Texti le Based Venti lat ion

Design Guide for Textile Ducting

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CHOOSE SUSTAINABLEVENTILATION

All KE Fibertec textiles are tested and approved according to the Oeko-Tex® Standard 100.

Our production is certified according to the ISO 14001 standard (Environmental Management System).

Transportation and disposal of textile duct systems produce less CO2 pollutants than conventional steel ducts.

W H A T I S A T E X T I L E D U C T ?In principle a textile duct (also called a ventilation duct) is a round, semi-round or quarter round duct made of a light-weight textile material instead of e.g. galvanized steel, stainless steel or aluminium, designed for delivery and distribution of cooled or heated air.

Read more at ke-fibertec.com/TBV

Why chooseTextile Based Ventilation?

Flexible and customized solutions >

Efficient and draught-free air distribution

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Quick installation and adjustment>

Fire approved materials>

Unique materials and colours>

Hygienic and washable>

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KE Fibertec offers advice and support from our experi-enced in-house sales engineers, who have all undergone extensive training on ventilation products and particularly on our TBV products. All the calculations are proven using our unique software WinVent 3D, which is offered to all our customers, regardless of the size of their project and, of course, free of charge.

Our quotation and design processes are described in detail in our ISO 9001 quality assurance system. This ensures that we prepare the basis for the quotation and the quota-tion itself according to the standardised guidelines, mak-ing sure that the customer’s requirements are specified and documented in sufficient detail.

KE Fibertec puts large emphasis on ensuring that the final solution is designed correctly even at the quotation stage. After all, it is not only about ensuring that the textile based ventilation system works properly, but also, to just as large extent, that the customer’s indoor climate re-quirements have been met. This is why we ask about the system’s functional requirements and the requirements for the indoor climate at the quotation stage.

Our quotation is based on the following information:

• Air volumes (possibly partial air volumes per socket) [m3/h]

• Temperature-set cooling and possibly heating [°C]

• Pressure available from the fan [Pa]

• Dimensions of the room L x W x H [m3]

• Location of the air inlet(s)

• Requirements on number of ducts and maximum duct dimensions

• Requirements on the room’s use (room category)

• Requirements on maximum permissible air velocity in the room [m/s]

• Requirements on the temperature in the room [°C]

• Requirements on the maximum sound pressure level in the room [dB(A)]

• Selection of duct colours

• Selection of suspension type

Given that an infinite number of combinations of system solu-tions and layout features can be designed for textile based ventilation, it is important that its function is specified precisely at the quotation stage.

In our role as consultants, we always endeavour to meet the relevant need with the solution that we have agreed with the customer to offer. We are highly innovative in our way of think-ing, which is why you must not always expect just a “plain” so-lution which ultimately cannot meet the requirements you set in terms of the system’s appearance and the indoor climate.

Our solution is based on the concept “AIR THE WAY YOU WANT” for the same reason.

Q U O T A T I O N A N D D E S I G N P R O C E S S E S

KE-Low Impulse System: A = diameter · p · duct length

KE-Interior System (D) A = (1/2) · diameter · p · duct length

KE-Interior System (½D) A = (1/4) · diameter · p · duct length

D I M E N S I O N I N G T B V S Y S T E M STo be able to dimension a textile based ventilation system, it is important to understand a number of essential parameters and concepts. A textile based ventilation system is not fundamentally different from conventional ventilation systems, but there are a number of key points where it is important to be extra cautious. A brief description is given below of the key parameters and concepts used when dimensioning KE Fibertec’s textile based ventilation systems.

The entire surface of the KE-Low Impulse System is permeable, which means that the total delivery area corresponds to the geometric surface area. The geometric surface area, A, is given in [m2].

In the case of the KE-Inject System and KE-Inject Hybrid System, KE Fibertec has, for the sake of manufacturability, grouped the holes in different standard patterns, depending on which type is selected. A standard pattern is made up of an exact number of hole steps and the delivery area can only be modified by changing the number of hole rows. Consequently, the unit, number of hole rows, is used as a parameter for the delivery area of the KE-Inject System. In the case of the KE-Inject Hybrid System, the whole of the duct’s surface, including the holes, will act as the delivery area.

In the case of the KE-DireJet System and KE-DireJet Hybrid System, the delivery area depends on whether a Ø12 mm, Ø18 mm, Ø24 mm, Ø48 or Ø60 mm nozzle is selected, as well as how many nozzles are used per running meter of ducting. With the KE-DireJet Hybrid System, the whole of the duct’s surface, including the nozzles, will act as the delivery area.

D E L I V E R Y A R E A

P E R M E A B I L I T YAir permeability through the textile material’s surface is crucial to how great the static pressure will be for a given volume flow. The tighter the material’s weave, the higher the pressure will be as a function of volume flow. For all KE Fibertec’s low impulse materials, the static pressure increase is given as a function of volume flow per m2 of the textile material’s surface. Permeability is expressed in the unit [m³/m²/h].

KE-Low Impulse System

KE-DireJet System

KE-Inject System

P s

P t

P d

Flow

P t

Flow P t

P s

P s

Flow

Pt = Ps + Pd

Where:Pt Total pressure in the duct [Pa]Ps Static pressure in the duct [Pa] Pd Dynamic pressure in the duct [Pa]

P R E S S U R E C O N D I T I O N S I N T E X T I L E D U C T SAs in any other air distribution system, pressure losses also occur in textile based ventilation systems. Calculating the pressure losses in a textile based ventilation system is not basically any different from the generally known practice. The flow in a duct system is only dependent, to a limited extent, on whether the material is made of steel or fabric. However, what is important to be clear about is that textile material is very flexible and it is only kept inflated by the static pressure in the system. As a result, even small turbulences can cause pulsations. This is why it is very important to perform pressure loss calculations to ensure that the textile based ventilation system is operating as it is supposed to without any pulsations, as well as ensuring the best possible energy economy.

