Exergy analyses of onion drying by convection: Influence of dryer parameters on its performance

M. CASTRO; C. ROMÁN; M. ECHEGARAY; G. D. MAZZA; R. A. RODRÍGUEZ

ENTROPY

MOLECULAR DIVERSITY PRESERVATION INTERNATIONAL-MDPI

Lugar: Basel; Año: 2018 vol. 20 p. 310 - 319

1099-4300

This research work is concerned in the exergy analysisof the continuous-convectiondrying of onion. The influence of temperature and airflow rate was studied in terms ofexergy parameters. The energy and exergy balances werecarried out taking intoaccount the onion drying chamber. Its behaviour wasanalysed based on exergyefficiency, exergy loss rate, exergetic improvementpotential rate and sustainabilityindex.The exergy loss rates increase with the temperatureand air flow rate augmentation.Exergy loss rate is augmented at higher drying airtemperatures and flow rates becausethe overall heat transfer coefficient increase. On theother hand, the exergy efficiencyincreases with the air flow rate augmentation. Thisbehavior is due to the energyutilization was improved because the most amount ofsupplied energy was utilized forthe moisture evaporation. However, the exergyefficiency decreases with thetemperature augmentation due to the free moisture isless, then, the moisture beginsdiffusing from the internal structure to the surface.The exergetic improvementpotential rate values show that the onion dryingprocess presents a high potential toimprove the exergy efficiency. The sustainabilityindex of the drying chamber variedfrom 1.9 to 5.1. To reduce the environmental impact ofthe process, the parametersmust be modified in order to ameliorate the exergy efficiency of theprocess.