Heat Transfer from a Row of Circular Water Jets.

Abstract

Experiments have been conducted to obtain local heat transfer coefficient distributions and average heat transfer associated with impingement of single water jet and a row of circular, free surface-water jets on a constant heat flux surface. The nozzle configuration is reverse cone type, and nozzle exit diameter is 8 mm in the case of single water jet, and nozzle arrays are a row of 3 jets (nozzle dia.=4.6 mm) and a row of 5 jets (nozzle dia.=3.6 mm). Nozzle-to-target plate spacings ranging from 16 mm to 80 mm were investigated for two jet center to center spacings 25 mm and 37.5 mm in the jet velocity of 3 m/s to 8 m/s. For the single jet, the nozzle-to-target plate spacings of maxima in the Nusselt number were observed at r/D≒3 in the jet velocity V0≥6 m/s for H/D from 4 to 10. Except for the condition of V0=8 m/s of H/D=10, the average Nusselt number reveals the following ranking : a row of 5 jets, a row of 3 jets, single jet. Compared with the single jet, average heat transfer enhancement for a row of 3 or 5 jets was presented. Correlations for average heat transfer were presented.