Assessment of performance and sustainability of waste heat dryer coupled with air conditioner unit during drying of banana slices

Abstract

The present work presents the effective application of waste heat rejected from window air conditioning (AC) in a waste heat dryer (WHD) for drying plantain banana slices. The comparison between drying with the waste heat dryer coupled with an AC unit (ACWHD) and a natural convective indirect solar dryer (SD) reveals significant differences in drying kinetics, supply air conditions, and thermodynamic performance. The drying kinetics of banana slices obtained with ACWHD and SD were validated by revisiting the concepts of dryer performance index (DPI) and generalized drying curve. The temperature of the hot air supplied to the drying chamber in ACWHD was 48 °C while the relative humidity of the supply air was below 30 %. The thermodynamic performance assessment revealed that the exergetic efficiency was about 45 % and 16 % for ACWHD and SD respectively. The results of exergy based sustainable index and environment impact factor indicated the potential application of the waste heat of residual air from AC units for drying applications. Thus, the results of the present study imply that this novel idea has appreciable potential for commercialization with large-scale central air conditioning units in commercial complexes and industries where the magnitude of heat rejection will be multi-fold.

Keywords

• Air conditioning
• Exergy. outdoor unit
• Solar dryer
• Sustainability
• Waste heat