Numerical investigation on solar air collector and its practical application in the indirect solar dryer for banana chips drying with energy and exergy analysis

Abstract

In this paper, a numerical investigation was carried out to identify a proper solar air collector (SAC) for an indirect solar dryer (ISD). Corrugated absorber surfaces were used to enhance the heat transfer rate between air and absorber. The manuscript aims to develop a numerical model to identify proper SAC and to execute the proposed SAC model in an experimental setup hence it is an innovative study. The drying behavior and drying characteristics of banana slices were estimated by conducting the experiments in an ISD dryer which was developed based on the outcomes of numerical analysis. The velocity and temperature inside the dying cabinet were estimated for both cases. Better performance was noticed in triangular corrugated SAC and therefore, an ISD was developed with triangular corrugated SAC. The thermal performance of ISD was investigated. Numerical and experimental results of temperature at the outlet of SAC were compared. Also, the drying kinetics of banana samples was studied. Different corrugation angles (θ) (5 to 30°) and corrugation heights (e) (0.5 to 2 cm) were used to identify the maximum thermo-hydraulic performance parameters (THPP). The maximum THPP was 1.83 at θ = 20° and e = 1 cm which helped uniform distributions of velocity and temperature inside the drying chamber. From the investigation, surface transfer coefficients, diffusivity, and activation energy of banana slices were calculated. The average collector and dryer efficiencies were 64.5% and 55.30%, respectively. Banana samples were dried from 3.5566 to 0.2604 kg/kg on a dry basis (db). The experimental drying curve was fitted to six thin layer drying models and a fitting model was identified. Effective moisture diffusivity, surface transfer coefficients, and activation energy were estimated. Exergy and cost analyses were performed.