Second Law Optimization of Pin Fin Heat Exchangers with Lateral Ejection Holes

The authors theoretically studied the entropy generation during heat transfer of a pin fin array in channels with lateral ejection holes for a turbine blade. The entropy generation model was established based on the second-law analysis. The distribution of the entropy generation due to heat transfer and fluid friction irreversibility respectively was analyzed and a comparison was made for three typical short pin fin channels. The entropy generation number component due to heat transfer decreases while Red increases, while the component due to fluid friction increases with the increase of Red. The entropy generation number takes its minimum value when the two components meet and the corresponding Reynolds number is optimal. The ejection holes influence the energy lost of the working fluid. For the three cases studied in the paper, case b with short ejection holes gives the best comprehensive thermal performance with comparison to cases with no and long ejection holes. The results would be helpful for the design of the heat dissipation of pin fin heat exchangers.