| Product(s): | HAMMER |
| Version(s): | 26.00.00.XXX and higher |
| Area: | Layout and Data Input |
Problem
For a transient simulation in HAMMER, it is easier to simply enter the inflow and outflow orifice diameters rather than defining the air flow rating curve. Is there a way to determine the orifice diameters based on data from the manufacturer?
Solution
Starting with HAMMER 2026 (26.00.00.XXX and higher), an Air Valve Orifice Diameter Calculator is available, either from the "..." button next to the inflow and outflow orifice diameter fields in the air valve properties, or from the Tools Menu > More > Air Valve Orifice Diameter Calculator
This enables you to easily use data from the manufacturer rating curve to calculate the equivalent diameter, so that you can then simply enter that diameter. This can be easier than defining the entire rating curve (which is always still an option, by selecting "Air flow curve" for the "Air flow calculation method")
If you need to change the units for any of the input fields, right click on the unit and choose "Units and formatting".
After entering the input data and clicking "compute", observe the calculated equivalent orifice diameter. You must then manually type in that value in the respective orifice diameter property and closing the calculator tool.
Calculations
This tool uses the Wylie-Streeter equations to calculate air inflow and outflow for 4 different conditions (Critical air flow out, subsonic air flow out, critical air flow in and subsonic air flow in). The Newton iteration method is used quickly find the root (orifice diameter) of air flow calculation equations.
Alternatives
If you are using version 2024 or earlier, you can either use the air flow rating curve method, or you can calculate the equivalent orifice diameter externally using your own methodology.