A fluid is retained and circulated within the circulatory path.

Preferably, the nitrogen gas is circulated.

Banknotes put into circulation by NHTO entities

Banknotes put into circulation by ECI banks

Banknotes put into circulation by ECI banks

Banknotes put into circulation by NHTO banks

I is the value of banknotes put into circulation

I is the value of banknotes put into circulation

The latter may be flowed by magnetic forces.

The former may be flowed by magneto-hydrodynamic effect or by electromagnetic induction.

Refrigerant is circulated through the system.

Further, the control unit periodically changes the flow amount of the gas circulated by the circulation unit.

The proppant or sand can be circulated or squeezed into position although, circulation is preferred.

A nutrient media is circulated through the tubes.

Preferably, inert gas is provided as circulating gas.