The Heavent program analyzes industrial ventilation and exhaust duct systems. With Heavent, optimal duct sizes can be determined that maintain both the minimum desired velocity and balanced static pressures at all duct junctions. Heavent can work with both round and rectangular ducts of any duct material desired. Heavent has provision for virtually all types of components found in ventilation and exhaust systems including: ductwork, hoods, fans, air cleaners, collectors, blast gates, system effect factors, and all types of fittings. Heavent aids the user in selecting duct sizes and computes all system pressures required for system design and fan selection using the method described in the ACGIH Industrial Ventilation manual.
Heavent is a true Windows program complete with menu bars and hyperlinked help. All input data is checked at the time of entry so that no improper data can be entered. The project data includes company name, address, contact person, design team, comments and instructions. Input for each duct includes length, roughness factor, material type and gauge as well as the number of elbows and other fittings. Hoods require a design cfm, duct entry loss factor, minimum air velocity, slot data, and additional loss data. All types of air cleaners and collectors are allowed including cloth bags, cyclones, chambers, scrubbers, afterburners, gas adsorbers and absorbers. Fans require entry of the inlet diameter, outlet area, fan speed, blast to outlet area ratio, outlet elbow direction, and fan performance data relating static pressure and cfm values.
The Heavent program provides the following five basic output reports: Project Information, Data Tables, List of Materials, Air Cleaners Information, Fan Information.
Heavent uses the design methods and data explained in the ACGIH Industrial ventilation Manual. Additional calculation procedures have also been implemented from the author's own published research. All output report results can be verified by hand.
More Details about Heavent
- Heavent requires no arbitrary subsystem "naming" conventions ("parent-child-daughter") as you define a duct system, yet you can design very large systems with up to 320 branches.
- There are no commands to memorize and required inputs are kept to a minimum through extensive user-settable defaults and intelligent guesses about your next selection.
- Automatically displays loss coefficients and other data in tables when they are needed.
Provides extensive input error checking. All inputs undergo sophisticated "reality" and "typical value" checks.
- Re-calculates flows and pressures immediately as you enter or change values, giving immediate feedback helpful in developing an intuitive sense of how well the system is working.
- Selects round duct diameters from user defined schedules of available duct diameters. Size schedules can be given names such as STAND_GAL, OUR_SHOP, PVC, KIRK&B, UMCGILL, etc. You can change the diameter or duct shape (round, rectangular or flat-oval) easily and as often as you like. Internal duct dimensions are corrected for gauge thickness if necessary.
What Heavent Doesn't Do
Heavent is intended for use with industrial exhaust ventilation systems. It is not intended for use with hvac supply or return air systems. It does not predict effects due to buoyancy, heat transfer, or combustion products. It doesn't allow booster fans in branches although there are ways to simulate that effect. Heavent is designed for air flow conditions typical of industrial exhaust ventilation systems, not for extremely low velocity (<1000 ft/min) or extremely high velocity applications (>10,000 ft/min). It does not allow "looped" systems involving interconnections between branches as is sometimes used in ventilation systems for mines. Even with these few limitations, Heavent is appropriate for 99.5% of all industrial exhaust systems installed to control airborne contaminants.
Other Programs Included
Three handy DOS programs are also provided with Heavent for functions such as data acquisition, calibration, and dilution. See descriptions of each program below.
HV_MEAS is a program intended to aid in monitoring and troubleshooting industrial exhaust ventilation systems. With this program, you can connect the most popular digital manometers on the market (such as models manufactured by Alnor and TSI) to the computer and send measurements directly from the manometer to the computer.
HV_MEAS computes the airflows from the measured values as measurements are taken. Common pitot traverse errors are flagged by the program. The ability to display velocity contours helps you spot missing data and other anomalies.
HV_MEAS lets you open files of previously collected data, and uses the information to compare the current data to the older data, providing instantaneous feedback in detecting measurement errors and in determining if an obstruction or leak has appeared since the last set of measurements.
CALIBRATE assists in the calibration of common digital manometers using inexpensive inclined manometers or other devices. It plots calibration curves and shows a curve fit using linear regression.
DILUTION assists in dilution calculations using the familiar one-cell model found in ventilation texts written for practitioners. The one-cell model is simple and nearly universally used, but it has dubious accuracy and can be misleading, especially when applied to complicated spaces and situations. The program does not use more sophisticated models because they require impractical input data requiring sophisticated knowledge of conditions within the ventilated space.
The DILUTION program results should be used cautiously, especially for confined space entry computations. Despite its limitations, the program is certainly more convenient than attempting the same calculations using spreadsheets or calculators.