Stirling engine thermal system improvements

A heat exchanger for transferring thermal energy from a heated external fluid across a cylindrical wall, the cylindrical wall characterized by a length direction parallel to a central axis of the cylindrical wall, the heat exchanger comprising:

• a. a set of staggered heat transfer protuberances, each heat transfer protuberance having an axis directed substantially away from the cylindrical wall;
• b. a plurality of dividers disposed substantially along the length of the cylindrical wall, for forcing fluid flow through the staggered heat transfer protuberances.

A heat exchanger for transferring thermal energy from a heated external fluid across a cylindrical wall characterized by an axial direction, the heat exchanger comprising:

• a. a set of heat transfer protuberances, each heat transfer protuberance having an axis directed substantially away from the cylindrical wall;
• and
• b. a backer for guiding the heated external fluid in a flow path substantially along the axial direction of the cylindrical wall past the set of heat transfer protuberances, wherein the spacing between the cylindrical wall and the backer varies.

A heat exchanger for transferring thermal energy from a heated external fluid across a cylindrical wall characterized by an axial direction, the heat exchanger comprising:

• a. a set of heat transfer protuberances, each heat transfer protuberance having an axis directed substantially away from the cylindrical wall;
• and
• b. a backer for guiding the heated external fluid in a flow path substantially along the axial direction of the cylindrical wall past the set of heat transfer protuberances, wherein a gap between the backer and the cylindrical wall decreases in the axial direction.

A heat exchanger for transferring thermal energy from a heated external fluid across a cylindrical wall characterized by an axial direction, the heat exchanger comprising:

• a. a set of heat transfer protuberances, each heat transfer protuberance having an axis directed substantially away from the cylindrical wall;
• and
• b. a backer for guiding the heated external fluid in a flow path substantially along the axial direction of the cylindrical wall past the set of heat transfer protuberances, wherein the heat transfer protuberances have a surface area transverse to the flow path that increases in the axial direction.

A heat exchanger for transferring thermal energy from a heated external fluid across a cylindrical wall characterized by an axial direction, the heat exchanger comprising:

• a. a set of heat transfer protuberances, each heat transfer protuberance having an axis directed substantially away from the cylindrical wall;
• and
• b. a backer for guiding the heated external fluid in a flow path substantially along the axial direction of the cylindrical wall past the set of heat transfer protuberances, wherein the heat transfer pins have a population density that increases in the axial direction.

A heat exchanger for transferring thermal energy from a heated external fluid across a cylindrical wall characterized by an axial direction, the heat exchanger comprising:

• a. a set of heat transfer protuberances, each heat transfer protuberance having an axis directed substantially away from the cylindrical wall;
• and
• b. a backer for guiding the heated external fluid in a flow path substantially along the axial direction of the cylindrical wall past the set of heat transfer protuberances, wherein at least one of the height and density of the heat transfer pins varies with distance in the axial direction.