Energy-Efficient Room Ventilation with the System TwinXchange

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Intermittent, non-steady air-handling with reversing regenerator
Energy-Efficient Room Ventilation
with the System TwinXchange
Technical information on energy-efficient room ventilation systems with high-performance
heat recovery – compiled for consultants, engineers and builders/installers of ventilation and
air conditioning equipment as an aid in designing, planning and specifying cost-effective air
handling solutions
The experts for energy-efficient air conditioning technology
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System TwinXchange
Energy-efficient room ventilation with high-performance heat recovery
Reversing regenerators can attain high thermal
transfer efficiencies of up to around 90%.
The System TwinXchange differs from known
heat recovery concepts (e.g., run-around coil
systems, thermal wheels) in that the storage
masses are not continuously moved from the hot
towards the cold airflow. Instead, they are switched back and forth by changeover dampers
between the heat absorption and desorption
cycle.
The key advantage of the System TwinXchange
with its intermittent operating mode over conventional technologies lies in the fact that the
number of components of the air-handling unit
– and hence, of the entire HVAC system – is effectively minimized.
Conventional room ventilation air-handling units
comprise an extract air unit and a supply air unit,
both of which are continuously in operation.
The System TwinXchange - our new energy-efficient room air ventilation solution - needs only
one fan, one filter and one heat exchanger (regenerator) which is used alternately for both
supply air and extract air modes.
In industrial plants, warehouse buildings and re-
The benefits of this new energy-efficient
room ventilation technology - based on a reversing regenerator plus high-performance
heat recovery - can be summarized thus:
reduction of steady indoor air currents
lower mean air flow velocities in the room
optimum ventilation efficiency
improved ventilation quality
Design advantages include the following:
clear minimization of components within
the unit
- only one fan
one filter
one heat exchanger
clear minimization of overall system
components
- only one air duct serving both directions
The new energy-efficient System TwinXchange: intermittent room ventilation AHU with reversing regenerator
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System TwinXchange
Efficient room ventilation with obvious cost savings
tail environments, a large number of units are
commonly installed to ensure a uniformly effective ventilation. With the System TwinXchange,
the same result can be attained with a minimum
of just two units.
alternately discharges extract air and supply air,
it would, in theory, have to be designed for
twice the airflow rate to achieve the same air
change rate, given that each unit conveys the respective airflow rate for only half the time.
How is this achieved? While one-half of the new
system operates in air extract mode, the other
works in supply mode. Ventilation effectiveness
is thus substantially improved and the room air is
mixed much more thoroughly, given the "burst"
effect of the non-steady airflow.
However, comparative CFD simulations (Computational Fluid Dynamics) carried out for both the
new system and a conventional ventilation unit
have shown that the required number of air
changes can in fact be reduced due to the intermittent operating mode (non-steady flow). The
pulsed ventilation principle provides a significant
improvement in air quality.
In normal operation, effective ventilation and increased convenience can be ensured even with
The pulsed airflow creates a markedly higher induction so that steady currents within the room
will be avoided. Since the System TwinXchange
Flow simulations
Optimized
design for
thermal
transfer rates
up to 90%!
A comparison of both system reveals that the
temperature distribution in the central room
plane, as well as the CO2 concentration marked
by the tracer medium, are lower and more ho-
mogeneously distributed if a non-steady ventilation airflow – or, in other words, the System
TwinXchange – is employed.
Special information
available - order or
download now!
System TwinXchange
non-steady room air currents - air change rate: 1
Conventional ventilation system,
steady room air currents - air change rate: 1
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CFD simulation
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System TwinXchange
It is evident from the CFD simulations that despite higher discharge velocities across the grille,
average flow velocities in the room are lower
and less directional. As a result, convenience and
comfort levels are increased since the induced
non-steady air current (diffuse flow field) allows
fewer stationary air circulation cells to build up
in the room.
The middle image illustrates the very homogeneous distribution of temperatures in the central
room plane and of the CO2 concentration marked by the tracer substance. It emerges that the
system provides clearly superior results when
compared to a conventional steady-type ventilation unit.
System TwinXchange: non-steady room air currents – air change rate: 1
Conventional ventilation system: steady room air current – air change rate: 1
Conventional ventilation system: steady room air current – air change rate: 2
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System TwinXchange
High-performance heat recovery
lower flow rates. At the same time, higher temperature differences can be tolerated due to the
superior temperature distribution.
