I never expected to hear about heat death and thermodynamics in a video on why radiators are so big , cool video must have taken a lot of research to present such complex topics
If I'm not mistaken, another significant component of how quickly a locomotive radiator has to shed heat (and therefore how large it is) is the use of dynamic braking. This switches the traction motors to generators, and the resulting current is sent through a load of big resistors, causing the train to slow down. Considering how much mass there is in a modern freight train (~10000 tons), this is a LOT of energy for even a small change in velocity.
I believe you are mistaken. The resistor grids are completely separate from the radiator, and don't use any liquid coolant whatsoever. The resistors are just hot metal with a fan blowing air over 'em.
While the dynamic braking doesn’t use radiators, they still dissipate heat much the same way (i.e. by getting air blown over the resistors) I found limited information after a quick google search but for the EMD SD70ACe at least, the „bulge“ is from the dynamic braking system.
@@Southern_Plains_Railfan You'd be wrong. The resistors, as klug said in his comment, are in the big side blisters. The whole area isn't filled with the radiator. It is shared with the resistor banks. I said much the same in my comment before seeing this comment thread.
I'm not an expert but from other stuff I've seen on youtube I learned that most part of these radiators is filled with resistors for the dynamic brake. Check out the vids about diesel-electric locos form Jared Owen or Hyce
This reminds me of the Indian Railways Diesel locomotives, where the older generation ALCO locomotives had flush radiator grilles as they were rated at 3100-3300 hp, making it easier for a smaller radiator to cool the charge down. However, the newer EMD GT46MAC (SD70MAC derivative) and the EMD GT50MAC (SD80MAC derivative) locos had much higher horsepower ratings (4500hp and 5000hp respectively), so they have large flared radiators, which made long hood operation inconvenient (India didn't use turntables to prevent delays). The visibility issues compounded so much that finally the Indian Railways research organization relented and redesigned the EMD locos to have dual cabs, with air-conditioning mounted into the cab attached at the radiator end to prevent it from heat damage.
Having failed thermodynamics at least once I feel I have an expert opinion on this subject. The waste heat is not expelled by the radiator but by the exhaust. The radiator simply keeps the engine from melting. The working flued that pushes the pistons down is air (mostly nitrogen) and exhaust gasses (CO2 and H2O). Removal of heat from these gasses completes the engine cycle. Since these gasses can't be reused they are simply dumped overboard. Same with steam engines. In (nuclear) power plants the steam is reused, so cooling must be done with those giant cooling towers. Imagine how big a radiator you'd need to cool the steam from a locomotive down to under boiling temperature, then multiply that by 100 (est.) to deal with the waste heat of the diesel trains in your example.
Another big reason for the massive radiators is due to Emission controls. In order to meet Tier 3 and tier 4 both EMD and GE had to put in intercoolers on their engines and with tier 4 going to EGR with coolers that requires more cooling back there. So the growth in the radiator sections of the locomotives. On a tier 3 GEVO you have a Radiator for the Engine then in front of that you have the intercooler for the turbocharger. On the Tier 4 you have the same plus the radiator for the EGR cooling system, EGR being Exhaust Gas Recirculation. Yes the EPA mandated that Diesel engines that produce soot particles suck down their exhaust to lower emissions. Which has the effect of lowering fuel economy and reducing reliability to the point where NO CLASS 1 wants to order NEW Locomotives instead just rebuilds their current fleets of Tier 3 and older. Why they have seen what EGR does on their other equipment like their heavy trucks used in MOW for over a decade and are like NOPE not touching this stuff with a 1000 Meter POLE. See what happens is the EGR cooler over time literally gets ate away by the acids produced by itself and then causes a failure in the cooling system and also the oiling system letting them mix.
That's better. I thought that this video was going to cover what you just covered. I see you didn't get a heart yet. The professor might be butt-hurt. LOL
@@chuckgillyThere’s a clear time cutoff about 15 hours ago where nobody after it is getting hearts on their comments. Dude is just away from his computer, genius. I’d like to see you make in-depth content like this and stay glued to your comments section for 24 hours straight.
