Eliturbo : Whitepaper
EXECUTIVE SUMMARY:
Heat rises and humidity falls. In buildings over 14 feet tall, warmer air accumulates up towards the
ceiling where it is of no use to people working on the floor, while humidity accumulates near the floor
where it can damage people and equipment. In order to heat the work level to a comfortable
temperature a significant inefficiency is created as the temperature at the ceiling is much higher than
the desired temperature at the working level. This heat stratification costs businesses and other
organizations residing in larger space structures huge amounts each year. A similar phenomenon is true
for humidity as businesses use heat to resolve their humidity problems.
The Eliturbo Air-Mixer prevents heat and humidity stratification via its patented convergent – divergent,
heli-centrifugal air mixing motion. As opposed to classic blade fans or turbine type fans which simply
push air in a column, the Eliturbo pulls air in from above and below, mixes it and expels it radially. The
result is constant air mixing which equalizes the temperature, humidity and air pressure throughout a
large space without any annoying or damaging downdrafts.
The Eliturbo Air-Mixer is designed for buildings with ceilings from 14 to 80 feet in height and each unit
can cover up to 100,000 cubic feet by mixing the air at 5,885 cubic feet per minute (CFM).
Eliturbo’s have been installed, and proven effective, in over 20,000 structures in Europe and are now
available in the US.
Problem: Stratification of warm air and heat loss in higher ceilinged buildings
Warm air delivered via a typical heat source (forced air, radiators, baseboard, fireplace, etc.) in a low
ceilinged space, such as a room, tends to develop minimal differences in temperature between the
ceiling and floor (called heat or thermal stratification). This is not the case in spaces with higher ceilings,
where thermal stratification becomes quite pronounced, and the taller the inside of a building the
greater the difference in temperature between floor and ceiling.
Hot air rises due to the difference of density between hot and cold air, accumulating just below the
ceiling precisely where heating is seldom needed. In building with ceilings of only 14 foot height can
have temperature differences of 5-10 degrees Fahrenheit between ceiling and floor while in higher
ceilinged buildings the difference can be up to 25/40° F.
Human physiology is such that we prefer warmer
temperatures near our feet, and can tolerate
cooler temperatures near head level. Therefore,
for comfort purposes, we want to avoid thermal
stratification as much as possible.
Energy consumption for heating is determined by three essential factors:
1. the type and efficiency of the heating unit (gas vs. electric, forced air vs. radiant, etc.);
2. the level of conductive heat loss through the building envelope (walls, glass, floor, roof); and
3. the amount of infiltration and exfiltration of outdoor air into the structure.
Clearly, the second and third elements are greatly affected by the exterior temperature which creates a
higher level heat loss at colder temperatures.
The amount of heated air accumulating near the ceiling is also tied to the variations of seasonal
temperatures. As the chart below shows heat difference between ceiling and floor ranges from none in
the warm seasons, to 39° F difference at an average winter low temperature of 23° F in many regions.
The result is that the stratification of heat is worse during the cold weather.
Effect of Outdoor Temperature on Stratification
To =
35
30
Ceiling
Height
Height Above Floor, feet
25
C = 9°F
C = 22°F
C = 39°F
20
15
To = Outdoor Temp.
C = Temperature
difference due to
stratification
10
Heat
Delivery
Height
5
Thermostat Height
0
50
60
70
80
90
100
Space Temperature, F
As interior temperatures are generally measured 5 feet from the floor and regulated by a wall-mounted
thermostats they reflect only the temperature at that point, not the temperature at floor or ceiling level.
The air temperature increases as elevation increases because warm air is lighter and rises. The rate of
temperature increase with elevation depends upon many factor including the output capacity of the
heating source and the distribution efficiency of warm air, in proportion to the volume
(length/width/height) of the space. Nonetheless, the temperature increase is regularly calculated at 1-2°
F per foot.
Considering the value “C” as the difference between internal and external temperature (Delta T°) , the
increase of heat loss from the roof and walls at great temperature differences compared to the loss
without thermal stratification is shown in the graph below.