To ensure a straightforward and effective supply
of thermal energy, HOWATHERM's engineers
have developed an efficient, compact heat recovery system suitable for intermittent operation.
At the core of this concept lies a heat recovery
system based on a reversing regenerator - a
technology that was key to the development of
this innovative air-handling unit which conveys
supply and extract air on an intermittent basis.
Thermographic view of the temperature distribution
inside the regenerator
Function of the System TwinXchange
The system efficiently stores heat from the extract air in extract mode, then releases it to the
supply airflow in a uniform and efficient manner
in supply mode. In other words, heat is transferred from the extract air to the supply air current
discontinuously via a heat storage cycle.
Recommended applications for the
TwinXchange air
ventilation system:
Industrial
buildings
Theatres /
cinemas
Event halls
Multipurpose
arenas
Sports facilities
DIY superstores
consumption and technical complexity are significantly reduced.
If additional primary energy should prove indispensable in a given application, it can be provided, e.g., by static heating surfaces in the room.
Due to the unit's intermittent operating mode,
one no longer needs to distinguish between extract air and supply air units in terms of design.
The requisite duct system can double as supply
and extract air ducting.
Since the System TwinXchange embodies an efficient high-performance heat recovery capability,
no additional primary energy carrier in the airflow is necessary. As a result, both its energy
Regenerator fins made of aluminium, copper or
coated aluminium
TwinXchange schematic diagram
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System TwinXchange
High-efficiency room ventilation using regenerative energies
reduced in this mode and electric power is saved.
If the AHU is used as a smoke extraction device,
the integrated bypass dampers may also serve to
bypass the heat exchangers.
Not least significantly, HOWATHERM high-performance heat exchangers attain high heat
transfer coefficients – a necessary condition for
optimum heat transfer. Needless to say, even in
intermittent mode this transfer of heat must
take place exclusively in counterflow since it is
only in counterflow that a heat exchanger can
achieve maximum transfer rates. To this end, the
regenerator is equipped with an integrated flow
reversing feature.
With optimized design, it is thus possible to attain thermal transfer rates of up to 90%. The differential pressure across the heat recovery
system will remain within the standard 200 Pa
limit.
This integrated flow reversal also allows the
dampers to serve as a bypass device if the heat
recovery function is controlled or not needed,
e.g., in an isothermal operating state. The bypass
dampers are also useful to prevent the unit from
icing up. As a result, pressure losses are clearly
Leakage across the control and shut-off dampers
affects the heat recovery efficiency. For energy
efficiency reasons, we therefore use air-tight,
fast moving dampers to minimize leakage during both during the operating cycle and during
the reversing operation.
Performance testing by TÜV Süd
As part of the prototype tests, the system's performance levels and pressure losses were confirmed
by TÜV Süd in accordance with DIN EN 308.
The measurements yielded an average daily dry
heat recovery efficiency of 73.2 % (74.4% average
across the measuring cycle, 80% peak recovery efficiency) at a maximum pressure loss of 145 Pa.
Curve of the measurement series over the air supply cycle
Flow testing with air discharge head (in the foreground) and extract air intake (at back)
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System TwinXchange
Optimum ventilation effectiveness
In most cases the internal building loads will suffice as a heat source so that no additional primary energy in the airflow will be needed. By
utilizing this principle we can effectively minimize the number of AHU components. For you,
this will translate into high investment and operating cost savings.
Since only one air duct is alternately used for
both air supply and extract modes, a much-improved ventilation effectiveness (i.e., more thorough intermixing of air in the room) is
obtained.
Flow simulations have shown that the necessary
number of air changes is substantially reduced
by the intermittent ('burst') operating mode
since the air quality is greatly improved by the
pulsed ventilation principle. As a result, comfort
levels in the room will likewise be enhanced significantly. Ultimately, therefore, benefits are
obtained not merely at the economic level – i.e.,
in terms of equipment size – but in terms of occupant convenience as well.
Patented design
The System TwinXchange is patented as an "Intermittent Reversing Regenerator" AHU under
No. DE 10 2007 012 198.0 by the German Patent
Office.
For more detailed information on the physics,
storage capacity and heat transfer of this rege-
nerator please consult our special off-print of
the technical report "New Room Ventilation Method using High-Performance Heat Recovery",
which can be downloaded from the Internet at
www.howatherm.de. You may also order your
hardcopy version there.
