Work

Comparative CFD study of heat transfer enhancement in a Solar-Exposed pipe using Al2O3–Water nanofluid

Year: 2026

Type: article

Abstract: Despite the potential of Direct Absorption Solar Collectors (DASC), there is a significant lack of high-fidelity numerical investigations focusing on their performance under extreme environmental conditions. This study addresses this gap by presenting a detailed three-dimensional numerical investigation into the heat transfer enhancement of a solar-exposed glass pipe using Al2O3–water nanofluid (1% vol.). The primary aim is to evaluate the system’s efficiency under the high-irradiance conditions of Basra, Iraq (1000W/m2), where thermal loads are maximum.The Computational Fluid Dynamics (CFD) framework employs the Discrete Ordinates (DO) model to accurately simulate volumetric solar absorption and radiative transport. The numerical model was rigorously validated against established experimental and analytical benchmarks, demonstrating high fidelity with a maximum deviation of only 1.8%. Simulations were conducted within a laminar flow regime (Re=6.19) to analyze the thermo-hydraulic synergy of the nanofluid.The results reveal a substantial thermal augmentation; the convective heat transfer coefficient (h) increased from 1476W/m2∙K for pure water to 9217W/m2∙K for the nanofluid, corresponding to a six-fold rise in the Nusselt number (Nu). Even at ultra-low flow rates, the nanofluid achieved a peak outlet temperature of 327K and a maximum irradiation absorption of 4500W/m2∙K. Significantly, the Overall Performance Index (OPI) and Performance Evaluation Criterion (PEC) reached 6.28 and 5.90, respectively.These findings indicate that the thermal benefits of using Al2O3 nanofluids far outweigh the minor hydraulic penalties, confirming their exceptional efficiency for DASC in arid climates. This study provides a robust solution for maximizing energy conversion in low-flow solar applications under peak thermal stress.

Source: Results in Physics

DOI: 10.1016/j.rinp.2026.108684

Authors: Usama Jawad Mizher, Mustafa Jawad Mezher, Anmar Ghareeb Alruhaimi, Iltifat Hameed Saud, Mahmood Alhafadhi

Institutions: Southern Technical University, Middle Technical University, University of Sumer, University of Dunaújváros

Language: English

Topic: Nanofluid Flow and Heat Transfer

Subfield: Fluid Flow and Transfer Processes

Field: Chemical Engineering

Domain: Physical Sciences

SDGs: Affordable and clean energy, Climate action, Clean water and sanitation

Open Access status: gold

Estimated APC paid: $1,920