Optimization of wavy direct absorber solar collector (WDASC) using Al₂O₃-water nanofluid and RSM analysis

In this paper, the best wavy profile for the bottom plate of a wavy nanofluid-based direct absorber solar collector (WDASC) is obtained by numerical and statistical methods. For this aim, thermal performance of a WDASC is evaluated by finite element method (FEM) using FlexPDE commercial package software and Al₂O₃-water nanofluid is considered as the working fluid in the collector. It is considered that bottom wavy plate remain in a constant temperature while the top flat plate is in constant heat flux due to solar radiation and the sides wall are insulated. To find the best wavy profile for the bottom plate, 9 different cases proposed by CCD are designed and by response surface method (RSM) analysis the best profile is introduced. Results show that the best case involves minimum possible wave amplitude (A_m) in average wave numbers (λ) for the wavy wall.