How efficient is an open fire?

[Stubby]

36 minutes ago, openspaceman said:

Let's just disagree amicably then Stubby

Oh Absolutely . No worries my friend

[kevinjohnsonmbe]

12 hours ago, openspaceman said:

Indubitably

Brilliant! Not getting into the debate, but that HAS to be the word of the day!!

 

anyone see the piece on wood fires on Newsnight last night...?  Although a ‘soft’ / early, fairly meaningless piece, it could be the harbinger of the potential demonisation of solid fuel probably leading to tax and dissuasion tactics to follow from government policy. 

[openspaceman]

10 minutes ago, kevinjohnsonmbe said:

Brilliant! Not getting into the debate,

Wimpout! ;-)

10 minutes ago, kevinjohnsonmbe said:

 

anyone see the piece on wood fires on Newsnight last night...?  Although a ‘soft’ / early, fairly meaningless piece, it could be the harbinger of the potential demonisation of solid fuel probably leading to tax and dissuasion tactics to follow from government policy. 

No I didn't see it but it's on the cards and in terms of the proportion of airborne particulates attributable to source it is claimed to be as bad as diesel engines, yet over time with diesel engines with their DPFs  reducing their particulates  Addblue their precursors by over 80% what's likely to be next in the firing line?

 

Just consider; if you look at a car exhaust now what do you see after it has warmed up, look at a woodburning chimney after it's been running half hour what there?

[Stubby]

6 hours ago, openspaceman said:

Wimpout! ;-)

 

 

 look at a woodburning chimney after it's been running half hour what there?

Nothing . On mine anyway .

[openspaceman]

15 minutes ago, Stubby said:

Nothing . On mine anyway .

As it should be but  we're probably in the minority.

[Bolt]

Although piping the air in from outside is clearly a more sensible and elegant solution, I can't see that cold air will have an discernable benefit over warmer air for a stove.

 

On a car, there are restrictions on how much air can be drawn in ( cylinder capacity, air filters, bendy ducting, etc)  added to the fact that the intake air is seriously heated in the turbo unit, getting the air as cold as possible before it hits the intake is clearly a benefit.

 

With a stove though, you just open a vent up a bit more.  I rarely run my stoves flat out, but if I really am desperate for more fierce combustion and all the vents are fully open,  I just crack the door open a bit.

[Billhook]

There are all different kinds of open fires, just as there are different woodburning stoves.

When I built my house I built a Rumford open fireplace.   I also put two four inch drain pipes under the concrete floor either side to feed air into the room and eliminating draughts.  The design not only has a smoke shelf with an air damper flap going across the whole width of the three foot wide fireplace, but also a pair of built in mesh doors to prevent sparks when unattended.

 

In the old farm house my parents had a similar sized open fire but it was totally inefficient and used twice as much wood as the Rumford.  My father used to sit by the fire with a rug on one side to shield him from the radiant heat of the fire, and a rug on the other side to protect him from the draught coming in from under the door!

 

I t was like stoking the Bismark and I became grumpy and told him that he would have to fit a wood stove or I would not bring any more wood in.  I bought him a Clearview 650 and we stood it on the hearth with a pipe coming out the back into a metal plate which covered the old fireplace.  I  lit the fire at about six o'clock and went out to play tennis.  Left him looking very unhappy and feared the worst on my return.

I cautiously poked my head round the door at about eleven and burst out laughing.  He was sitting in his vest and underpants.  He said that he had gone to sleep and when he woke up he thought that he was in Hell!

The stove was very popular after that as it reversed the air flow in the old house and pushed heat into most areas.

 

I would say that the Rumford is about 80% as effective as the wood stove as it heats a large area of the central chimney brickwork.

The old Hall fireplace was about 25% as effective as a stove.

 

 

What is a Rumford Fireplace,
Anyway?

by Jim Buckley

Rumford fireplaces are tall and shallow to reflect more heat, and they have streamlined throats to eliminate turbulence and carry away the smoke with little loss of heated room air. Rumford fireplaces were common from 1796, when Count Rumford first wrote about them, until about 1850. Jefferson had them built at Monticello, and Thoreau listed them among the modern conveniences that everyone took for granted. There are still many original Rumford fireplaces - often buried behind newer renovations-throughout the country. Count Rumford, for whom the fireplace is named, was born Benjamin Thompson in Woburn, Massachusetts in 1753 and, because he was a loyalist, he left (abruptly) with the British in 1776. He spent much of his life as an employee of the Bavarian government where he received his title, "Count of the Holy Roman Empire." Rumford is known primarily for the work he did on the nature of heat.

Back in England, Rumford applied his knowledge of heat to the improvement of fireplaces. He made them smaller and shallower with widely angled covings so they would radiate better. And he streamlined the throat, or in his words "rounded off the breast" so as to "remove those local hindrances which forcibly prevent the smoke from following its natural tendency to go up the chimney..." Rumford wrote two papers detailing his improvements on fireplaces in 1796 and in1798.* He was well known and widely read in his lifetime and almost immediately in the 1790s his "Rumford fireplace" became state-of-the-art worldwide. Today, with the extensive restoration of old and historic houses and the renewed popularity of early American and classical architecture in new construction, Rumford fireplaces are enjoying a comeback. Rumford fireplaces are generally appreciated for their tall classic elegance and their heating efficiency.

____________

 

*Most recently Rumford's two essays on fireplaces have been published in The Collected Works of Count Rumford; Vol. 2; Sanborn Brown, ed.; Harvard Univ. Press; 1969; available in most libraries or through Inter-Library Loan or On Line Version

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