for cooling. Some combi-
nation of spot and area EACs can reduce heat stress conditions to acceptable levels. Where temperatures
are exceedingly high, such as at workstations near large boilers, shielding can be used in combination
with spot cooling to reduce radiant heat. Properly directed evaporatively cooled air washing over hot
surfaces
can reduce radiant heat
as well. The climate will
determine whether the heat
load or the ventila-
tion load will require the larger capability. In moderate climates, the ventilation load may be greater than
the airflow required for cooling; the opposite may be true in hot climates.
Industrial Applications
Evaporative air-conditioners and packaged heat/cool
ventilating makeup air units combine many fea-
tures which make them applicable in diverse industrial applications. EAC systems can be the most eco-
nomical approach to comfort, increased equipment efficiency, and code compliance under a variety of
conditions. The uses of EACs in heat treating, forging, casting, welding, milling, rolling finishing, clean-
ing and assemblies is also due to safety and comfort concerns for employees and government regulations
pertaining to employee
welfare.
Direct EAC is often used to combat problems
such as:
* Intense heat, as in many forging, foundry and casting areas.
* Low humidity, as in computer
and electronic control rooms.
* Airborne contaminants, as in welding, plating and cleaning areas.
The hot, stagnant conditions present in many casting and furnace rooms may reach indoor dry-bulb
temperatures that exceed outdoor temperatures from 100 to 15'C, and may reach nearly 70°C in some
extremely hot casting areas. Molten steel at 1,300'C, must be cast by workers. In many basic metal plants
where casting, annealing, forging, baking, and drying occur, shutdowns and work slowdowns are typi-

cal during summer months. In some factories work reductions and shift stoppages are required if tem-
peratures climb too high. Some plants curtail operations or even close during the peak summer cooling
periods. The reasons may be union contracts, walk-outs under hot conditions, and so on. Government
regulations vary in different countries,
but many countries have legally enforceable
occupational heat/
stress standards. Even without government regulations, many industries attempt to relieve the problem
of heat in their plants out of basic practicality. Using evaporative air-conditioning in the plant environ-
ment can help prevent mandatory and spontaneous work reductions.
Spot or area cooling with EAC systems, combined with other heat-control methods such as radiant
heat shielding, can effectively meet government heat/stress standards. EAC can increase summer-
time productivity
by as much as 40 to 60 percent in plant
areas too large to air-condition with vapor-
compression systems.
EAC is used in industries including
aluminum production and fabrication;
electronics assembly; power
generation; shop work such as welding, plating and milling; metal fabrication and battery manufacturing.
The benefits of cooling hot workers remain
essentially the same in most applications:
increases work effi-
ciency, lengthened work seasons, lowered costs, code compliance and increases equipment efficiency.
Factory Air-Conditioning
Design Considerations
Spot cooling is used in
industrial areas where people are in close
proximity to high-heat processes and
cooling of the entire
installation is either inefficient or extremely expensive. Spot cooling with EAC

48 Evaporative Air-Conditioning: Applications for Environmentally Friendly Cooling
provides two principal benefits: evaporatively cooled air and air movement. The effect of air motion,
air temperature and humidity must be combined to derive an index to worker comfort (i.e., effective
temperature). Spot cooling essentially isolates the worker from the immediate hot environment by
displacing hot air with a stream of cooled air. Thus, the effect on the worker is determined by the outlet
air temperature and velocity. Calculations for spot cooling are based on the amount of air being deliv-
ered, the heat rise and static pressure in the duct, and the size of the outlet. All of these variables will
determine the amount of comfort or relief felt by the worker.
Ventilation Control
Makeup air systems, in addition to providing space cooling, help in ventilating high-fume areas and in
reducing airborne contaminants in accordance with government standards. Makeup
air is typically re-
quired by regulation in the design of areas containing plating tanks and paint-spray booths, for example,
and it is highly recommended in all areas with industrial exhaust. Makeup air is highly recommended in all
areas requiring industrial exhaust. "Air starved" buildings may not be able to provide sufficient flow to
operate the hoods, spray booths, and appliances properly. Inadequate makeup air will cause drastic reduc-
tions of efficiency that will affect propeller fans and natural drafts; in some instances the flow may be
reversed. In addition, some contaminated areas require
a large supply-air flow to the dilution of airborne
contaminants with or without associated exhaust-for
example, areas using industrial solvents. When year-
round air supply is needed, heating-cooling-ventilation makeup air systems or EACs are often specified.
