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November 28

Bathing

100 years ago people bathed anywhere from once a month to once a year. 200-300 years ago it was once a year. Have there been any studies done on bathing frequency and skin infection (staph infection, boils, fungal infection ect) and also UTI's. Most people bath 1-7 times a week now and I'm curious if skin infection and UTI's have gone down or remain the same. --Wrk678 (talk) 06:31, 28 November 2012 (UTC)[reply]

I don't think you can generalize on bathing frequency like that. In tropical areas on the beach, people probably bathed far more often than in cold climates inland, due to the difficulty of obtaining and heating the necessary water. Then there were those who didn't bathe because they thought it unhealthy, which it was, if they didn't have the sense to keep warm until they dried off. Also, lye soap can be rough on the skin, if used daily. StuRat (talk) 06:40, 28 November 2012 (UTC)[reply]

It also depends a lot on place. During the Roman Empire, people frequented the Thermae several times per week. --Jayron32 06:53, 28 November 2012 (UTC)[reply]

Nearly always, if you go to the doctor and tell him about some skin rash you've got, unless it is certain specific diseases, he'll tell you to stop using normal soap and instead use a bag of oats or some dermatitis "soap" that isn't actually soap. And quite often the rash will then clear up, or at least get better. Trouble is, without soap, you don't feel clean, and you smell a bit. Also, in hot climates (eg Australia), a daily wash with soap seems to help you keep cool and not sweat so much. Ratbone 58.169.233.62 (talk) 07:54, 28 November 2012 (UTC)[reply]

What's so unhealthy about being cold? I hope you're not referring to this unfortunate misconception. Evanh2008 ^{(talk|contribs)} 09:57, 28 November 2012 (UTC)[reply]

Your link doesn't say it's a misconception. Dry, cold air leads to cracked, chapped lips and an irritated throat and nasal passages, both of which allow viruses in. The rest of your body is normally protected, being covered with clothes and oil, but, after a bath, you have neither, if you used lye soap and no moisturizer. StuRat (talk) 23:57, 28 November 2012 (UTC)[reply]

Maybe, but if you are low on calories (most people would be 200 years ago or earlier) cooling off your body in winter is a bad idea for your health in general, because calories will be used to rewarm it, intead of being invested in building up your imune system. Any germ can take advantage of a slightly weaker imune system. --Lgriot (talk) 10:13, 28 November 2012 (UTC)[reply]

Do you have a reference for most people being malnourished 200 years ago? That's the early days of the industrial revolution in Europe, so the vast majority of people were still living in the country (even more so outside Europe). My understanding is that most people grew their own food so, except in bad years, would have eaten pretty good diets. It was only after moving the cities that food became a significant problem. --Tango (talk) 01:22, 1 December 2012 (UTC)[reply]

can anyone answer my original question? In the usa 100 years ago on the east coast they didnt bathe much. --Wrk678 (talk) 23:51, 28 November 2012 (UTC)[reply]

I doubt anyone can answer your question for the simple reason that information about the frequency of skin infections and urinary tract infections occurring 200 ago is not widely available (if available at all). Richard Avery (talk) 08:23, 29 November 2012 (UTC)[reply]

Lots of US families a hundred years ago had the Saturday night bath as a standard. I question the OPs assertion that they only bathed once a month back then. Maybe people who liked being filthy, or those who vnever did enough work to get dirt on their bodies. 75.34.30.62 (talk) 20:02, 29 November 2012 (UTC)[reply]

Or those who lived in places where water was very scarce. 24.23.196.85 (talk) 09:18, 30 November 2012 (UTC)[reply]

The vast majority of US settlers wee clever enough to live where there was water a hundred years ago. 75.34.30.62 (talk) 20:48, 1 December 2012 (UTC)[reply]

Fluoroauric acid

As gold(V) fluoride is a stronger fluoride accepter than antimony pentafluoride, I'd imagine it would create a stronger acid than fluoroantimonic acid based purely on fluoride affinity if mixed with hydrogen fluoride (as with fluoroantimonic acid). Am I right, or are there other factors affecting the strength of such an acid?--Jasper Deng (talk) 06:55, 28 November 2012 (UTC)[reply]

