Investigation of impingement heat transfer in double-wall cooling structures with corrugated impingement plate at small Reynolds numbers

This study investigated an impingement/effusion cooling scheme with a corrugated jet plate applicable to a high-temperature exhaust cooling nozzle. The primary objective was to evaluate the effect of the corrugated wall jet on the impingement heat transfer and flow loss in a narrow target chamber under a low jet Reynolds number ranging from 450 to 2700. Sinusoidal curves with different wavelengths were employed to model the corrugated jet plate, where impingement holes were located at the trough of the plate. The location of the impingement holes creates a staggering pattern relative to the effusion holes. The corrugated jet plates with relative ripple amplitudes (A/d) considered were 0.2, 0.5 and 0.8, and the results were compared with those of a flat jet plate. Three relative average jet-to-plate spacings, H_ave/d, were selected for use: 1.6, 2.6, and 3.6. The heat transferred over a smooth target surface by multiple jets was measured using the transient liquid crystal (TLC) method. Results show that the amplitude of the corrugated plate was found to profoundly influence the heat transfer of the target surface. The use of corrugated jet plates yielded a better heat transfer performance at a relatively high Re and low impinging distance. The optimal heat transfer performance was achieved at A/d of 0.5, which was 28 % higher than the flat plate. The discharge coefficient for the corrugated jet plate was 2–9.4 % lower than that of the flat jet plate at all H_ave/d and Re values, and the minimum discharge coefficient was reached at A/d of 0.2. Furthermore, internal impingement heat transfer and flow resistance characteristics of the corrugated impingement/effusion were correlated according to the experimental data.