A cast turbine nozzle, comprising: an airfoil having a body including a suction side, a pressure side opposing the suction side, a leading edge spanning between the pressure side and the suction side, a trailing edge opposing the leading edge and spanning between the pressure side and the suction side, and a cooling cavity defined by an inner surface of the body; at least one endwall (120, 122) connected with the airfoil along the suction side, the pressure side, the trailing edge and the leading edge; and a plurality of heat transfer protrusions extending inwardly from the inner surface of the body within the cooling cavity, characterised in: the plurality of heat transfer protrusions extending from the leading edge along the suction side and along the pressure side in a radially staggered columnar pattern and in a range of 28% to 32% of a camber length along the suction side and a range of 9% to 13% along the pressure side, the camber length representing a distance from the leading edge to the trailing edge through a center of airfoil equidistant between the suction side and the pressure side, wherein the inner surface includes a planar surface extending between adjacent heat transfer protrusions; and wherein the inner surface downstream of the plurality of heat transfer protrusions is devoid of the plurality of heat transfer protrusions or other structures that cause turbulence in the coolant flow in the aft direction towards the trailing edge. an airfoil having a body including a suction side, a pressure side opposing the suction side, a leading edge spanning between the pressure side and the suction side, a trailing edge opposing the leading edge and spanning between the pressure side and the suction side, and a cooling cavity defined by an inner surface of the body; at least one endwall (120, 122) connected with the airfoil along the suction side, the pressure side, the trailing edge and the leading edge; and a plurality of heat transfer protrusions extending inwardly from the inner surface of the body within the cooling cavity, characterised in: the plurality of heat transfer protrusions extending from the leading edge along the suction side and along the pressure side in a radially staggered columnar pattern and in a range of 28% to 32% of a camber length along the suction side and a range of 9% to 13% along the pressure side, the camber length representing a distance from the leading edge to the trailing edge through a center of airfoil equidistant between the suction side and the pressure side, wherein the inner surface includes a planar surface extending between adjacent heat transfer protrusions; and wherein the inner surface downstream of the plurality of heat transfer protrusions is devoid of the plurality of heat transfer protrusions or other structures that cause turbulence in the coolant flow in the aft direction towards the trailing edge. the plurality of heat transfer protrusions extending from the leading edge along the suction side and along the pressure side in a radially staggered columnar pattern and in a range of 28% to 32% of a camber length along the suction side and a range of 9% to 13% along the pressure side, the camber length representing a distance from the leading edge to the trailing edge through a center of airfoil equidistant between the suction side and the pressure side, wherein the inner surface includes a planar surface extending between adjacent heat transfer protrusions; and wherein the inner surface downstream of the plurality of heat transfer protrusions is devoid of the plurality of heat transfer protrusions or other structures that cause turbulence in the coolant flow in the aft direction towards the trailing edge.