Heat exchangers

Heat exchangers

PostBy: oliver power On: Tue Feb 25, 2014 9:03 am

I know what they are intended for; Exchanging Heat......... I've often wondered just how well the heat exchange efficiency is. Lets use a water to water heat exchanger as example. If water from boiler is 180* before the heat exchanger, what would be the rate of transfer? It doesn't seem like the transfer of heat would be quick enough, to be effective enough at the radiation. Does it take longer to heat a space when the BTU's have to go through a heat exchanger. Or does an heat exchanger store heat like the boiler does. Kind of an extension of the boiler. I know what I'm trying to ask, but can't seem to put my thoughts into words. Apparently, heat exchangers do work. Oliver
oliver power
 
Stoker Coal Boiler: KEYSTOKER Kaa-2
Hand Fed Coal Stove: Hitzer 50-93 & 30-95, Vigilant (pre-Vigilant-II)
Baseburners & Antiques: MANY (Mostly when burning wood)
Stove/Furnace Make: HITZER / KEYSTOKER
Stove/Furnace Model: 50-93 & 30-95 , Kaa-2

Re: Heat exchangers

PostBy: Rob R. On: Tue Feb 25, 2014 9:12 am

Heat exchangers work very well...as long as they are sized correctly. Most of the time you see plate exchangers on residential systems, and the physical size, # of plates, temperature of the water (on each side!) and flow rate will dictate the btu's transferred.

Plate type heat exchangers are normally used on hydronic systems when one part of the system is different than the rest...such as one zone might have glycol in it, or there is a non-pressurized boiler tied into a pressurized system.

:idea: A tankless coil is also a heat exchanger.
Rob R.
 
Stoker Coal Boiler: EFM DF520
Hand Fed Coal Stove: Hitzer 50-93
Other Heating: Dad's 1953 EFM Highboy

Re: Heat exchangers

PostBy: waldo lemieux On: Tue Feb 25, 2014 9:13 am

This is a guess and only a guess based on some internal gut feeling but, It seems that if the exchanger and all piping are within the same structure you dont lose heat you lose speed at which the produced heat can be delivered to the delivery system :? now maybe its more clear why I get myself in so many predicaments :oops:
waldo lemieux
 
Stove/Furnace Make: efm
Stove/Furnace Model: s-20

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Re: Heat exchangers

PostBy: blrman07 On: Tue Feb 25, 2014 9:14 am

Heat exchanger's are a science all unto themselves. Just one quick google on heat exchanger efficiency got an unreadable amount of information. If you really want to delve into this try this website.

http://www.hcheattransfer.com/coefficients.html

I love the tag line at the end of the page above.......
The information is provided for educational use only – use at your own risks.

Rev. Larry
New Beginning Church
Ashland Pa.
blrman07
 
Hand Fed Coal Boiler: Bucket a Day
Hand Fed Coal Stove: Vigilant Casting 2310
Baseburners & Antiques: rebuilding a 1906 March Brownback Double Heater, reblacking a UMCO 1920's Pot Belly
Coal Size/Type: Pea/Nut/Wood in the VC and anything that will fit in the Bucket a Day. It's not fussy.

Re: Heat exchangers

PostBy: McGiever On: Tue Feb 25, 2014 11:12 am

No storage to speak of...and yes it can transfer effectively.
Only limitations to transfer are what RobR mentioned...size, water temp and rate of flow.
McGiever
 
Stoker Coal Boiler: AXEMAN-ANDERSON 130 "1959"
Hot Air Coal Stoker Stove: HARMAN MAGNUM
Hand Fed Coal Stove: RADIANT HOME AIR BLAST
Baseburners & Antiques: OUR GLENWOOD 111 BASEBURNER "1908"
Coal Size/Type: PEA / ANTHRACITE, NUT-STOVE / ANTHRACITE
Other Heating: Ground Source Heat Pump
Stove/Furnace Make: Hydro Heat /Mega Tek

