A heat exchanger, comprising:
- a gas-tight shell, delimiting a combustion chamber, said shell including a gas discharge coupling,
- a heat exchange device for circulating a to be-heated heat-transfer fluid, the heat exchange device being mounted fixedly in an interior of the shell,
- said heat exchange device comprising:
- a first interior tube bundle, and at least one other bundle of tubes, the first interior tube bundle being disposed closer to a central location of the heat exchange device than the at least one other tube bundle and the at least one other bundle of tubes being disposed concentrically around the first interior tube bundle, all tubes of all bundles being made of a thermally conductive material and being configured to circulate fluid therein, each bundle of tubes comprising a series of tubes each of which has the shape of a circular arc and has a first end and a second end, the tubes of each bundle being disposed in parallel planes with a gap between two adjacent tubes,
- a single collector, made of a thermally conductive material, delimited by walls, a first end and a second end of each tube of the different bundles being connected to the collector, so that they lead inside said collector,
- the collector being provided with an inlet connector allowing the collector to be supplied with heat-transfer fluid to be heated and with an outlet connector allowing the discharge of said fluid once heated,
- means for producing hot gases in the combustion chamber of said shell, said means for producing hot gases being disposed in the vicinity of said heat exchange device, so that the hot gases pass radially through the different concentric bundles of tubes, from the interior to the exterior, by passing through the gaps provided between said tubes, before being discharged outside the heat exchanger, through said discharge coupling,
- wherein the heat exchanger is a condensation heat exchanger,
- wherein the shell comprises a condensation chamber, fewer than all the tubes of the interior tube bundle and fewer than all the tubes of the at least one other bundle being disposed in said condensation chamber, and the remaining tubes of the interior tube bundle and of the at least one other bundle being disposed in the combustion chamber,
- wherein said collector comprises several interior partitions, welded together and to the walls of the collector, and wherein the partitions delimit different channels, which are arranged to cause the fluid to be heated to circulate from said inlet connector, through all the tubes, to the outlet connector where the fluid once heated is discharged, the circulation being carried out through different groups of at least two tubes of each successive bundle,
- wherein the channels are also arranged so that, inside the tubes located in the combustion chamber, the circulation of the fluid is carried out through the different groups of at least two tubes of each successive bundle, successively, bundle by bundle, from the outermost bundle to the interior bundle,
- wherein said inlet connector is put into communication with a first end or a second end of at least one group of at least two tubes, exclusively of the remaining tubes of the outermost bundle which are disposed inside the combustion chamber, through at least one channel of said collector and through the tubes of the interior bundle and the tubes of the at least one other bundle located in the condensation chamber, and
- wherein the collector comprises at least one channel which allows a first end or a second end of at least one group of at least two tubes, exclusively of the remaining tubes of the interior bundle which are disposed inside the combustion chamber, to be put into communication with said outlet connector.