Turbomachinery airfoil with optimized heat transfer

A coolable airfoil, comprising:

• a peripheral wall having an external surface comprised of a suction surface and a pressure surface laterally spaced from the suction surface, the surfaces extending chordwisely from a leading edge to a trailing edge and radially from an airfoil root to an airfoil tip;
• a primary cooling system comprised of chordwisely adjacent radially extending medial passages, at least two of the medial passages being interconnected to form a cooling serpentine;
• and
• an auxiliary cooling system comprised of at least one cooling conduit substantially parallel to and radially coextensive with the medial passages, the conduit disposed in the wall between the medial passages and the external surface, the conduit being chordwisely coextensive with at least one of the interconnected medial passages so that coolant flowing through the conduit absorbs heat from the peripheral wall thereby thermally insulating coolant flowing through the at least one medial passage.

A coolable airfoil, comprising:

• a peripheral wall having an external surface comprised of a suction surface and a pressure surface laterally spaced from the suction surface, the surfaces extending chordwisely from a leading edge to a trailing edge and radially from an airfoil root to an airfoil tip;
• a primary cooling system comprised of at least one radially extending medial passage bounded at least in part by the peripheral wall;
• and
• an auxiliary cooling system comprised of at least one cooling conduit substantially parallel to and radially coextensive with the medial passage, the conduit disposed in the wall between the medial passage and the external surface, the conduit having a chordwise dimension and a lateral dimension, the chordwise dimension being no more than about three times the distance from the conduit to the external surface.