Effect of Nanofluid Thermophysical Properties on the Performance Prediction of Single-Phase Natural Circulation Loops

Nur Çobanoğlu and Ziya Haktan Karadeniz
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Nur Çobanoğlu: Graduate School of Natural and Applied Sciences, İzmir Kâtip Çelebi University, 35620 İzmir, Turkey
Ziya Haktan Karadeniz: Department of Mechanical Engineering, İzmir Kâtip Çelebi University, 35620 İzmir, Turkey

Energies, 2020, vol. 13, issue 10, 1-23

Abstract: Specifying nanofluids’ thermophysical properties correctly is crucial for correct interpretation of a system’s thermo-hydraulic performance and faster market-uptake of nanofluids. Although, experimental and theoretical studies have been conducted on nanofluids’ thermophysical properties; their order-of-magnitude change is still a matter of debate. This numerical study aims to reveal the sensitivity of single phase natural circulation loops (SPNCL), which are the passive systems widely used in solar thermal and nuclear applications, to thermophysical property inputs by evaluating the effects of measured and predicted nanofluid thermophysical properties on the SPNCL characteristics and performance for the first time. Performance and characteristics of an SPNCL working with water-based-Al 2 O 3 nanofluid (1–3 vol.%) for heating applications is evaluated for different pipe diameters (3–6 mm). The thermal conductivity effect on SPNCL characteristics is found to be limited. However, viscosity affects the SPNCL characteristics significantly for the investigated cases. In this study, Gr m ranges are 1.93 × 10 7 –9.45 × 10 8 for measured thermophysical properties and 1.93 × 10 7 –9.45 × 10 8 for predicted thermophysical properties. Thermo-hydraulic performance is evaluated by dimensionless heat transfer coefficients which is predicted within an error band of ±7% for both the predicted and measured thermophysical properties of the data. A Nu correlation is introduced for the investigated SPNCL model, which is useful for implementing the SPNCL into a thermal system.

Keywords: thermal conductivity; viscosity; nanofluid; single phase natural circulation loop; Nu correlation (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: 2020
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Citations: View citations in EconPapers (1)

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