Re: Heat exchangers

PostBy: Lu47Dan On: Tue Feb 25, 2014 12:07 pm

If a heat exchanger is sized right and installed correctly than efficiency will be quite high.
One thing with plate type heat exchangers that are installed to make DHW, is water chemistry. If you are going to run a plate type with water that is high in minerals, you will end up with it plugged up. I used to clean plate type heat exchangers for a couple of friends who had OWB's set up to make their hot water. After several seasons of this they got water softeners installed to take care of the problem.
If they had installed a shell and tube heat exchanger they could have had a drain valve installed on the shell and then blown out the buildup.
With a plate type it is tough to get the build up out of all the plates, I had a system that pumped CLR through them, the pump could produce pressures up to 100psi.
One year I had to trouble getting then one heat exchanger to flow anything. After soaking for weeks in an acetic acid bath, and several attempts to push the acid through. I made a stand pipe to hold the acetic acid, I connected the stand pipe to the exchangers outlet spud and set it on the ground. Set up my ten foot step ladder and then attached the pipe to the ladder with a bungee cord, climbed up and filled the stand pipe with acetic acid and let it set for a few days. I had a shorter stand pipe on the inlet spud. I kept the stand pipe full of acid and when the acid migrated to the shorter stand pipe I knew that I had at least one passage opened up. I made another set of stand pipes that I could fill and let set on my one work bench. I would drain out the acid and fill the pipes with fresh acid once they stopped bubbling. I ran through four gallons of acid and it took three months to get the heat exchanger cleaned out.
Was it worth the bother, no it was not. He probably spent more money saving it than it would have cost to replace it with a tube and shell type. I have two Shell and tube heat exchangers from a dumpster dive. that I plan on using on my system eventually. Both are a little too big for their purpose but should work out.
Dan.
Lu47Dan
 
Hand Fed Coal Stove: Sears circulator air tight stove.
Other Heating: Crown 115,000 BTU oil fired boiler(house) Weil Mclain 150,000BTU oil fired boiler(Shop)

Re: Heat exchangers

PostBy: oliver power On: Tue Feb 25, 2014 6:42 pm

Lu47Dan wrote:If a heat exchanger is sized right and installed correctly than efficiency will be quite high.
One thing with plate type heat exchangers that are installed to make DHW, is water chemistry. If you are going to run a plate type with water that is high in minerals, you will end up with it plugged up. I used to clean plate type heat exchangers for a couple of friends who had OWB's set up to make their hot water. After several seasons of this they got water softeners installed to take care of the problem.
If they had installed a shell and tube heat exchanger they could have had a drain valve installed on the shell and then blown out the buildup.
With a plate type it is tough to get the build up out of all the plates, I had a system that pumped CLR through them, the pump could produce pressures up to 100psi.
One year I had to trouble getting then one heat exchanger to flow anything. After soaking for weeks in an acetic acid bath, and several attempts to push the acid through. I made a stand pipe to hold the acetic acid, I connected the stand pipe to the exchangers outlet spud and set it on the ground. Set up my ten foot step ladder and then attached the pipe to the ladder with a bungee cord, climbed up and filled the stand pipe with acetic acid and let it set for a few days. I had a shorter stand pipe on the inlet spud. I kept the stand pipe full of acid and when the acid migrated to the shorter stand pipe I knew that I had at least one passage opened up. I made another set of stand pipes that I could fill and let set on my one work bench. I would drain out the acid and fill the pipes with fresh acid once they stopped bubbling. I ran through four gallons of acid and it took three months to get the heat exchanger cleaned out.
Was it worth the bother, no it was not. He probably spent more money saving it than it would have cost to replace it with a tube and shell type. I have two Shell and tube heat exchangers from a dumpster dive. that I plan on using on my system eventually. Both are a little too big for their purpose but should work out.
Dan.
Kind of reminds me of my kitchen sink drain. Wife said water will not go down. I tried all kinds of things to un-plug the clog, including running a manual operated snake. No success. I ran out of time, so hired my brother(Handy Man) to come unclog the 2" kitchen drain line. He was un-successful. We each had lots of time trying to un-plug the drain line. Finally, we decided to cut the drain line. WOW!, the 2" drain line was plugged solid, the whole 10' or so with grease. Wife was dumping all the grease she could find, down the kitchen sink. If I would have known that to begin with, It would have been a fast easy fix. Instead, we had many hours into trying to clear a 2" PVC drain line, packed solid with grease. Needless to say, she doesn't dump grease down the drains any more. There's a reason why I always said NOT to dump grease down the drains. Now she knows the reason. By the way, I Thank You All for your "heat exchanger" replies. Oliver
oliver power
 
Stoker Coal Boiler: KEYSTOKER Kaa-2
Hand Fed Coal Stove: Hitzer 50-93 & 30-95, Vigilant (pre-Vigilant-II)
Baseburners & Antiques: MANY (Mostly when burning wood)
Stove/Furnace Make: HITZER / KEYSTOKER
Stove/Furnace Model: 50-93 & 30-95 , Kaa-2

Re: Heat exchangers

PostBy: oilman On: Tue Feb 25, 2014 7:36 pm

Oliver, I think your wife and mine are related. :D
oilman
 

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