Raidant heat and convective currents....

Floyd

In the "gut rehab"... post the discussion led to the fact that radiation is mostly or somewhat convective...
I have been rolling this around for the last day or so and in defense of Ed I have to say that I believe
that he may be on to something that is so suttle that many of us have not thought of it in this way.

Yes, it seems as though radiant, while radiating heat to objects of mass, does also provide some heat to the surrounding air.... the ideal trick with radiant is to have the convection be low enough to the point where it does not heat the air enough to stratifiy the air and still heat the objects in the room.... ie...people, furniture etc...

Now, as the air at the floor is heated it does rise, and is replaced by the cooler air in the room.... if the floor is so hot that it produces too warm of air it will still cause stratification in the room... but if the air cools off before it get to the ceiling and begins to fall again, then a consistent air temp. can be maintained in the room.... that is why it is important for the btu's coming from the radiant emiters to be closely matched to the btu loss of the room.....

Am I making any sense here????

Now, one of the reasons that I have come to this conclusion is that I was trouble shooting a problem the other day, where there was too much heat in a room..... the steam rad. was cool and there was no other heat source in the room.... the room temp. was in the 100* range!!!!! Further investigation revealed that there was a 2-1/2" steam line, along with some other smaller branch lines running underneath this room... the old insulation had been removed and had not been replaced!!!!!! That room was being heated totally with radiant energy and had some major stratification going on in there!!!!!! The heat output btu's were way more than the loss btu's......

Hope this makes some sense here....


Bottom line here guys.... Heat losses ARE extremely important and the days of doing jobs by the set of your pants are GONE!!!!! If we are selling comfort, then the time and energy needed to make a comfortable system, need to be invested into every job. The days of throwing in tons of radiation and boilers that are WAY oversized are long gone!!!

Now if we could just get the message out to those that still think that "bigger is always better"!!!!!

Thanks for putting up with my Saturday rant!!!!

Floyd

eleft(retired)

Good Thinking

Good thought and reasoning...now I'm looking forward to Sundays rant.

Happy Holidays

al

Boilerpro

Floyd..

I believe Ed also mentioned the idea that since the whole floor is heated it tends to block convective air currents. If you create a cloud of warm air evenly below a cloud of cooler air, there wont't be much mixing. If you only heat half the floor, the cool air will be able to drop down to floor level where there is no heating and begin a convective air current. I am really glad Ed has brought some of that engineering/ scientific analsis to the discussion... it beem since high school that I worked with that stuff. Guess I should take another good look.

Boilerpro