| FREQUENTLY ASKED QUESTIONS |  |
| 1/What does a textile diffuser look like when the fan is switched off? | |
 |
|
| 2/ Is it possible to use textile diffusers for air outlet? | |
Příhoda
s.r.o. were the first worldwide to introduce textile diffuser on
the market. It is made with quadrangle or triangle cross-section.
The principal is based on sufficient stretching of all ducting walls
by means of tensioning system. The construction enables simple disassembly
and re-installation. Perforation is used for air inlet in the ducting.
|
|
|
|
|
| 3/What is the service-life duration of textile diffusers? | |
This
is not a short term solution. Diffusers made from good quality
fabrics will last for fifteen years or longer. Light fabrics (approx.
100 g/m2) with maximum permitted number of 50 washing procedures
(typically polyethylene foils susceptible to tearing) may have
limited durability.
|
|
| 4/ What is the pressure loss of a textile diffuser? | |
In
a well designed diffuser which does not utilise shaped pieces there
is an almost constant static pressure throughout. The fabric perforation
is calculated based on the average value of the static pressure.
In other words, the diffuser is designed based on the fan's external
pressure to which it is adapted. Shaped pieces and turbulence equalisers
present certain pressure loss which needs to be taken into consideration.
Loss caused by friction is usually minimal due to the decreasing
air speed inside the diffuser. The minimum utilisable pressure
is 50 Pa, with light materials 20 Pa. |
|
 |
 |
| Typical static and dynamic pressure progression inside the diffuser. | Washing-instruction tag |
| 5/What to do with diffusers when they get clogged by contamination? | |
Diffusers
with micro-perforation and even diffusers with larger holes never
get completely clogged by contamination (if used with minimum pre-filtration
EU3). The maintenance (typically washing in a washing machine)
is therefore necessary for hygienic and aesthetic reasons only.
Each individual piece separable by a zipper contains a washing-instruction
tag which contains sufficient instruction for washing. Our experience
has proven that our fabrics made of endless fibres remain internally
almost clean even after many years of operation.
|
|
| 6/Can textile diffusers get mouldy? | |
Mould
can form on any kind of material if it is moist and unventilated.
This goes for fabrics with antibacterial treatment, too. It is
caused by the fact that moulds are not bacteria. Therefore, never
store moist diffusers packed-up or do not let them out of operation
for long periods of time. Moulds cannot be removed from fabrics
by any means.
|
|
| 7/ Is it possible to use quadrangular diffusers? | |
Příhoda
s.r.o. has developed a special construction which enables to use
quadrangular cross-section. The principal is based on stretching
the fabric in transverse and longitudinal direction by means of tensioning
system. The construction enables simple disassembly and re-installation.
Fabric ducting with quadrangular cross-section can be assembled directly
on the ceiling or suspend in the area
|
|
|
8/ Does the textile diffuser function as a filter at the same time? |
|
If
permeable materials are used, the fabric functions as a filter for
the part of the transferred air that goes through the fabric. As
the fabric contamination gradually increases, the pressure loss grows
and the air flow decreases. Therefore, it is necessary to wash the
fabric. We consider the utilisation of perforated fabric to be by
far the best solution. Although perforated fabrics do not function
as filters they do not change the pressure loss value and the number
of necessary washing procedures significantly drops. We are a manufacturer
of distribution (not filtering) elements.
|
|
|
|
|
| 9/ Why Prihoda s.r.o. does not use plastic nozzles or slots | |
Use of plastic nozzles or longitudinal slots of sieve can
be explained on historical basis. These tools used to enable directing
of certain airflow, the nozzles in addition stiffened the burred margins
of the holes. When they began to use laser technology that allows cutting
of accurate holes with sealed margins, their utilization became useless.
Rightly designed rows of holes fulfil the same purpose, whilst being
cheaper and nicer. This is the reason why Prihoda s.r.o. need not use
either slots or plastic nozzles and yet achieves the same air distribution. |
|
| 10/ Why Prihoda s.r.o. does not use more permeable fabrics | |
We use permeable materials to avoid condensation in air
distribution with temperature below the dew point of environment. However,
we only have material of a single permeability value. It is very low
and serves just to prevent condensation. For air distribution we use
exclusively holes (perforation or microperforation or a combination of
these). Our product portfolio includes also impermeable materials, use
of which is often unavoidable. |
|
| 11/ Why Příhoda does not use CFD? | |
Experience has shown quite small compliance of CDF and reality particularly as regards more difficult or special cases. Our air distribution by means of microperforation is very different from permeable or only perforated materials. We prefer to provide our clients with the results of our tests rather than the expensive model by means of CFD. We can prepare smoke test in our testing room during the simulation of real conditions for special applications. The results are the closest to practise! |
|