D E F I N I T I O N S O F P R E S S U R EThe types of pressure that occur in a textile based ventilation system are shown in the figure on the right. The total pressure (Pt) can be calculated anywhere in a textile based ventilation system as the sum of the static and dynamic pressures.

The following expression applies:

Total pressureThe total pressure is the pressure that needs to be produced by the fan to overcome the total resistance in the textile based ventilation system, i.e. the loss from the individual types of resistance, such as elbows, frictional loss and the static pressure in the system.Static pressureThe static pressure, which is measured in relation to atmospheric pressure, has an identical impact in every direction and keeps the textile material inflated, as well as pushing the air out through the holes/nozzles. Dynamic pressureThe dynamic pressure, or velocity pressure, has an impact on the direction of the air and carries it from A to B. The dynamic pressure is related to the mean air velocity in the duct and is calculated using the following expression:

Where:r Density of the air [kg/m3]v Mean air velocity in the duct cross section [m/s]

Pd = ½ · r · v2

• Across cross section modifications • Across branches• Across elbows• Friction• Across flow components (SRD’s) • Across holes, nozzles and textile material (“fittings loss”)

The pressure loss which occurs in a textile based ventilation system originates from the following sources:

It is very obvious when a textile based ventilation system has been dimensioned incorrectly because the ducts will be oval and “sagging” when you look at them. The difference in the static pressure between two parallel ducts may be quite considerable too. This not only has an impact on the aesthetic appearance, but to a great extent also on air distribution. If the pressure distribution is uneven this can cause draught problems below and around the duct with the highest static pressure, while in the opposite case, the air quality will be poor in the area where the static pressure (and therefore the volume of air) is not sufficient.

P R E S S U R E L O S S I N T E X T I L E D U C T S

Where:x Pressure loss coefficient [-]Pd2 Dynamic pressure after the component [Pa]

KE Fibertec AS has documented pressure loss measurements for all the components featuring in our TBV systems. Contact us for further information.

The pressure loss across these various components is a loss that is related to the velocity, and thus is proportional to the dynamic pressure, Pd, and dependent on what is known as the pressure loss coefficient, which is found when measurements are taken in KE Fibertec’s full-scale laboratory. The pressure loss across a component (DPe ) is determined using:

DPe = x · Pd2

120 110 100 90 80

Flow

P t

P d

P s

[Pa]

0 25 50 100 75 [%]

Flow

P t

P d

P s

120 110 100 90 80

[Pa]

0 25 50 100 75 [%]

P t

P d

P s

5,0

4,0

3,0

2,0

1,0

Længde af kanal [m]0 10 20 30 40 50 60 70 80 90 100

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P P [-]s d

Length of duct [m]

P s / P d R A T I OAs a result of their permeable surface, the volume of air and air velocity in textile ducts, unlike in ordinary steel ducts, continually decreases along the duct. This means that the dynamic pressure falls along the duct, while the static pressure rises. This results in a large portion of the air being delivered at the end of the duct where the dynamic pressure is zero. As the volume of air continually decreases along the duct friction loss may often be ignored. This means that the total pressure and static pressure will be more or less identical at the bottom of the duct.

One solution frequently used to ensure that air is distributed uniformly through very long ducts is to restore the dynamic pressure in the system by inserting a duct reduction, in the middle of the duct, for instance. This will break the static pressure in the duct, thereby achieving a more even distribution of air. This is also the most economical solution if duct reductions are acceptable. To facilitate installation, single suspended ducts should have duct reductions with flat edge on top, while double suspended ducts should have centred duct reductions.

In order to produce a uniform distribution of air along the entire system’s longitudinal direction, the static pressure in the middle of the textile duct should always be at least double that of the dynamic pressure in the duct’s inlet. KE Fibertec recommends that the ratio between the static pressure, Ps, and dynamic pressure, Pd, should at least follow the curve on the right. The longer the duct is, the higher the static pressure needs to be in the middle of the duct in relation to the dynamic pressure in the inlet, in order to ensure that the air is distributed uniformly.

M A X I M U M I N L E T V E L O C I T I E SThe inlet velocity is a critical design parameter for textile based ventilation systems as it has a major impact on aspects such as pulsation, noise gen-eration, the material’s durability and the air dis-tribution from the duct. The recommended inlet velocity for round ducts is no more than 6-8 m/s, depending on the entry method.

KE Fibertec ASIndustrivej Vest 21DK-6600 Vejen

Tel. +45 75 36 42 00Fax +45 75 36 20 20www.ke-fibertec.com

ke-fibertec.com/intex

I N T E X ® - I N T E L L I G E N T T E X T I L E D U C T S

Be notified when the textile duct needs cleaning. This is the idea of InTex® which monitors the air pressure of your textile based ventilation system. InTex® will result in a healthy indoor climate and energy savings that will benefit both the environment and the operating economy of the plant.

All ventilation ducts, steel or textile, must be cleaned regularly in order to stay efficient. The InTex® sensor makes it easy to keep the textile ducts operational to ensure that they always provide draught-free air distribution and a good indoor climate.

See documentation and cases at www.ke-fibertec.com

KE Fibertec AS is market leader in Tex-tile Based Ventilation. We create good indoor climate through our tailored textile ducts for installation in sports arenas, offices, laboratories, schools etc. Textile ducts are customizable, easy to install, washable, hygienic, and come in all shapes and colours. For more information visit ke-fibertec.com.

This Guide is an extract of KE Fibertec’s technical cata-logue. E-mail to info@ke-fibertec.dk to order the entire catalogue.

ke-fibertec.com/intex