Effects of Stratification on Heat Loss via Walls of
Industrial Buildings based on "C"
Percent Increase in Heat Loss Compared to that due to
Stratification
100
80
60
40
20
0
0
0.4
0.8
1.2
1.6
UA RATIO = UA Roof / UA Walls
Similar to the heat loss from walls and roofs,
the heat loss from air-exchange and
infiltration is also negatively impacted by
thermal stratification. As the temperature at
the roof level increases due to stratification
the amount of heat loss increases up to 2.8%
for each degree difference in Fahrenheit
between the floor and the ceiling. For example
if the outdoor temperature is 32° F then the
resultant heat loss in a structure with stratified
heat is 70% greater than the same structure
with an even thermal pattern. (C=86-61=25° F
at ceiling level -> Heat loss = 2.8 * 25 = 70%).
2
Heat loss in a sample building with and without stratification
Example #1: Industrial Factory or Warehouse – Older (pre-1980) Construction
For the purposes of our first example, we will use a moderate sized steel-framed structure with sawtooth roof and clerestory windows. It is an older building as are many throughout the US and does not
conform to the latest standards for energy efficient construction. The heating required is calculated using
the prescribed 23°F average nighttime winter outdoor temperature as is usual for design purposes.
Floor Dimensions
Perimeter
Floor Area
Average Ceiling Height
Max. Ceiling Height
Volume
Infiltration Air Changes
Min. Outdoor Temp.
Average Seasonal Temp.
Floor Temp.
Temp. at Ceiling
Heating Unit Capacity
330 x 100
860
33,000
26'3"
32'10"
866,250
2
23
41
61
100
2,450,000
719
feet
feet
sq. feet
feet
feet
cubic feet
per hour
°F
°F
°F
°F
BTU/hr
kW
If the air in this structure were to be fully mixed resulting in zero difference in internal temperature
between the ceiling, the walls and the floor then the heat loss calculated in BTU/Hr would be 2,523,371
as shown in the table below .
Projected Heat Loss with No Stratification
Aspect
U
BTU/hr ft2 F
Area,ft2
U*Area
BTU/hr °F
ΔT, °F
Walls
Floors
Roof (total)
Glass
Roof Panels
0.335
0.106
0.557
1.022
0.441
22,389
32,292
43,056
8,611
34,444
7,497
3,414
23,977
8,802
15,175
37.8
37.8
37.8
37.8
37.8
Ventilation 2x
Total Heat Lost
0.062
258,334
31,868
37.8
Q Heat Loss,
BTU/hr
283,370
129,065
906,325
332,702
573,624
1,318,761
1,204,610
2,523,371
This theoretical calculation is based on there being zero temperature stratification in the building with
the air totally mixed. However, in most cases there would be significant thermal stratification leading to
ceiling temperatures that can
Outside Air
T = 23°F
reach as much as 39°F higher
Floor Temp.
T = 61°F
Ceiling Temp. T = 61 + 39 = 100°F
than the floor temperature on a
Roof
ΔT = 100 - 23 = 67°F
cold winter night – even in this
Walls, average ΔT = [(100 + 61)/2] - 23 = 57.5°F
relatively short building. The
Infiltration Air ΔT = 61 - 23 = 38 °F (outside air heated to floor temp.)
same concept holds true for the
average temperatures of the walls and for the temperature of air-exchange; all of which can have a
significant impact on heat loss.
Most the heated air sits trapped near ceiling where the difference in temperature from the ceiling to the
outside can reach 67 degrees F or more as shown above. As expected, much of the heat lost by
conduction is through the roof, especially through the glass window panels. The result is a significantly
larger heat loss. In the case below example, where we have used a lower than maximum heat
differential form floor to ceiling (only 28°F), the heat loss with thermal stratification is 43% higher than
with the air fully destratified, or over an additional 1,000,000 BTU/Hr.
Calculated Heat Loss with Stratification
Aspect
Walls
Floor
Total Roof
Glass
Coverings
Infiltration
Total Heat Loss
U*Area
BTU/hr °F
7,497
3,414
23,977
8,802
15,175
ΔT, °F
46.8
37.8
55.8
55.8
55.8
31,868
55.8
Q Heat Loss,
BTU/hr
350,840
129,065
1,337,911
491,132
846,779
1,817,816
1,778,236
3,596,051
38%
48%
43%
Qs
Qv
QT
Example #2: Industrial Factory or Warehouse – Newer Construction (post-1980)
In this second example we will use the same type of building, a moderate sized steel-framed structure
with saw-tooth roof and clerestory windows, however in this case it will be constructed to comply with
the 1980 Seattle Energy Code. It is built using non-pressurized loose construction and has a U factor of
0.046 for the roof and 0.109 for the walls. Here again, the heat required is calculated using the
prescribed 23°F nighttime winter outdoor design temperature for Seattle and the differences of internal
vs. external temperature due to stratification are the same as above.
