Help needed sizing a flat plate....

[deerefanatic]

Hi all. I'm going to need to use a flat plate HX on my milk tank as Redox was right, even with 3 feet of head pressure on my tank, it was groaning and pushing the lid off of it's seal.


Sooooo. I'd like to achieve the ability to transfer 350,000 BTU/H on my HX. I'm going to use a flat plate. I was looking at this unit here: http://cgi.ebay.com/Brazed-70-Plate-Outdoor-Wood-Furnace-Heat-Exchanger_W0QQitemZ200255424104QQcmdZViewItem?hash=item200255424104&_trkparms=72:1205|39:1|66:2|65:12|240:1318&_trksid=p3286.c0.m14

Is it overkill or will it be about right? I'm hoping to get by with a 007 taco on both sides with short runs of 1.5" pipe..... I'm not finding much info on BTU/H sizing info on heat exchangers.

Thanks for the help!

 

[deerefanatic]

Ok.... I dug up this site: Flatplateselect.com

Looks pretty interesting...... Punching in my values, looks like with 190 boiler water & 007 circulators on both sides of the hx I should manage to get 200,000 btu/hr across that hx..... Which equates to a 37 degree temperature rise/drop..........

Looks golden to me.... Lots of BTU's with small pumps. I'm probably going to use 15-58 Grundfos 3 speeds on the tank side to help with efficiency for light load requirements......

 

[Nofossil]

That's a big temperature drop - most systems are designed for about half of that. You certainly won't be able to maintain 200,000 BTU per hour once the tank starts to heat up. What does it tell you for the situation when the return from storage is 140 or 150?

Even so, I expect it will work fine and make you happy.

 

[WoodNotOil]

I have a 30 plate with 3 speed pumps on it. It works great until the tank gets up around 150*. I am think if I had a larger one it would transfer better at high temps. I think you should be in good shape with the 70 plate. I would suggest using the variable speed pumps as it allows a good amount of experimentation. I keep my boiler side on high and my tank side on medium. Seems to work well. Good luck!

 

[deerefanatic]

Good, I'll probably order it tomorrow..............

-Matt

 

[pybyr]

Matt & all--

I am in the same spot, needing to order a flat plate, real soon.

IS there indeed a consensus that the 70 plate referenced above can push 150,00 + btu/ hour into a big tank even as the storage gets all the way up to near max storage temperature?

the only thing that's concerning me more than buying too big a HX and spending some extra $ is buying one that's not big enough, and then having my system fail to run up to its best, given all the $ and time I'll have in it

thanks!

 

[deerefanatic]

I went ahead and ordered the 70 plate. One thing about the bigger units, is that the more plates they have, the less headloss they have. So if you can then get away with a 007 vs a 0010 for instance, the electrical savings will be significant.

 

[pybyr]

I went ahead and ordered the 70 plate. One thing about the bigger units, is that the more plates they have, the less headloss they have. So if you can then get away with a 007 vs a 0010 for instance, the electrical savings will be significant.

Matt- have you received it and been able to hook it up?

If so, I am very interested in knowing whether it can and does move the full heat output of your boiler with as little "idling" as possible- other folks' input welcome too as I need to order a flat plate for my 150kbtu boiler tomorrow

thanks!

 

[deerefanatic]

I have it mounted to the tank... but unfortunately, it's not plumbed to the boiler yet, nor do I have my tank circ pumps either... (Darn Pexsupply..... GRRRRR........)

All I have to say is a 70 plate "should" do it....... My boiler is 320K btu and I figure I should be able to sink more heat than my boiler can make!