We are looking for a detailed physical description of the process by means of numerical modelling, developing a multiphase CFD model of the solar light absorption in nanofluid. The commercial STAR-CCM+ was extended through user coding to account for the features inherent for nanofluids. An example of the model-predicted temperature field is shown below for a solar collector heated from the top, a pseudo-random motion of the nano-particles is highlighted by vectors of their magnitude.
Model-predicted temperature field
The model was tested against the third-party experimental data, the validated experimental plot is indicated in the figure below in terms of the superheat vs dimensionless height of the collector.
The model, described in this article, was studied parametrically, altering: size and concentration of nanoparticles, tilt angle and the geometry of the collector, gradient of an external magnetic field.
Considered heating alternatives and boundary conditions
The parametric analysis outcomes with the following conclusions:
– a typical DAC ought to be designed in a way, which insures inherent dispersion of nanoparticles all over the nanofluid due to natural convection
Collector efficiency for different heating alternatives
– the nanofluid-based DACs are at least 10% more efficient than the flat-plate collectors
Collector efficiency as a function of: tilt angle, particle size and volume fraction
– the magnetic convection enhances the efficiency by 30%.
Influence of magnetic filed: temperature profile and flow configuration
Collector efficiency vs magnetic field