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- p
_{1}- inlet pressure - Absolute pressure at the pipe start
- p
_{2}- outlet pressure - Absolute pressure at the pipe end
- Δp - pressure drop
- Pressure difference between pipe start and pipe end
- q - volume flow rate
- Fluid flow rate in terms of units of volume per unit of time
- ṁ - mass flow rate
- Fluid flow rate in terms of units of mass per unit of time
- L - pipe length
- Length of a pipe in which pressure drop is calculated
- D - pipe diameter
- Internal circular pipe diameter
- H - channel height
- The height of channel for rectangle shaped pipe
- W - channel width
- The width of channel for rectangle shape pipe
- k
_{r}- pipe roughness - Pipe internal surface roughness
- V - velocity
- Flow velocity in terms of units of distance per unit of time
- A - area
- Internal pipe cross section area
- f - friction coefficient
- Coefficient of friction for pressure drop due to friction calculation
- Re - Reynolds number
- Dimensionless number representing viscous versus inertial forces ratio
- δ - boundary layer
- Thickness of laminar layer formed in turbulent flow connected to pipe wall surface
- ρ - fluid density
- Mass per unit of volume
- ν - kinematic viscosity
- Result of fluid particles colliding to each other and moving at different velocities in terms of area per square unit of time
- μ - dynamic viscosity
- Result of fluid particles colliding to each other and moving at different velocities in terms of mass per square unit of distance and time
- K - resistance
- Coefficient used for calculation of minor losses due to local resistances in pipe line like bends, tees, reducers, valves, etc.

- Select value to calculate. You should enter not selected one.
- Δp
- pressure drop
- q / ṁ
- volume/mass flow rate
- D
- internal pipe diameter

- Select value to input. You should enter selected one. The other one will be calculated
- p
_{1} - pressure on the pipe start
- p
_{2} - pressure on the pipe end

- Select value to input. You should enter selected one. The other one will be calculated
- q
- volumetric flow rate
- ṁ
- mass flow rate

- Select value to input. You should enter selected one. The other one will be calculated
- ν
- kinematic viscosity
- μ
- dynamic viscosity

- Select pipe shape
- round pipe
- full cross section fluid flow
- rectangle pipe
- for rectangle channels and full cross section flow