Module with damper control drive
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System TwinXchange
Key benefits for you
The new intermittent-operation AHU system
provides you with standardized air-handling
units featuring
highly-efficient heat recovery
high heat exchange rates (up to 90 %)
operating capability without additional
afterheating.
Damper actuation for bypass mode
Air flow in supply and extract mode
Air flow in extract mode System TwinXchange with
reversing regenerator
Air flow in supply mode System TwinXchange with
reversing regenerator
Nominal dimensions / Performance data - System TwinXchange
Size / type
Air flow capacity (m3/h)
Height + baseframe* (mm)
Width (mm)
Length (mm)
Weight (kg)
Mean heat recovery transfer rate (%)
*
2.0
3.500
1035
1035
4425
1085
78
4.0
7.000
1365
1365
4755
1640
77
6.0
11.250
1695
1695
5415
2348
77
9.0
16.500
2025
2025
5745
3159
77
Unit height not including baseframe (150 mm)
For outdoor-mounted units up to size 6.0 please add 660 mm to length shown
Project-specific variations available
12.0
22.500
2355
2355
5745
3948
77
>#<
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Excerpt from our references:
Aachener Münchener Versicherungen, Köln • Aachener Quarzglas, Aachen • Archiv Dommusik, Würzburg • B. Braun AG,
Melsungen • BASF Coatings AG, Münster • Bayer Schering GmbH, Berlin • Bayer Schering Pharma AG, Wuppertal • BIOLAC GmbH &
Co. KG, Harbarnsen • BMW, Düsseldorf • BNP Paribas, Luxembourg • Boehringer Ingelheim Pharma GmbH & Co. KG, Ingelheim • Burger King, Ramstein • Carl Zeiss Jena GmbH, Jena • Centre Hospitalier Emile Mayrisch, Niedercon Luxembourg • Centre Hospitalier
Luxembourg, Luxembourg • CERN Conseil Européen pour la Recherche Nucléaire, Genf Schweiz • Chocoladenfabriken Lindt & Sprüngli GmbH, Aachen • CNSC Centre National Sportif et Culturel D´Coque, Kirchberg Luxembourg • Cognis, Düsseldorf • Cour des
Comptes Europäischer Rechnungshof, Kirchberg Luxembourg • Covance Laboratories GmbH, Münster • Crucell GMP, Leiden Niederlande • Decoma Exterior Systems GmbH, Obertshausen • Degussa AG, Wesseling • Die Fernsehwerft GmbH, Berlin • 3M Deutschland GmbH, Kamen • AG der Dillinger Hüttenwerke, Dillingen • DLR Deutsches Zentrum für Luft- und Raumfahrt,
Hardthausen-Lampoldshausen • Dorint Hotel, Köln • Dr. August Oetker Nahrungsmittel KG, Wittlich • Dr. Kade Pharmazeutische Fabrik GmbH, Konstanz • Evonik Power Saar GmbH, Völklingen • Fachhochschule Weihenstephan, Freising • Ford GmbH, Saarlouis •
Fraunhofer Institut für Grenzflächen- und Bioverfahrenstechnik IGB, Stuttgart • Fresenius SE, Biebesheim • Geschäftshaus Louis
Vuitton, Luxembourg • Goodyear Dunlop Tires Germany GmbH, Riesa • Grünenthal GmbH, Aachen • Helios Klinik, Berlin Buch • Henkel AG & Co. KGaA, Düsseldorf • Henning von Tresckow Kaserne, Geltow • Hermes Pharma GmbH, Wolfsberg Österreich • Hexal
Pharma GmbH, Radebeul • Hilton Hotel International Germany GmbH, München • Hilton Hotel International Germany GmbH, Dresden • Hirschvogel Umformtechnik GmbH, Denklingen • IBM, Mainz • IFA Leipnitz-Institut für Arbeitsforschung der TU, Dortmund •
Johannes Gutenberg Universität, Mainz • Kernkraftwerk Krümmel, Gheesthacht • Kerrygold Butterverarbeitungswerk, NeukirchenVluyn • KKW Kernkraftwerk, Mülheim-Kärlich • Klinikum der Universität, Heidelberg • Knorr Unilever Deutschland GmbH, Bremen •
Kunstsammlung Nordrhein-Westfalen, Düsseldorf • Ludwig Schokolade GmbH & Co. KG, Saarlouis • MAN Ferrostaal AG, Essen • Maredo Restaurants Holding GmbH, Mainz • Mariott Hotel International Ing., Frankfurt • Merck KGaA, Darmstadt • Merck Serono, Zug
Schweiz • MLU Martin Luther Universität, Halle Wittenberg • MOBOTIX AG, Winnweiler • Molkerei Ammerland eG, Dringenburg • MPI
