A study of turbulent flow in a superheater model using laser velocimetry

An experimental study was conducted of the turbulent flow in a model superheater using laser velociraetry. The primary objective of the superheater model study was to determine the aerodynamic behavior of the gas flow through the superheater in order to help explain heat transfer and ash deposition characteristics of the superheater.

The 1/4 scale superheater model used air at standard conditions to generate sufficiently high Reynolds number flows in the model. Two component vector velocity data was obtained using a dual Bragg cell laser velocimeter. Measurements of mean velocity, turbulence intensity, and velocity-time data were obtained at many axial stations along the flow.

The data from the superheater model study showed that nonuniform flow conditions exist in the first section of the superheater. This flow nonuniformity is expected to reduce the efficiency of the superheater operation because of the effects on heat transfer and ash deposition. The flow becomes uniform after the gas has passed through enough tube banks. Periodic flow oscillations occur behind each row of cooling tubes because of vortex shedding. Wakes occurring behind each row of tubes increase turbulence intensity which is expected to increase ash deposition in real superheaters. No large scale flow unsteadiness was found in frequency analysis of the data.