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Eco Fan

mrsmelly

By mrsmelly
in General Boating

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mross

Posted
Posted
1 minute ago, Jim Riley said:

Heat travels up the mass of the fan by conduction, some of it radiates away, some of it conducts into the air, this is of course assisted by the fan causing a greater air flow over the fins. 

You have just described forced convection!  But it's still convection.  The amount of heat radiated is small compared to the forced convection, which itself is very small!  Almost zero in fact.

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Posted
Posted
On 09/12/2017 at 10:01, Jim Riley said:

Yes, but repeating something doesn't make it right. Heat travels up the mass of the fan by conduction, some of it radiates away, some of it conducts into the air, this is of course assisted by the fan causing a greater air flow over the fins. 

 

Nor does repeating THIS make it right!

(More shouting, see?!)

Heat energy travels up the stem to the Peltier cell, then mostly leaves the peltier cell in the form of electricity, driving the fan motor. 

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Jim Riley Experienced

Jim Riley

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Posted (edited)

It'

5 minutes ago, mross said:

You have just described forced convection!  But it's still convection.  The amount of heat radiated is small compared to the forced convection, which itself is very small!  Almost zero in fact.

It's both. I think it travels through the peltier cell, this creating electrickery, sending the heat the other way cools the peltier cell , as in car cool boxes. Of course conservation of energy means that some becomes electrickery, some is dissipated by the fins.

5 minutes ago, mross said:

You have just described forced convection!  But it's still convection.  The amount of heat radiated is small compared to the forced convection, which itself is very small!  Almost zero in fact.

But not zero. Therefore correct. Pedantically speaking. IMHO.

Edited by Jim Riley
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Posted
Posted
On 08/12/2017 at 10:57, mross said: 

14 minutes ago, Mike the Boilerman said:
Air movement can be demonstrated though using a smoke pen or the smoke trail from an incense stick. 


Have you tried this with fan off?  The air movement may actually be caused by convection.  You seem to agree that the temperature doesn't change!

 

 

Not tried it with the fan off exactly, but after lighting the smoke pen away from the fan, the trail of smoke rises approximately vertically. When I put the smoke pen in front of the fan, the smoke trail changes from vertical to about 45 degrees from horizontal. 

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Dr Bob Veteran II

Dr Bob

Posted
Posted
10 minutes ago, mross said:

If you hold the smoke pen in front of the fan and walk away from the fan, how far before the smoke stops moving horizontal y:giggles:

I tried this yesterday  and the smoke was blowing horizontally when 50 yards from the back of the boat.

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rusty69 Veteran II

rusty69

Posted
Posted
5 minutes ago, ditchcrawler said:

I think MR S Melly started this tread so that he could go to Ecofan and show them all the publicity he had created for them in the hope they give him a free one so he can come back and say he was wrong and they are great.

They will more likely send a wetsuit clad rep round his boat with an waterproof drill and holesaw:)

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WotEver Veteran II

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Posted
Posted
2 hours ago, Jim Riley said:

Yes, but repeating something doesn't make it right. Heat travels up the mass of the fan by conduction, some of it radiates away, some of it conducts into the air, this is of course assisted by the fan causing a greater air flow over the fins. 

I repeat it because you keep repeating that no-one has answered your question about the kettle. Which I have. Three times.  I note that others have given you the same answer.

The assistance offered by the fan (perhaps one watt) is an insignificant percentage of the output of the fire, which is what, 4000 Watts?

2 hours ago, Mike the Boilerman said:

Heat energy travels up the stem to the Peltier cell, then mostly leaves the peltier cell in the form of electricity, driving the fan motor. 

One Watt. Let’s be generous and say two Watts. What’s that as a percentage of 4kW?

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Jim Riley

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Posted (edited)

The problem is, no one has given a satisfactory answer. Comparing the wattage of the fire, yes 4kw, has no relationship with the wattage needed to drive the fan. Other than the hotter the fire, of whatever kw, the faster the fan, until the bimetal strip lifts it and cools it down. 

Edited by Jim Riley
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Posted
Posted (edited)
On 09/12/2017 at 12:10, WotEver said:

The assistance offered by the fan (perhaps one watt) is an insignificant percentage of the output of the fire, which is what, 4000 Watts?

 

Nope. A stove might be rated at 4kW but that will be with it running flat out, rammed full of fuel and roaring away as red hot as the manufacturer can get it under laboratory conditions. Why would they do anything other?

Real boaters don't use their stoves like that. Mine when 'ticking over' is chucking out about 1kW I'd estimate. It heats the saloon about the same amount as the 1.1 kW radiator when its on. When running mine quite hard and the Stirling engine fan is chuffing furiously, I'd guess 3kW as it could still be persuaded to burn hotter, but I don't like to. 

Anyway I was saving that up for another thread. "What is the true heat output of your solid fuel stove?"

 

Speeling edit.

Edited by Mike the Boilerman
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Dr Bob Veteran II

Dr Bob

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Posted
13 minutes ago, Mike the Boilerman said:

Real boaters don't use their stoves like that. Mine when 'ticking over' is chucking out about 1kW I'd estimate. It heats the saloon about the same amount as the 1.1 kW radiator when its on. When running mine quite hard and the Stirling engine fan is chuffing furiously, I'd guess 3kW as it could still be persuaded to burn hotter, but I don't like to. 

Anyway I was saving that up for another thread. "What is the true heat output of your solid fuel stove?"

This is really interesting. This was going to be part of the test I will carry out after christmas - at the conclusion of Auntie Wainrights auction. The Nondescript cheap metal thing with the lion smoking a pipe,a flaming tail, a head like Oliver Cromwell and extremely short back leg is an ideal item to assist in determining the heat transfer rates from the top of the stove to something placed above it. By determining how much energy is transferred to the Nondescript cheap metal thing with the lion smoking a pipe,a flaming tail, a head like Oliver Cromwell and extremely short back leg, I can then predict the likely heat flow into the Ecofan ( but mine isnt an Ecofan) and thus how much additional heat is transferred to a point 3.1M away and 0.5M below from said fan. I hope to be able to calculate accurately the number of Watts used providing I get past first base.

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rusty69 Veteran II

rusty69

Posted
Posted (edited)
7 minutes ago, Dr Bob said:

The Nondescript cheap metal thing with the lion smoking a pipe,a flaming tail, a head like Oliver Cromwell and extremely short back leg. 

How can it be nondescript, with such a descriptive title? 

Perhaps  its an oxymoron (or oxyroaron) 

Edited by rusty69
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