Save energy by inverting a wall heater’s heat flow

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 Fans top view

Everybody knows it, heat goes up. Almost all kind of heater use this principle. Heated air thru contact to the fins inside the heater flows up and goes out thru the top grid.
In this process it can pull the cold air from the bottom of the heater.
This way the air near the roof tends to go warm up fast meanwhile the air near the ground takes much later advantage of the heat produced.

To counter this principle I tried an experiment.

By inverting the air flow inside the heater the global efficiency of the heat produced is increased.

It seems logical since the hot air now flows out from the bottom and then naturally moves in direction of the roof. This way the floor is first heated and the heater can be turned off much sooner. The whole process permits a saving of energy and money.
The concept of flux inversion is not new. It is used in some kind of fan-based convectors to reduce the “cold-feet” effect.


The picture here below shows the difference between an ascending flow and a descending flow (inverted flow). It is clearly visible that the living space takes much more advantage of the heat produced when the hot air coming from the bottom.

Comparison of hot air flow


To invert the flow I used 14 computer fans placed on top of the heater and pushing the air downwards. The energy consumption is:

With the leds a fan consumes 0.18 A under 12V which are 12*0.18= 2.16 Watts
The whole system: 14*2.16 = 30.24 Watts.

This electrical consumption is quite high; ideally I should test it without the leds.


Here are the data about the fans: 8*8*2.5cm, 38.4 CFM, 17.5 dB, 1200 RPM

The price: 1.5 euro each and thus 21 euros for 14 units.


It is easy to calculate the noise produced by the 14 units:

17.5 + (13*3) = 56.6 dB which is comparable to the noise in a supermarket.


In real life, the flow inversion highly increases the heating speed. The heat is as well better spread around, less cold zones. The noise on its side is pretty consequent.

In conclusion the flow inversion is a success and I would recommend it to who wants to optimize on room’s heating process.

 PC Fans grouped by three units
 Flow inverter fans top view
Flow inverter fans overview
14 PC Fans in line

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