The results using fully modern construction change dramatically in terms of heat loss – reducing it by
2/3rds in the case of both stratified air and mixed air cases; however the benefits of destratification
continue to be significant with heat loss reduced by fully mixing the air and thereby eliminating
stratification remain significant as shown in the following table.
In this case with the outdoor temperature of 23°F, the building with destratified air will save the same
43% of the heat input to maintain the same floor level temperature than the building with fully stratified
air. In many buildings, the effect of stratification is much worse. Although this is the case in deep
winter, heat loss percent improvements will be similar at higher ambient temperatures. This evaluation
also points out the need to control ventilation as much as possible, as much of the gains possible by
mixing are lost by infiltration of cold outside air.
Hot Air Heating Units:
Heating via hot-air heating units works in two phases:
1. the heating of ambient room air by conductive or radiant heat exchange using electric heater
coils or gas burners, and then
2. the distribution of the hot air in the space using fans with or without ducts.
The ambient air is drawn from the lower area – generally at a height of 5 to 8 feet, and it is occasionally
mixed with exterior air. The heating unit increases the temperature of the air normally between 45 and
90°F; most frequently about 55-60°F. This corresponds to a volume of air equal to 3,530 cf/hr, or 59 cfm
per kW of thermal power.
The greatest challenge in heating large rectangular spaces is how to obtain a uniform, evenly distributed
temperature both vertically and horizontally so that the vertical space and four corners are equally
heated. Warm air stagnating in the upper portion of the building is heat wasted; which means energy
wasted and money wasted. Meanwhile, the lower portion of the space must suffer a less-than-optimal
temperature. Often, an owner will adjust the thermostat higher to achieve comfort at floor level,
making the problem worse by sending more heat to the ceiling.
Heating units are often placed in less-than-optimal positions dictated by access, work-flow or machinery
locations, exacerbating the temperature imbalance.
An uneven distribution of air is not only uncomfortable for those living or working in the space, but can
also affect the longevity of machinery. Humid air can concentrate in lower areas and form condensation
on cold surfaces near the floor and on lower portions of the walls, leading to metal corrosion and an
unhealthy environment for working. Additionally, condensation on walls can also foster dangerous mold
growth.
The Distribution of Hot Air
To resolve these problems, a constant mixing of the air in a space is desired. Ceiling fans are often
designed to merely push warm ceiling air downward, but this can cause drafts and stir up accumulated
dust. Space heaters usually direct heated air flow in only one direction, angled towards the floor. Only a
limited area is heated, and it does not circulate the air to reduce stratification.
Ideally, the goal is to recycle the volume of air in the space 5 times per hour. One solution is to install
heating units that have a CFH heating capacity of 5
times the volume of space.
Sample Industrial Building
In order to achieve this level of air movement with
heat stratification it is necessary to install significantly
more heating capacity than would be needed if the air
were destratified. Taking any number of industrial
heating units available on the market the difference in
price of purchasing additional heaters to create the
needed air flow is well above the cost of installing the right number of Eliturbo Air-Mixers to destratify
the air as we heat.
Surface Area
Ceiling Height
Internal Volume
Required Heat
33,000 sq. ft.
26.25 feet
866,250 cu. feet
2,453,500 BTU/hr
719 kW
Additionally, condensation on the walls and the resulting corrosive impact on machinery is eliminated,
along with improvements in comfort and temperature uniformity for workers. The heating units can
cycle as needed without the burden of maintaining even air distribution, as that function is now assured
by the Eliturbo units. Applying the Eliturbo’s thermal and humidity destratification capabilities to HVAC
installations at the design phase will lower the initial investment needed as well as save energy costs
over time.
