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Thermosyphon Cooling Tank

I'm using a screen cooling tank on a 17 HP Ruston engine, running slow and not under load. I have tried a belted pump but the engine would not warm up. I have the bottom of the tank higher than the water level in the block of the engine. After it comes out of the engine, the water has to go up about 38 inches to the screen. Is 38 inches too much of a rise from the top of the cylinder to flow to the screen cooling tank? -- Terry

For thermo-siphon to function the top pipe must be below the water level to make a complete loop. A screen cooled tank won't allow thermo-siphoning. Could you install a valve before the pump to throttle the flow? -- Bill

You can use any kind of tank for your cooling system. If you use a pump you can certainly use a screen cooler. If you do not use a pump you have a thermo-siphon system and the water will circulate by convection as it gets warm. If you want a screen cooler you must use a pump, thermo-siphon cannot "pump" water up to a screen. You mentioned that you used a pump and your engine did not get warm. Remember that you were circulating water from your cooling tank and that the engine would have to heat up all that water. I had a 15HP Reid and it would run for about 4-5 hours before it would heat all of the 40 gallons in my tank - give it time! -- Norm

Aren't some screen cooled IHC (Moguls) "thermo-siphons" yet they have a screen tank? The water barely trickles out if you run them slow, but until the engine is pretty warm nothing comes out! -- Laura

Some of the smaller Moguls are in fact screen cooled without a pump. Until the engine reaches 212 degrees nothing happens but when the water starts to boil it bubbles up the pipe and runs down the screen. This makes for quick warm up and keeps the engine at a good temperature for burning Kerosene. The only big downfall is there is no Hopper to put the bratwursts in to cook them. (4HP Mogul Photo by Patrick Livingstone) Notice the screen tank is mounted high so the cylinder is filled with water all the time. Can you see any pump on this one? -- Ken

A friend of mine has a 6hp and it also does not have a water pump. This is how they left the factory and it works fine. The base of the tank is higher than the cylinder so there is always water in there. Once the engine warms up it pushes a lot of water over the screen and it keeps the engine nice and warm to run on kerosene. Australs and Blackstones have in line taps in the water line to limit the flow of water. This is common to both the thermo-siphon tank cooled engines and the engines fitted with water pumps and cooling towers. It allows for adjustment in the flow of water which is a big help in keeping the hot-bulb engines warm. – Patrick

When I set up my model YH Fairbanks I put the pipe back into the tank below the water level. The water will begin to circulate as soon as there is a temperature difference. If the water gets low the water in the engine will get up to 212 degrees and will bubble up the pipe and drip into the tank. Either way as long as the cylinder is covered with water there is not problem with overheating. Many old farm tractors and the model T Ford did not have a water pump. Actually an aftermarket water pump on a Model T would often hamper circulation due to the small passages and poor belt system. If the water level is below the cylinder as in the Famous and Titan engines then a pump is required. – Ken

I had the bottom of my tank higher than the cylinder. I guess maybe I didn't let the engine warm up enough. Today I dropped the tank down 6inches and installed a pump. I'm going to try a valve under the tank to restrict water flow to the pump. My concern is that the pump might not hold its prime. If it doesn't work the tank might still be high enough for thermo-siphoning without the pump. Thanks to all for the great comments and suggestions. I'm sure I'm not done experimenting yet! --Terry

For cooling our Bessemer engines we found it better to place a "T" after the pump. One line goes to the engine and the other line goes to the top of the tank for a bypass. Put a valve in each line and it is easy to control the flow through the engine to allow the engine to warm up. -- Kent

In my thermo-siphon (open system - no pump) cooled 10HP IHC Mogul, the water tank/cooling screen is considerably higher than the cylinder it cools. There is no real thermo-siphoning going on, in the true sense of molecular heat transfer that is obtained in a closed loop system where heated water rises from the top of the cylinder and the cool water from the tank enters the cylinder from the bottom. I’ll attempt to tell you how it works in the Mogul's case. When the engine is running and under a load, it gets hot. In fact it can reach the temperature of boiling water (212 degrees F, or 100 degrees C) rather quickly, which is great for a kerosene burning engine. As the water begins to boil it creates steam and forces itself (steam and hot water) up the pipe and out of the holes in the return pipe on top of the screen where it cools itself as it falls back into the tank. Let me tell you, the water is HOT. As this happens, it creates a partial vacuum, in the cylinder proper, which allows a critically balanced, in line horizontal check valve from the bottom of the cooling to partially/momentarily open (weight of the water in the cooling tank pushing on it) allowing cooler water to enter the water jacket around the cylinder. As soon as the cooler water enters the water jacket, it cools the cylinder enough so that it stops steaming, the vacuum is broken and the check valve closes. As the engine heats up again, it goes through the same cycle. Sure is neat to see it in action. On the Famous lines they "usually" have a water pump that circulates the coolant through the engine up and across the screen (not thermo-siphon). -- Paul

So really, it's more of a "percolating" effect rather than thermo-siphoning in the mogul's case? -- Laura

"Percolator Cooler", I love it! That's exactly what it is, not a thermal siphon system. Enjoyed reading this thread and learned something I didn't know about percolator cooling systems. -- Mike

You guys making fun of my "percolator"? We'll see who's laughing on that cold engine show night. I'll have my coffee cup dipping into my screen cooled "percolator" -- maybe even put some instant coffee in it, giving "International Coffee" a whole new meaning! I bet NOBODY has ever had home brewed coffee that's "percolated" through the complete innards of an old gas engine! -- Laura

An old gentleman who worked in the oil fields told me that if the cooling system was closed, meaning that the top pipe entered the tank below the water level, it was called "thermo-siphon" and if the system used boiling water and steam to push the water up and over the top into the tank it was called "slugging" Not sure he was right but I believed him. I've used both and for displaying the first method takes much longer to heat up everything. -- Howard

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