Class: `PressureDropHazenWilliams`

The PressureDropHazenWilliams class calculates the pressure drop (ΔP) in a pipe using the Hazen–Williams equation.
It is part of the ProcessPI Calculations module and inherits from CalculationBase.

📖 Description

The Hazen–Williams equation is an empirical formula for estimating head loss due to friction in water distribution systems.
It is simpler than the Darcy–Weisbach equation since it avoids iterative calculations for friction factors.

This method is mainly used for water flow in pipes.

📊 Formula

Head Loss (SI Units):

\[ h_f = 10.67 \cdot \frac{L \cdot Q^{1.852}}{C^{1.852} \cdot D^{4.87}} \]

Pressure Drop:

\[ \Delta P = \rho \cdot g \cdot h_f \]

Where:

Symbol	Description	Units
\( h_f \)	Head loss	m
\( \Delta P \)	Pressure drop	Pa
\( L \)	Pipe length	m
\( Q \)	Volumetric flow rate	m³/s
\( C \)	Hazen–Williams roughness coefficient	–
\( D \)	Pipe diameter	m
\( \rho \)	Fluid density	kg/m³
\( g \)	Gravitational acceleration	9.81 m/s²

⚙️ Inputs

length → Pipe length (m)
flow_rate → Volumetric flow rate (m³/s)
coefficient → Hazen–Williams roughness coefficient (dimensionless)
diameter → Pipe internal diameter (m)
density → Fluid density (kg/m³)

📤 Output

Returns a Pressure object containing the pressure drop in Pascals (Pa).

🛠️ Methods

validate_inputs()
Ensures all required inputs (length, flow_rate, coefficient, diameter, density) are provided.
Raises ValueError if any are missing.

calculate()
Performs the Hazen–Williams pressure drop calculation:

Computes head loss (\(h_f\))
Converts \(h_f\) into pressure drop using \( \Delta P = \rho \cdot g \cdot h_f \)

Returns:
Pressure: The computed pressure drop in Pascals.

💻 Example Usage

Using the PressureDropHazenWilliams

from processpi.calculations import PressureDropHazenWilliams
from processpi.units import Pressure, Length, Diameter, Density, FlowRate, Dimensionless

# Define pipe and fluid properties
length = Length(100, "m")                 # Pipe length
flow_rate = FlowRate(0.05, "m3/s")        # Volumetric flow rate
coefficient = Dimensionless(130)          # Hazen–Williams coefficient for water
diameter = Diameter(0.15, "m")            # Pipe diameter
density = Density(998, "kg/m3")           # Water density

# Create calculation instance
pd_calc = PressureDropHazenWilliams(
    length=length,
    flow_rate=flow_rate,
    coefficient=coefficient,
    diameter=diameter,
    density=density
)

# Perform calculation
deltaP = pd_calc.calculate()

print(f"Pressure Drop (Hazen-Williams): {deltaP}")

**Using the CalculationEngine

from processpi.engine import CalculationEngine
from processpi.units import Pressure, Length, Diameter, Density, FlowRate, Dimensionless

# Initialize engine
engine = CalculationEngine()

# Define pipe and fluid properties
length = Length(100, "m")
flow_rate = FlowRate(0.05, "m3/s")
coefficient = Dimensionless(130)
diameter = Diameter(0.15, "m")
density = Density(998, "kg/m3")

# Perform Hazen-Williams pressure drop calculation using the engine
deltaP = engine.calculate(
    "pressure_drop_hazen_williams",
    length=length,
    flow_rate=flow_rate,
    coefficient=coefficient,
    diameter=diameter,
    density=density
)

print(f"Pressure Drop (via Engine): {deltaP}")

Class: PressureDropHazenWilliams