Heating unit for a fuel air heater, method for manufacturing said heating unit, and fuel air heater comprising said heating unit

1. A portable fuel heater for heating ambient air, comprising a heating unit comprising:

a first side wall defining an inner space, said inner space forming a combustion chamber;

a second side wall arranged outside around said first side wall, said first side wall and said second side wall defining a first annular gap therebetween, said first annular gap forming a cooling chamber adapted to be crossed by a cooling air flow to subtract heat from the first side wall and transfer it to an external environment to be heated;

wherein said first side wall forms a first plurality of bosses adapted to promote a thermal exchange of said first side wall with the combustion chamber and with the cooling chamber, a third side wall arranged outside around said second side wall, said third side wall and said second side wall defining a second annular gap therebetween, said second annular gap forming a fumes evacuation chamber adapted to be crossed by a flow of combustion fumes from said combustion chamber, wherein said second side wall forms a second plurality of bosses adapted to promote a thermal exchange of said second side wall with said cooling chamber and with said fumes evacuation chamber, wherein the bosses of the first plurality of bosses are unaligned with respect to the bosses of said second plurality of bosses.

2. A portable fuel heater according to claim 1 , further comprising:

a first forced ventilation device for supplying oxidizing air in said combustion chamber;

a fuel dispensing device for dispensing atomized liquid or gas fuel in, or towards, the combustion chamber;

an ignition device for starting a combustion of said fuel;

a second forced ventilation device for supplying said cooling air flow in said cooling chamber,

an outer casing containing said heating unit;

a supporting cart with wheels for moving said heater.

3. The portable fuel heater of claim 1 , wherein the bosses of said first plurality of bosses project towards the outside of the combustion chamber so as to be hit by said cooling air flow.

4. The portable fuel heater of claim 1 , wherein the bosses of the first plurality of bosses are distributed according to parallel rows, wherein the bosses of each row are offset with respect to the bosses of each adjacent row.

5. The portable fuel heater of claim 1 , wherein the intersection between at least one boss of said first plurality of bosses and a plane tangent to the first side wall at said at least one boss, forms a boss base section, wherein said boss base section is substantially circular ring-shaped.

6. The portable fuel heater of claim 1 , wherein the intersection of said at least one boss of said first plurality of bosses with a plane orthogonal to the tangent plane at the boss is substantially arc-shaped.

7. The portable fuel heater of claim 1 , wherein the bosses of said second plurality of bosses project from said second side wall towards the outside of said cooling chamber so as to be hit by said flow of combustion fumes.

8. The portable fuel heater of claim 1 , wherein the bosses of the second plurality of bosses have a substantially equal shape or size to that of the bosses of the first plurality of bosses.

9. The portable fuel heater of claim 1 , wherein said second side wall has a first base end and an opposite second base end, and the third side wall has a third base end and an opposite fourth base end, wherein the fumes evacuation chamber is further defined by a first annular base wall connecting the first base end and the third base end together, thus closing a first end of the fumes evacuation chamber, and by a second annular base wall connecting the second base end and the fourth base end together, thus closing a second end of the fumes evacuation chamber, wherein at least one of said first annular base wall and said second annular base wall comprises at least one opening adapted to allow the interior of said fumes evacuation chamber to be cleaned, and at least one corresponding closing member to close said at least one opening in a removable manner.