The computer program DONKEY determines the size of a duct network,
carries out a complete acoustical analysis and determines quantities
for costing purposes. The program operates via a set of add on menus
in AutoCAD. The user enters
the duct layout as a line diagram including all the terminals, fittings
and the fan. All the parameters
relating to these components including air quantities, duct insulation,
sizing method, fan type, etc; are entered in dialogue boxes that are
called up on screen. Once the duct layout is entered on the drawing
the program will then calculate the duct sizes and the noise levels
throughout the system. These
results can then be selectively displayed on the drawing or printed
from a text file.
program has many features that make the inputting of data quite
simple including automatic connection of run out ducts to terminals,
automatic insertion of fittings and many other features. These enable
the powerful and very comprehensive calculations of the program
DONKEY to be utilised. Various alternative designs can be quickly
and thoroughly investigated and a cost effective design achieved
that satisfies the design objective for noise with minimal damper
balancing pressure and cost.
Typical DONKEY Duct Layout
The Conference Room
with Listener at Position 1
Ducts are drawn, the fan, terminals and fittings
are inserted via a series of pull down menus. These menus also
cater for the entry of VAV boxes and plenums and provides for
the nomination of a listener position for the detailed noise calculations.
The data for the calculations is extracted from the drawing and
the calculations performed via items on the Utilities Menu
The overall results including duct sizes, pressure drops terminal
NR levels, damper out-of-balance pressures and noise levels at
selected frequencies can all be displayed on screen on the actual
duct layout drawing. In addition detailed results for individual
terminals, fittings and the fan can be displayed selectively in
convenient list boxes.
Quantities for costing including the weight of sheet metal, the
number of terminals, dampers, etc. fabrication erection and shop
drawing manhours can also be displayed to enable the user to find
cost effective solutions.
Supply Ducts Menu
|Supply and Return networks can be
entered and in duct coils and silencers can be entered.
Fitings (Bends, Divided Flow, Combined Flow, Dampers, etc.) are
selected from Slide Boxes and the program calculates the pressure
loss, self generated noise level and attenuation of all of these
Fittings are selected from slide boxes and placed manually or the
program can automatically place bends and branch fittings over areas
of the layout nominated by the user
Summary Results Menu
Detailed Results Menu
The Place Divided Flow Fitting Selection Box
For the acoustical analysis
the program assumes a "standard" 3m x 3m typical room
under each terminal, taking into account the self generated
noise and the attenuation of all duct elements in the network.
From this the program determines sound transmission throughout
the whole network and then displays sound pressure levels and
NR levels in each "room".
Alternatively the user can specify "Special rooms"
with use defined acoustical properties and up to 6 ducts and
6 terminals in each room.
Setting a Special Room Acoustic Properties
After the duct layout has been
drawn, the program extracts the information from the drawing,
numbers the ducts and produces a file in a format suitable for
the calculation program. The calculation program then sizes
the ducts and determines the noise level at each terminal and
the noise breaking out from each duct.
The overall results can be selectively displayed on the drawing
whilst detailed results for specific items (terminals, the fan,
etc.) are selectively displayed in dialogue boxes.
Overall Results Displaying Duct sizes and Terminal NR Levels
Typical Detailed Results for a Special Room
- The ductwork system and with some limitations different parts of the system
can be sized by any of three sizing methods, static regain,
constant pressure gradient or balanced pressure drop.
The program incorporates pressure loss data for a wide range of fittings
and balancing dampers can be manually or automatically inserted.
For rectangular ducting, practical size selections are made avoiding where
possible more than one dimension being changed between duct
segments. Provision is also made for fixing a duct's
dimensions or velocity.
- Duct leakage can be allowed for on the basis of a l/s per joint per kilopascal
pressure difference. Duct heat gains (or losses) with compensating
adjustments to air quantities can also be allowed for, if required.
between fittings in close proximity can be accounted for.
- The sound power levels throughout the entire network are calculated at
each of the seven octave band frequencies from 63 to 4000 Hz
taking into account noise generated by the fan, ducts, fittings,
VAV boxes, registers, grilles and the noise attenuation of ducts,
fittings, plenums and any duct silencers specified.
Account is taken of noise transmitted both from the fan
down to the terminals and from the terminals back up the network.
- The noise level algorithms in the program are very comprehensive many being
quite unique and representing the very latest methodology available.
- Noise levels in terms of an NR level and a sound pressure level can be
determined at any location in up to 9 user defined rooms. The acoustical properties of these rooms are
determined from the entered quantity and material types of all
components in the room including any people or objects.
- The program has a range of material absorption coefficients and transmission
loss data readily accessible through drop down lists. In addition users can define their own material
- The 'break out' NR level is calculated for each duct individually on the
basis of the duct being located in the ceiling space above the
- The total weight of sheet metal and the fabrication, erection and shop
drawing manhours are determined for the ductwork and fittings
and all other entered items (eg silencers, dampers, terminals
and VAV boxes.
- Comprehensive range and data checking
is provided on all input items in the various dialogue boxes. A comprehensive check on the entered duct layout
can be carried out prior to the calculations, to ensure ducts
are connected, correct fittings have been used, fittings have
not been omitted, etc.
- Comprehensive help is provided in all dialogue boxes and on each drop down
menu describing the various commands and input time.