Variants of this have been asked several times over the past year or two. Executive summary has been IIRC "no matter what you think, you're missing something (or something isn't fully known period) if you think you're making something stronger than fluoroantimonic". Likely places to search are the archive of WP:RD/S, the talkpage of the acid, and maybe my talk-page.DMacks (talk) 07:06, 28 November 2012 (UTC)[reply]

From ^[1]:

It can therefore be assumed HF/AuF₅ solutions are stronger Bronstedt acids than the so far strongest acid HF/SbF₅. But the extreme acidity of such HF/AuF₅ solutions is also the reason why AuF₅ dissolved in HF decomposes to AuF₃ and F₂. It is well known that the highest oxidation states are destabilized in acidic solutions. Were it not such an unstable system, HF/AuF₅ could be used for protonation reactions that are otherwise not even possible with HF/SbF₅.

If you want a copy of the paper, let me know on my talk page and I can e-mail it to you. Buddy431 (talk) 03:35, 2 December 2012 (UTC)[reply]

Did Carl Sagan know the intended use of his calculations and still willingly participate?

From this story: "According to the report in The Sun, the US would have used an atom bomb, because a hydrogen bomb would have been too heavy. The planning reportedly included calculations by astronomer Carl Sagan, who was then a young graduate." 20.137.2.50 (talk) 15:02, 28 November 2012 (UTC)[reply]

The author of one of Sagan's biographies suggested that he may have committed a security breach in 1959 after revealing the classified project in an academic fellowship application. Reiffel concurred. Read Project_A119#Consequences Trio The Punch (talk) 15:15, 28 November 2012 (UTC)[reply]

He certainly knew about it, and he willingly participated. It's one of those ideas that seems silly or crazy in retrospect, but from a scientific standpoint, a nuclear blast would not have done much more to the moon than creating another crater. The craziest part of the project is the idea that the American people — much less American allies internationally — would have considering testing nuclear weapons on the moon to be a positive public relations stunt. --Mr.98 (talk) 15:51, 28 November 2012 (UTC)[reply]

I have to agree with Mr.98. Those crazy American people should have known bombing a little country no one likes would have been a much better idea than exploding a device on the moon, where it would harm no one (what's the point in not harming anyone?) and where everyone could actually see what they were up to! μηδείς (talk) 17:25, 28 November 2012 (UTC)[reply]

It would certainly show how powerful the US was, without contaminating the Earth. This seems a good way of working on your self-marketing during the cold war. I don't see anything crazy here. OsmanRF34 (talk) 18:58, 28 November 2012 (UTC)[reply]

Mr98 says "from a scientific standpoint, a nuclear blast would not have done much more to the moon than creating another crater." But our article says

Another factor [in the cancellation of the project], cited by project leader Leonard Reiffel, was the possible implications of the nuclear fallout for future lunar research projects and colonization.

Duoduoduo (talk) 18:52, 28 November 2012 (UTC)[reply]

Umm... what fallout? There's something known as solar wind which would very quickly sweep all fallout off the Moon and into deep space. The only radioactive material left on the surface of the Moon would be the debris welded into the Moon's surface by the heat of the blast, and even that would be slowly broken up by continual bombardment by meteoroids of all sizes and itself swept off the Moon by the solar wind. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 20:51, 28 November 2012 (UTC)[reply]

Haha, the solar wind is not that strong, man! The moon is covered in dust. I agree the issue would be of no concern at all because the moon is huge and you'd ask scientists where they were least likely to go for the next few years, because cosmic rays would be worse than the radioactivity, and for a host of other reasons. But the solar wind doesn't sweep the moon clean. μηδείς (talk) 20:58, 28 November 2012 (UTC)[reply]

Every sample of lunar soil and ice will be contaminated from that point on. We could possibly never find out the exact process of lunar formation thanks to that. Consider how it's no longer possible to manufacture steel that's free from Cobalt-60 contaminants on Earth.Dncsky (talk) 21:28, 28 November 2012 (UTC)[reply]

Yes it is - just make steel without cobalt. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 22:27, 28 November 2012 (UTC)[reply]

