- Nov 27, 2012
- 0
Question:
I am a thermodynamic engineer- but have no real life experience with open fire fireplaces. I would be very grateful if you could make your comment on the following;
1)a fresh air intake direct to the fire chamber increases drastically the heating efficiency-
2)"a minimum mean frontal inlet velocity of 0.24m/s- in conjunction with a chimney gas temperature of at least 165 to 280 k above ambient- should control smoking in a well-constructed conventional masonry fireplace." (from- 1996 ASHRAE Systems and Equipment Handbook) Does experience show that open fire fireplaces with direct fresh air intake have smoking problems? (since there is near zero frontal inlet velocity) If not- are there any special rules for the construction of open fireplaces with direct fresh air intake? thanks in advance
Answer:
I am not an engineer- but here is the real world experience of those involved with outside air.
1. It increases the efficiency because it does not use the house air for combustion- but the combustion efficiency is lowered because the outside air is usually cooler that the inside air - causing a cooler and dirtier fire
2. Smoking problem have not been common with outside air intakes. In fact- they have eliminated the smoking in many tightly built homes.
3. There are no special rules...pre fab fireplaces usually come with an optional outside air inlet- while most masonry fireplaces bring it up thru a grate below the fire or grate. It helps to have a method to close off the air when the fireplace is not in use. A good set of Glass doors and screen helps the installation become more efficient
I am a thermodynamic engineer- but have no real life experience with open fire fireplaces. I would be very grateful if you could make your comment on the following;
1)a fresh air intake direct to the fire chamber increases drastically the heating efficiency-
2)"a minimum mean frontal inlet velocity of 0.24m/s- in conjunction with a chimney gas temperature of at least 165 to 280 k above ambient- should control smoking in a well-constructed conventional masonry fireplace." (from- 1996 ASHRAE Systems and Equipment Handbook) Does experience show that open fire fireplaces with direct fresh air intake have smoking problems? (since there is near zero frontal inlet velocity) If not- are there any special rules for the construction of open fireplaces with direct fresh air intake? thanks in advance
Answer:
I am not an engineer- but here is the real world experience of those involved with outside air.
1. It increases the efficiency because it does not use the house air for combustion- but the combustion efficiency is lowered because the outside air is usually cooler that the inside air - causing a cooler and dirtier fire
2. Smoking problem have not been common with outside air intakes. In fact- they have eliminated the smoking in many tightly built homes.
3. There are no special rules...pre fab fireplaces usually come with an optional outside air inlet- while most masonry fireplaces bring it up thru a grate below the fire or grate. It helps to have a method to close off the air when the fireplace is not in use. A good set of Glass doors and screen helps the installation become more efficient
