Which device can create a positive circulation in closed heating systems?

A circulator is specifically designed to create positive flow in closed heating systems. Its primary function is to move the heated fluid, typically water, through the pipes and radiators of the heating system. By maintaining a continuous flow, the circulator ensures that the heat generated by the boiler or other heating sources is effectively distributed throughout the entire system.

In a closed heating system, just relying on the natural convection may not be sufficient to efficiently circulate the heated water, particularly in larger systems where gravity alone cannot maintain the flow. The circulator uses mechanical energy to pressurize the fluid, helping to overcome any resistance due to the system’s design and maintaining consistent circulation.

An expansion tank, while important for absorbing excess pressure and accommodating thermal expansion, does not actively circulate fluid. A pump with a pressure valve might maintain pressure but doesn't directly ensure a positive fluid flow like a circulator does. A flow regulator, on the other hand, controls the rate of flow but doesn't inherently generate it. Thus, the circulator is the most appropriate device for ensuring positive circulation in these systems.