The cooling with double working fluids of water mist and air is an innovative technology designed for protecting turbine blade under elevated temperature conditions. This study applies this cooling approach to a first stage guide vane with double-wall structure for the first time

based on experimental validations. Numerical simulation of conjugate heat transfer is carried out under actual operating conditions. The investigated double-wall vane features a complete cooling structure incorporating impingement holes

film holes

and pin-fins. The effect of radiative condition is considered

and comparative simulations using air and steam cooling are performed to validate the findings. Results indicate that by adding mist with a mass ratio of 10% and droplet diameter of 30 μm into the coolant air

the average cooling effectiveness on the pressure and suction sides reaches 0.773 and 0.749

respectively. Compared to air-only cooling

mist cooling achieves a remarkable improvement of 24.4% in leading-edge cooling performance. However

the application of mist/air cooling results in a less uniform surface temperature distribution compared to both air and steam cooling methods

suggesting the need for vane structural optimization to achieve better coolant matching.