Eliturbo = Air MIXING, Not Pushing
The Eliturbo Air-Mixer recycles air continuously throughout a space, preventing the stratification of
temperature and buildup of humidity.
Traditional blade ceiling fans or turbine type fans attempt to destratify the air in a space by pushing
warm air from the ceiling downward to the floor, creating a turbulent, narrow column of air resulting in
uncomfortable drafts, the stirring up of dust, and, as fans work only in vertical columns, they often do
not cover the entire space needed. What’s more, once strong fans have “emptied” the ceiling area of
heat, they need to be turned off awaiting a new build up so that they can then be turned on again to
forcefully push the heat down. From all of this, one can easily conclude that these types of fans are a
very incomplete solution to thermal stratification and humidity accumulation problems.
Eliturbo on the other hand, leverages a set of uniquely designed, heli-centrifugal curved blades that
create a fluid-aerodynamic, “convergence-divergence” action, mixing the air continuously without
producing unnecessary turbulence and downdrafts. The result is no accumulation of hot air at the
ceiling, no costly stopping and starting of heating systems and no dust stirred up. Eliturbo works
constantly creating, in effect, its own low-velocity micro-climate.
The two graphical renderings above (excerpted from the Eliturbo Air-Mixer patent) show the key design
factors of curved heli-centrifugal blades and exterior “open enclosure” that creates the unique airmixing capabilities of the Eliturbo. The benefits of their revolutionary design are detailed below.
VERTICAL MIXING
The Eliturbo Air-Mixer is a complete solution to heat stratification and humidity build-up. The way it
works, is both quite complicated and quite simple. Referring to the drawing below:
Cooler air is drawn from below the unit, while at the same time
warmer air is drawn from above. These streams are mixed in
the interior of the Eliturbo unit and expelled horizontally and
radially in all directions (360°) through sloped deflectors
creating ‘convergence – divergence’.
The air is expelled at a low speed, forming a cylindrical
circulating cell defined by its throw radius. Air slowly travels
downward along the walls to the floor and back up to the units
without strong drafts, promoting vertical mixing and
preventing heat stratification.
Continuous mixing of air throughout the space provides even distribution of heat, humidity and
pressure, with minimal controls and maintenance.
Horizontal Mixing
The Eliturbo Air-Mixer distributes temperature mixed air radially, dispersing it in 360° as it exits the unit.
In doing so it balances the temperature throughout a space horizontally at the same time as it
destratifies the heat vertically. The Eliturbo insures the temperature is evenly distributed thereby
making heating systems more efficient in this way as well.
The illustrations below show how installed Eliturbos work to distribute air/heat evenly throughout a
space.
Heating systems push air into a space
creating pockets of hot and cold
With Eliturbos deployed the heat is
balanced throughout the building
Heating Elements pushing air into a space


The Eliturbo air-mixers are manufactured with ‘clock-wise’ or ‘anti-clockwise’ rotation and are
best installed in a ‘checker-board’ fashion with each Eliturbo rotating in an alternate direction to
the adjacent units.
Air expelled from an Eliturbo unit rotating clock-wise encounters air expelled from an adjacent
unit rotating counter-clockwise and is similar to meshing gears. Less fan energy is lost due to
unnecessary turbulence.
The Advantages of the Eliturbo Air-Mixer:
As has been shown so far, there are many advantages to the Eliturbo. Clearly, having no thermal
stratification provides huge advantages in cost savings, comfort and machinery and people safety vs. a
stratified environment. Further, the Eliturbo’s continuous air-mixing is superior to any “classic” fan type
point, air-pushing solutions.
Destratified air results in dramatically lower ceiling temperatures, lower heat loss through roof and
upper wall areas, and lower energy costs. Typically the savings amount to 20 to 30% on heating bills. A
heating unit may be the right size for the volume of a space, but without an efficient method to
distribute the heat to the lower levels of the space, two things will happen:
1. the space will have inconsistent temperatures, and/or
2. the heating unit will work overtime, continually providing heated air at work level, which
will quickly rise to the ceiling.
Eliturbos take the heated air and
distribute it evenly throughout the space
To recap the benefits of Eliturbo Air-Mixing are:
In Winter
 Reduction of thermal stratification between floor and ceiling resulting in uniform temperature
within different vertical zones of a structure.
