Heating system and annealing furnace using such system

A heating system, comprising:

• a fan, comprising a shell with an air inlet and an air outlet, wherein an air inlet direction of the shell is perpendicular to an air outlet direction of the shell;
• an air inlet tube connected to the air inlet of the shell, wherein the air inlet direction of the shell is consistent with an axial direction of the air inlet tube;
• and
• a heater, comprising a cylindrical inner housing, wherein a heating assembly is disposed in the inner housing, a circumferential wall of the inner housing is provided with an air inlet, a first end of the inner housing is closed, a second end of the inner housing is provided with an air outlet, the air outlet of the shell communicates with the air inlet of the inner housing, an air flow output from the shell enters the inner housing in a tangential direction and spirally flows along an inner wall of the inner housing, and is discharged from the air outlet of the inner housing, an air inlet direction of the inner housing is perpendicular to an air outlet direction of the inner housing, and the air inlet direction of the shell is parallel but opposite to the air outlet direction of the inner housing.