Impingement heat transfer investigations using liquid crystals for single unconfined and semi-confined and semi-confined jets

Eastwood, D., 1994. Impingement heat transfer investigations using liquid crystals for single unconfined and semi-confined and semi-confined jets. MPhil, Nottingham Trent University.

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Abstract

Impingement heat transfer investigations using liquid crystals for single unconfined and semi-confined jets. Donald Eastwood Experimental results are presented for a single unconfined and semi-confined air jet impinging normally onto a heated flat plate. The nozzle to plate distances, expressed as a ratio of the nozzle diameter are 2, 4 and 6 and the Reynolds number range is 31 000 to 145 000. Heat transfer rates were determined from measured values of temperature difference across the plate and the thermal properties of the plate. The radial variation of the plate surface temperature was obtained by using liquid crystals. These measurements provided the data for the determination of local values of Nusselt number for radius to nozzle diameter ratios of 1 to 10.

Correlations are presented for the two jets relating Nusselt number to Reynolds number, the nozzle distance ratio and the radius distance ratio for radius ratio values in excess of 2.5. For both modes the jets show a dependence of the Nusselt number on Reynolds number, this being stronger in the case of the semi-confined jet. The dependence on the radius ratio is characteristic of a wall jet. For radius ratios greater than 5 and for both jets the thermal energy transfer rates are almost independent of the nozzle distance. The transfer of thermal energy for the unconfined jet is greater because of the increased entrainment of surrounding air into the jet as it develops. For radius ratios greater than 2.5 the difference between the jets increases with increasing radius but decreases with increasing Reynolds number and increasing nozzle distance ratio. Over the range of geometric and flow conditions the Nusselt number for the unconfined jet is from 5 to 50 per cent greater than for the semi-confined jet.

Item Type:	Thesis
Creators:	Eastwood, D.
Date:	1994
ISBN:	9781369325539
Identifiers:	Number Type PQ10290304 Other
Rights:	The data within this thesis may be used for the purpose of furthering the understanding and knowledge of thermal energy transfer. The data may be used for commercial gain only with the permission of the author.
Divisions:	Schools > School of Science and Technology
Record created by:	Laura Ward
Date Added:	06 Jul 2021 08:51
Last Modified:	20 Mar 2024 16:18
URI:	https://irep.ntu.ac.uk/id/eprint/43330

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