I've been busy measuring the heat output from our original Recoheat installation using an industrial thermometer with a probe. It's a fascinating exercise and demonstrates extraordinary results. I've made a couple of videos, and you can see a still from one below, with a picture-in-picture of the thermometer and clock so that they show clearly as I demonstrate how the Recoheat stove accessory works.
This still is taken 4 minutes after the stove was lit, in which time the temperature has gone up from 13°C to 521°C. In four minutes. The air is being pumped into the system at a flow rate of 3600 litres per hour - 1 litre per second. Because air doubles in volume at 238°C, it expands in the unit and accelerates out much faster - you can clearly hear the acceleration as it vents from the unit. The heat is quickly dispersed into the air in the room, as this warmed air shoots out and is pumped around.
On my small stove, it seemed to stabilise at around 520°C though that was still just burning kindling, so it will keep pumping at that rate and temperature whilst the stove is being refueled, then for several hours whilst the stove itself cools, but the temperature of the exhaust gases does not because it's being drawn up and out.
I'll post the video in the next entry, and will produce more to demonstrate further the extraordinary efficiency of the system.
You do not show where you are measuring the flow rate. Aquatic air pumps do not give 1l/S- even large ones give barely a tenth of that. And that is against less than a metre of water head- about 0.1 bar. At 500C, the pressure inside the coil will rise to ~3 bar (gas laws) so that is the head being pumped against. This cannot be achieved with a 37W pump- around 10 times that would be required (do the math).