Time-Resolved Heat Transfer Measurements on the Tip Wall of a Ribbed Channel Using a Novel Heat Flux Sensor—Part II: Heat Transfer Results

Abstract

Measurements using a novel heat flux sensor were performed in an internal ribbed channel representing the internal cooling passages of a gas turbine blade. These measurements allowed for the characterization of heat transfer turbulence levels and unsteadiness not previously available for internal cooling channels. In the study of heat transfer, often the fluctuations can be equally as important as the mean values for understanding the heat loads in a system. In this study, comparisons are made between the time-averaged values obtained using this sensor and detailed surface measurements using the transient thermal liquid crystal technique. The time-averaged heat flux sensor and transient TLC results showed very good agreement, validating both methods. Time-resolved measurements were also corroborated with hot film measurements at the wall at the location of the sensor to better clarify the influence of unsteadiness in the velocity field at the wall on fluctuations in the heat flux. These measurements resulted in turbulence intensities of the velocity and heat flux of 20%. The velocity and heat flux integral length scales were about 60% and 35% of the channel width, respectively, resulting in a turbulent Prandtl number of 1.7 at the wall.

Ultra-High-Sensitivity and -Stability Thin-Film Heat Flux Sensor Based on Transverse Thermoelectric Effect

“…When light/heat is applied to the surface of the film, a temperature difference is generated along the thickness direction and a voltage signal is obtained. In the same year, Jenkins et al and Zhang et al compared the heat flux sensitivity performance of the YBa 2 Cu 3 O 7-δ , LaCaMnO 3 , LaPbMnO 3 , and LaSrCoO 3 material systems [24,25]. They also compared the transverse thermoelectric properties of YBa 2 Cu 3 O 7-δ films of different thicknesses, and found that at a thickness of 700 nm, the sensitivity was 6.9 µV/(kW•m 2 ) with a response time of less than 0.3 µs and a response frequency of 700 kHz.…”