Will this thermosiphon?

[bschwartz]

I don't want to add a coolant pump if I don't need to.
My angles and sizes can't change from the drawing, so the only question is, do i need to pump my coolant, or will it thermosiphon?
The rectangle on the left is a radiator with a fan, the top rectangle is a heat exchanger.
The total climb from the lowest point on the radiator up to the lower cooling port is 3"
The total climb from the upper coolant port to the heat exchanger is 28".
The horizontal distance from the radiator to the coolant ports is 48"

Oops, forgot some important info.....
plumbing is 3/4 copper pipe, heat exchanger ports are 1/2" (copper necks down to 1/2" at those points)

6/1 engine.
Did I forget any other relevant info?

[LowGear]

Pipe Lines are too small.

Radiator is too low.

Look at the factory 6/1 system.  Masters they be.

Casey

[squarebob]

If it worked in 1937, it should work for you now. I use 1/2 " heater hose on my GM 90 but my heatex is 48" above the outlet in the head. You could always angle the radiator so the bottom is not below the inlet point. Give it a try. Nothing ventured, nothing gained!!!

Bob

[bschwartz]

Casey,

I would love to change the shape of my radiator, make the hoses/lines bigger etc.
I know it isn't the best of layouts.
This is the radiator I have to work with.
I can not mount it higher (or I already would have)
The line restrictions are what I have.
Placement is what it is.

I know the 'masters' have put together systems designed to thermosiphon well, and mine is NOT designed well for that purpose.

I considered changing the angle, to raise the lower part of the radiator up, but due to other limitations of space, that is not practical.

There are a million things I could do to change what I have, but right now, the only variable I am looking at is pump or no pump. 

If I use a pump, and it fails, I overheat (no comments about auto shutdowns for now please).
If I don't use a pump, and thermosiphon doesn't work...... I overheat.

Bob, your system can get rid of enough heat at full load with thermosiphon only through 1/2" lines?
If so, my system should be OK line size.

The only real question then would be is, would the 3" rise over 4 feet kill the thermosiphon?

[cognos]

If this is the design you are stuck with, and you have no other options, then Mr. Spock would say that the only logical option left to you is to just try it and see if it works.

I'm sure it will thermosiphon. Whether it will do so in a way that will carry away the heat in the quantities that you will be requiring remains to be seen.

[LowGear]

Very important notice.  I haven't done any of this stuff.  I'm shooting from the hip and relying on information I've read over the years on this site and LEF. 

Put in two pumps?  Higher temperature thermostat on the second pump along with an alarm.

I'd also insulate the hot line and find someway to put a cooling line on the return.  I keep seeing some sort of finned line - copper or aluminum.

Have you considered fans for the radiator? 

Casey

[vdubnut62]

Brett, in my admittedly limited experience with thermosiphon cooling systems I have only one tip.
If you are using antifreeze in the cooling system, make sure that it is either pre-mix or that you mix the ethylene glycol with water before you pour it in.
Once upon a time, I had a 1947 "B" John Deere with the thermosiphon cooling system. I was going to come a cold snap, and I figured that I would
winterize the old tractor, and since the plain water in it was pretty nasty looking, I drained everything. After draining, I poured the antifreeze in
and then I topped it off with water and fired the Old Girl up.  I let it run a while until I noticed curls of vapor/smoke coming off the engine, but the
coolant lines were still cold. It got up to around 230 degrees if I remember right. I had to drain everything back out and mix it in a bucket , then pour it back in. I guess antifreeze is heavier than water and effectively creates a  plug against the natural rise of heated coolant.
Sorry for the long winded story..
Ron

[squarebob]

Brett, Current setup is 1/2" rad hose from engine to heatex and back. Other side of heatex has 1/2" rad hose, a circ pump, and a transmission oil cooler with a fan to remove the heat. The cooler is a 16 pass with 650 cfm fan. It measures about 12 x 15. With 2 ~1500W heaters and a small battery charger draw on the ST7.5, the engine is working pretty hard and the temp stays at ~ 190oF. The thermostat is a napa 253 195oF unit. I am using RV antifreeze (propylene glycol) as the coolant.
The setup is just like Ronmars pic except the large tank on mine is a 1 gallon jug 1/2 full of liquid !

[LowGear]

Fan Question:

Has anyone ever used a couple of low watt computer fans?  Really low current and very low noise (just in case the radiator is in another location from the engine).

Casey

[bschwartz]

Thanks for all the feedback!!

I decided that I didn't want to have to drain my antifreeze/water mixture (mixed before adding as per Ron) if what I did today didn't work.
I put in the pump on the lower side between the radiator and the lower cooling port on the engine.
My hope is that if the pump (taco) dies, it has a chance to thermosiphon.  I understand that these circulator pumps will flow when not running.

As of right now, things seem to be running nicely.

I have the engine turning an ST-5 to produce 240v AC
The 240v AC powers a 48v DC power supply putting out about 37 amps at 51.8 v DC.
The DC feeds a set of 4 el-cheapo Sam's Club marine batteries (in series)
Also connected to the batteries are the MX-60 fed by 4 Evergreen 210w panels.
The batteries feed the GVFX-3648.
Between the Sun and the listeroid, I'm feeding 2KW back into the grid right now!!

THANKS GUYS!!!!

[squarebob]

Are you running a thermostat on the engine?

[cognos]

Sooo... shut off the pump, and test the theory while you're right there to monitor it, and everything has stabilised.

[LowGear]

Sooo... shut off the pump, and test the theory while you're right there to monitor it, and everything has stabilised.

Troublemaker.

Casey

[mike90045]

Low watt computer fans are not rated to withstand much heat.  Even if they suck cold, and blow cold toward the rad, the heat from the rad may cook them,  just try it, and keep an eye on them

[vdubnut62]

Alright already, so turn off the pump. I'm dying in anticipation here.
Ron