Heavent industrial ventilation design software by Steven E. Guffey

Industrial Exhaust Ventilation Software:

Heavent Screens

The following are screen shots or other information taken from Heavent on 5 July 2001.

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Toggles [modified screen shot] back to top

Modeling predicts effects of altering installed systems
Flows can be adjusted with dampers using a revolutionary field adjustment method
[Other choices are explained in the manual]

Defaults back to top

Setting defaults for a system reduces the number of necessary user inputs
Values can be changed as often as you like
Can over-ride previous inputs with default, if you wish
[Downstream and upstream offsets allow the program to compute values at locations where you can measure them]

Creating a simple duct system layout back to top

As shown below you can generate a simple system (i.e., no subsystems) by selecting from a menu.
As discussed later, you can modify a simple system to make it as complex as you like.
- Schematic grows as you attach new runs of ducts and air-cleaning devices
- Systems can be of any complexity and have up to 100 branch ducts and 10 air-cleaning devices
- Relatively easy to re-arrange which ducts are connected to which if you need to change the layout
- Heavent determines the relationship of ducts to each other from their linkages -- so you don't have to worry about "mother-daughter-cousin" issues.

Modifying a Duct Layout back to top

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.

Inputing duct data back to top

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.

Estimating airflows for hoods back to top

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.

Psychrometrics back to top

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.

Air-cleaning devices back to top

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.

Help back to top

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:
1. set defaults to reduce the number of necessary inputs
2. choose or create a file of available duct diameters
3. build the schematic of the system on screen
4. input data
5. 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.

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Steven E. Guffey, PhD, CIH
1403 Far Meadows
Morgantown, WV 26508
ph: (304) 685-1298 cell
[do not call 9-1 PM during 15 Aug to15 May]
fax: (304) 594-2557
Internet: seguffey@gmail.com