Forced and Natural Circulation

It was known that any time that fluid flows is some friction related with the movement, that will cause head loss. It was indicated that this head loss is generally compensated for in piping systems by pumps which do work on the fluid, reimburse for the head loss due to friction. The circulation of fluid in systems by pumps is termed to as forced circulation.

It is probable to design few fluid systems in a manner which does not need the presence of pumps to give circulation. The head needed to compensate for the head losses is generated by density gradients and elevation changes. The flow which occurs under such circumstances is termed as the natural circulation.     

The Natural circulation is the circulation of fluid in piping systems or open pools which is due to the density changes caused by temperature differences. The Natural circulation does not need any mechanical devices to sustain flow.