Pipe Sizer

Based on NCC 2025 Section J6D8 Limits

System Type

Pipe Type

System Network

*Distributive: Pipework system has branches and different flow rates throughout the network.

Speed

Yearly Operating Hrs

Design Fluid Temp (°C)

*Adjust to calculate worst-case thermodynamic density and viscosity parameters.

Water Flow (L/s)

Min Recommended Pipe Size (mm)

DtS Max PD/m (NCC Limit)

Pressure Drop at Required Size

Actual Velocity

Pipe Cross-Section Profile

Calculation Methodology

This sizing engine automates the rigorous hydraulic calculations required to align fluid physics with the statutory Deemed-to-Satisfy (DtS) energy efficiency limits set out by the Australian National Construction Code.

1. NCC 2025 Section J6D8 Limits

The engine iteratively evaluates the fluid dynamics of the pipe network against standard manufacturing dimensions. It extracts the maximum allowable pressure drop (Pa/m) from Tables J6D8a, J6D8b, J6D8c, or J6D8d based on the system's operational profile (Speed, Network Type, and Annual Hours). The engine systematically loops through standard pipe sizes from smallest to largest, selecting the first nominal diameter that generates a friction loss strictly lower than the NCC limit.

2. Thermodynamic Property Integration

Water density (ρ) and kinematic viscosity (ν) are not static; they fluctuate significantly with operational temperature. Cold water is physically "thicker" (higher viscosity) than hot water, resulting in elevated friction factors and higher pressure drops. To ensure absolute compliance under worst-case operational bounds, the engine processes the user-specified design temperature through active thermodynamic polynomial equations to precisely determine the fluid properties in real-time before executing the friction logic.

3. The Darcy-Weisbach Equation

Actual pressure drop is mathematically modeled using the fundamental Darcy-Weisbach equation:

ΔP = f · (L / D) · (ρV² / 2)

ΔP = Pressure Drop (Pascals)
f = Darcy Friction Factor
D = Internal Pipe Diameter (m)
ρ = Fluid Density (kg/m³) at Design Temp
V = Velocity (m/s)

4. Friction Factor & Absolute Roughness

To accurately determine the friction factor (f) for turbulent flow, the engine employs the Swamee-Jain approximation of the Colebrook-White equation. This accounts for the precise absolute roughness (ε) of the selected material:

Copper Type B: Assumed exceptionally smooth with an absolute roughness of ε ≈ 0.0015 mm.
Steel Schedule 40: Calculated with an absolute roughness of ε ≈ 0.045 mm, reflecting heavier drag and subsequent elevated pressure drop compared to copper.

5. True Internal Diameter (ID) Application

To ensure precision, the algorithm does not use nominal (DN) sizes for mathematical calculations. It cross-references the selected Nominal Size against standard manufacturing tables (AS 1432 for Copper, ANSI B36.10 for Steel) to derive the exact internal free area, compensating for varying wall thicknesses before determining the final fluid velocity and friction rate.