Flat Plate Heat Exchanger Performance

[Nofossil]

Does anyone have any hard performance data on flat plate heat exchanger performance? The manufacturer sites for the affordable ones have nothing that I can find. I need to have an estimate of the temperature drop vs. flow rates for both sides. I understand that it's a complex multidimensional beast, but I can't figure out how to size an exchanger.

For instance, if I want to provide 4 gpm of water at 170 degrees through one loop, and I'm pushing 4 gpm at 150 degrees through the other loop, what can I expect for outlet temps? What pressure drops will I see for any given exchanger?

Any online resources? I'm coming up empty on this one.

 

[Eric Johnson]

This looks like it might answer some of your questions, nofo:

(broken link removed to http://www.xetexinc.com/pdfs/XetexSelection.pdf)

 

[DenaliChuck]

I couldn't find fluid exchange information on your link Eric, only air...am I missing it?

 

[Eric Johnson]

tru.dat

My bad.

 

[TCaldwell]

Nofossil, call flatplate at717-767-9060, they have a tech named chad, he has a program to input your parameters and will help.

 

[Nofossil]

Nofossil, call flatplate at717-767-9060, they have a tech named chad, he has a program to input your parameters and will help.

Thanks - will do. I was hoping for an online tool, but seems like there aren't any.

 

[DenaliChuck]

nofossil,

Post what you find out if you would...

DC

 

[Nofossil]

nofossil,

Post what you find out if you would...

DC

GEA Flatplate has a tool on their site. It's free, but you have to create an account to use it. You plug in enough parameters to constrain the design, and it tells you which of their products is the best fit.

You have to interpolate a bit, but I'm guessing that an FG5X12-50 is a 5" x 12" 50 plate heat exchanger.

 

[jebatty]

I think your 170-165 is one impt parameter. As noted in other posts, I use a 5x12x30 plate. At 170 boiler in, I think the greatest temp rise on hx in-out was from 50 to 130. As hx temp in rises, the temp differential starts to close. This is approximate, but at 170 boiler in, I will see about 140-160 hx in-out, and about 150-165 hx in out. Somewhere I read that about the best a plate hx can do is a 3* temp drop, but I don't know what parameters this was based on.

I have never measured fluid flow on the boiler side (Taco 009, 1-/14 to 1 copper lines), but I have measured 5-6 gpm on the tank side (Taco 007, 1 to 3/4 copper/hose lines).

No objection to going with more plates, but I think there are diminishing returns. More plates should have less internal fluid resistance and greater heat transfer, but what the gain is for 30 vs 50 plates I don't know.

I have to note that my previous hx (approx 3x8x20 plate) was too small in that it could not strip all the heat the Tarm could output at low hx in temps (even my current hx can't do this at hx in temps of about 130 and above, and boiler temp will gradually rise to limit), but it transferred an impressive amount of heat to my then 800 gal open storage.

Ihave the AIC LB31-30 hx. See attachments for data on AIC hx's.

 

[WoodNotOil]

I posted this link in another post. It gives a BTU rating for the hx plates. Not sure if that helps any.

(broken link removed)

 

[Nofossil]

Thanks for the resources. I think I have a design now. Does anyone see any reason why this won't work as intended?

I'm planning on circulating boiler water through the tankless heater, urged along by a Grundfos 26-99FC, which should give me just under 5gpm through the tankless heater. If I'm heating DHW, then zone valve Z5 is open allowing a loop directly back to the Grundfos after passing through the flat plate HX. For DHW, the Laing 303 circulator cycles potable water through the second circuit of the flate plate HX, drawing from the bottom of the DHW tank and returning to the top. Both Z5 and the DHW circ can be run directly off of the DHW aquastat. I'd need an additional relay to turn on the Grundfos at the same time.

If I'm using the tankless as a backup heat source for the house, then Z5 is closed and the DHW circ is off. Some other zone valve is open, and water is heated by the tankless and circulated through the zone(s) that are calling for heat.

5gpm is a bit lower than what I get from the wood boiler circ, but I think it's close enough. I'm looking at the Tagaki T-Kjr which can modulate down to 19,500 BTU/hr.

 

[Nofossil]

Oops - maybe this will make more sense.

 

[jebatty]

As hx temp in rises, the temp differential starts to close. This is approximate, but at 170 boiler in, I will see about 140-160 hx in-out, and about 150-165 hx in out.

I got a PM asking a better explanation of this and info as to from whom I actually purchased the hx. Bought mine off of ebay; don't remember actual seller. I pay attention to seller feedback ratings.

As to quote, if hot water output from boiler is 170, and return water from whatever source the hx is supplying (in my case it is storage) is 140, the hot water supplied from the hx to that source will be about 160, a 10* differential from boiler output.

Similarly, if hot water output from boiler is 170, and return water from whatever source the hx is supplying (in my case it is storage) is 150, the hot water supplied from the hx to that source will be about 165, a 5* differential from boiler output.

Hope this clears up any confusion.

 

[Sawyer]

As hx temp in rises, the temp differential starts to close. This is approximate, but at 170 boiler in, I will see about 140-160 hx in-out, and about 150-165 hx in out.

I got a PM asking a better explanation of this and info as to from whom I actually purchased the hx. Bought mine off of ebay; don't remember actual seller. I pay attention to seller feedback ratings.

As to quote, if hot water output from boiler is 170, and return water from whatever source the hx is supplying (in my case it is storage) is 140, the hot water supplied from the hx to that source will be about 160, a 10* differential from boiler output.

Similarly, if hot water output from boiler is 170, and return water from whatever source the hx is supplying (in my case it is storage) is 150, the hot water supplied from the hx to that source will be about 165, a 5* differential from boiler output.

Hope this clears up any confusion.

Thanks for this post Jim and Nofossil, I have a chance to buy a LB31-50 at a good deal that a neighbor bought and does not need. I was unsure of the company as this is the first time I will have a need for a heat exchanger. I am still amazed at the amount of information available just for the time spent reading and a few visits to Google, I say this just to let you and others know that your time spent presenting this information is not definitely not wasted. Living out in the sticks, I would never had been able to make good choices (I hope) without this source of information, at best I would have had a WB.