Investigation of Thermal-Flow Characteristics of Pipes with Helical Micro-Fins of Variable Height

Piotr Bogusław Jasiński, Michał Jan Kowalczyk, Artur Romaniak, Bartosz Warwas, Damian Obidowski and Artur Gutkowski
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Piotr Bogusław Jasiński: Institute of Turbomachinery, Lodz University of Technology, 90-924 Lodz, Poland
Michał Jan Kowalczyk: Institute of Turbomachinery, Lodz University of Technology, 90-924 Lodz, Poland
Artur Romaniak: Institute of Turbomachinery, Lodz University of Technology, 90-924 Lodz, Poland
Bartosz Warwas: Institute of Turbomachinery, Lodz University of Technology, 90-924 Lodz, Poland
Damian Obidowski: Institute of Turbomachinery, Lodz University of Technology, 90-924 Lodz, Poland
Artur Gutkowski: Institute of Turbomachinery, Lodz University of Technology, 90-924 Lodz, Poland

Energies, 2021, vol. 14, issue 8, 1-18

Abstract: The results of numerical investigations of heat transfer and pressure drops in a channel with 30° helical micro-fins are presented. The main aim of the analysis is to examine the influence of the height of the micro-fins on the heat-flow characteristics of the channel. For the tested pipe with a diameter of 12 mm, the micro-fin height varies within the range of 0.05–0.40 mm (with 0.05 mm steps), which is equal to 0.4–3.3% of its diameter. The analysis was performed for a turbulent flow, within the range of Reynolds numbers 10,000–100,000. The working fluid is water with an average temperature of 298 K. For each tested geometry, the characteristics of the friction factor f ( Re ) and the Nusselt number Nu ( Re ) are shown in the graphs. The highest values of Nusselt numbers and friction factors were obtained for pipes with the micro-fins H = 0.30 mm and H = 0.35 mm. A large discrepancy is observed in the friction factors f ( Re ) calculated from the theoretical relationships (for the irregular relative roughness values shown in the Moody diagram) and those obtained from the simulations (for pipes with regular roughness formed by micro-fins). The PEC (Performance Evaluation Criteria) heat transfer efficiency analysis of the geometries under study is also presented, taking into account the criterion of the same pumping power. The highest PEC values, reaching 1.25, are obtained for micro-fins with a height of 0.30 mm and 0.35 mm and with Reynolds numbers above 40,000. In general, for all tested geometries and for large Reynolds numbers (above 20,000), the PEC coefficient reaches values greater than 1, while for lower Reynolds numbers (less than 20,000), its values are less than 1.

Keywords: heat transfer coefficient; micro-fins; friction factor; numerical methods; CFD (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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