If it were that easy we wouldn't be digging up battleships for steel.Dncsky (talk) 22:47, 28 November 2012 (UTC)[reply]

The escape velocity on the moon is 2.4 km/s (5400 miles / hr), and the local gravity is 1.6 m/s². A substantial fraction of the dust and rock fragments kicked up by a nuclear explosion on the moon will fall back onto the moon. I'm not sure where you get the idea that the solar wind would scour the moon, but for anything heavier than gas molecules it is basically not true. The solar wind moves ~400 km/s but has a density of only about 6 protons / cm³ at the Earth's orbit. That implies a solar wind pressure of around 10^-9 Pascals. Unless an object has an extremely low mass in relation to its cross-sectional area, the force imparted by solar wind bombardment won't be large enough to move it away from the moon's gravity. Dust particles on the moon can't be dislodged by the solar wind. Dragons flight (talk) 21:20, 28 November 2012 (UTC)[reply]

Practically all of the radiation which is not welded into the Moon's surface would be atomised gas. Unlike on Earth, there is zilch blast wave to generate dust, so anything which is not directly vaporised by the radiation from the detonation would stay firmly attached to the Moon's surface. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 22:27, 28 November 2012 (UTC)[reply]

If it is at the surface of the moon, the mere act of vaporizing rock will create a blast wave and excavate a crater. It may be smaller than on Earth, but it wouldn't be inconsequential. They could diminish the effects by placing the explosion well above the surface, but if you just wanted to set off a bomb in space then why carry it all the way to the moon? Dragons flight (talk) 22:51, 28 November 2012 (UTC)[reply]

I can see the contamination being an issue from a scientific standpoint — it could make it hard to do certain types of future measurements on lunar soil, and this is from a pre-Apollo understanding of the lunar surface anyway. I wasn't trying to imply it was a good idea, just that the "blow up the moon" stuff is a bit hyperbolic. It's an awful idea from a P.R. standpoint, as the attention given to this (decades old) story makes somewhat clear: people have at best mixed feelings about setting off nukes anyway, but to do it to something as timeless, visible, and apparently "pristine" as the moon ought to have been an absolute no-go. (I wonder how people would feel, incidentally, if they knew that we left several small plutonium power generators on the moon as a result of Apollo...) --Mr.98 (talk) 23:44, 28 November 2012 (UTC)[reply]

My question is not about any of the technicalities of the consequences of trying to blow up the moon, but how in the hell a man like Carl Sagan, who seemingly placed great value on natural celestial objects and not destroying them, was convinced to contribute to the project. 67.163.109.173 (talk) 22:23, 28 November 2012 (UTC)[reply]

That amounts to a request for speculation and opinion. Unless on the off chance he explained himself, say in The Collected Letters of Carl Sagan, we can't help you with that, we do not make windows into men's souls here. μηδείς (talk) 22:54, 28 November 2012 (UTC)[reply]

Of course I'm only interested in what he himself said of it. "Off chance"? Seems like something people would definitely have asked him or pressed his response on if it came to light before he died. 67.163.109.173 (talk) 23:12, 28 November 2012 (UTC)[reply]

Based on the information in Project A119, it would appear that the project was mostly secret until after Carl Sagan's death. Dragons flight (talk) 00:07, 29 November 2012 (UTC)[reply]

The ostensible goal of the project, aside from the P.R. aspects, were to find out more about the constituents parts of the moon. They wouldn't really "blow up the moon" — that's just journalistic hyperbole. For a comparable sort of thing, see also Operation Argus. --Mr.98 (talk) 23:39, 28 November 2012 (UTC)[reply]

The OP seems to be starting with the premise that nuclear devices are inherently evil (the Evilonium-235, no doubt) and that any use of them is therefor unimaginable. But many scientists supported notions like Project Orion in principle. And if a demonstration of the destructive power of the bomb were visible worldwide, not to mention would give plenty of scientific data, is it impossible that a man like Sagan might consider the possible experiment? Questions framed in the form of "how in the hell" seem to imply a very strong desire to engage in soapboxing, rather than research. μηδείς (talk) 01:56, 29 November 2012 (UTC)[reply]