 Considerable improvement in comfort in the work space with the heat designed for occupants
comfort, remaining at the human level (floor to 6-7 feet).
 Reduction in heat loss through roof and wall areas.
 Better use of the heat generated by heating unit and/or heat produced by machinery.
 Reduced needed capacity, running time and therefore energy costs of heating units.
 Less wear and tear on heating unit (less frequently turned on and off).
 Minimal air turbulence at floor level and very little stirring of dust improving worker comfort
and extending machinery life.
 Reduction in heating differences throughout a space.
 Reduced air stagnation in isolated areas of the space (corners, behind equipment, etc.)
 Reduces risk of condensation forming on machinery, walls, windows, etc.
 Overall energy savings and increased worker comfort.
In Summer




Greater exchange/recycle of air through ventilation.
Greater efficiency of natural ventilation.
Reduced concentration of odors/fumes.
Reduced areas with stagnant, high humidity in isolated areas of the space (corners, behind
equipment, etc.) resulting in increased life and decreased maintenance for machinery.
 Reduces risk of condensation forming on machinery, walls, windows, etc.
 Greater efficiency of air conditioning units.
Economic advantages of the Eliturbo Air-Mixer
Installing Eliturbos in existing structures can reduce energy consumption costs immediately leading to
the capital investment being paid back within the first year. Therefore, all subsequent years’ energy cost
savings would go straight to the bottom line as the
maintenance costs of Eliturbo are basically zero.
Sample Industrial Building
Surface Area
Ceiling Height
Internal Volume
Required Heat
33,000 sq. ft.
26.25 feet
866,250 cu. feet
2,453,500 BTU/hr
719 kW
To show an example of how this works using real
costs, using the same sample building from above, the
heating need for this structure is approximately
2,400,000 BTU/hr. or 57,600,000 BTU per day.
The most cost effective power/heating source, readily available in the US today is natural gas and the
Oppenheimer investment and analysis firm predicts that industrial natural gas prices will stay between
$3.50 and $4.50 per 1,000 cubic feet (McF) over the next year as increased demand consumes the
“storage overhang” and production aligns better with consumption (1). The US Energy Information
Administration states that each McF produces energy of 1,021,000 BTUs.
BTU X McF
BTU/Hr Needed
Cost per Mcf
Cost per BTU/Hr
Cost per day
Cost per month
Cost per winter
Cost for 12 Eliturbos
Reduction in heat loss
from destratification
Heating Savings
$
$
$
$
$
1,021,000
2,453,500
4.00
9.61
231
6,921
48,445
$
9,600
$
20%
9,689
The table to the side shows how by reducing heating loss
by just 20% through reduced stratification, the cost of
installing 12 Eliturbos in this sample industrial building will
be recuperated within the first year.
The calculations for heat needed come from the site of a
major manufacturer of industrial heating units and using
modern code U-Factors. In older buildings with with
higher U-Factors the payback period for installing
Eliturbos will be even shorter.
Additional savings associated with installing Eliturbo Air-Mixers with existing and new HVAC systems
come from:
1) The ability to reduce the thermostat to achieve the desired temperature at human level by
destratifying the air and therefore no longer needed to overheat a space at the ceiling in order to get
the right ambient temperature. The US Energy Administration estimates that 3-5% of heating costs are
saved for every 1°F a thermostat can be lowered; and
2) Reducing the size and quantity of heating units needed as thermal destratification closes the gaps
between theoretical heat loss calculations and actual heat loss
Summary
As shown throughout this white paper, heat or thermal stratification is a major cost to organizations.
Reducing thermal stratification can provide significant savings on energy costs and, if achieved via the
right technology, can noticeably improve the environment for working and for machinery.
The Eliturbo Air-Mixers revolutionary method of continuously mixing air to balance temperatures and
humidity both vertically and horizontally instead of simply pushing air, provides a more complete
solution than classic fan alternatives.
An organization that installs Eliurbo Air-Mixers to resolve thermal stratification and humidity issues can
expect to see payback for the investment within the first year and then enjoy the long-term,
maintenance free economic and workplace comfort and efficiency benefits from that point forward for
many, many years to come.
Copyright 2013: Import – IT LLC . All rights reserved.