Banana slice drying using waste heat from an air conditioner for enhancing performance and sustainability

As waste heat dryers (WHD) exhibit conservation of energy with environmental and economic benefits, the direct use of waste hot air rejected from the outdoor unit of a window air conditioning (AC) unit for drying banana slices is demonstrated experimentally in the present research work. For this purpose, a drying chamber was directly coupled to an AC unit (AC-WHD) and analyzed its performance during banana slice drying by revisiting the concepts of generalized drying curve and drying performance index (DPI). The experimental data set of moisture content ratio obtained with AC-WHD matched well with the generalized drying curve and the DPI value was found to be 0.999. It was found that the waste air supplied by the AC unit to the drying chamber was hot (≈ 50°C) and 28% dry, which aided the drying process. The thermodynamic performance of AC-WHD was also evaluated using warm and wet exergy to provide insight into the mechanism of AC-WHD drying. The exergy based sustainability index was higher while the exergetic destruction coefficient and environmental impact factor were lower for AC-WHD when compared to literature values of the solar drying method. The findings of this research work indicate the practicality of coupling AC units with dryer units to address sustainable development goals (SDG).