Heat exchanger and use thereof

A burner unit comprising:

• a burner, and
• two heat exchangers, wherein each of the two heat exchangers comprises:
• a shell extending in a longitudinal direction D from a first end to a second end and comprising a mantle extending from the first end to the second end, and
• a solid inner core made of a core material and located inside the shell, the core extending in direction D from a first extremity towards the first end to a second extremity towards the second end,
• whereby:
• at least one first flow path is provided inside the core each first flow path extending from the first extremity to the second extremity of the core,
• n circuitous second flow paths extend through the core and/or between the core and the mantle, so that the at least one first flow path is surrounded by the n second flow paths over a non-zero rectilinear distance ΔL in direction D, n being an integer greater than 1,
• whereby each second flow path has an outer wall which:
• is formed by the core material when said second flow path extends through the core, and
• is formed by combination of the core material and the mantle of the shell when said second flow path extends between the core and the mantle,
• whereby the at least one first flow path of each heat exchanger is fluidly connected, via the second extremity of the core and the second end of the shell, to a fluid inlet of the burner.

A burner unit comprising:

• a burner, and
• a heat exchanger comprising:
• a shell extending in a longitudinal direction D from a first end to a second end and comprising a mantle extending from the first end to the second end, and
• a solid inner core made of a core material and located inside the shell, the core extending in direction D from a first extremity towards the first end to a second extremity towards the second end,
• whereby:
• at least one first flow path is provided inside the core, each first flow path extending from the first extremity to the second extremity of the core,
• n circuitous second flow paths extend through the core and/or between the core and the mantle, so that the at least one first flow path is surrounded by the n second flow paths over a non-zero rectilinear distance ΔL in direction D, n being an integer greater than 1,
• whereby each second flow path has an outer wall which:
• is formed by the core material when said second flow path extends through the core, and
• is formed by combination of the core material and the mantle of the shell when said second flow path extends between the core and the mantle,
• wherein the heat exchanger further comprises 2*m first flow paths, m being an integer ≥1, said 2*m first flow paths being divided in:
• a first set of m first flow paths and
• a second set of m first flow paths,
• the first set being located on one side of a median plane extending in direction D across the core from the first extremity to the second extremity, and the second set being located on the other side of the median plane,
• whereby the first set of m first flow paths and the second set of m first flow paths are each fluidly connected, via the second extremity of the core and the second end of the shell, to a fluid inlet of the burner.