I think that's probably the main point, especially in recent years. Engine power has leveled off at around 4,400 horsepower, railroads not really interested in anything bigger, yet the radiator sections keep growing. This is the real explanation. Could even look at it as two separate eras - the "more power" evolution from the '50s to maybe the '90s, then the "less stink" era from the '90s to present. Even as a very environmentally conscious person, I sometimes wonder if stricter emissions standards are reasonable, or if they're counter-productive to their own goals. Especially if grandfathering is allowed (based on some of the old rattle-traps I see chugging around yards belching smoke, it must be), while new requirements are impractical to comply with, railroads will keep their older, much dirtier stuff in service and not buy new, cleaner stuff. More reasonable requirements would encourage upgrading to something maybe not quite as good, but a lot better than the old dirty stuff. I've heard of a lot of things like this, industries keeping old, grandfathered, worse things because the new laws are too strict, making the policy defeat itself. Though of course the EPA making policies with reverse the intended effect is not a new thing. Car fuel efficiency laws encouraged automakers not to make cars more efficient but instead to market trucks and SUVs that are in more lenient categories, and overall less efficient.
Fairly good explanation, but a few things were off. In short, radiators getting bigger because engines are getting more powerful is the main reason, though I get the sense emissions compliance, requiring engines run cooler and stuff like cooling exhaust gas for recirculation are also factors. The hot and cold reservoir isn't really a direct explanation. This would make sense in a closed-loop cycle, like a Stirling engine as mentioned, or a condensing steam locomotive. In those cases, the recirculating working fluid has to expel all its waste heat through a radiator like this, that being the "cold reservoir," before re-entering the cycle into the "hot reservoir." A condensing steam locomotive is a perfect example of this cycle, the water/steam a closed loop, the boiler being the "hot reservoir," the condensors and air that cooled them being the "cold reservoir." The greater the difference in temperature between these, the more effective the radiator and even cooler the ambient air, the more efficient they were. There were a few condensing steam locomotives built, they had massive condensers, I believe usually on the tender. They were thermodynamically more efficient than open-loop steam locomotives, and didn't need to refill water, but complexity and bulk of the condensers made them rare. Internal combustion engines work rather differently in terms of the "hot" and "cold" reservoirs and the radiator's role. These are open-cycle engines, where the working fluid is ambient air drawn in, used, and expelled as exhaust (disregard EGR). The "cold reservoir" is the cold air being drawn in through the intake. In an "ideal" engine, as analyzed in my 300-level thermodynamics course, no heat is exchanged with the cylinder walls, all heat is added via combustion and expelled via the exhaust when the hot gases are exchanged for a new charge of fresh air. The waste heat leaves via the exhaust, not the water jacket. However in reality some heat is conducted into the cylinder walls and piston, which causes two things, both bad: For one thing, a reduction in efficiency as the heat leaving the cylinder that way is lost energy that otherwise could (partially) provide power. For another, this heat would heat up the engine block until it melted or seized if not removed by a cooling system, which adds a lot of complexity, weight, absorbs some mechanical power, and so on, but is necessary for the engine to not melt down. Heat dissipated from the radiator isn't an inherent part of the thermodynamic cycle but an unavoidable byproduct. The larger the volume to surface area, the less heat is lost this way, so fewer larger cylinders in theory would need proportionally less cooling (and be more efficient) than an engine with more smaller cylinders, hence the trend in that direction - this was something the video got wrong. It is still overall a fairly small fraction of the overall heat energy though, the majority of the leftover waste heat exits in the exhaust. The radiators, even if seemingly huge, are a lot smaller than they would need to be if expelling all the heat from a closed-loop cycle of equivalent power and efficiency. The overall heat to be dealt with is still at least roughly proportional to engine power, hence why more powerful engines need bigger radiators. I feel like that intuitively makes sense even without all this thermodynamics discussion - more power = more heat = bigger radiators. Then, as briefly mentioned, as well as more powerful engines there's also emissions and efficiency stuff. I don't know the details of split-cooling, but overall modern diesel locomotives would need to cool not only the block, but also an intercooler and EGR. Earlier locomotives didn't have EGR, and I'm guessing didn't have intercoolers - many weren't even turbocharged in the early days. I also understand that, probably for NOx reduction, the engine has to be kept cooler than in the old days. This to my understanding is why Porsche had to eventually switch the 911 series to watercooling, the air-cooled engines worked pretty well but ran too hot to be capable of complying with modern emissions standards.
