High power density insulated exhaust heating system

An exhaust gas heating unit for an exhaust system of an internal combustion engine, the exhaust gas heating unit comprising:

• a tubular housing comprising an outer peripheral wall defining a tubular shape and having an interior hollow space;
• and
• a heating element that has a first end proximate the outer peripheral wall and a second end proximate a center of the interior hollow space, the heating element extending longitudinally between the first end and the second end along a spiral path within the interior hollow space, wherein the heating element comprises:
• an external sheath, the external sheath formed of a thermally conductive material;
• an electrically conductive resistance element that extends longitudinally within the external sheath;
• and
• electrically insulating material disposed about the resistance element between the resistance element and the sheath;
• and
• a heat transfer member positioned within the interior hollow space, the heat transfer member being formed from one or more strips of thermally conductive material,
• wherein the one or more strips are coupled to the external sheath at a plurality of locations between the first end and the second end, and
• wherein the heat transfer member has a shape that follows the spiral shape of the heating element and includes a plurality of substantially “V-shaped” segments, each V-shaped segment is associated with a bent portion of the one or more strips.

An exhaust gas heating unit for an exhaust system of an internal combustion engine, the exhaust gas heating unit comprising:

• a tubular housing comprising an outer peripheral wall defining a tubular shape and having an interior hollow space;
• and
• a heating element that has a first end proximate the outer peripheral wall and a second end proximate a center of the interior hollow space, the heating element extending longitudinally between the first end and the second end along a spiral path within the interior hollow space, wherein the heating element comprises:
• an external sheath, the external sheath formed of a thermally conductive material;
• an electrically conductive resistance element that extends longitudinally within the external sheath;
• and
• electrically insulating material disposed about the resistance element between the resistance element and the sheath;
• a heat transfer member positioned within the interior hollow space, the heat transfer member being formed from one or more strips of thermally conductive material;
• and
• a spacer disposed in a gap that is radially between an outermost section of the heat transfer member and the tubular housing, the spacer being configured to inhibit exhaust gas flow through the gap,
• wherein the one or more strips are fixed to the external sheath at a plurality of locations between the first end and the second end,
• wherein the heat transfer member has a corrugated shape that follows the spiral shape of the heating element, and
• wherein the first end is connected to a first power pin and the second end is connected to a second power pin, the first and second power pins extending outside the interior hollow space of the tubular housing.