Zhang, Peipei;
(2020)
Development of system balancing approach for complex vapour compression refrigeration systems.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Currently, component selection and matching (also referred as system balancing) performed at design stage of vapour compression refrigeration (VCR) systems can adopt either the mathematical or graphical approach, using components’ performance data from manufacturers. However, the balancing concept has been mainly developed and applied to basic single stage VCR systems. This thesis presents the development and implementation of the mathematical approach for balancing complex VCR systems. Particularly, the capability of the conventional mathematical iterative looping approach is expanded to deal with a more diverse range of system operations and configurations. The work involves a careful analysis of component/system operations, catalogue data and existing regression models for components. Logics of iterative loops are developed for balancing components of the chosen systems, including two-stage systems, two-evaporator systems, a single-stage trans-critical CO2 system, a room air dehumidifier system and an air cooling system with dehumidification. Characteristic representations of different components including evaporator pressure regulating valves, CO2 gas coolers, trans-critical CO2 compressors and dehumidifying coils, etc. are established based on regression analysis of manufacturers’ data. Apart from component selection and matching, ways to achieve size and operation optimization for energy efficiency are explored. Sensitivity analysis of components’ sizes is performed for a two-stage VCR system to achieve the optimal inter-stage pressure and COP. Guidelines are proposed for optimizing components’ sizes or/and the gas cooler pressure by assessing the system performance under various loading/operation conditions. Practical factors such as pressure drop, superheat, sub-cooling, fouling factor, etc., and in some cases, transient behaviour as in frost coils, are taken into account.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Development of system balancing approach for complex vapour compression refrigeration systems |
| Event: | UCL (University College London) |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2020. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10099576 |
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