Pipeline Pressure Drop Calculations in NeqSim

Overview

NeqSim provides three main pipeline models for calculating pressure drop:

Model Class Best For
AdiabaticPipe Single-phase compressible gas High-pressure gas transmission
AdiabaticTwoPhasePipe General two-phase flow Moderate accuracy, fast computation
PipeBeggsAndBrills Multiphase flow with correlations Wells, flowlines, complex terrain

Quick Start

Single-Phase Gas Pipeline

// Create gas system
SystemInterface gas = new SystemSrkEos(298.15, 100.0); // 25°C, 100 bara
gas.addComponent("methane", 0.9);
gas.addComponent("ethane", 0.1);
gas.setMixingRule("classic");

Stream feed = new Stream("feed", gas);
feed.setFlowRate(50000, "kg/hr");
feed.run();

// Simple pipe model
AdiabaticPipe pipe = new AdiabaticPipe("pipeline", feed);
pipe.setLength(10000);        // 10 km
pipe.setDiameter(0.3);        // 300 mm
pipe.run();

double pressureDrop = feed.getPressure() - pipe.getOutletPressure();

Two-Phase (Gas-Liquid) Pipeline

// Create two-phase system
SystemInterface fluid = new SystemSrkEos(333.15, 50.0); // 60°C, 50 bara
fluid.addComponent("methane", 5000, "kg/hr");
fluid.addComponent("nC10", 50000, "kg/hr");
fluid.setMixingRule(2);

Stream feed = new Stream("feed", fluid);
feed.run();

// Beggs & Brill correlation
PipeBeggsAndBrills pipe = new PipeBeggsAndBrills("flowline", feed);
pipe.setLength(1000);           // 1 km
pipe.setDiameter(0.1);          // 100 mm
pipe.setElevation(50);          // 50 m uphill
pipe.setPipeWallRoughness(4.6e-5); // Steel roughness
pipe.setNumberOfIncrements(20);
pipe.run();

// Get results
double dp = pipe.getInletPressure() - pipe.getOutletPressure();
String flowRegime = pipe.getFlowRegime().toString();
double liquidHoldup = pipe.getSegmentLiquidHoldup(20);

Calculate Flow Rate from Outlet Pressure

All pipeline models support a reverse calculation mode where you specify the desired outlet pressure and the model calculates the required flow rate:

// Create gas system with initial flow estimate
SystemInterface gas = new SystemSrkEos(298.15, 100.0); // 25°C, 100 bara
gas.addComponent("methane", 1.0);
gas.setMixingRule("classic");
gas.setTotalFlowRate(10000, "kg/hr"); // Initial estimate (will be recalculated)

Stream feed = new Stream("feed", gas);
feed.run();

// PipeBeggsAndBrills - most accurate for flow calculation
PipeBeggsAndBrills pipe = new PipeBeggsAndBrills("pipeline", feed);
pipe.setLength(10000);           // 10 km
pipe.setDiameter(0.3);           // 300 mm
pipe.setPipeWallRoughness(4.6e-5);
pipe.setNumberOfIncrements(10);
pipe.setOutletPressure(90.0);    // Specify target outlet pressure (bara)
pipe.run();

// Get calculated flow rate
double flowRate = pipe.getInletStream().getFlowRate("kg/hr");
double achievedOutletP = pipe.getOutletPressure();
// flowRate ≈ 144,000 kg/hr for 10 bar pressure drop

Supported Models for Flow Calculation

Model Method Accuracy Notes
PipeBeggsAndBrills setOutletPressure(double) Best Uses bisection iteration
AdiabaticPipe setOutPressure(double) Good Single-phase gas only
AdiabaticTwoPhasePipe setOutPressure(double) Moderate Two-phase capable

Model Selection Guide

Use AdiabaticPipe when:

Use AdiabaticTwoPhasePipe when:

Use PipeBeggsAndBrills when:

Accuracy Comparison

Based on validation against Darcy-Weisbach reference:

Condition AdiabaticPipe TwoPhasePipe BeggsAndBrills
Single-phase gas +0.9% -0.1% +0.5%
Single-phase liquid (turbulent) -4.1% -1.4% -1.4%
Single-phase liquid (laminar) N/A ~0% ~0%
Two-phase horizontal N/A N/A Validated
Inclined pipe N/A N/A Validated

Calculation Modes

Forward Mode (Default)

Specify flow rate → Calculate outlet pressure

feed.setFlowRate(50000, "kg/hr");  // Known flow rate
pipe.run();
double pOut = pipe.getOutletPressure();  // Calculated

Reverse Mode

Specify outlet pressure → Calculate flow rate

pipe.setOutletPressure(90.0);  // Target outlet pressure
pipe.run();
double flow = feed.getFlowRate("kg/hr");  // Calculated

The reverse calculation uses a bisection algorithm that iteratively adjusts the flow rate until the calculated outlet pressure matches the specified target.

See Also