ISSN Online: 2377-424X
ISBN Print: 0-85295-345-3
International Heat Transfer Conference 10
UNSUBMERGED JET IMPINGEMENT HEAT TRANSFER AT LOW LIQUID SPEED
Abstrakt
The heat transfer between a round unsubmerged water jet
normally impinging from above on a flat horizontal heated
surface was experimentally studied in a range of low jet
velocities, in operating conditions not yet reported in the open literature. A range of Re from 10000 to 50000 was
investigated, with pipe-type nozzles of 10, 14 and 17 mm inner
diameters at a distance from the plate ranging from 6 to 20
diameters.
A free jet at low Froude numbers exhibits a cross-area
contraction in the flow direction and a consequent increase in
the mean velocity which heavily affects the heat transfer rate
on the wall at the stagnation point. After developing a simple
one-dimensional model of the jet motion, only accounting for
the effect of gravity, a new and successful way of correlating
the heat transfer data at low jet velocity is proposed. The need of accounting for the jet parameters (diameter and velocity) close to the surface, instead of those at the nozzle exit, is clearly emphasized.