Edit post

Edit your reply below.

Post Body
Enter your post below.
[quote]QUOTE: Originally posted by edblysard Quentin, A closed cooling system with antifreeze would require a themostat and a presurized system. You understand that the water pump in your car isnt a pump, but presure device, an impeller, to keep a constant pressure (appox 14 psi) on the block, or hot side of the system? Water under pressure boils at a highter tempature. Water under pressure with coolant/antifreeze even higher. Your closed system uses convection and the pressure from the water pump to cause a partial exchange of the cool water in the radiator with the hot water in the block when the thermostat opens, usually about 195 degrees for most GM V8 engines. This temp keeps the engine running at the most efficent temp, too cool and oil dosnt flow enough, too hot, oils burns and thickens. The thermostat in your car is the "sensor" that decides when the enging is too hot, and allows cooler water from the radiator, to flow into the block, or too cold, and restricts the flow of cool water. By the way, this isnt to remove the heat of the combustion, most of that heat is blown out the tailpipe, it is to keep the lubricating oil at the correct temp to allow it to do its job, prevent wear. (Volkswagon had a very successful air cooled motor, with a oil cooler. Add a oil cooler to your car, and watch the efficency and gas milage increase.) This exchange is almost a complete exchange at first, but as the water temp rises, the thermostat begins to open and close quickly, several times every few minutes, until a balance is established, and the termostat remains partially open all the time, allowing a small amount of cooler water from the radiator to enter the block all the time, keeping the engine at the required temp for efficent performance. Speed up, and the process changes, the thermostat closes even more, because the air blowing through the radiator removes even more heat quicker, so the water becomes cooler, and less of this cooler/colder water is needed to maintain the correct engine temp. Slow down, the amount of air blowing through the radiator decreases, the heat exchange process between the radiator and the outside air lessens, so a fan is needed to pull cooler air through the radiator, and the thermostat opens wider, because more of this warmer, or less cool water is needed to kept the engine temp correct.. At highway speed, a fan clutch cuts out the radiator fan completly, it freewheels, because enough air is blowing across the radiator to remove the excess heat. Closed systems are designed for short, constant speed use, where cooling efficency is a requirement, due to space limitations. All of that to get to this. Locomotives require a long term, constant use system, moderatly efficent, and having no real space limitatons. (you can use as big a radiator as you need to) Locomotive water pumps are just that, pumps that move water in GPM rates. Because it is a open, or non pressurized system, evaporation will occure, but leaks of any kind are, for the most part, small. In your closed system, a pin hole in a radiator hose will empty most of the system, because it is under pressure. A pin hole in a locomotive dosnt empty the system. You car, and a closed, pressurized system, requires quite a few complicated parts, a locomotive dosnt. Your car operates at a almost constant speed, and part of that speed is used to cool the engine, a locomotive operates at several different throttle setting constantly, and, unless you mount the radiator on the nose, air flow over the radiator due to the speed of the equipment is nill, it has to be created by a fan. A closed system requires a precise mixture of water and coolant/antifreeze, with a fixed amount of water, change any of those, and you change the efficency of the system. Closed systems are pressurized, any leak is massive. Open systems require water, pumps, cooling fan ,a simple temp probe in the radiator, and something a closed system cant use, a reserve supply of water. Leaks, unless they are into the crankcase/oil system, are not a problem, and are usualy slow and small, and you have a reserve supply of water. Again, size and location play/use a large role. You car blows a radiator hose, you tow it to a shop, or home, and fix it with relatively simple tools. Lose a thermostat or a hose on a locomotive in the middle of Kansas, and your stuck, real stuck, because now you not only have to find a way to move the locomotive, but the train it is attached to. The simpler a system is, both in design and maintaiance, is the key for locomotives. These things run from Canada to Brownsville, there isnt too many places where the crew can pull in and get it fixed. The kiss principle applies here, the less moving parts or complicated systems and subsystems, the less likely the system will fail. All of that said, yes, you could design a closed system, but it wouldnt survive long without heavy maintainance, and maintainance cost are a big part of railroading. Ed [/quote] Ed, while I will never dispute anything you say pertaining to the railroads(as you are god!), I do however dispute your description of the automobile water pump and cooling system. Water pumps on conventional automobile cooling systems are not pressure devices- they are simply pumps. The pressure in an enclosed auto cooling system is a by-product of heat through combustion and is regulated and maintained by the thermostat, cooling fans, and radiator. A trans or engine oil pump relate directly to pressure. Your insight and info on the loco engines is great! Pure mass is an issue- I've seen align-bore equipment for auto eng blocks but can't imagine what that would take for massive locomotive diesels. I can see why they would 'module design'.
Tags (Optional)
Tags are keywords that get attached to your post. They are used to categorize your submission and make it easier to search for. To add tags to your post type a tag into the box below and click the "Add Tag" button.
Add Tag