LPG calculator

liquefied petroleum gas - propane/butane - pipe size, heat power

online since 2007

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LPG Flow Rate and Heat Power Calculator for Furnaces and Burners

The calculator can be used for estimating flow rate, pipe diameter, and heat power output of liquefied petroleum gas (LPG) in various engineering applications.

LPG is a commonly used fuel composed of a mixture of propane, butane, and smaller quantities of other hydrocarbons. It exists in either liquid or gaseous form under moderate pressure.

This tool is especially useful for designing and analyzing fuel systems, such as heating systems, industrial burners, or gas furnaces. For instance, you can use the calculator to determine the required LPG flow rate needed to deliver a specific heat power output for a burner. Whether you are working on residential, commercial, or industrial equipment, this calculator simplifies complex thermodynamic calculations and helps ensure efficient fuel usage.

How the Calculator Handles LPG Mixture Properties

If the fluid being analyzed is a mixture of multiple components, the calculator determines physical properties—such as density—based on the properties of each individual component, weighted by their volume or mass ratios.

One common example of such a mixture is liquefied petroleum gas (LPG), which consists primarily of propane (C₃H₈) and butane (C₄H₁₀), along with smaller amounts of other hydrocarbons. This calculator accurately computes mixture properties based on the selected propane–butane ratio, ensuring reliable results for both engineering and energy calculations.

LPG components ratio
Liquid phase flow
Gas phase flow
Mass flow rate and heat power
LPG gas phase properties

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LPG composition

Select volume or mass percent composition
Volume fraction %vol
Ratio of propane or butane volume to the total volume of the mixture
Mass fraction %wt
Ratio of propane or butane mass to the total mass of the mixture

Description

q liq - volume flow rate of the liquid phase
LPG flow when it is in the liquid phase, before the evaporator
q gas - volume flow rate of the gas phase at normal conditions
LPG flow when it is in the gas phase, after the evaporator
V liq - velocity of the liquid phase
The velocity of LPG when it is in a liquid phase before it evaporates
V gas - velocity of the gas phase
The velocity of LPG when it is in the gas phase, after the evaporator
D liq - pipe diameter of the liquid phase
Internal pipe diameter of the LPG line liquid phase before the evaporator
D gas - pipe diameter of the gas phase
Internal pipe diameter of the LPG line gas phase after the evaporator
ṁ - mass flow rate
LPG flow rate in terms of mass flow in the unit of time. Conserved between liquid and gas phase of LPG
P - combustion heat power
Heat power generated after the combustion of LPG. Actual heat power should be reduced for the efficiency loses
LHV_G - lower heating value - mass
The heating value of LPG mixture - energy released during the combustion of a unit of mass
p - absolute pressure of LPG gas
The pressure of the LPG after the evaporator or after the pressure control valve
T - gas temperature
The temperature needed to calculate LPG density after the evaporator or after the pressure control valve
ρ gas - gas actual density
Calculated density for entered pressure and temperature, and mixture components ratio
ρ gas_nor - gas density at normal conditions
A density of LPG mixture at normal conditions p=101325 Pa and t=00C
M -molar mass
Calculated molar mass for the selected ratio of propane and butane in the LPG mixture

Calculation setup

Select value to calculate. You should enter not selected one.
P
combustion heat power calculation
q liq/q gas/ṁ
LPG flow rate calculation
Select value to input. You should enter selected one. The other two will be calculated
mass flow rate
q liq
liquid phase flow rate
q gas
gas phase flow rate
Select value to input. You should enter selected one. The other one will be calculated. Available only if the gas is selected fluid
V liq
liquid phase velocity
D liq
liquid phase pipeline diameter
Select value to input. You should enter selected one. The other one will be calculated. Available only if the gas is selected fluid
V gas
gas phase velocity
D gas
gas phase pipeline diameter

Why Use This LPG Flow and Heat Power Calculator?

This calculator is a practical tool for estimating the flow rate, pipe diameter, and heat power of liquefied petroleum gas (LPG). LPG is a hydrocarbon fuel composed mainly of propane, butane, and their mixtures. For example, you can use this tool to determine the required LPG flow rate for a gas furnace burner based on the desired heat output.

How the Calculation Works?

The calculator supports flow and heat power calculations for both liquid and gaseous phases of LPG. It can also be used for pure propane or butane flow calculations.

In gas form, propane and butane are compressible, but this tool assumes incompressibility, which is accurate only for the liquid phase of LPG. The calculator computes key physical properties—such as mixture density and partial pressures—based on your selected propane–butane ratio.

You can also use the calculator to determine the required pipe diameter for a given flow rate. Flow rate inputs can be entered as mass flow rate, liquid volume flow rate, or gas volume flow rate at standard conditions.

It also provides convenient unit conversion between mass and volume flow rates, for both liquid and gas. The standard conditions for gas phase flow rate are:

  • Pressure: 101,325 Pa (1 atm)
  • Temperature: 273.15 K (0°C)

When Should You Not Use This Calculator?

This tool does not calculate pressure drop in a pipeline. If you need to estimate pressure loss, please use a dedicated liquid or gas pressure drop calculator.

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Services

  • Save/Open multiple results
  • Export to Word and Excel
  • Print results
  • Create list of custom fluid properties
  • Resistance factor K for valves/fittings
  • Pipe surface roughness selection
  • Pipe material selection
  • Gauge vs absolute pressure toggle
  • Compressible isothermal flow
  • Dry air isothermal flow
  • Gas offtake flow
  • Natural gas flow
  • No admin rights required to install

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