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Small Valves, Large Valves, Fittings, Inlet/Outlet

Overview

These components represent key elements in the system that influence Pressure Drop, and are great areas to visit to check flow and pressure. They are designed to work in tandem with the Pipes or Ducts they connect to, which is where their flow and Velocity inputs come from.

Peak Flow Rate

The Peak Flow Rate represents the maximum calculated water flow at that point in the system.

The Peak Flow Rate is taken directly from the adjacent connecting Pipes/Ducts.

To troubleshoot the Peak Flow Rate, refer to the pipe Flow Rate result section and troubleshoot from there.

Pressure (Including Residual and Static Pressure)

Pressure measures the force exerted by the Fluid at that specific point in the system.

Influences of Pressure (Including Residual and Static Pressure):

  • Upstream Components: Pressure depends on upstream elements, including Flow Sources, Pipes, Fittings, Valves, Level heights, Height changes, and Equipment.

Troubleshooting of Pressure (Including Residual and Static Pressure):

Step-by-step

  1. Inspect upstream components for discrepancies in pressure values.

  2. Look for potential issues at Flow Sources, Height changes, and Equipment connections.

  3. Use Heat Maps to identify areas with unusual pressure variations.

Pressure Drop

Pressure Drop is the reduction in pressure across a component or segment caused by resistance to flow.

Pressure Drop Formula:

Ξ”P = k Γ— (vΒ²) / (2 Γ— g)

Where:

  • Ξ”P = Pressure drop (mH or ft)

  • k = Resistance coefficient (unitless, based on component geometry)

  • v = Velocity of fluid (m/s or ft/s)

  • g = Acceleration due to gravity (9.81 m/sΒ² or 32.2 ft/sΒ²)

Pressure Drop Formula for Duct Systems:

Ξ”P = ΞΆ Γ— (ρ Γ— vΒ²) / 2

Where:

  • Ξ”P = Pressure drop (mH or ft)

  • ΞΆ = Zeta coefficient (unitless, based on component geometry)

  • ρ = Air density (kg/mΒ³ or lb/ftΒ³)

  • v = Velocity of air (m/s or ft/s)

Influences of Pressure Drop:

  • Kv/Zeta Values: Most of the Fittings and Valves utilise industry standard Kv values that inform most components' resistance.

  • Graphs: Some Valves look up a graph to determine the Pressure Drop based on the associated Flow Rate.

  • Pipe/Duct Size: Smaller Pipe/Duct sizes result in greater Pressure Drops. The size is commonly taken from the adjacent Pipe/Duct.

  • Velocity: Higher Velocities result in greater Pressure Drops. The Velocity is taken from the adjacent Pipe/Duct.


Troubleshooting of Pressure Drop:

  • Compare Pressure Drop values with the catalog data to identify inconsistencies.

  • Confirm Flow Rate, Velocity, and Pipe/Duct size results to ensure they align with your expectations.

Size

The size of a component is based on the size and Flow Rate of the adjacent connected Pipes/Ducts.

Influences of Component Size:

  • Pipe or Duct Size Matching: Components generally match the connected Pipe/Duct size unless independently sized.

  • Specialized/Independent Sizing: Some components, like backflow prevention devices, may require independent sizing. This will use the flow rate of the adjacent connected Pipe/Duct.

Troubleshooting of Component Size:

Step-by-step

  1. Verify the component size matches the adjacent Pipe or Duct unless it's designed for independent sizing.

  2. If the size is different from the adjacent Pipe or Duct, check the Flow Rate result of the adjacent Pipe or Duct and compare it against the size in the catalog for the component.

  3. Review System Settings to confirm Sizing configurations are accurate.


K Value

The K value indicates the Flow Coefficient of a valve or fitting, representing the Pressure Drop for the calculated Flow Rate.

K Value Formula:

Ξ”P = (k Γ— ρ Γ— vΒ²) / 2

Where:

  • Ξ”P = Pressure drop (kilopascals, kPa; pounds per square inch, psi)

  • k = Loss coefficient (dimensionless, specific to the fitting type, e.g., elbow, valve)

  • ρ = Fluid density (kilograms per cubic meter, kg/mΒ³, e.g., 1000 kg/mΒ³ for water; slugs per cubic foot, slug/ftΒ³, e.g., 1.94 slug/ftΒ³ for water)

  • v = Flow velocity (meters per second, m/s; feet per second, ft/s)

Influences of K Value:

  • Component Type: K values vary depending on the Valve or Fitting type and are based on industry standards.

  • Pressure and Velocity: The K value is used in conjunction with Pressure Drop and Velocity to calculate flow performance.

Troubleshooting of K Value:

Step-by-step

  1. Check the component's properties to see if the K value can be changed.

  2. Review catalog data for standard K values and built-in graphs for specific components.

  3. Make sure Velocity and Pressure Drop settings match the K value requirements.


Fan Duty

Fan duty reflects the Total Flow Rate and pressure a ventilation fan Exhaust system needs.

Influences of Fan Duty:

  • System Flow Rate: The Fan Duty matches the total flow rate of the connected Diffusers/Grills upstream.

  • Pressure on the Index Node Path: The Fan must overcome Pressure Drops across Ducts, Fittings, and Equipment along the Index Node Path.

Troubleshooting of Fan Duty:

Step-by-step

  1. Verify the fan's flow rate against the total system demand.

  2. Check Pressure Drop values along the Index Node Path to ensure the fan can handle the load.

  3. Use Heat Maps and the Design Report Spreadsheet to find areas with high-Pressure Drops and make adjustments.