Tools · Interactive

Drying-time & dryer-sizing calculator

The drying math from the engineering chapter, live: how much water must leave your batch, how long it will take in your air, and how much drying area you actually need — all built on the chapter's own rates and rules of thumb. No data leaves your browser.

Rates are engineering estimates — calibrate to your dryer, climate and batch · figures are guidance, not guarantees

1 · Batch & moisture targets

Your batch — everything sizes from this
One day's pick, or one dryer load.
Fleshy calyces typically run 85–90% water.
≤12% for safe storage; 8–10% for export.
Dry solids — never change Water that must be removed Water left in the dried product

2 · Estimate drying time

Your conditions & setup
Each method carries a base rate from the chapter.
Inside the dryer. Above ~55–60 °C anthocyanin color starts to suffer.
The single biggest weather variable — humid air can't absorb water.
Cutting multiplies surface area — up to ~1.5× faster.
Total effective drying surface you can spread right now.

3 · Size your drying capacity

From daily pick to drying floor
The heaviest day of the season — size for the peak, not the average.
Fresh calyces won't wait forever — 2–3 days is the usual target.
Sets the base drying rate (kg water removed per m² per day).
Chapter guidance: add 30–50% for cloudy days and the slow falling-rate phase.
For the tray count. A typical screen/tray is ~1 m².
Optional: enter your own measured rate from a weigh log; leave empty to use the method default.

How the math works

Moisture balance (section 1). Dry solids never change. In a batch at fm% moisture with tm% as the target, final dry mass = solids ÷ (1 − tm), and water to remove = fresh mass − final mass. For the chapter's example — 200 kg at 88% down to 12% — that is 24 kg of solids → 27.3 kg dry product → ≈173 kg of water removed, a fresh-to-dry ratio near 7.4:1.

Drying time (section 2). The chapter's anchor rate is ~2.5–3 kg of water removed per m² per sunny day for a well-built solar dryer. The model scales that base rate by your method, then by the drying power of your air — the vapor-pressure deficit (VPD ≈ saturation vapor pressure × (1 − RH)), normalized to a reference of ~48 °C / 35% RH — and by form (whole vs. cut, up to 1.5×). An ideal time comes out of water ÷ (area × rate); the model then adds the falling-rate tail (+~25–45%, more the lower your target), and the chapter's 30–50% weather margin stays your own planning number on top.

Dryer sizing (section 3). Required effective area = water per day ÷ drying rate, then × (1 + margin). With the chapter's defaults — 200 kg/day at 88%, 3 days, 2.8 kg water/m²/day — you need ≈20 m² before margin, ≈29 m² at 40%. The load-depth line assumes a loose bulk density of ~150 kg/m³, so ~7 kg per m² ≈ 4–5 cm deep — inside the chapter's 3–8 cm band.

Before you buy trays or a dryer These rates are estimates, not specs. The single most valuable calibration is a weigh log: load a known tray area, weigh daily, and measure how much water your dryer actually removes per m² per day in your season — then feed that number into the measured-rate override and size for real. In humid conditions (VPD factor well below 1), heat and airflow beat adding more area every time.
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