If you or others transfer the blowing up of the moon part to the journalists or append obtained knowledge about the true state of mind of the project runners that they meant "but not really blow it up, just scare 'em" (just talking desired intent, not at all thinking the ability were ever there) then I retract my soapbox-impression-inducing use of "hell." 67.163.109.173 (talk) 02:18, 29 November 2012 (UTC)[reply]

Okay, hehe. I thought it was obvious the notion was not actually to blow up (think Death Star) the moon. 03:18, 29 November 2012 (UTC)

Yes when I first saw this question and saw the article, I thought what the hell, there's no way they seriously thought they could blow up the moon, and a few quick searches as well as a look at our article confirmed that the never the intention or belief but simply journalistic hyperbole (present in too many sources). But the fact they couldn't do so seemed obvious enough and the OP themselves didn't comment on this point so I decided there was no point commenting. Nil Einne (talk) 12:55, 2 December 2012 (UTC)[reply]

It's worth remembering a fair bit of Carl Sagan's fame and quite a few of his writings came later in his life. People's opinions of things often change over time and they may not even always remember the change in their opinions. In other words, even if it's true the personality you understood Carl Sagan had from his writings, interviews, television shows etc, would not have liked the concept, and even if your understanding isn't that far off the mark from Carl Sagan's real personality at some point in his life (perhaps a melding over time), it doesn't necessarily mean he would always have felt that way. In fact, this project is probably a decent example of that. I suspect if you ever ask any people involved who are still living, most would say it was a dumb idea even though obviously a fair few did not think this at the time. Nil Einne (talk) 15:11, 29 November 2012 (UTC)[reply]

Harold White / NASA research on warp drive

Going off of this article here -- so I'm not a scientist by any stretch of the means, and most of the stuff in the Alcubierre drive article makes my head hurt. Main thing is - even if White did legitimately find a way to reduce the energy requirements - doesn't this still all depend on the existence of the same theoretical exotic matter Alcubierre's original idea talked about? If that's the case, what are White and his people at NASA even researching? --Brasswatchman (talk) 16:41, 28 November 2012 (UTC)[reply]

NASA is a huge organization; it directly and indirectly supports an absolutely vast amount of research. Here's a very useful and informative website maintained by NASA's Glenn Research Center: Warp Drive, When?. It provides links to numerous research avenues that have been explored, and helps explain in plain language exactly why this problem is so difficult. I find that NASA web-page far more insightful than most pop-science publications on the topic. And, for the enthusiastic reader, there are links to more technical research papers. The NASA "Breakthrough Propulsion Physics" laboratory is also very helpful if you're not familiar with the topic. You might find this summary enlightening, as well: All NASA support to sustain cognizance on these possibilities has been withdrawn as of October 1, 2008.[1] In other words, it is the official position of the current administration that this research does not warrant NASA support: irrespective of whether the physics is interesting or impossible or even completely legitimate, the expected returns on the investment of time, talent, and money, are not seen as particularly worthwhile. Nimur (talk) 17:31, 28 November 2012 (UTC)[reply]

Thanks for the idea of searching at NASA - can't believe I didn't think of that. Wound up finding these papers, if anyone is curious: Warp Field Mechanics 101 and Eagleworks Laboratories: Advanced Propulsion Physics Research. It looks like White and his team are specifically focusing on trying to measure the expansion of spacetime to see if they can measure any possible preexisting "warps" -- which I suppose would be a precursor for trying to hunt down any kind of the exotic matter Alcubierre's ideas require. Scanning the papers, I get the impression that White and his cohorts may perhaps be motivated more by enthusiasm and a certain amount of optimism rather than solid experimental fact... still, I suppose this is something that's worth looking into, just in case. --Brasswatchman (talk) 19:03, 29 November 2012 (UTC)[reply]

It may be worth looking into but not by these guys, who are pretty clueless. In the second document they talk about a "quantum vacuum plasma thruster", which is apparently a reactionless drive that pushes against vacuum fluctuations. They think not only that this is possible but that models have actually been built and work, and they seem to think there's nothing controversial about the concept. I conclude from this that they've never talked to a real particle physicist. -- BenRG (talk) 06:39, 30 November 2012 (UTC)[reply]

