Lister Engine Forum

How to / DIY => Engines => Topic started by: Montana on April 12, 2009, 03:04:41 PM

Title: Radiator for 12/1
Post by: Montana on April 12, 2009, 03:04:41 PM
Im looking at using a radiator for my 12/1 and found one for a Suzuki Samurai 1.3l gas car.  It has mounting flanges on the side, 1 1/8 inch connections with 2 rows of down flow cooling and the core size is 15x13.75 inches.  I'll have to use a fan to help cool it.  What you guys think?  Is there any thing else out there that may be better?
Title: Re: Radiator for 12/1
Post by: compig on April 12, 2009, 04:45:35 PM
Depends if your going to use a circulation pump. Without a pump a much larger rad is needed for thermosyphon to be adequate.
Title: Re: Radiator for 12/1
Post by: ronmar on April 12, 2009, 06:26:13 PM
It should work, but there are a few things that must happen. 
1.  It must be high enough so there is enough cool water in the radiator and return line to the cylinder to outweigh the volume of hot water in the cylinder, head and uppipe to radiator.  Think of it like weights on the end of a balance type scale.  The weight of the cold water on the down side MUST weigh more than the weight of the warm water on the upside in order to get good flow.  Making the return line as large a diameter as possible would also help here.  In setting this up, I would use a bucket and compare the water volumes from base of cylinder to top of up pipe where it meets the radiator, and from top of radiator to bottom of downpipe where it meets the cylinder.  You need at least an equal volume of water from the two sides.  Then it is up to the radiator and airflow to maintain the weight difference that powers the flow.

2. Thermosiphon is powered by gravity and the difference in weight between a volume of warm water and a volume of cold water.  The greater the difference, the greater the flow.  In order to power it, you MUST cool the water.  This means a good volume of airflow thru the radiator and an adequately sized radiator to remove the heat from the water. 

3.  To work, the rad MUST remove the ammount of heat placed into the cooling system by the engine.  At full load, I would guess a 12/1 is going to need to dissipate about 36,000 BTU/HR thru the cooling system.  A 1.3L suzuki Samari gets what kind of gas mileage?  30 MPG maybe on the highway?  At 30MPG it would burn 2 gallons per hour at 60MPH.  With gas at around 115,000 BTU/gal, that is 230KBTU/HR of heat input to the engine.  Rule of thirds says that about 76,666 BTU/HR should be dissipated by the cooling system under these conditions.  Better mileage would mean less BTU per hour thru the cooling system, but I don't think the Samari gets much better than that on the highway.  That rad is also sized to do this job in pretty high ambient temps.  At 30MPG, that demonstrated heat dissipation capacity is more than twice what you can feed it at full load from the 12/1 so the rad should work OK for you.

A larger radiator would have the advantage of larger capacity and more water weight which would enhance thermosiphon flow.  It also would have the advantage of more surface area which would require less airflow to cool a given ammount of water.  But a larger rad also requires a larger volume of coolant and takes up more space. 

I think your suzuki radiator will work OK for thermosiphon.

Good Luck   
Title: Re: Radiator for 12/1
Post by: compig on April 12, 2009, 08:29:08 PM
Lack of forced air flow is the reason I suggested a larger rad. Using a fan is ok but if electrically driven the possiblity of failure should be considered , especially if the fan is run continuously. Thermosyphon is almost fail safe. Using a big truck rad thats been cleaned and painted matt black would be my choice.
Title: Re: Radiator for 12/1
Post by: BruceM on April 12, 2009, 10:26:16 PM
I have a large V8 sized radiator (turned sideways for vertical flow) and thermosiphon flow for my 6/1.  With no fan, I only occasionally start to boil off coolant (just twice now in the last 2 years).

http://picasaweb.google.com/lh/photo/9Iaov5np7yildzoiRqCaHw?feat=directlink

If I were starting over, I would use a Metro (small) sized vertical flow radiator, with exhaust inducted cooling air flow.  While this adds some sheet meta ducting work, it would keep my outside the shed radiator protected from hail, and eliminates the need and power drain of a thermal switch and electric fan.  The latter I don't want because I also pump air with my 6/1.

There are lots of good cooling systems out there, and in a large part it depends on your individual needs/uses are. 

Title: Re: Radiator for 12/1
Post by: Montana on April 13, 2009, 05:25:55 AM
Wow nice pict Bruce.
Well I just bought a Taco pump to use with the radiator.  I'll tie it in with the generator.  A thermal switch will turn the cooling fan on when needed.  So it looks like I'll order up the radiator tomorrow.
Title: Re: Radiator for 12/1
Post by: vtmetro on December 13, 2010, 04:04:50 AM
It should work, but there are a few things that must happen. 
1.  It must be high enough so there is enough cool water in the radiator and return line to the cylinder to outweigh the volume of hot water in the cylinder, head and uppipe to radiator.  Think of it like weights on the end of a balance type scale.  The weight of the cold water on the down side MUST weigh more than the weight of the warm water on the upside in order to get good flow. 

 ??? I had a wood chip furnace with a separate 275 gallon hot water storage tank in an outside shed that thermo-siphoned up to the house baseboard units with a total "cool side" volume of about 10 gallons, including the piping baseboard units and relief tank.

The weight of water in the cool side in this case was about 83 pounds while the hot side was about 2500 lbs. They didn't have to equal each other in order to circulate.
Title: Re: Radiator for 12/1
Post by: LowGear on December 13, 2010, 05:38:59 AM
Hi Montana,

What the heck do you do in your lab.  Wow!

Casey