Abstract:
This thesis reports the results of an experimental
study into the flow and heat transfers associated with
both inclined and orthogonally impinging axisymmetric
air jets. The majority of previously reported studies
have been mainly confined to orthogonally impinging jets
in stagnant surroundings. In this investigation, free
jets as well as the effects of crossflows are considered.
This investigation is Primarily concerned with local
heat transfer variations. The experimental tests were.
conducted with a single 12.7 mm diameter jet impinging on
a flat surface, and heat transfers were evaluated using a
heat-mass transfer analogy (t e Chilton-Colburn analogy).
The sublimation of naphthalene was employed as the mass
transfer technique.
The flowfield associated with impinging jets has a
significant influence on their heat transfer characteristics.,
In view of the present limited level of understanding of
this 'complex' flowfield, extensive flow visualisation techniques
were employed in this present investigation. Those
were primarily intended to aid interpretation of the experimental
heat transfer results, and also to provide further
physical understanding of the flowfields resulting from the
interactions between impinging jets and crossflowing streams.
The flow and heat transfer tests conducted in the
programme of work reported in this thesis covered typical
ranges of flow parameters of interest in many practical
applications of jet impingement systems. Jet inclinations
of 45°, 600, and 90°, nozzle to target spacings of 2,11,
and 8 nozzle diameters were studied. The Reynolds nuinbers
were 30,200,32,700 and 55,100 and mass velocity ratios In
the range 4.0 to 3.8 were studied.
The effects of these parameters on the flow and heal
transfers associated with impinging jets are reported.
Comparisons were drawn between the heat transfer results
and those of previously reported studies where appropriate.
