Heat exchangers heat vs. fuel heat

Anderson

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imhave a question that I have Ben researching
How do you measure heat exchanger heat???
Propane is 80-240 btu' per hour
Kerosene heater is 230-350 Btu...that is British thermal units.
This is my attempt to measure hx's!!!!
Diesel and gas have 125-135 btu per gallon
A small engine is 40% efficient....30% cooled and 30% exhausted.
My engine 33 hp burns about 2 gallons per hour
That means it uses 100 btu' and exhausts 75 btu per hour.
The question I have is how ificient are heat exchangers at converting heat.??
I believe fuel heaters are 85-95% efficient at converting btu's.
I am guessing hx's may be the same or a little bit less.????
If my calculation is correct it would be at best 80 btu per hour more like the small little giant propane????
I would prefer feedback from anyone as I am not a physicist just doing research.
 

Kipp

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This is where the technology really becomes apparent in big name brand machines.

People complain about how expensive they are and say the machine is just a blower pump and motor.

But the technology in capturing and correctly utilizing HX heat is complex.

I wouldn't worry about the BTU calculations. I'd just focus on what heat the machine can maintain with a min 8 flow wand. And at the same time not dump water when not keying the wand...
 

Anderson

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Ok forget the btu thing.
I need to know if hx's will hold at 180-200 degrees at 12-14 continual flow..that is about 1 1/2 gallon per minute water flow.????
When I bought a kero heater they give you specs ...350 btu...can be confusing...
They gave me a 140 degree heat rise above water temp. At 4 gallons per minute.
Water temp. Is about 60 degree = 200 at 4 gallons continual flow but we only use 1-2 gallon.
everything on a truckmount has specs accept hx's.....
Hp for engines
CFm for blowers
Btu for fuel heaters.
How can one truckmount claim more heat than another without some form of measurement???
We are spending 1500$ per hx and 20-30 k for truckmounts that claim all this heat but
I can't find there calculations.
 
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Kipp

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You need a big engine machine to handle 12-14 flow

That's a big selling point on fuel fired...you can get great heat with a 20 hp motor

There no standard measurement because how the capture and retain heat are often proprietary to the manufacturers
 

Anderson

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It would be easy to calculate for instance:
8 flow or 1 gpm keeps 200 degrees with pro hem x machine
Continual flow for 15 minutes.
Or 30 hp with 2 exhaust hx give 120 degree heat rise at 1 gpm
I am talking to manufacturers to sell me hx as I am looking to go back to hx as I am going up to a 40 hp suburu engine.
I am guessing these heat exchangers will give me a 100-120 degree heat rise above water temp. At 1 1/2 gpm or 12 flow.
 

rob allen

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Everest 650 may be just the ticket you need.
 

Rick Imby

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The real issue with HX units is how well they control heat spikes when you set the wand down for 5 minutes. Another issue is how long it takes to start heating.

There are two different souces of heat for a heat exchange unit. Heat from the engine exhaust and heat from the Blower exhaust. Some machines have one exchanger others have two. If you have a watercooled engine you can also get heat from the coolant.

To harvest the heat is really easy, if you have a continuous flow of water. But when you stop the flow of water even for a short time the water gets really really hot fast. Really hot water already under high pressure is really dangerous.

The major manufacturers like Hydramaster, Sapphire Scientific, and others have fairly sophisticated systems to manage the heat. Trying to maximize out put but not dumping a lot of water into your waste tank when you set the wand down. This is not an easy task as the control systems age.

Propane is really easy because it lights and burns easily. The flow switch or temperature switch can easily work without any electrical power. The most common propane heater is the LG 2, 3 ,4 series. For most single wand units the lg 3 works fine, for dual wand units the 4 will probably work fine.

Kerosene heaters need to have a powerful fan to mix air and kerosene for them to work. This requires another power source as most motors used for the TM will not power the fan without puttting a generator onto the TM (another system). Kerosene/Diesel has more energy per gallon than Propane or Gasoline.

What this board has seemingly learned in the last couple of years is the major manufacturers machines are much safer and consistant and durable. There have been several horror stories about garage built machines that in the hands of a cleaner self destruct in a fairly short time span.
 

Joe cool

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Since 1992 =24 years I turn the key and go to work . Never had a issue with HXs .
I dont need to burn up hoses fast with fuel fired , or ever worry while in in a home cleaning away for 45 mins .
Extra expense and time going to fuel up in a special station .
After all these years it still gets hot enough to do a knock out job .
Fuel fired on a open trailer is the way to go especially doing patio pavers and outside tile , driveways and such .