Abstract: Gas turbine hot section components are being pushed to the limit with every increasing combustion firing temperatures and improved expectations of life and durability. Improved internal cooling of turbine blades is a critical need for the interest. With the advent of additive manufacturing, the design of internal cooling feature options are unlimited. With that in mind, detailed heat transfer measurements are presented for complex internal cooling channels with and without rotation to evaluate performance and applicability of such cooling designs to turbine blade cooling. A transient liquid crystal technique is used to measure detailed heat transfer coefficient distributions inside these channels. The cooling channels have features such as ribs, dimples, impinging jets and a combination of these features. The challenge of making detailed measurements inside such rotating channels is displayed through the measurements.