Reynolds number and its importance in water system

Reynolds number and its importance in water system

Purified water is the most used ingredient in pharmaceutical industries its used directly for the drug manufacturing process and also used for equipment’s cleaning.

Purified water and Purified water generation and distribution system is one of the most important and critical part of a pharmaceutical facility and during designing purified water generation and distribution system a number of parameter required to set/designed carefully,in which Reynolds number is also playing very importance role to control the level of water turbulence in loops

Reynolds number is used to defined water flow, it generally used for determine the water flow is laminar or is the ratio of inertial forces to viscous forces and consequently quantifies the relative importance of these two types of forces for given flow conditions. Reynolds number is unit-less. If the Reynolds number is less than 2300 that means the flow of water is laminar. If Reynolds number over 4000 that means flow of water is turbulent flow.

In water system (or in any fluid flow system) Reynolds number indicated the nature of fluid flow in pipelines. There is direct relation of nature of flow & biofilm formation inside the pipelines. It is considered that if water flow in pipeline is laminar type it may cause formation of biofilm & this can be avoided by having turbulent flow in water distribution system.

Formula for Reynolds’s Number Calculation

Water Flow can be laminar, turbulent, or between two states (a transient flow). It is calculated by dividing the fluid’s inertial force by its viscous force. Low Reynolds’s numbers show laminar flow, meaning it is smooth and constant and more Reynolds’s numbers indicate turbulent flow, meaning it is chaotic. Reynolds’s numbers in between indicate transient flow, meaning the flow changes with time. The Reynolds’s number can be used for a number of water flow situations, as well as items moving through fluids.

Reynolds’s Number =  Fluid density X  fluid velocity  X  Characteristic length/diameter of fluid flow                                                                                                              Viscosity of the fluid

R = ρ v L/ μ

R = Reynold’s number (unitless)

ρ = the density of the fluid (kg/m3)

v = the velocity of the fluid (m/s)

L = the “characteristic length “or diameter of the fluid flow (m)

μ = the viscosity of the fluid

( Pa.S = kg/m.s)

In a circular pipe, the length is the diameter of the pipe. The boundaries between the types of flow are:

  • Laminar flow when R < 2300
  • Transient flow when 2300 < R < 4000
  • Turbulent flow when R > 4000



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