The accurate prediction of pipe contraction pressure loss is important in the design of pipe system such as heat exchangers, particularly when close control of the flow distribution in a network of pipes is required. The prediction of contraction pressure loss depends heavily on experimental data. Large discrepancies in these predictions are evident in the literature. Experimental results giving pres!? re loss coef fici ents for a range of Reyno 1 ds numbers of 4x 10 -2x 10 and area ratios of 0.135 - 0.692 are presented and compared with predictions from a method developed that allows for velocity profile variation through the contraction. The results show a Reynolds number dependence and good agreement between predicted and measured values. It is also important to be able to predict the variation of pressure loss coefficient with variations in the small-bore inlet geometry, referred to as the inlet sharpness. There are no know experimental data for the effects of inlet sharpness on the pipe contraction loss coefficient, but there are data for intakes set flush in a plane wall which are used as approximations. Experimental data showing the variation of pressure loss coefficient with inlet sharpness up to 13.4% are presented and compared with approximate data. The comparison shows significant differences. A three beam laser doppler anemmeter has been used to measure the detailed flow field for an area ratio of 0.332 and a Reynolds number of 153.8 x 10. The mean velocity, turbulent intensity and Reynolds stress distributions are presented for twenty-two axial stations between four large-bore diameters upstream to fourteen small-bore diameters downstream of the contraction. These experimental measurements are compared with computer predictions using the FLUENT code with the k-e- turbulence model. The general trends in the flow are predicted, however there are significant differences in the detailed flow field which are highlighted.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:253734 |
| Date | January 1990 |
| Creators | Hussain, Liaqat Ali |
| Publisher | Kingston University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://eprints.kingston.ac.uk/20538/ |
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