3.1.3.3 Use of worn nozzles
The cooling efficiency of the used and worn nozzles was compared with the new nozzles. The flat jet
nozzles were supplied by Corus, at the end of the nominal service life in the mill. A visual
comparison shows significant wearing of the used nozzles (Figure 3.1.7). The outer surface of the
nozzle appeared to be more worn-off than the orifice of the nozzle. The measurements of flow rate
show an increase of 11% at a pressure of 2.4 bar (g). The HTC measurements show negligible
differences when comparing the results of old and new nozzles. The results of HTC measurements
with identical pressures are shown in Figure 3.1.8. This is consistent with the expectation that the heat
transfer coefficient would increase approximately in proportion to the square root of water impact
density, based upon previous knowledge of the influence of impact density upon heat transfer
coefficient for sprays.