Heat transfer of impinging jet array with web-patterned grooves on nozzle plate

•Heat transfer improvements by webbed grooves for impinging jet arrays at 0.1 ≤ S/dj ≤ 8 were demonstrated.•Rej and S/dj effects on local and average Nu for smooth and grooved nozzle plates were revealed.•Parametric conditions with improved heat transfer uniformity due to grooves on nozzle plates were identified.•Empirical correlations for average Nu of jet arrays using smooth and grooved nozzle plates were devised. Heat transfer performances of the impinging jet arrays issued from the nozzle plates without and with the two types of the interconnected grooves were experimentally studied at jet Reynolds numbers (Rej) and nozzle-to-plate distances (S) in the respective ranges of 1500–20,000 and 0.1–8 times of the nozzle diameters (dj). Owing to the significant spent flow confinement formulated between the smooth nozzle plate and the impinging surface at S/dj