Calculate the minimum water flow needed by a condenser or dephlegmator at a given heating power, plus total water consumption and cost during distillation.
How much water does a condenser need?
All the heater energy that turns into vapour must be removed in the condenser. Water absorbs 4.19 kJ per kilogram per degree, so the more you let it warm up, the less of it you use.
Saving water
Set the flow so the outlet water is warm but the distillate comes out cool. A needle valve is best for precise control of small flows. A closed loop with a pump, reservoir and air cooler saves even more.
How we calculate
Mass flow ṁ = P / (c × ΔT), where c = 4186 J/kg·K. For water 1 kg ≈ 1 l, so flow in l/min = P / (4186 × ΔT) × 60.
Frequently asked questions
How can I save water when distilling?
Set a higher outlet water temperature (e.g. 40–50°C), use a needle valve for precise control, or a closed loop with a pump and reservoir.
How do I descale a condenser?
Fill the condenser jacket with a citric acid solution (about 50 g per litre of warm water), leave for an hour and rinse thoroughly. Scale acts as an insulator and reduces cooling performance.
Can I cool with a closed loop?
Yes. You need a pump, a water tank (at least 50–100 l) and ideally an air cooler with a fan. The water in the loop gradually warms up, so the tank must be large enough.
What should the condenser outlet water temperature be?
For a product condenser usually 30–45°C. Water warmer than about 55°C risks under-cooling the distillate and losing alcohol vapour.