Solar dryer with double pass flat plate solar collector and carbon nanodots-coated absorber surface

The present study details the development of a solar dryer with double pass flat plate solar collector having carbon nanodots (CNDs) coated absorber surface. Among the various concentrations of CNDs (0.1, 0.2, 0.5, 1, and 2%), the 0.5% CNDs coated absorber surface recorded the highest absorptance and lowest reflectance with higher spectral selectivity of 0.933. Hence, the 0.5% coating was selected as the optimum concentration and coated over the absorber surface of flat plate solar air collector. SEM image of black painted surface is clear and smooth and CNDs coated absorber surface is having dispersed particle with rough surface. FTIR absorption peak values revealed that the presence of black paint and CNDs in the 0.5% CNDs coated aluminium sheet. The efficiency of collector coated with 0.5% CNDs was calculated at various air flow rate of 0.008, 0.016, 0.018, and 0.021 kg/s and results revealed that the rise in air flow rate from 0.008 to 0.021 kg/s increased the efficiency from 39.22 to 82.99%. The solar dryer connected with the developed collector was tested for the performance and the drying studies revealed that shrimp and false white sardine required 10 h and 11 h drying time during the experimental studies.