2.1. Physical Model and Governing Equations
Fig. 1 illustrates schematic diagram of the simulated three-dimensional
parabolic through solar collector equipped with obstacles as turbulator.
The length of the collector is 860 mm and the absorber diameter and
glass cover diameter are 50 mm and 80 mm, respectively. Also the inlet
length of 600 mm and outlet length of 100 mm are determined, because it
is important that the inlet flow is fully developed and there be not any
flow comeback at exit section of the channel. The absorber system is
made of stainless steel 304 with 2mm thickness and the glass cover is
made of normal glass with the thickness of 5mm. Also three different
Reynolds numbers, Re=2000, 5000 and 8000. It is clear that these studied
Reynolds numbers are in transient and turbulent regime. For all studied
models, initial nanofluid temperature is Tinitial= 450K and the solar irradiation of I = 900W/m2is adopted. The heat transfer fluid is water-based
MWCNT-Al2O3 (80%:20%) hybrid nanofluid
which makes a Newtonian nanofluid. Due to achieving the most efficient
Newtonian nanofluid in the present study, solid nanoparticles of MWCNT
and Al2O3 are added to the base fluid in
volume concentration of 0.01 with diameters of 20 nm. Table 1 reports
the thermophysical properties of the Newtonian base fluid and solid
particles. As it is noted previously, the main aim of the present study
is to analyze the thermal-hydraulic effects of using turbulators inside
a parabolic through solar collector filled with hybrid nanofluid.
Different geometrical parameters of obstacles are shown in Fig. 1. Also,
Table 2 reports all properties of studied configurations.
Table 1 Base fluid and nanoparticles numerical values for
thermophysical properties [56-58]