Heated Channel Wall Research Articles

An experimental study of heat transfer in a simulated turbine blade cooling passage

This paper describes an experimental investigation of heat transfer inside a simulated cooling channel for a gas turbine rotor blade. The channel is circular in cross-section and rotates about an axis which is orthogonal to its centre line. The study is aimed at the development of an experimental procedure and method of data processing which permits the determination of full axial and circumferential heat transfer data over the tube's inner surface. This is referred to as full field heat transfer data. In this respect a study of the combined effect of Coriolis and centripetal buoyancy forces on the forced convection mechanism inside the tube is the strategic aim. The experimental technique involved the determination of the inside surface temperature and heat flux distribution using a solution of the channel wall heat conduction equation. A series of wall temperature measurements on the leading and trailing edges of the channel, together with a prescribed electrically generated heat flux on the external surface, were used as boundary conditions with which to solve the channel wall heat conduction equation. The resulting internal heat flux distribution over the full inner surface was subsequently used to determine the local variation of heat transfer coefficient. The method was validated using data available in the technical literature and subsequently used to study the individual effects of Coriolis induced secondary flow and centripetal buoyancy using new data generated for the investigation.

On the Droplet Deposition and Mist Supercooling in a turbulent channel flow

AbstractA combined experimental and theoretical study of the droplet deposition and mist supercooling in a turbulent channel flow has been performed. The measurement of droplet deposition on the unheated and heated channel wall was carried out using a particle‐sizing two‐dimensional reference‐mode laser‐Doppler anemomentry technique in a 41 mm × 41 mm vertical square channel at Re = 1.0 × 104 − 6.05 × 104. The dimensionless deposition coefficient kd/uZ. H. Yang Prof. S. L. Lee Department of Mechanical Engineering, State University of New York at Stony Brook, Stony Brook, NY 11794 (USA) is analyzed theoretically based on a new unified theoretical approach for the entire transverse flow region from the turbulent core to the quasi‐laminar region next to the boundary wall. The proposed analytical model shows satisfactory agreement with the results of present experimental measurement. In the mist supercooling, the heated surface is cooled by the evaporation on the outside surface of an extra thin continuous liquid film which is maintained by the continuous deposition of extremely small droplets of an optimal size determined by a selection process on the droplets transverse migration due to the dynamic interaction between the phases in a parallel turbulent mist flow. The heat transfer enhancement coefficient depends on droplet deposition rate, droplet size, concentration and the Reynolds number.

METHOD AND SOME RESULTS ON EXPERIMENTAL STUDY OF UNSTEADY TURBULENT HEAT TRANSFER

Abstract An experimental setup is described for studying unsteady heat transfer where both the heat generation rate in the channel wall and the fluid flow rate vary in time. For measuring the surface temperature and the wall heat flux, the temperature field in the thermal sublayer is used. The results of the first experiments carried out for a sudden change in channel wall heat generation are discussed. Unsteadiness rates much greater than those in previous work known to the authors were achieved

Potassium-seeded wall-stabilized arc source for Stark broadening studies

A potassium-seeded wall-stabilized arc source has been developed to provide a stable well-characterized plasma in which to measure the Stark broadening parameters of potassium excited-state transitions. Low-pressure (20-Torr argon) operation of the arc source reduces the argon collisional broadening contribution to the Stark-broadened line shapes, while a heated channel wall minimizes radial cataphoresis in the mixed-gas plasma. The arc source is designed for end-on observation and is compatible with far-infrared laser interferometry which is used to determine the effective plasma path length and on-axis electron density over the current operating range of 5–35 A.