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  • Writer's pictureWill Burrows

Data Sheet for Recoheat stove heat recovery

Updated: Nov 3, 2020

Here are the calculations for heat output of the Recoheat unit, based on the readings taken in the little demo I did that you can see in the video at

Essentially, that shows - what is completely consistent with the Recoheat's output over the last two years - that air pumped in at about 15°C is pumped out at about 515°C (I'm understating it a bit).

So how does that translate into output in kilowatts, such as your stove is rated with? The stove I was demonstrating it with is a 5kw Ecosys.

Here are the calculations:

Calculating the heat transfer value


Surface area is

@100mm length of 8mm internal diameter s

tainless steel tube = 0.00251 m2

@ 1830mm length of 8mm internal diameter stainless steel = .045933 m2

Properties of Air

1 litre per second = 0.001 m3/sec = 3.6m3/hour

Temperature in approx. 15 °C

Temperature out approx. 515°C

ΔΤ = Change in temperature ≈1.205 kg/m3

Flue gas temperature ≈ 500°C - 600°C

U = for air to air heat exchanger 10-40 W/m2 °C

Heat Transfer


Q = Heat transfer (watts)

U = Overall Heat Transfer Co-efficient (w/m2k) = 40 w/m2k

A = Surface area =.045933 m2

ΔΤ = Change in temperature = 500°C


Q = 40 x .045933 x 500 = .91866w

Q = .91866kw

Yes, that's right. A small fire in a 5 kw capacity stove is producing an ADDITIONAL .9kw of heat within 4 minutes of lighting.

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