Plate HX directly _in_ primary loop of primary/secondary?

[pybyr]

over in another thread, Kabbott raised the fascinating idea of putting a plate HX directly in the primary loop of a primary/secondary system (the HX will be my interface between the unpressurized storage tank and the boiler and heat loads) rather than having the HX "hanging off" a secondary; his approach, as he noted, would allow deletion of one circulator.

https://www.hearth.com/econtent/index.php/forums/viewthread/21028/

Anyone have any reactions?

Suggestions, please, as to whether it's possible to find/spec a plate HX that can move the right # of BTUS (150,000 boiler here) not introduce too much flow resistance or pressure drop in the primary loop, and won't cost something unusually astronomical?

Thanks

Trevor

 

[WoodNotOil]

As I said in the other thread my 30-plate has 12 feet of head. I think some resistence is just a part of using a plate hx. A larger pipe diameter on it my reduce that some. Mine is 3/4". Perhaps others can chime in with there experience with larger diameter plates. Give the guy at http://www.radiantheatproducts.com/ a call and he can answer a bunch of these technical questions.

 

[BrownianHeatingTech]

There will be a lot of flow resistance with a plate heat exchanger. A shell-and-tube heat exchanger has much less flow resistance (particularly on the "shell" side).

For example: http://www.triangletube.com/HeatExchangers/MaxiFlo/HEMaxiFloSpec.htm

Ignore the btu ratings, though, as those are for swimming pool applications.

Joe

 

[in hot water]

As I said in the other thread my 30-plate has 12 feet of head. I think some resistence is just a part of using a plate hx. A larger pipe diameter on it my reduce that some. Mine is 3/4". Perhaps others can chime in with there experience with larger diameter plates. Give the guy at http://www.radiantheatproducts.com/ a call and he can answer a bunch of these technical questions.

You might check that HX spec with the sizing software. Plate HXers should really be sized to the application, not what's "on the shelf." Like pumps, pipes, valves, storage and everything else hydronic.

Here is one that Flat plate sized for me yesterday. Moving 120K, with glycol on the B side. Nowhere near the pressure drop you are talking. This is a 30 plate 5X12"

hr

 

[jebatty]

I can't be as technical as you might want, but I used a plate hx in the primary loop with unpressurized storage (now pressurized but same plumbing setup because I use anti-freeze in the primary loop). See the simplified schematic.

The boiler is 140,000 btu Tarm Solo 40; the plate hx is 1" inlets/outlets, 5 x 12, 30 plate. Elevations of components schematically reflect actual. The 009 on the boiler is used because that's one that I had. Through-put on the 007 is approximately 5-6 gpm. I don't know through-put on the 009.

This setup, with water from tank up to about 130F, will allow the Tarm to run continuously, full-burn, no idle. As input water from tank rises above 130, Tarm will start to cycle, with cycling increasing in frequency as input water temp rises.