Max Plank Institut, Göttingen • Musee National, Luxembourg • Neurologisches Rehabilitationszentrum, Bad Godesberg • Novartis
Behring, Marburg • Orangerie Café-Restaurant, Ansbach • Pfanni Unilever, Stavenhagen • Pizza Wagner Tiefkühlprodukte GmbH, Otzenhaus • Pressehaus, Stuttgart • Q-Cells SE, Thalheim • Qiagen, Hilden • Rentschler Biotechnologie GmbH, Laupheim • Residenztheater Bayerisches Staatsschauspiel, München • Roche Diagnostics GmbH, Penzberg • RWE, Dortmund • RWTH
Rheinisch-Westfälische Technische Hochschule, Aachen • Sanofi-Aventis, Frankfurt • Schott Glaswerke AG, Mainz • Sheraton Hotel,
Frankfurt • Sinnack Backspezialitäten GmbH & Co. KG, Bocholt • SMA Solar Technology AG, Kassel • Solon SE, Berlin • Staatsbibliothek zu Berlin - Preußischer Kulturbesitz, Berlin • Thüringer Pharmaglas GmbH, Neuhaus • ThyssenKrupp Steel AG, Duisburg •
TICONA, Kelsterbach • TIKO Kaufland, Dortmund • TIKO Kaufland, Bulgarien • TRIDOMUS Medizinische Fakultät der Universität
Heidelberg, Mannheim • TU Technische Universität, Garching • Tutogen Medical GmbH, Neunkirchen am Brand • Unilever Deutschland Holding GmbH, Heilbronn • Universität, Leipzig • VDI Haus, Düsseldorf • Vetter Pharma GmbH, Langenargen • Villeroy & Boch
AG, Mettlach • Winterberg Klinikum, Saarbrücken • ZDF Nachrichtenstudio, Mainz • Zentis GmbH & Co. KG, Aachen • Zentrum für
Biochemie u. Molekulare Zellforschung ZBMZ der Universität, Freiburg • • •
HOWATHERM Klimatechnik GmbH
Manufacturers of energy-efficient ventilation and air conditioning products
Keiperweg 11-20
55767 Brücken / Germany
Phone: +49 6782 9999-0
Direct Call phone: 0700HOWATHERM
Telefax: +49 6782 9999-10
E-mail: [email protected]
Further product
information available
upon request:
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Technical information on energy-optimized modular air-handling units (AHU) with more than 80%
Technical information on air-handling units, energy-efficient room ventilation techniques
and HOWATHERM components – compiled for planners, engineers and builders/installers
of ventilation and air conditioning equipment as an aid in designing, planning and
specifying cost-effective air handling solutions.
Technical information on energy-optimized AHU fan systems – compiled for planners, engineers and
Technical information on heat recovery systems based on counterflow heat exchangers – compiled
builders/installers of ventilation and air conditioning equipment as an aid in designing, planning and
for planners, engineers and builders/installers of ventilation and air conditioning equipment as
specifying cost-effective air handling solutions
an aid in designing, planning and specifying cost-effective air handling solutions.
The experts for energy-efficient air conditioning technology
The experts for energy-efficient air conditioning technology
The experts for energy-efficient air conditioning technology
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"Air-handling units"
Air-Handling Units
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Air Handling
Systems and
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Highly efficient
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efficiency – compiled for planners, engineers and builders/installers of ventilation and air conditioning
equipment as an aid in designing, planning and specifying cost-effective air handling solutions.
The experts for energy-efficient air conditioning technology
Technical information
"Energy-efficient fan systems"
Technical information
"System HPWRG"
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Ed. 05/2011
Development: eka;MedienStudio, Frankfurt
Design: Atelier Schiller-Krenz, Frankfurt
Printing: HBO-Druck, Einhausen
Air Handling Systems and
Components