**7. Conclusion**

The aerothermal design of gas turbine components has progressed at a rapid pace in the last decade with all gas turbine manufacturers, in order to obtain higher thermodynamic efficiencies. This has been achieved by using higher turbine inlet temperatures and pressures, advanced turbine aerodynamics, efficient cooling systems for turbine airofoils and advanced high temperature alloys, metallic coatings, and ceramic thermal barrier coatings.

In this chapter, some of the basic heat transfer phenomenon associated with both the external hot gas side and the coolant internal flows in turbine airofoils has been outlined. The external hot gas side heat transfer is largely driven by the unsteady and transonic high pressure and high temperature aerodynamic flows. By establishing the hot gas side external heat loads, which generally varies with different turbine design, it is possible to design for efficient airofoil internal cooling systems. The gas turbine airofoil internal cooling systems are however complex and varied in design, particularly with static and rotating airofoils. The internal cooling design of airofoils generally involves integration of several technology features such as film cooling, three-dimensional turbulators, pedestals, impingement cooling, and thermal barrier coatings.

Due to the complexity of the heat transfer phenomenon associated with gas turbine airofoils, it is also relatively common that final airofoil designs are thermally validated in several validation carriers which are representative of engine conditions. These validation carriers include high speed cascade rigs, scaled perspex models, airflow and qualitative heat transfer flow benches, and gas turbine test engines.