This was a very good video. Great job with the mini engineering lecture about thermo and heat transfer. Growing up I always noticed those rear upper radiator sections on the GE locomotive
thanks for this topic, Ive been looking for this for so long. one of the reasons why I love modern gevos like the Tier 4 because of its massive prominite radiator block
Very good with explaining the basic physics behind engine cooling systems! The concept of "Work" is very slippery - sometimes even physicists argue over what exactly "Work" is. But you explain it in a nice simple way.
Yeah, a lot of "work" that goes into running modern society just gets pointlessly wasted by us foolish humans, anyway ;P ...But yeah, I understand the concept of work from a physics standpoint.
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Long ago I was taught by a techie at Fairbanks Morse that engines turned some of their heat into power and the rest was waisted and had to be dissipated, about half of that was exhaust and that problem took care of itself, the rest of the wasted heat went into the engine itself and that the engine would eventually self destroy if it wasn't gotten rid of. That function was taken care by the cooling system, generally engines use liquid cooling, generally water but the engines oil lubricating system is also a major player here. The water jacket around the cylinders removes the major heat from the engines while the oil flowing thorough the major moving parts of the engine cools these down. Over the years builders have added additional turbocharging systems to engines to increase the power output of the engine as well as reducing emissions, the turbocharger needs to be cooled as well, again the oil cools the bearings while many use a water jacket to keep the housing cool. Boyles law says that increasing the air pressure will increase the heat and it is more efficient to supply cooler air to the engine so intercoolers were added and these had to be cooled, most highway trucks use air to air systems for intercooling but most locomotives with five to ten times the horsepower needed to use water cooling. All of this along with a more than double horsepower output requires a larger radiator. I believe that most locomotives use only treated water in their cooling while trucks and cars that are routinely allow to cool down to ambient temperature that might be freezing, use an antifreeze mix that not only prevents freezing but allowing a much higher water temperature before reaching the boiling point, this higher temperature allows relatively small radiators to still be efficient and do their job. it is essential that the cooling system be of adequate size to meet the power potential of the engine, an engine cannot sustain operation at a given power level unless it can reject the heat generated. Some aircraft engines have two power ratings, one for takeoff and a second for continuous power (i.e. cruise speed), the first is time limited, five minutes is common, but especially on very hot days, the pilot must monitor his cylinder head and oil temps to stay out of the red line. Railroad locomotives might run at full output for hours when pulling a long freight train up a mountain range so full power is rated at only the continuous duty number. I had discounted the exhaust issue but it is also essential to have an efficient exhaust system, back pressure is the enemy. Generally one of the first things hotrodders do to an automotive engine is to modify the exhaust i.e. reduce back pressure. Again looking at hot rod and tractor pull engines, in both of these cases the engine is asked to run far above its heat rejection limit but only for a few seconds for the drag racer and less than a minute for the puller. Automotive engine designers have multiple goats to accomplish, the want the engine to heat up fast for car heating and defrosting as well as smoother running but the still want it to be able to climb long hills without overheating. They also want the engine to be small and light along with a small and light radiator but remember while a car needs power to get away from the stop light, most of the time it is cruising down the road making about 25% of rated power. This engine might not be too happy if you add a trailer and take a trip up to the mountains on a hot day. The engine reaches its heat rejection limit. You might note that the car engine when compared to even a light truck for a similar hp engine, has less water in the cooling system and less oil in the crankcase.
Totally defeats the purpose of being a hood unit, might as well go back to carbody style. Originally manufacturers intended for carbody locomotives as mainline freight engines (such as the EMD FT and F3/F7/F9), but railroads liked the rear visibility of hood unit road switchers. But modern ones don't really have that, and I get the sense railroads never operate them long-hood-first anymore anyway. I'm guessing hood units are easier for maintenance access though, that's probably why they're still the standard.
