Unit Conversion Guide

Documentation for unit conversion and unit systems in NeqSim.

Table of Contents

Overview

Location: neqsim.util.unit

NeqSim provides comprehensive unit handling capabilities:

Class Description
Units Unit system management and switching
PressureUnit Pressure unit conversion
TemperatureUnit Temperature unit conversion
LengthUnit Length unit conversion
EnergyUnit Energy unit conversion
PowerUnit Power unit conversion
RateUnit Flow rate unit conversion
TimeUnit Time unit conversion
BaseUnit Abstract base for unit classes
NeqSimUnitSet Complete unit set definition

Supported Units

Pressure Units

Unit Symbol Description
Pascal Pa SI unit
Bar absolute bara Metric (default)
Bar gauge barg Bar relative to atmosphere
PSI absolute psia Field units
PSI gauge psig PSI relative to atmosphere
PSI psi Same as psia
Atmosphere atm Standard atmosphere
mmHg mmHg Millimeters of mercury
kPa kPa Kilopascals
MPa MPa Megapascals

Temperature Units

Unit Symbol Description
Kelvin K SI unit
Celsius C Metric (default)
Fahrenheit F Field units
Rankine R Absolute imperial

Flow Rate Units

Unit Symbol Description
kg/s kg/sec SI mass flow
kg/hr kg/hr Metric mass flow (default)
kg/day kg/day Daily mass flow
mol/s mol/sec SI molar flow
mol/hr mole/hr Metric molar flow
kmol/hr kmole/hr Kilomoles per hour
m³/hr m3/hr Volume flow
Sm³/hr Sm3/hr Standard volume flow
Sm³/day Sm3/day Standard daily flow
MSm³/day MSm3/day Million Sm³/day
bbl/day bbl/day Barrels per day
lb/hr lb/hr Pounds per hour

Energy Units

Unit Symbol Description
Joule J SI unit
kJ kJ Kilojoules
MJ MJ Megajoules
kWh kWh Kilowatt-hours
BTU BTU British thermal units

Power Units

Unit Symbol Description
Watt W SI unit (default)
kW kW Kilowatts
MW MW Megawatts
hp hp Horsepower
BTU/hr BTU/hr BTU per hour

Length Units

Unit Symbol Description
Meter m SI unit (default)
Kilometer km Kilometers
Centimeter cm Centimeters
Millimeter mm Millimeters
Inch in Inches
Foot ft Feet
Mile mile Miles

Unit Systems

NeqSim supports three predefined unit systems:

SI Units

International System of Units (scientific standard).

import neqsim.util.unit.Units;

Units.activateDefaultUnits(); // SI
Property Unit
Temperature K (Kelvin)
Pressure Pa (Pascal)
Enthalpy J/mol
Density kg/m³
JT coefficient K/Pa

Metric Units (Default)

Engineering metric units - commonly used in European industry.

Units.activateMetricUnits();
Property Unit
Temperature °C (Celsius)
Pressure bara
Enthalpy J/kg
Density kg/m³
Viscosity Pa·s

Field Units

Imperial/oilfield units - commonly used in US oil & gas.

Units.activateFieldUnits();
Property Unit
Temperature °F (Fahrenheit)
Pressure psia
Enthalpy BTU/lbmol
Density lb/ft³
Viscosity cP

Usage Examples

Getting Properties with Units

Most NeqSim methods accept a unit string parameter:

import neqsim.thermo.system.SystemSrkEos;

SystemSrkEos gas = new SystemSrkEos(298.15, 50.0);
gas.addComponent("methane", 1.0);
gas.setMixingRule("classic");
gas.init(3);

// Pressure
double p_bara = gas.getPressure("bara");    // 50.0
double p_Pa = gas.getPressure("Pa");        // 5000000.0
double p_psia = gas.getPressure("psia");    // 725.19

// Temperature  
double T_K = gas.getTemperature("K");       // 298.15
double T_C = gas.getTemperature("C");       // 25.0
double T_F = gas.getTemperature("F");       // 77.0

// Density
double rho_kgm3 = gas.getDensity("kg/m3");  
double rho_lbft3 = gas.getDensity("lb/ft3");