Yes, it still needs exotic matter. I don't know how White used/uses his grant money, but according to the article one thing he did was build a modified Michelson–Morley interferometer and a ring of ceramic capacitors. Don't ask me why. -- BenRG (talk) 17:47, 29 November 2012 (UTC)[reply]

Size of bubbles in weightlessness

What determines the size of bubbles in weightlessness and do all liquids have the same bubble diameter in weightlessness? Thanks--93.174.25.12 (talk) 20:36, 28 November 2012 (UTC)[reply]

Surface tension determines the size of bubbles. As not all liquids have the same surface tension, different liquids have different bubble diameters even in weightlessness. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 20:45, 28 November 2012 (UTC)[reply]

Unless you are saying that density actually varies in weightlessness, Whoop, all that matters is volume, i.e., mass divided by density. Surface tension holds the bubble together and makes it tend toward spherical shape when not perturbed or sticking to something else. But surface tension is not affected by gravity. μηδείς (talk) 20:55, 28 November 2012 (UTC)[reply]

Yes, that is why gravity or lack thereof does not and cannot make different kinds of liquid have the same sizes of bubble. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:05, 28 November 2012 (UTC)[reply]

Moving this down to first indent for clarity: per Medeis, volume is a function of mass and density, and the basic sizes are unchanged between microgravity and any Earthbound laboratory. If liquid A fills less of a beaker than liquid B here on Earth, it will likewise form a smaller blob in space (assuming otherwise equal conditions like temperature and pressure). — Lomn 21:29, 28 November 2012 (UTC)[reply]

Now, for the counterpoint: if you're instead asking "how big of an air bubble can I create within a blob of liquid in microgravity?" then yes, surface tension is a significant factor. Again, you'll observe a basic correlation between behavior on Earth and behavior in space, though I would expect a substantial scaling factor. You might also have to quibble over definitions of what constitutes "a bubble of air within a blob of liquid". — Lomn 21:36, 28 November 2012 (UTC)[reply]

That would make sense of Whoop's statements--although gravity would still not matter, and only certain mixtures will allow you to make air bubbles. μηδείς (talk) 22:48, 28 November 2012 (UTC)[reply]

Cooling of Air-cooled engines

I'm trying to track down the original source of this claim from Air-cooled_engine: "In all combustion engines, a great percentage of the heat generated (around 44%) escapes through the exhaust, not through either a liquid cooling system nor through the metal fins of an air-cooled engine (12%). About 8% of the heat energy finds its way into the oil, which although primarily meant for lubrication, also plays a role in heat dissipation via a cooler.". The given source [2] does not contain any references. I'm interested in the breakdown of the remaining 36% of the waste heat.

Googling "engine heat 44% 12% 8%"[3] only produces sites with a verbatim copy of the erroneous quote from WP.

Alternatively if anyone knows where I can similar figures like this that would be great too; basically any ballpark break-down of how much waste heat is exhausted via each route in an ICE.Dncsky (talk) 21:17, 28 November 2012 (UTC)[reply]

I notice that only adds up to 64%. I wonder where the remaining 36% goes. Radiating off the rest of the engine block and heating the passenger compartment when the heat is on ? In any case, those numbers don't seem that unreasonable, to me. StuRat (talk) 00:10, 29 November 2012 (UTC)[reply]

The left over 36% is the mechanical power output to the pistons. Radiation of the engine surfaces is much much lower. Ratbone 124.178.55.2 (talk) 16:40, 29 November 2012 (UTC)[reply]

Have a llook in Heywood "Internal Combustion Engine" Greglocock (talk) 00:19, 29 November 2012 (UTC)[reply]

You, sir, are a Godsend. Page 675[4] had exactly what I was looking for. Do you have a script that checks this page for engine related questions or something? ;)Dncsky (talk) 00:42, 29 November 2012 (UTC)[reply]

