研究目的
To develop and validate a multiphase CFD model for direct absorption solar collectors with nanofluids, and to perform parametric analysis to optimize collector efficiency, including the study of thermomagnetic convection.
研究成果
The developed multiphase CFD model effectively simulates direct absorption solar collectors, showing that convective heating improves efficiency by up to 6% compared to conductive cases, and thermomagnetic convection can enhance efficiency by 30%. Optimal parameters for nanoparticle concentration and size were identified, and the model provides a tool for tailoring nanofluids for better solar energy harvesting.
研究不足
The model relies on simplifications such as constant-wavelength approximation for extinction coefficients, which may lead to discrepancies. Experimental uncertainties in thermal resistance and particle size estimation also affect accuracy. The study is limited to specific nanofluids and collector geometries, and real-world applications may involve additional complexities not captured.
1：Experimental Design and Method Selection:
A multiphase CFD model using the Eulerian-Eulerian technique was developed to simulate heat transfer and fluid dynamics in a direct absorption solar collector with nanofluid. The model incorporates absorption of thermal radiation, Brownian forces, rarefaction effects, natural convection, and thermomagnetic convection.
2：Sample Selection and Data Sources:
The model was validated against two experimental datasets: one from Liu et al. (2015) involving a nanofluid with graphene nanoparticles in an ionic fluid, and an in-house experiment with carbon black nanoparticles in water.
3：List of Experimental Equipment and Materials:
Equipment includes thermocouples (K-type and T-type), ultrasound bath (Branson 3510), optical microscopy, static light scattering device (Fritsch Analysette 22), halogen lamps (OSRAM Haloline 400 W), and computational tools (STAR-CCM+ software). Materials include nanofluids with various nanoparticles (e.g., graphene, carbon black, MnZn ferrite) and base fluids (e.g., water, ionic fluid).
4：Experimental Procedures and Operational Workflow:
Simulations were conducted using STAR-CCM+ with specific grid sizes and time steps. Boundary conditions included pressure and thermal settings, with variations in collector orientation, nanoparticle concentration, size, and magnetic field application.
5：Data Analysis Methods:
Data analysis involved comparing temperature profiles, efficiency calculations using Eq. (8), and statistical comparisons with experimental results to validate the model.
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