Exergy Analyses of Onion Drying by Convection: Influence of Dryer Parameters on Its Performance

Abstract

This research work is concerned in the exergy analysis of the continuous-convection drying of onion. The influence of temperature and air flow rate was studied in terms of exergy parameters. The energy and exergy balances were carried out taking into account the onion drying chamber. Its behaviour was analysed based on exergy efficiency, exergy loss rate, exergetic improvement potential rate and sustainability index.The exergy loss rates increase with the temperature and air flow rate augmentation.Exergy loss rate is augmented at higher drying air temperatures and flow rates because the overall heat transfer coefficient increase. On the other hand, the exergy efficiency increases with the air flow rate augmentation. This behavior is due to the energy utilization was improved because the most amount of supplied energy was utilized for the moisture evaporation. However, the exergy efficiency decreases with the temperature augmentation due to the free moisture is less, then, the moisture begins diffusing from the internal structure to the surface. The exergetic improvement potential rate values show that the onion drying process presents a high potential to improve the exergy efficiency. The sustainability index of the drying chamber varied from 1.9 to 5.1. To reduce the environmental impact of the process, the parameters must be modified in order to ameliorate the exergy efficiency of the process.

Comparison of two artificial intelligence methods ( ANNs and ANFIS ) for estimating the energy and exergy of drying cantaloupe in a hybrid infrared‐convective dryer

“…Increasing the input air temperature and IR power indeed enhanced the enthalpy of the drying chamber. Increased EIP due to elevated temperature was also reported for rough rice (Beigi et al, 2017), onion (Castro et al, 2018), and okra (Agarry et al, 2021; Okunola et al, 2021).…”

“…Okunola et al (2021) similarly reported an increase in ESI at higher air temperature and load density for drying Okra. Castro et al (2018) dried onion with a convective dryer and concluded a decrement in ESI with increasing the temperature and decreasing air flow rate.…”

“…By raising the temperature and IR power, the input exergy to the drying chamber gains, thus a large amount of input exergy is evacuated from the drying chamber without being used to evaporate the water content of the cantaloupe slices (Yogendrasasidhar & Pydi Setty, 2018). Moreover, the rate of exergy loss rised at higher air temperatures and IR powers as the overall heat transfer coefficient was increased (Castro et al, 2018; Dincer & Sahin, 2004). Aghabshlo (2015, 2016), and Motevali et al (2018) also reported similar observations.…”

“…Note that the highest ESI values indicate the smallest impact on the environment. Thus, exergy efficiency should be improved to decline this effect (Castro et al, 2018).…”