A Village Solar Dehydrator for a 50 kg Mango Batch: Water Budget, Collector and Airflow Sizing, Drying Time and the Humid-Season Failure Line

When a mango crop ripens it ripens at once: prices crash, the surplus rots, and the same village is hungry months later. This paper designs an indirect solar dehydrator for a 50 kg daily mango batch and computes the full budget from the accompanying script: 40.34 kg of water removed to 12.0% moisture (water activity 0.57), an 8.0 m2 collector at 5.5 kWh/m2/day insolation, 110 m3/h airflow, a drying time of 1.96 days, and a net advantage of $66.89 per batch against glut-season fresh sale after hardware amortisation of $1.54 per batch. The design fails past a printed climate line: below 3.10 kWh/m2/day insolation, or above 81.7% ambient relative humidity at any insolation, drying stretches past the three-day mould window; a typical humid-season day takes 3.22 days. Design performance is simulated, not measured.