Equipment Protection
To last and run efficiently over their design lifetime, many pieces of equipment require appropriate
cooling. Again the use of EAC is a valid option, certainly
when the use of vapor-compression cooling is
too expensive, humidity ratio is not the limiting factor,
and ventilation alone is not enough. For ex-
ample, considerable waste heat is generated in power generation equipment. Whether the power is
generated by gas or steam

turbines (run on fossil fuel, nuclear energy,
or even solar power), the tem-
peratures of the
installations in which the turbines run must
be kept under 41°C, which is the maximum
operating condition for the windings in common alternators. EAC may be used to keep room tempera-
tures lower than 41°C allow generators to operate at overload outputs; the general rule is that approxi-
mately 6 percent overload capacity is available for every 4.5°C below rated ambient temperature (usu-
ally 41°C) achieved by cooling. Other types of equipment also
operate more efficiently under cooler
conditions. Electric motors, particularly high-horsepower units (200 HP and larger), can require direct
cooling of the windings for proper operation.
Agricultural Applications-Poultry
Indoor confinement
of agricultural livestock is a growing trend worldwide because it yields higher
qual-
ity and improved productivity. The comfort and well-being of
indoor livestock is also becoming of para-
mount importance from an ethical point of view. Environmental control of livestock housing such as
poultry has become an increasingly critical technology in which EAC plays an important part.
One of the most commnon areas for applying EAC is in poultry houses. Of the farm buildings commonly
found in the poultry business, evaporative air-conditioning improves conditions in four major types: the
broiler house, the hatchery, the laying house and the processing plant (see Figure 8.1 for an overview).
Better Growth Rates and
Feed Conversion. Proper evaporative air-conditioning of broiler houses
allows birds to achieve a weight gain of from 5 to 8 percent with a corresponding
cut in the growth period
of 2 to 8 percent. Closely related to poultry growth rates is the factor
of feed conversion.
Reduced

Mortality Rates. Improved Hatch Rates, Increased Egg-Laying Rates and Egg Size.
High
temperatures-37°C and above-will
kill poultry. EAC has been found to decrease poultry production
Commercial Evaporative Air-Conditioning 49
Figure 8.1. Typical Evaporative Air-Conditioning Applicationfor Poultry Houses
_
~~~~Evaporative
' T ~~~~Cooler
Evaporative
F G
b(7 Cooler,'
Source: ECI.
mortality rates by 35 percent or greater. The use of environmental control with EAC in the hatcheries has
been shown to improve hatch rates from 3 to 10 percent. A commercial egg-laying house, or egg ranch,
depends in part on lay rate-the number of eggs laid per hen per day-for its profitability. Appropriate
EAC systems have reportedly improved overall poultry egg-laying rates by as much as 15 percent in-
creased overall quality, and boosted average egg size from
5 to 6 percent.
Improved Conditions for Workers. EAC in poultry houses improves the life and comfort of the
birds, as well as their overall productivity, but it also improves conditions for people working in these
houses during the summertime heat. In addition, EAC provides ventilation and other benefits
of particu-
lar value in the
poultry environment.
Greenhouses
Excessive summertime temperatures can reduce plant
growth and, if high enough, can kill the plants.
Temperatures above 29°C constitute a danger to the health and growth of many greenhouse plants, and
sustained temperatures above 35°C are a serious threat

to most types of plant life. EAC provides signifi-
cantly lower indoor air temperatures that enhance plant viability, reduce mortality, improve plant size
and increase weight.
Fan and Pad versus Evaporative Air-Conditioners
Evaporative air-conditioning is used in horticulture, floriculture and other high-productivity
greenhouse
agricultural systems, where the environmental conditions are critical for production. Basically two sys-
tems, with different areas of application, are used. Fan and pad systems have one air inlet into the green-
house, where the
wetted medium is installed and ventilating
equipment on the far wall
of the building
(see Figure 8.2). This
approach causes a significant temperature
gradient from the inlet
side to the venti-
lation side of the greenhouse
because of the heat the air
picks up as it travels the length of
the greenhouse.
The other
system uses external packaged coolers
that maintain a positive pressure
in the greenhouse.
They are installed
outside the greenhouse and
blow humidified air through many
polyethylene ducts
into the greenhouse
(see Figure 8.3). The system

maintains a constant overpressure
inside the green-
house, with exhaust
air leaving the greenhouse at an
exit louver. This approach supplies
an even tem-
perature gradient
in the greenhouse, since the cooled
supply air is delivered through
the poly ducts
throughout
the greenhouse before it picks
up additional heat from the greenhouse.
This approach creates
a more uniform growing
environment inside the greenhouse
than does the fan and pad
system.
50
Evaporative Air-Conditioning: Applicationsfor
Environmentally Friendly Cooling
Figure 8.2. Evaporative Cooling Pad Section of Rigid Cellulose Pads
11 ~- I-=-
Pads shown are along west wall of New Mexico State University grower greenhouse maintained
by SWTDI in Las Cruces, New
Mexico.
