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Author Topic: Help With Lister Cooling  (Read 5531 times)

Dave

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Help With Lister Cooling
« on: June 06, 2007, 01:25:08 AM »
I am getting very close to finishing the Generator project I have been working on. I need some help figuring out the details on the cooling.

I have been reading the previous posts about radiators and I have some questions.

How big of a radiator do I need for 24/2 with no water pump?
When I went to the radiator shop, the first thing they asked me was, "What is the make, model and Year?", "Thermosyphon?"

When it was mentioned in the posts to install the radiator at a slant, which way do I tilt it and to what degree would be optimum?
Top tilted away from the engine?

Thanks again to all the guys who have been helping me over the last year to get this far..... Maybe I will be ready for hurricane season this year

theboss

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Re: Help With Lister Cooling
« Reply #1 on: June 06, 2007, 02:33:58 AM »
These listers do not generate lot of heat. Keeping water pump out will reduce point of failure. Use a large radiator vertical flow radiator and thermostat controlled electric fan. Should keep things under control.

xyzer

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Re: Help With Lister Cooling
« Reply #2 on: June 06, 2007, 04:05:54 AM »
Dave,
I don't have a specific answer but I'm on my 2nd 6/1 portable unit and both are using auto radiators. The first is using one out of a Saturn and my 2nd will be out of a Metro. The Saturn will keep it from overheating on an 85deg day with no fan. It is a tilted radiator. You have to be careful when you tilt them you don't get any air pockets in inlet lines. I would also recommend installing a large reservoir to increase the reserve volume of water.

On a auto cooling system with a pump it will still circulate water if it gets a little low, but with a thermo siphon you can't even think of breaking the siphon! A 24/2 will make a fair amount of heat and I myself would be looking in the truck category. I helped my stepson pull the radiator out of a 7.3 Ford and thought to myself That would do some cooling! What ever you do I would have a plan to attach a small fan after I saw how it behaved on hot day full load. 
Dave
« Last Edit: June 06, 2007, 04:12:23 AM by xyzer »
Vidhata 6/1 portable
Power Solutions portable 6/1
Z482 KUBOTA

phaedrus

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Re: Help With Lister Cooling
« Reply #3 on: June 12, 2007, 06:50:25 PM »
The following is for a 6-1, but since a 24-2 is four times a 6-1, you can simply multiply the number and get an approximate size. I worked it to about 269 square inches of 4 row automotive type radiator for a 6-1 at full power and in equalibrium. Four times that is 1,076 square inches of 4 row radiator, that's about 33 inches square, 33" x 33". This assumes a fan of considerable vigor. "Truck" is a good suggestion, I think, for a 24-2. So is a very robust fan.

I did as follows: The specific fuel consumption for a 6-1 is given ordinarily at 255 g per kwh. Assuming this is true and that the given engine is at full power when it is making 4 kw at the flywheel, that's 1,020 grams per hour of fuel, releasing about 34.8 megajoules. (A liter of fuel is about 850 g, and fuel releases about 40.9 megajoules per liter). A kilowatt-hour is the equivalent to 3.6 megajoules, and 4 kwh is therefore equal to 14.4 megajoules, giving a (claimed) efficiency of about 41%. Not bad.

Anyway, 1 BTU is about 1,060 joules, and 34.8 megajoules is therefore about 36,888 BTU. That is about the maximum amount of heat that must be removed to stabilize a 6-1 running at 4 kw, if the factory fuel data is true. Obviously 1/4 of that, 1 kw, would require 9,222 BTU per hour of heat removal. This assumes that the engine is just as efficient at 1 kw as it is at 4 kw, that can't be true, but it ought to be fairly linear.

A surface radiator, a simple closed tank, to cool that would be (given Lionel Marks' "handbook"* 200 BTU per sq foot figure) require about 185 square feet of radiating surface, or more, depending primarily on air temperature.

