Heat Exchanger Performance and Optimisation

Clarke, Terrence (2021) Heat Exchanger Performance and Optimisation. [USQ Project]

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CLARKE Terrence dissertation_redacted.pdf

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Heat exchangers are used throughout industry, in various forms, to remove excessive heat created and allow continual operation of the equipment. A common type of heat exchanger is the liquid/liquid non-direct heat exchanger, typically with flow rates adjusted using a butterfly control valve to maintain desired operating temperatures. A modern option for reducing some of the system inefficiencies of heat exchangers is replacing the fixed output pump and butterfly control valve system with a variable speed pump which does not require a control valve. This improvement provides: • Improved efficiency as the variable speed pump uses less power • Longer pump life by reducing cavitation from throttling • Longer life and efficiency out of the heat exchanger core due to less ‘hot-spots’ resulting in fouling.

An extensive literature review was carried out, however little published information is available on the effects of a butterfly control valve at the entry of a heat exchanger. This dissertation investigates the knowledge gap surrounding the influence of a control valve at the entry of a heat exchanger. It addresses both the global heat distribution and the local transfer wall temperatures near the entry region. The following stepwise phases were completed in succession and form the structure of this investigation: • Phase 1: Conduct physical experiments of a simple heat exchanger arrangement and gather experimental data • Phase 2: Undertake a computational fluid dynamics (CFD) simulation of a heat exchanger modelled on the physical experiment • Phase 3: Compare the results of the experimental and simulation studies. Refine the CFD model until the results are within an acceptable error range • Phase 4: Conduct a physical experiment and CFD modelling of a simple heat exchanger using a control valve at the process water entry point and analyse the temperature distribution at a global level. • Phase 5: Analyse the temperature distribution at the entry of the heat exchanger for localized hot spots on the transfer wall • Phase 6: Scale the CFD model to the size and boundary conditions of the real-life application and repeat global and localized analysis.

With respect to the global heat distribution, the study found that both the USQ experimental jig and scaled analysis showed no influence from the control valve at the entry. However, for the local transfer wall distribution, the simple experimental jig and the scaled analysis both showed that the maximum temperature on the wall was significantly higher in the region 1.9 to 2.9x the diameter of the valve diameter into the heat exchanger. The study also found that as the angle of the control valve became more closed, both the average and maximum temperature across the transfer wall in the 1.9-2.9x valve diameter region increased.

These results indicate a variable speed pump reduces temperature spikes on the transfer wall and is preferable to a fixed speed pump with butterfly control valve.

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Item Type: USQ Project
Item Status: Live Archive
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering (1 Jul 2013 - 31 Dec 2021)
Supervisors: Saleh, Khalid
Qualification: Bachelor of Engineering (Honours) (Mechanical)
Date Deposited: 03 Jan 2023 00:15
Last Modified: 26 Jun 2023 01:01
Uncontrolled Keywords: heat exchanger, butterfly control valve, variable speed pump, efficiency, computational fluid dynamics
URI: http://sear.unisq.edu.au/id/eprint/51805

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