Source; ECIL
Additional Crops
EAC can allow an extra growing season for
greenhouse crops where summers normally would be too

hot, thus increasing annual yields. Where shading is normally required to lower
indoor temperatures
during summer, it may be
reduced or eliminated, depending on the crop, when EAC is used. This can
Figure 8.3.
External Evaporative Air-Conditioners on a Research Greenhouse, New Mexico State University,
Las Cruces, New Mexico
l _
_11 k .
f.

Source: ECI.
Commercial Evaporative Air-Conditioning 51
further increase
plant yields. Increasing the
velocity of air movement permits
shade requiring plants
to
be grown at
higher than recommended
light levels without
reducing plant quality.
Uniformity
among individual
plants in a crop is enhanced
by EAC. Variation
among individual plants
in a crop is reduced by lower summer temperatures.
This effect benefits commercial growers attempting
to

increase
control over the produce
they sell. Both size and the date
of harvesting of a crop are
more uniform.
The former
is a benefit in business planning, simplifying pricing,
while the latter affords the grower more
control over the seasonality
of the crop, allowing
better matching of target
dates and deadlines.
Within limits, high relative
humidity (RH) is good
for plants; however, RH
decreases as temperature
rises. EAC
provides two benefits to plants
under these conditions.
The cooling reduces heat stress
on a
plant, thereby
reducing the need for its
own "evaporative air-conditioning"-that
is, transpiration
by its
leaves. The increased RH means greater
saturation of the air surrounding the leaf, inhibiting the vapor-
ization of water from the leaf itself.
Because of the critical nature

of temperature in the maintenance of healthy plants, cooling systems that
fail to maintain conditions
necessary to the health and development threaten
the success of a greenhouse.
Fine Tuning Greenhouse
Environments with Evaporative Air-Conditioning
In warm climates, EAC
is useful to ensure that heat-sensitive
plants are maintained
within safe limits.
Cooling may be necessary
for plant survival. In milder
climates, however, EAC
may be used for special
greenhouse applications. If
a greenhouse that is oriented to low-temperature-preferring plants is desired,
EAC can be an essential
component, no matter the
outdoor climate. To maintain
such planned environ-
ments,
EACs can be operated at
night or on cool days. For example,
air that is 27°C and 30 percent
RH can
be cooled to 19°C
through EAC. Even at night-when
cool-house plants
require 7° to 13°C tempera-
tures-an EAC either with

or without the pump operating can help maintain proper
conditions.
Annex 1
Introduction to Evaporative Cooling
Let us first look at the principle of evaporative air- In Figures A1.2 and A1.3, the effect of EAC is
conditioning, which can be explained by way of psy- explained. In the cases shown the DB temperature
chrometric charts. These charts present the moisture is 40°C, and the air is not saturated with water,
ratio versus the temperature, as it is registered by a RH is only some 15 percent. One can add water,
normal thermometer (the dry-bulb temperature; and the temperature will drop until it reaches the
DB), in a certain situation. The lines in Figure Al.1 saturation line. What happens is that the heat in
connect the points with the same relative humidity the air is "absorbed" by the evaporating water. The
RH. At a given temperature air can contain an sensible heat is transformed into latent heat. The ef-
amount of water vapor. When this amount of wa- fect is that the temperature is lowered to 20°C in
ter vapor reaches its maximum (100 percent RH), this case. The difference between 400 and 20° is
the dew point is reached and the water starts to con- called the wet-bulb depression. The wet-bulb tem-
dense. The dew points are connected by the satura- perature, or WB, is registered by a normal ther-
tion line. The
higher the temperature
in a certain
mometer that
is wrapped in a wet
sock or other
volume, the more water it can contain in
its gas- piece of textile. The constantly evaporating water
eous stage. In a desert this effect can explain why from the sock causes a drop of the temperature.
in
the morning, when
the temperature is
still low, The WB

temperature is always
lower than the
DB
one sometirnes sees drops of water on the scarce temperature, except when the RH is 100 percent-
vegetation. In the
afternoon, when the temperature that is, when the air contains
the maximum amount
reaches its maximum, the air feels very dry and hot. of water it can hold at a given temperature. The
T1he same
amount of water is in the air in terms of WB depression line connects the points
with the
kilograms of water per kilogram of dry air, but the same enthalpy-the same amount of energy-the
feeling it gives is completely different. sum of latent and sensible heat.
Figure Al.l. Psychrometric Chart and Saturation Figure A1.2. Complete Psychrometric Chart
Line
Humidity Ratio Humidity Ratio
kg water/kg air kg water/kg air
J
/
.030
3 80%
60/ 4%
.030
.025
/-
.025
L < :3I'
*. gi{
.020
25aDW

Point Temperature
.020 ~~~~~~~~~~~~~~.020
Rain or Saturation Line .015
2 .015
100% Relative Humidity .010 X 7.010
1 005
.005 00
5 10
1'5
iO
i.005 3'5
-45005
5 10 15
20 25 30 35
40 45 50
5 10 15 20
25 30 35 40 45
50
Dry-Bulb Temperature
°C
Dry-Bulb
Temperature °C
Source: The Munters Corporation.