For an automotive type fin-and-tube "radiator", assuming Lionel Marks' "Handbook" figure of 6-8 square inches of surface per BTU/MIN, and changing minutes to hours, that's 60 BTU per hour for 6-8 square inch of fin-and-tube surface, or, assuming 7, about 4,304 square inches of fin-and-tube to cool a 6-1 at full power. That's about 65.5 inches square, but as automotive fin-and-tubes have more than one row of "surface", or tubes, and we can assume 4 rows, that's something like 65.5/4, or  about 16.4" x 16.4" of 4 row fin-and-tube a 269 square inch "radiator". A big heater core or a little radiator... 'course a fan is necessary to make that work and there must be some air flow rate. I would assume something like 44 feet per second, that's about 30 mph. That's a lot of fan... less fan means more fin-and-tube, maybe half the fan means twice the fin-and-tube, that remains to be found out.

An implication is that the factory cooling tank systems must rely on evaporation to a considerable extent for cooling, as the tank dimensions Lister gives do not provide enough radiant surface to cool an engine of this size and efficiency, not, at least, according to the published data.


*Lionel S. Marks, Mechanical Engineer's Handbook, 4th ed.
if ya don't ask permission they can't deny it...

ronmar

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Re: Help With Lister Cooling
« Reply #4 on: June 12, 2007, 07:53:08 PM »
Dave
   Do you have a fuel consumptin figure for your engine under load?  If so convert that to BTU's and divide by 3.  That is roughly the ammount of heat your cooling system needs to dissipate(Rule of thirds, 1/3 mechanical/friction/engine radiation, 1/3 exhaust and 1/3 cooling).  The same rule can be aplied to an automotive engine so if you can find some figures for mileage/fuel consumption and convert that to BTU's consumed per hour, it might help you find a suitable automotive radiator for your application.  But remember the auto application size is based on ram airflow and fan at up to highway speed so the greater airflow mean greater BTU transfer to the air. 

If you are not using a fan, your system will rely more on convection and the stacked radiator rows mounted vertically without a fan will actually trap air amongst the fins(dead air is about the best insulation there is) really lowering the heat transfer.  Ideally, you would want the radiator laying flat in a vertical duct.  This would act like a chimney and as air warmed and rose in the duct, fresh cooler air would be drawn into the core to increase cooling(air thermosiphon:)).  Unfortunatly, flat mounting is not good for maintaining a coolant thermosiphon flow thru the engine.  Perhaps 45 degrees with a duct to enhance the chimney draft effect would work.

Better to have too large a radiator.  If it is cooling the water too much and the flow is pulsing you can block airflow thru the radiator to match it to your application, same as truckers do to their diesels in the winter.  Ideally you want a steady flow of coolant around the cylinder and thru the head for a steady transfer of heat to the radiator.  If things are matched up correctly, at low load, the thermostat will be just open and flowing only a little coolant to maintain temp.  At full engine load the thermostat should be open a good ways and much more fluid flowing to maintain temp.  A pulsed flow is caused by letting in too low a water temp from the radiator(excessive cooling) which flows till it hits the thermostat which promptly closes untill the water warms and the thermostat opens again letting in another gulp of cold water from the bottom of the radiator and repeating the cycle.  This pulsing  leads to thermal expansion and contraction of the parts, increased wear and more tendency for gaskets to leak and stuctures to crack.
PS 6/1 - ST-5.

phaedrus

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Re: Help With Lister Cooling
« Reply #5 on: June 12, 2007, 09:47:23 PM »
I looked up the published specific fuel consumption for a 24-2, and found it is claimed to be 268 g per kwh or 197 g per bhph.
     http://www.poweranand.com/slow_speed_lister_type.htm

This is about 5% more fuel than my given data was, eg about 5% more heat. Pretty close, if the published claim is true and if I did not make some dumb mistake....
if ya don't ask permission they can't deny it...

Dave

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Re: Help With Lister Cooling
« Reply #6 on: June 15, 2007, 02:29:01 AM »
I am going back to the radiator shop to look for a very large truck radiator.

I am also installing an alternator so a 12 vdc fan is no big deal if I need one.

Thanks again for all the help guys....

Dave