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Delta T

Started by Central Boiler 6048, February 25, 2015, 09:35:29 PM

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Gary_C

The heat exchange capacity of a unit heater is mostly predetermined by such factors as the length of tubes in the air flow, the fins on the tubes, and the overall size of the heater. Without changing the fixed design, there is not much you can do to increase the heat exchange capacity. And those heaters are able to to exchange the same amount of heat under a wide range of water and air flows. Yes, some things like changing the approach temperatures (difference between the incoming air temperature and max hot water temperature) can give you slight improvements in heat transferred, but the improvements will not be significant.

So bottom line is increasing the flow of water will proportionally decrease the delta T, but that will not significantly change the overall heat transferred in the heat exchanger. That's why I asked what is the objective here. If your objective is to change the delta T, you can expect little change in the overall heat transferred. If you want to transfer more heat, add more square feet of heat exchanger.
Never take life seriously. Nobody gets out alive anyway.

Holmes

The objective is to heat the barn with a 220,000 btu unit heater suspended from the barn ceiling. The unit heater is already large enough to do the job, but he can only get the barn up to 40 ish temperatures.
Think like a farmer.

Gary_C

Quote from: Holmes on March 06, 2015, 06:59:59 AM
The objective is to heat the barn with a 220,000 btu unit heater suspended from the barn ceiling. The unit heater is already large enough to do the job, but he can only get the barn up to 40 ish temperatures.

That's not what CB 6048 wrote and it doesn't make sense anyway.  ::)
Never take life seriously. Nobody gets out alive anyway.

Central Boiler 6048

This is to everybody on this forum, thanks to everybody for your input.
I'm going to reiterate my problem: I would like my water to air heat exchanger to put off more btu. I bought it from central boiler. It has a fan,motor,transition box and a 220k rated emitter. I have 215 ft of total length pipe  that includes my water line fittings and my equivalent length of the emitter. I am using a 007 taco pump which has a max head of 10ft. Well I know that's to much for the circulater. My delta T when there is a demand is 55 degrees, thanks to Gary a high delta isn't always a bad thing. I understand now that the higher the delta the more heat transfer there is. The 220k emitter needs 18-20 gpm to move 220 btu's. I'm well aware that I will never get that high with 1 inch pex however I think I can achieve half of that? Right now from everybody's calculations I might have 2 gpm, I think I need a higher flow rate so my fan can't suck that much heat out of it at once. I have faith in a Grundfos 26-99 to move at least 7-9 gpm with a Delta difference of 30? if I was to do it over again I would put 1 1/4 thermopex in to move more  Gpm.
Well I just Took delivery of the new circulator today (Grundfos) 26-99. The only thing that sucks is I'm not going to be able to try it for another week as I just started my vacation in the Caribbean. I will have results on March 15th.     Thanks

Holmes

  I believe the grunfos pump will be a big improvement.  Good luck
Think like a farmer.

LittleJohn

Quote from: Central Boiler 6048 on March 06, 2015, 03:40:43 PM
...Well I just Took delivery of the new circulator today (Grundfos) 26-99. The only thing that sucks is I'm not going to be able to try it for another week as I just started my vacation in the Caribbean. I will have results on March 15th.     Thanks

Your definition of "SUCKING" is different than MINE

Central Boiler 6048

Well I'm back into the country, today I will be hooking up the new Grundfos circulater pump. I'm crossing my fingers I see some result changes from my current setup. It has been warming up in the Midwest, I've seen temps in the 30s-40s for a low at night. Prolly getting close to shutting the 6048 down for the heating season. I will have circulater results within 24 hrs. Standby

WmFritz

Well, about time. I can't believe that you would put a Caribbean Cruise in front of our curiosity.    :D :D :D
~Bill

2012 Homebuilt Bandmill
1959 Detroit built Ferguson TO35

Central Boiler 6048

Well the Grundfos is installed, for starters on low my air is warmer coming off my fan. To me that means I have more flow! When I run the circulator on med I have a delta t of 40. So it has dropped some. On med I'm figuring around 7-8 gpm and 13-17 ft of head. That translates to around 140k-160k with a 40 degree delta. Any comments on this? My boiler seems to hold its temp but it does go down quicker due to more gpm out of the water jacket.

Holmes

 Sounds like you solved the problem.  8)  You will be warm in the barn.
Think like a farmer.

beenthere

No comment, as long as you are happy then all is well. smiley_thumbsup
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

garret

QuoteMy boiler seems to hold its temp but it does go down quicker due to more gpm out of the water jacket.
Means that rate of heat delivery has increased.  Good for you.
E-Classic 2400 comfortably heating 4,200 sq.ft. and unlimited DHW, Off-grid, Photovoltaic-powered pumps in gloomy SW PA , 34 t splitter, numerous Husky chainsaws

LittleJohn

Quote from: beenthere on March 15, 2015, 12:26:15 PM
No comment, as long as you are happy then all is well. smiley_thumbsup
Correction, as lons as you the WIFEY is happy ;)

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