[cbzook]

Hey guys,

Currently messing around with the idea of making a heat exchange for my xl7 to be able to have hot water showers whilst camping, of coarse the easy thing is to get an on demand unit like Coleman etc but I don't want to take up space in the car etc.

I have access to all the materials needed and could possibly get away with building one for under $50 which is more funds for other equipment!!!

So my plan is to get about 300mm of 3inch maybe 2.5" aluminium pipe probably minimum 2mm wall but ideally I wanna go 3mm wall. Will cap each end with aluminium plate and weld the appropriate Hose fittings on. Use 3/8 or 5/16 aluminium Aeroflow hardline (aftermarket fuel line) try to get as many coils as I can inside the pipe. I'll use 1" pipe to rap the hardline around to take shape n drop it inside the pipe. Tig it all together. Mount it into the car and hook the hoses up so water feeds straight from the heater tap thru the exchange unit then back onto the motor.

Has anyone built one on here before?? Looking for ideas and tips on this.. Any help, feedback or suggestions would be great.

Thanks

Nic

[buzbox]

If you can do it on the cheap, sure why not. But boiling a jug on the fire and pouring it into a bucket of cold water and having a whore's bath does it for me.

[jdk81]

I made one 6 years ago.

Looked at doing an in car type set up.
Unless the flow rate is low, or the change in temp of water is low, or the water is recirculated a lot, it wont get hot enough and/or be capable of a decent shower.

You need an efficient system with a lot of energy to heat water on demand at the rate suitable for a pleasant shower.

I ended up making mine a coil of copper wire and placing the coil into the fire.
It needed to be a proper big fire, as the coil/water sucks the heat out of the fire.
There may be photos around here of the bush hottub.
We chucked a tarp in a hole in the ground and pumped water in the river and heated it up. It was 4 degrees out and we were all drunk and hot tubbing in the bush

Theory

Water spec heat 4.19 kJ/kg degrees C
Ideal water temp for a shower 44 degrees C
Flow rate (home 9l/min, camping 4l/min)
Water intake 10 degrees C (delta T = 44-10 = 34 degrees)
So 4 kg/min and 34 degrees C
So 4.19 kJ/kg.degrees C x 4kg/min x 34 degrees C
= 4.19 × 4 × 34 kJ/min
570 kJ/min required heat
570 kJ/min /60
Thats 9.5 kW.

Idle fuel consumption is approx 1.5l/hr
Petrol energy density 46.4 Mj/kg
Petrol density 0.737 kg/l
So 46.4 x .737 x 1.5 MJ/hr = 51.3 MJ/hr (14.25 kW)

So 70% of fuel energy needs to go into the shower water for a semi pleasant on demand shower.
Its not going to happen.

If you're winter camping, the task is more difficult as the delta T is gugher.

Far easier to recirulate the water to heat it up and then pump from that. Then you can have a better shower with a higher flow rate.

And you may as well just put a jug on the fire.
Hill billy billies pour out hot water as you place water in.
Would be able to pump water into one and mix it with cold water, using it like a conventional hotnwater system, and have a very good shower for a lot of people but it's dangerous.

If you're going to do it, donit properly.
There's plenty of ways already available to have a shitty camp shower.

[shep]

Metal bucket + fire + cheap eletric pump = cheap temp controlled shower.

[rustyzook]

Plate heat exchanger. It works, temp is about 40 Celsius. Used to run it on my old F10a and before that it was on a hilux 2.4. It was a 30 plate with a 12v pump