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Title: Development of system balancing approach for complex vapour compression refrigeration systems
Author: Zhang, Peipei
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2020
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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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available