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Feasibility of expanders’ application in refrigeration systems based on R774

Katarzyna Anna Magryta

Abstract

The aim of the thesis is to estimate the feasibility of expanders’ applications in cascade refrigeration systems based on carbon dioxide. In the introduction, a literature review was conducted on the principle of operation and applications of expanders, as well as their design and specific technological solutions. The advantages and disadvantages of individual solutions were analysed and a scroll expander was selected for further analysis. Studies in the field of its geometric and thermodynamic models have been extended. The information obtained was used to assume the possible isentropic efficiency that the device could achieve during operation. In the main part, there was created a model of a refrigeration cascade system with throttling valves with a constant evaporating temperature - 40°C. The low-pressure cycle is a subcritical when a high-pressure one - supercritical cycle. The condensing pressure was set at a constant level of 150 bar. A computational model was distributed. The object of optimisation is to find a low-temperature condensing temperature level, for which the refrigeration efficiency coefficient is the maximum. Similar models were also created for modified systems with expanders in the lower, upper or both cascade cycles. Parameters of wet refrigerant vapours were determined by two methods: graphically or by means of approximation with state equations for wet steam. Chapter 4 presents the results of the conducted simulations. It shows that in a system with one expander in the lower cascade cycle, the maximum increase is 16.6%, in the system with the expander in the upper cycle - up to 20%. In a system with two expanders, EER can be 36.0% higher than in the reference system with expansion valves for graphical calculations. The calculations showed small differences between the two calculation methods, but the method of approximation with equations of state can give underestimated results.
Diploma type
Engineer's / Bachelor of Science
Diploma type
Engineer's thesis
Author
Katarzyna Anna Magryta (FPAE) Katarzyna Anna Magryta,, Faculty of Power and Aeronautical Engineering (FPAE)
Title in Polish
Supervisor
Adam Ruciński (FPAE/IHE) Adam Ruciński,, The Institute of Heat Engineering (FPAE/IHE)Faculty of Power and Aeronautical Engineering (FPAE)
Certifying unit
Faculty of Power and Aeronautical Engineering (FPAE)
Affiliation unit
The Institute of Heat Engineering (FPAE/IHE)
Study subject / specialization
, Energetyka (Power Engineering)
Language
(pl) Polish
Status
Finished
Defense Date
12-02-2019
Issue date (year)
2019
Pages
44
Internal identifier
MEL; PD-4951
Reviewers
Artur Rusowicz (FPAE/IHE) Artur Rusowicz,, The Institute of Heat Engineering (FPAE/IHE)Faculty of Power and Aeronautical Engineering (FPAE) Adam Ruciński (FPAE/IHE) Adam Ruciński,, The Institute of Heat Engineering (FPAE/IHE)Faculty of Power and Aeronautical Engineering (FPAE)
Keywords in Polish
Keywords in English
scroll, expander, Energy efficiency rating, carbon dioxide, cascade refrigeration systems, steam equations of state
Abstract in Polish
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Local fields
Identyfikator pracy APD: 31322

Uniform Resource Identifier
https://repo.pw.edu.pl/info/bachelor/WUT5770eda7aa1341daa19bd0339da2f474/
URN
urn:pw-repo:WUT5770eda7aa1341daa19bd0339da2f474

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