A wind machine produces no heat of its own — it only mixes the air. On a still, frosty night the coldest air collects near the ground, with a warmer layer sitting above it; the wind machine stirs these two layers together. The Vormair heat generator adds real extra heat to this: placed in front of the wind machine, the machine draws in the already-warmed air and spreads it across the orchard.
To put this extra heat into numbers, we ran an instrumented measurement one summer night. We placed the heat generator next to the wind machine and mounted four data-logging thermometers behind the propeller — spaced vertically.
The measurement
What did the thermometer show?
The chart splits into two phases. First we lit the heat generator, and only started the wind machine a little later. The faint section on the left shows this warm-up phase, so that part does not yet show relevant data.
The important part begins where the wind machine starts, and the curve shifts into a rhythmic pulsing. In this meaningful phase the intake air temperature jumped on every rotation: at the peaks the lower half of the propeller reached 28–30 °C, while the surrounding air was around ~21 °C — that is the +6–10 °C of extra heat the machine fed into the wind machine, rotation after rotation. At the end of the measurement, as we closed the test, the curve settles nicely back to the ambient level.
Why it pulses
Why does the heat peak keep returning?
The regular, recurring heat peaks have a simple cause: the wind machine does not stay in one place but rotates all the way around, a full turn taking roughly 5–6 minutes. Once per turn it faces exactly toward the heat generator — that is when it draws in the warmed air directly, and the temperature jumps. When it turns away from the machine, it takes in the cooler surrounding air, and the value drops back. The cycle time calculated from the measurement is ~5.5 minutes, which matches the wind machine's rotation time exactly — so the instrument traced out the machine's own rhythm. In an orchard, the rotating machine thus spreads the heat across the whole area.
It is worth knowing that these numbers show how much warmer the air becomes that the machine draws in from the direction of the heat generator. When the wind machine blows the other way, into the warm air above the heat generator, it spreads the heat across the orchard even more effectively.
How to read this
What this shows — and what it doesn't
- The heat generator carries real heat into the air: during operation, on every rotation the wind machine received air +6–10 °C warmer than the surrounding air. This extra heat is what makes frost protection far stronger than if the wind machine merely mixed the existing air.
- This was a summer measurement, not a frosty night: the goal here was to see clearly how much heat the machine adds to the air. On a real frosty night the exact values may differ, but the scale of the temperature rise — and thus Vormair's effectiveness — is clearly visible from these numbers.
- This was a small, mobile wind machine: we ran the measurements with this unit — with a larger, fixed machine the heat produced should be used even more efficiently.
- The initial big peak would be misleading: it formed while the wind machine was idle, when the machine was not yet making any wind. We deliberately highlighted the numbers from the meaningful, in-operation phase — so the data reflects real use.
- It ran automatically, without an operator: during the measurement the heat generator maintained combustion on its own — no need to work beside it through the night; it can be set ready during the day.