Both EMD and GE were already offering *BIG* radiators on their locomotives in the 1990's in anticipation of the arrival of 6,000 bhp prime movers such as the EMD 265H or GE/Deutz HDL. But both engines suffered excessive fuel consumption and reliability issues, and they were dropped for smaller prime movers with other power efficiency improvements.
Merch This was amazing, thanks keep them coming I have seen all your videos but one new one with very flared radiator wings looks like it may fall over lol
Yup, every radiator accelerates heat death. Nah, if our beautiful flat earth makes it to 2036 years old, then it’s time to throw in the towel I think. At least we had time enough to invent ice cream and goldfish, though!
That is an excellent explanation, referring to the entropy. The increased use of dynamic braking reverts kinetic energy, switching motors into generator mode to electricity, which is sent to the radiator to disparate as heat. I read that some test models had a battery to store extra power to assist during shunting and maneuvers. Just my 2c. Cheers!
Plenty of energy actually exists the exhaust. You kept saying, the heat that is wasted goes into the engine block. However, a fair amount actually goes out the exhaust ports.
Great video! One question, I've never seen the road railers (8:25) being used around Michigan. Are they still used much, and if so, where are they most often seen?
Casual existential dread, just a way of life for younger people (I'm a substitute teacher so this is what I always see - it's a mix of amusing and depressing.)
I wonder why these companies never thought to use the exhaust manifold as a steam boiler and put an extra turbine on the turbocharger as an assisting system? Steam could also be used to spin a small standalone turbine for extra electric power in a closed loop.
My friend is a mechanic at the bnsf shops in Minneapolis and I think you need to work there. You would obviously love it. Plus I know he makes about 120k per year. Pretty good if you ask me.
You interpretation of the carnot diagram is incorrect. Radiator isn't the temperature sink, its a leak in your heat reservoir (not shown in the picture). The cold reservoir is the atmosphere to which the exhaust escapes. For efficiency, you want the highest temperature from burning the fuel + air mixture inside the cylinder, and have the coldest exhaust temperatures. Lowering exhaust temperature is hard, you need to expand the exhaust a lot before it's released to atmosphere. Compound steam engines used to so that by using multiple cylinders in series. At some point, the juice becomes not worth the squeeze due to size and weight constraints of the engine. Raising temperature of the fuel+air is easy, run higher compression ratios and or add more forced induction. A turbocharger also extracts energy from hot exhaust gasses, and its a win-win. The downside is materials of the engine can only get so hot before the strength is compromised, hence the need for bigger radiators.
The statement that a100% thermal efficient engine would be a perpetual motion device is not accurate. A 100% efficient engine would produce double the power is a 50% efficient engine but would still need fuel to run. No fuel means no power. 100% of 0 = 0.
They make the rear of the locomotive look like a huge battering ram lol. Remember also diesel and gasoline engines operate at a certain temperature range for maximum efficiency. Run them too cold and your oil flows too slow and puts heavy wear on the engine and lowers fuel mileage. Another reason why you want to dissipate the rather insane amount of heat those engines produce is to put less stress on the other locomotive components and thus lower maintenance costs in general. Having more cooling also helps reduce the risk of fire. Did you know a BNSF loco caught fire this weekend in Rogersville, MO?
The other factor aside from aesthetics is that it probably blocks most of the view looking back, making these locomotives not possible to operate long-hood-forward, as had been the original appeal of hood units over carbodies. I pretty much never see modern locomotives running like that anyway, I think not for that reason but just railway practice has changed and there's really no reason to (they almost always operate in pairs coupled back-to-back, effectively creating a dual-cab pair). Which makes me wonder why we stick with hood units rather than going back to carbodies - my guess is easier access for maintenance is a bigger advantage than anything carbodies would have to offer.
