Fan placement puzzle

[nitrogenase]

Hello all,

We have an Enviro Venice 1700 and keep it roaring, especially with it being -20C outside this past week. To heat our house more efficiently, we supplement air movement with a separate plug-in fan, extracting heat to the rest of the house from the living room. I've been scratching my head about the physics of optimal heat extraction and wonder if others might be able to help.

The options are:
1. Fan beside the insert, blowing immediately sideways across the face of the insert, ripping radiant heat away from the unit into the room (and beyond).
2. Fan beside the insert, blowing in the same forwards direction as the insert blows, pushing the air even faster away from the fireplace.
3. Fan at the other side of the room, pushing the room's warmer air out of the room a bit better.

If you could only pick one, which would it be, and why?

Josh

 

[DAKSY]

I would try the fan in the doorway, moving cooler air into the room & forcing the heated air back out.

 

[Neufie]

A fan won't "rip radiant heat away from the unit" since radiant heat can only be absorbed by some surface and "air" is a lousy absorber of heat. Your insert gives off heat by convection as the insert fan blows hot air into the room. Supplementing that by placing fans blowing into or out of the room is a common practice based on feedback from fireplace insert users that I have talked to, but in my experience, doesn't work very well, but is better than doing nothing.... so best suggestion is to experiment with fans, but the name of the game is to move warm air away from the insert into directions of the house that are not benefiting... but at best, you are moving marginally warm air around that has limited heat capacity, and readily gives it up.... probably long before it reaches your intended target zone. Another down side is that fans reduce the enjoyment by users of the heated area since air is being blown around.
The radiant heat on the other hand can't be blown around. It must be directly absorbed by a surface, like your body, furniture, walls, or fireplace stone, and doesn't go around corners. It is the warm feeling that you experience when you are sitting in front of the fireplace, even on the far side of the room. Dark objects absorb radiant heat better than light colored objects, so for example, painting the opposing wall or ceiling a dark color, would improve absorption of radiant heat, but nobody would want to do that for aesthetic reasons and drywall is designed to he a good insulator.
If the target areas of the house are upstairs areas, then in my experience, heated air will effectively rise up due to lower density, which can be encouraged with fans. On the other hand, the upstairs areas directly above the downstairs heated area will have toasty floors so at least your feet will be comfy and that may help to warm the upstairs room.
Getting the heated air down into a basement area is a bit like herding cats.
I am suspecting that there may not be a satisfactory solution to the problem that you raise, but suspect that there may be many including myself who would like to see a better way of distributing heat from an insert more uniformly around the larger area of the house.
Ron

 

[Shaun643]

I agree with DAKSY I also use a small fan on the other end of my house and blow cold air towards the stove it works great to get the heat back to the fan. If you blow hot air through a fan it will cool quickly. Letting the hot air form the stove move itself it will stay much warmer.