Source:
The Munters Corporation.
53
54
Evaporative Air-Conditioning: Applications for Environmentally Friendly Cooling
Figure A.3. Wet-Bulb Depression of Ambient Air Figure A1.4. Saturation Effectivenessfor an 80
Percent Effective Evaporative Cooling Pad

5 0J 15
25 30X 20d 40
40 5 2 1
3 2 30/ 351 fi,C
A /
s lc
s la t; 23 25~~~~~ 30 3 43 5 5
Dwy-5BdbThTh, C
Dl-mmd Tcn~ab sC
Source: The
Munters Corporation.
Source: The
Munters Corporation.
Figure
A1.4 explains the cooling
effect of an The outgoing
air thus has a DB temperature
of 40°C
EAC. When water
and dry air are mixed in
an EAC, - 16°C = 24°C.
the
air will cool down following
the WB depres- Figure
A1.5 explains what happens
in different
sion line. The efficiency
of a certain EAC defines
situations when an EAC
is used. The arrows point

thie degree of cooling. In this
case, the dry air of 40°C at
certain combinations of DB temperature
and RH.
is led through a pad of corrugated
paper, which is It
is clear that not all these situations
are "comfort-
constantly wetted with
water. The appliance has
an able." Only certain
combinations of DB and
RH are
efficiency of 80 percent,
which means it cools the
actually sensed as comfortable
by human beings,
airwith O.80OXWB depressionof40°C-20°C
= 16°C.
and this limits the use of
the EAC technology for
F'igure
A1.5. Saturation Effectiveness
of 80 Percent
Figure A1.6. Effect of
Indirect Evaporative Cooling
for Evaporative Cooling
Pads at Different Ambient
on Ambient Airstream
Conditions

tiuiai;~~~~~~~~~~~~~~~~~~~~~~~.U Lhgig,=. EbcdtRs
_; : ~~~~~~~~25
2w
20 .< 15 20 < 1
S
.C 0g
=
.C
.500
- .010
O 15
15 25 20
30
c 40 1 3
10 IS
20 2Z 30
35 40 45
S0
1),Y-BWb T-M~~~ -C Lty-BWb TDs-Bx bT C
Note:
All are 80 percent effective;
in drier conditions
the Source: The
Munters Corporation.
cooling effect is more
pronounced than in hu
ecid regions.
Source: The
Munters Corporation.
Annex 1: Introduction

to Evaporative Cooling
55
Figure A1.7. Effect
of Combined Indirect Evapora- Figure A1.8. Energy-Saving Effect of Using a
tive Cooling Coupled with Direct Section Smaller Coil Coupled with Indirect and Direct
Evaporative Cooling Sections
025'
wN-
co,, .000
10 no,o,2~3 /
.010
C'Il 04a0,
.D05
25/
.025
~~~~~5
,.020 s %/17
5 10 1S 20 2 30 35 40 45 S0 5 10 15 20 25 30 35 40 45 so
DQ-2oOT=00epaoDC y-Bo1bTon-p-:C
Note: This allows
evaporative conmfort cooling
to be applied in Source:
The Munters Corporation.
more huumid regions, as compared wit- direct EAC alone.
Source: The Munters Corporation.
certain applications. In some cases, hovwever, such the effect that the direct cooling follows another
as greenhouses or cattle sheds, the RH can be in- (lower) WB depression line. In this way the end of
creased without any problem. the arrow comes into the "comfortable zone" again.
EAC technicians have succeeded in reducing Figure A1.8 shows the effect of adding a cooling
the amounts

of water that are in the
air, so as to coil after
an indirect evaporative cooling
section (us-
increase the possibilities
for applying EAC
in hu- ing the indirect
as a precooler). This
allows for a
mid areas also. Figures A1.6 ard Al .7 explain the smnaller-sized coil to be used, thus saving energy over
effect in an indirect-direct air-conditioner. Before conventional systems. A direct section can be added
entering the wetting air stream, the air is first after this as well if needed. Other systems reduce the
cooled by a normal heat exchanger, in which wa- amounts of water by using desiccants, chemicals that
ter and air are also mixed. In this case, the DB tem- can remove the water from the air stream before it
perature of the entering air is reduced from 37.7'C enters the direct cooler. With these types of combined
to 26.1'C by the heat exchanger. After this, the processes, EAC can be made more efficient in more
26.1 'C air is cooled
in the direct cooler to a DB of humid
areas. The price of these coolers increases with
19.6 C. The indirect cooler
in the beginning has the more
complicated technology.