The combustion temperatures have also been increasing to get the very last drop in increased efficiency. The excess nitrogen oxides are dealt with additional equipment
Liquid radiators can be made thicker for more liquid tubes, to handle larger engine heat transfer. The heat sinks for the dynamic braking need to be more exposed to dissipate the heat. When the engines pulling power increases, they also have to increase the dynamic braking capabilities of the locomotive proportionally, thus they have to increase the ability to dissipate the heat generated by the increased dynamic braking. Since there is not a water jacket around the dynamic braking load banks, the ability to move air over a larger heat sink has to has to happen.
I find this video cool! Keep up the good work Southern Plains Railfan! If your ever in Houston, go to the Rosenberg Railroad museum. They get alot of BNSF and UP trains and they got other cool things like a garden railroad (which runs a warbonnet dash 9), a Mo-Pac caboose, and a wig wag!
I put an enormous radiator in my vehicle. Oil stays cleaner, the electic fan rarely runs, it seems to make more miles to the gallon. The benefits of a large radiator are great.
I'm curious just how much horsepower these engines are putting out now, but when searching for the one with the largest radiators mentioned, I couldn't find anyone even asking the same question.. so how much horsepower do they have??
In a diesel heat engine the cold reservoir is the atmosphere accessed through the exhaust. The cooling system is there to solve the materials condition of not melting the engine.
what is the purpose of stating an energy of 1500 joules ? the context is missing, such as per second or per engine revolution or per piston ignition etc. ...
Thank you! - As a European I had assumed these radiators to double as places to dispose of heat during electric braking: when the electric motors are reversed to generators (to spare the brake shoes). (In Europe many locomotives are electric using overhead wires. Ever more of these can "upload" part of their braking energy into the catenary grid.)
@@harrimanfox8961 Thank you! - But I'd expect these to be well-ventilated too. I mean, braking an American-length train descending from mountain passes (well, keeping it in check) must generate considerable heat in those resistors, therefore require considerable cooling. So this is another cooling circuit?
A video about something I thought I’d never knew for a long time. Well now I know the reasons for these radiators (I use to know some about it before though).
4:08 you say that the radiator is the cold reservoir of a heat engine. That’s not correct, ambient air is the cold reservoir. Cooling the engine is about protecting the engine from too much heat and about emissions. Probably other things as well, but it‘s *not* about the working principle of an ICE. In fact, a single stroke is often simplified as adiabatic (i.e. no heat transfer to the environment) as the heat transfer is minimal. Need more proof: top-fuel dragster don‘t have a cooling system as they only run short times and wouldn’t be able to transfer much heat anyway
Isn't some of the radiator space used to disipate the heat generated by resistive heat coils in the dynamic braking system? There was no mention of dynamic braking in the video.
In 1980s when we got more powerful Class 56 loco's the radiator size did not increase I questioned one of the tech guys when we were loadbank testing , he said we run the cooling system much hotter so the smaller radiator dissipates more thermal energy (heat) . Seems strange running hotter for better cooling , loco's didn't have overheating problems
Hmmm a few points, firstly in an internal combustion engine more of the heat energy is lost out of the exhaust than through the coolant. Secondly these are turbo diesels, part of the reason why radiators are larger is to intercool the incoming air more effectively allowing for a higher effective compression ratio in the engine and greater efficiency. Thirdly larger cylinders result in a lower ratio of cyclinder volume which trends with power to surface area which trends with heat losses.
Couple points on efficiency: 1. A bunch of heat pisses right out of the exhaust pipe. Maybe more even than what ends up heating the engine block. 2. The absolute BEST case scenario is a gas turbine engine with recouperation (heating the compressor inlet using turbine exhaust air) and co-generation (an additional steam generator heated by exhaust heat). Those peak around 60% if they've been implemented well, but even then, they only get that at their rated power output. Soon as you ask for any less power, efficiency falls off a cliff.
Don't forget that as much of the energy waste in a combustion engine is in the exhaust stream as absorption by the block, cylinder head and other engine components.
Its not really counterintuitive if you remember its about optimizing efficiancy. Better cooling allows more power per unit of displacement so less displacement is needed to achieve a given power level.
