Exergy-Based Efficiency Assessment of Fans vs. Isentropic Efficiency
The efficiency definition allows us to compare two machines with each other. In general, the efficiency is defined as the ratio of usable power to the required power. This raises the question: what is the usable power? Most engineers discuss efficiency on the basis of the energy balance, i.e., the f...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-02-01
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| Series: | International Journal of Turbomachinery, Propulsion and Power |
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| Online Access: | https://www.mdpi.com/2504-186X/8/1/4 |
| _version_ | 1827749440903970816 |
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| author | Johannes Brötz Christian Schänzle Peter F. Pelz |
| author_facet | Johannes Brötz Christian Schänzle Peter F. Pelz |
| author_sort | Johannes Brötz |
| collection | DOAJ |
| description | The efficiency definition allows us to compare two machines with each other. In general, the efficiency is defined as the ratio of usable power to the required power. This raises the question: what is the usable power? Most engineers discuss efficiency on the basis of the energy balance, i.e., the first law of thermodynamics. In this paper, we derive the exegetic efficiency taking the second law of thermodynamics into account. Exergy analysis takes into account work and heat and is able to model reality very accurately. On this basis, a comparison between the isentropic and exergetic efficiencies is given. A high-pressure radial fan is used as an example, and the differences are discussed. Therefore, measurements of a non-adiabatic fan are evaluated, and the role of the heat flux in the environment is discussed. The investigations show that a relevant difference between the isentropic and exergetic efficiencies becomes apparent in the partial-load range with high-pressure build-up. The thermal energy contained in the flow belongs proportionally to the exergy, i.e., the working capacity of the gas relative to its environment. For a standard such as ISO 5801 “Fans—Performance testing using standardized airways”, the efficiency must not only be physically correct, it must also be simple and practical. Against this background, the outlook of this paper discusses when and which efficiency definition is appropriate and best suited for a standard. |
| first_indexed | 2024-03-11T06:24:09Z |
| format | Article |
| id | doaj.art-87192648d1474060bf32284d3ffadfdb |
| institution | Directory Open Access Journal |
| issn | 2504-186X |
| language | English |
| last_indexed | 2024-03-11T06:24:09Z |
| publishDate | 2023-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | International Journal of Turbomachinery, Propulsion and Power |
| spelling | doaj.art-87192648d1474060bf32284d3ffadfdb2023-11-17T11:43:02ZengMDPI AGInternational Journal of Turbomachinery, Propulsion and Power2504-186X2023-02-0181410.3390/ijtpp8010004Exergy-Based Efficiency Assessment of Fans vs. Isentropic EfficiencyJohannes Brötz0Christian Schänzle1Peter F. Pelz2Department of Mechanical Engineering, Technische Universität Darmstadt, Otto-Berndt-Straße 2, 64287 Darmstadt, GermanyDepartment of Mechanical Engineering, Technische Universität Darmstadt, Otto-Berndt-Straße 2, 64287 Darmstadt, GermanyDepartment of Mechanical Engineering, Technische Universität Darmstadt, Otto-Berndt-Straße 2, 64287 Darmstadt, GermanyThe efficiency definition allows us to compare two machines with each other. In general, the efficiency is defined as the ratio of usable power to the required power. This raises the question: what is the usable power? Most engineers discuss efficiency on the basis of the energy balance, i.e., the first law of thermodynamics. In this paper, we derive the exegetic efficiency taking the second law of thermodynamics into account. Exergy analysis takes into account work and heat and is able to model reality very accurately. On this basis, a comparison between the isentropic and exergetic efficiencies is given. A high-pressure radial fan is used as an example, and the differences are discussed. Therefore, measurements of a non-adiabatic fan are evaluated, and the role of the heat flux in the environment is discussed. The investigations show that a relevant difference between the isentropic and exergetic efficiencies becomes apparent in the partial-load range with high-pressure build-up. The thermal energy contained in the flow belongs proportionally to the exergy, i.e., the working capacity of the gas relative to its environment. For a standard such as ISO 5801 “Fans—Performance testing using standardized airways”, the efficiency must not only be physically correct, it must also be simple and practical. Against this background, the outlook of this paper discusses when and which efficiency definition is appropriate and best suited for a standard.https://www.mdpi.com/2504-186X/8/1/4exergyefficiencyfansecond law |
| spellingShingle | Johannes Brötz Christian Schänzle Peter F. Pelz Exergy-Based Efficiency Assessment of Fans vs. Isentropic Efficiency International Journal of Turbomachinery, Propulsion and Power exergy efficiency fan second law |
| title | Exergy-Based Efficiency Assessment of Fans vs. Isentropic Efficiency |
| title_full | Exergy-Based Efficiency Assessment of Fans vs. Isentropic Efficiency |
| title_fullStr | Exergy-Based Efficiency Assessment of Fans vs. Isentropic Efficiency |
| title_full_unstemmed | Exergy-Based Efficiency Assessment of Fans vs. Isentropic Efficiency |
| title_short | Exergy-Based Efficiency Assessment of Fans vs. Isentropic Efficiency |
| title_sort | exergy based efficiency assessment of fans vs isentropic efficiency |
| topic | exergy efficiency fan second law |
| url | https://www.mdpi.com/2504-186X/8/1/4 |
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