// Flow rates (for streams)
stream.getFlowRate("kg/hr");
stream.getFlowRate("Sm3/day");
stream.getFlowRate("MSm3/day");
stream.getFlowRate("bbl/day");

Setting Properties with Units

// Set temperature
stream.setTemperature(25.0, "C");
stream.setTemperature(298.15, "K");
stream.setTemperature(77.0, "F");

// Set pressure
stream.setPressure(50.0, "bara");
stream.setPressure(5.0, "MPa");
stream.setPressure(725.0, "psia");

// Set flow rate
stream.setFlowRate(1000.0, "kg/hr");
stream.setFlowRate(5.0, "MSm3/day");
stream.setFlowRate(10000.0, "bbl/day");

Direct Unit Conversion

import neqsim.util.unit.PressureUnit;
import neqsim.util.unit.TemperatureUnit;

// Pressure conversion
PressureUnit pu = new PressureUnit(50.0, "bara");
double p_psia = pu.getValue("psia");  // Convert to psia

// Temperature conversion
TemperatureUnit tu = new TemperatureUnit(25.0, "C");
double t_K = tu.getValue("K");    // 298.15
double t_F = tu.getValue("F");    // 77.0

Switching Unit Systems

import neqsim.util.unit.Units;

// Switch to field units for display
Units.activateFieldUnits();

// All subsequent property output uses field units
System.out.println("Temperature: " + 
    Units.activeUnits.get("temperature").symbol);  // "F"
System.out.println("Pressure: " + 
    Units.activeUnits.get("pressure").symbol);     // "psia"

// Switch back to metric
Units.activateMetricUnits();

Equipment with Unit Parameters

// Compressor with different unit specifications
Compressor comp = new Compressor("K-100", stream);
comp.setOutletPressure(100.0, "bara");

// Get power in different units
double power_W = comp.getPower("W");
double power_kW = comp.getPower("kW");
double power_hp = comp.getPower("hp");

// Heat exchanger duty
HeatExchanger hex = new HeatExchanger("E-100");
hex.setDuty(1000.0, "kW");
double duty_BTU_hr = hex.getDuty("BTU/hr");

Unit Conversion Classes

PressureUnit

import neqsim.util.unit.PressureUnit;

// Create from any unit
PressureUnit p1 = new PressureUnit(50.0, "bara");
PressureUnit p2 = new PressureUnit(5000000.0, "Pa");
PressureUnit p3 = new PressureUnit(725.0, "psia");

// Convert to any unit
double inPa = p1.getValue("Pa");
double inBara = p1.getValue("bara");
double inPsia = p1.getValue("psia");
double inBarg = p1.getValue("barg");

TemperatureUnit

import neqsim.util.unit.TemperatureUnit;

TemperatureUnit t = new TemperatureUnit(100.0, "C");
double inK = t.getValue("K");       // 373.15
double inF = t.getValue("F");       // 212.0
double inR = t.getValue("R");       // 671.67

RateUnit

import neqsim.util.unit.RateUnit;

// Mass flow conversion
RateUnit massFlow = new RateUnit(1000.0, "kg/hr");
double inKgSec = massFlow.getValue("kg/sec");
double inLbHr = massFlow.getValue("lb/hr");

// Standard volume flow
RateUnit volFlow = new RateUnit(1.0e6, "Sm3/day");
double inMSm3Day = volFlow.getValue("MSm3/day");  // 1.0

Best Practices

Always Specify Units Explicitly

// Good - explicit units
stream.setTemperature(25.0, "C");
stream.setPressure(50.0, "bara");

// Avoid - ambiguous
stream.setTemperature(25.0);  // What unit is this?

Use Consistent Unit System

// Choose one system for a project
Units.activateMetricUnits();

// Document assumptions
// All temperatures in °C, pressures in bara

Convert at Boundaries

// Convert external inputs to internal units
double externalTemp_F = 77.0;
double internalTemp_C = new TemperatureUnit(externalTemp_F, "F").getValue("C");

// Convert internal results to external units for output
double internalPressure_bara = 50.0;
double outputPressure_psia = new PressureUnit(internalPressure_bara, "bara").getValue("psia");