Design a coil for a condenser, dephlegmator or reflux head. Enter the tube diameter and the coil diameter and length – the calculator works out the number of turns, tube length, heat transfer surface, approximate cooling power, as well as the coil's weight and water capacity.
What does coil performance depend on?
The key factor is the tube surface in contact with the vapour: the longer the tube and the larger its diameter, the more heat the coil removes. Water temperature and flow matter too, as does the material – copper conducts heat better, while stainless steel resists corrosion and does not affect the taste.
How do I choose the gap between turns?
A tightly wound coil has a large surface but resists the vapour and reflux. Dephlegmators and reflux heads usually have a 1–3 mm gap; in product condensers the turns can touch.
Made-to-measure coils
Once you know the dimensions, you can order a coil made to measure – single or double, with axial or 90° inlet and outlet. Just copy the calculator results into the order form.
How we calculate
Turn pitch = tube diameter + gap, number of turns = working length / pitch. Length of one turn = √((π × Dm)² + pitch²), where Dm = coil diameter − tube diameter. Heat transfer surface = π × tube diameter × tube length in the working section. Condensing power is estimated as Q = k × A × ΔTlm at a vapour temperature of 78°C with k ≈ 800 W/m²·K for stainless steel (about 1000 for copper).
Frequently asked questions
What cooling surface per 1 kW?
With 15–40°C water and condensing alcohol vapour, about 0.025–0.035 m² of stainless tube surface per 1 kW of heating power is assumed. A 20–30% safety margin is advisable.
Single or double coil?
A double coil of the same length gives almost twice the surface, so it suits short, high-power condensers and dephlegmators. A single coil has lower water flow resistance and is cheaper.
How do I clean a coil?
Flush the tube with a citric acid solution (about 50 g per litre of warm water), leave for 30–60 minutes and rinse with clean water. Wash the outer surface with washing-up liquid. Scale inside the tube lowers cooling performance, so descale it every few runs.
What tube diameter for a coil?
Dephlegmators and reflux heads most often use 6–8 mm tube, product condensers 8–10 mm. Thicker tube has more surface and lower water resistance but takes up more space in the pipe.
How much tube does a coil need?
One turn is roughly π × the mean coil diameter. A 45 mm coil from 8 mm tube uses about 116 mm of tube per turn – the calculator adds the inlet and outlet.
Copper or stainless steel?
Copper conducts heat better and binds sulphur compounds but needs cleaning. AISI 304 stainless steel is durable, easy to maintain and does not affect the taste.