A Popup menu appears when you click on a duct ID number. Among many
other choices, you can add or disconnect ducts or air-cleaning devices.
Keep adding air-cleaning devices, junctions of ducts, and ducts until
the schematic matches the proposed system. Note that it is a schematic,
not a to-scale representation of the system.
Data inputs minimized by user-settable defaults (see Defaults above).
Nearly all data for ducts can be inputed from the spreadsheet-style
QuickInputs screen or from screens customized for particular sets of data
inputs (e.g., hood losses, elbow losses, etc.)
Temperature and humidity requires no user use or knowledge of psychrometric
tables or charts (Heavent does it all by computation).
As you change conditions, the program continues changing the duct diameter
for round ducts so that the duct velocity exceeds the minimum (target)
duct velocity. If you turn off automatic duct sizing in the Toggles menu,
Heavent will make only the initial duct diameter selection, leaving changes
to you. You also can fix a particular duct's size by selecting "Fix
duct size".
Help screens show almost all loss coefficients you will ever need.
When inputing airflow requirements, you are given the options of either
inputing a number directly or having the program help you estimate the
airflow requirements for that type of hood.
The estimates are based on the hood type and on the severity of the
conditions.
You simply input the desired dry bulb temperature and the wet bulb temperature
or relative humidity. The program computes all other values for you.
When you inputed altitude in the Defaults menu, you did all you need
to do for altitude effects. The program takes care of the rest behind
the scenes.
Showing different
parameters on the schematic back to top
Selecting "ShowValues" from the Schematic screen's bar menu
brings up the drop-down menus below. You can chose to show any of those
parameters on the schematic instead of the duct ID numbers.
The most important parameters to show are "%Airflow" and "%Velocity."
You will wonder how you ever got along without this feature (and program)
before!
Showing
Percent of Target Airflow
Allows Optimization back to top
Selecting "%Airflow" from the ShowValue menu displays the
percent of the minimum possible airflow that is going through that duct.
If a duct is getting 200% of its target value, you should consider decreasing
its target airflow. You might also try leaving it alone and INCREASING
an adjacent duct's diameter.
What was the best strategy? The one with the least %Airflow at the fan
inlet! How did you optimize system design without this? It makes it really
easy.
But be careful: be sure to check "%Velocity", also, to make
sure every duct velocity is high enough.
If the fan pressures are ridiculously high, check "%Velocity."
You probably turned off duct sizing, then forgot to increase a duct size
somewhere, and that duct is acting as a bottleneck and driving up pressures
throughout the system.
Vendors usually can estimate how much pressure should be required at
a given airflow, so that is what the program asks you to compute.
The "Exponent for known" is 1.0 for filters and 2.0 for cyclones
and most other types of air-cleaning devices.
A "Hood entry" coefficient is inputed for the exit from a
baghouse because that is what it looks like to the air.
Fan
information displayed, including system effects back
to top
The program allows you to input the most common system effects on fan
performance.
The program also computes the pressures and flows you otherwise would
look up on a fan table (they are not the same as the actual flows and
pressures because the fan tables are determined for ideal, standard conditions).
Note that building pressure also affects the fan pressure.
When ordering a fan, you should give the inlet and outlet pressures
and let the vendor rep make the fan selection, but it is nice to understand
what is going on.
Each screen has its own Help menu, which explains the purpose of the
screen and all the options presented on it.
You can do things in any order you choose, but it is most convenient
to do things in the following order:
set defaults to reduce the number of necessary inputs
choose or create a file of available duct diameters
build the schematic of the system on screen
input data
tweak duct size selections
Remember, you can do things in any order. The order above is by far
the most convenient, but the program doesn't care what order you input
information -- or how often you change your inputs or the system schematic.
A "Navigation" Screen will help you do things in the order
shown above. You may find that assistance helpful until you understand
what you are doing.
