In some industrial air-cooled heat exchangers, such as those in the generating set industry, the flow must turn through 90° after exiting the heat exchanger. In such arrangements, the plenum depths are typically very shallow. Furthermore., the axial fan often operates in the mixed-flow region of the fan characteristic, due to the restrictive nature of the system. These two factors lead to a reduction in the thermal performance of the system. The purpose of this study was to investigate the effect on thermal performance of inclining the heat exchanger relative to the axial fan. It was also important to compare this with simply increasing the plenum depth without inclining the heat exchanger, since inclination itself may increase the mean plenum depth. This was achieved through an isothermal experimental investigation, complemented with a numerical study using CFD. The results showed that as the heat exchanger was inclined, the low velocity core at the centre of the heat exchanger tended to move to one side. The opposite side had increased flow through the heat exchanger due to the inclination. For a mixed-flow fan operating point typical of some industries, it was found that inclination has a negligible effect on the performance of the system, when compared with a baseline case. Increasing the plenum depth also had no significant effect. At the axial fan operating point investigated, it was found that an angle of approximately 30° inclination gave the best performance. Increasing the plenum depth was found to improve the performance more than inclination. The best performing case was the non-inclined case with a plenum depth of 0.65 fan diameters. This gave an increase in flow of2.8% over the baseline case, and a corresponding 1.1 % increase in thermal performance.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:601789 |
| Date | January 2013 |
| Creators | Kennedy, Ian James |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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