For a good discussion, with typical values, in an easy to read format (without math or proof), of where the fuel energy goes, see later editions of Harry Ricardo's classic The Hight Speed Internal Combustion Engine (Blackie pub). A very good treatment, theory and data, is Charles Fayette Taylor's 1960's era textbook. The amount of heat lost in the exhaust is easily calculated approximately by applying the otto formula, with some corrections for the finite combustion time and for dissociation, and the heat lost to the coolant. As the heat lost to coolant via cylinders and head is quite small, you need only make a rough approximation. (Note that the heat rejected to ambient by the radiator is considerably greater than the heat lost from combustion gasses within the cylinder, as it includes heat generated by friction and heat lost from exhaust gasses to the exhaust passages in the head and manifold. Plenty of measured data is available to support such approximation. Manufacturers data for sales and application purposes of industrial engines usually includes the fractions of fuel energy converted to mechanical output at the flywheel, heat lost to coolant, and heat lost to exhaust. There is always a gap between the total of the three and the energy value of the fuel, this gap being the heat lost from engine surfaces by radiation and convection, being typically (in large engines) about 5 to 8% of the engine maximum output fuel energy. Ratbone 121.221.30.167 (talk) 01:09, 29 November 2012 (UTC)[reply]

So, are the numbers in our article correct ? StuRat (talk) 01:49, 29 November 2012 (UTC)[reply]

I seem to remember answering a similar question from you on Ref Desk before. The numbers look roughly right. I don't have any measured data immediately to hand, and I'm not familiar with aircooled engines, however I have a computer software package that gives accurate (+,- 2%) calculations for large diesel engines (after you enter a large amount of engine physical measurements). For a typical large truck size engine, (15 litres, 4 valves per cyl, compression ratio 15:1): The data (naturally aspirated at full output, 1500 RPM) from this package is :-

Brake Power Output:........265 kW (39%)

Total Loss to Coolant:....164 kW (24%)

Loss to exhaust:..............233 kW (34%)

Loss from engine surfaces..19 kW ( 3%)

The sum of the heat lost to coolant and to air from engine surfaces (164 + 19 kW) is made up of:-

Cylinder wall loss to coolant/air:.........57 kW (includes combustion heat loss to oil via pistons)

Exhaust port loss to coolant/air..85 kW

Friction loss to coolant/air:.......41 kW

These figures look somewhat different to the data cited by the OP. However, it should be noted that : 1) diesel engines are substantially more eficient than gasoline engines, due to higher compression ratio, no air throttling, and lower combustion temperatures; 2) aircooled engines are most commonly small engines, so the surface area compared to power is relatively high. So the data cited by the OP is not unreasonable.

This of course is something you have to take on trust, as you don't have my software, but you can check in C F Taylor's book. Ratbone 121.221.30.167 (talk) 02:53, 29 November 2012 (UTC)[reply]

The first number is how much energy is used, not excess heat, which is what we're discussing here. The total energy produced by an engine, of course, being mechanical, heat, exhaust pressure, and a tiny bit as sound and engine wear. The "loss to exhaust" might include both heat and pressure. StuRat (talk) 03:11, 29 November 2012 (UTC)[reply]

I can't see what you are trying to say, Stu - your first sentence is too cryptic. The OP said 44% (of the combustion heat) is lost to exhaust, compared to my calculated estimete of 34%. The discepancy is accounted for by the higher thermodymanic efficiency of the diesel engine used in my example, as I said. The figure "Loss to exhaust" in both cases is the energy lost out the exhaust pipe - yes, this lost energy is manifested in the temperature (most of the energy) and pressure (some of the energy) of the exhaust gasses, both temp and press being above that of the ambient air. For the 15 litre diesel example, the acoustic power generated from engine surfaces is of the order of a few tens of watts at most and is always ignored in engine thermodynamic efficiency calculations. If this surprises you, consider a domestic stereo system - typical electrical output 50 W RMS per channel, Loudspeaker efficiency 3%, music mean to peak ratio 0.1, mean acoustic power output 150 milliwatt. And, while it's not like a big engine in full cry, you can certainly deafen people with a stereo. Most of the acoustic energy comes from the exhaust, which is already accounted for. In theory, the wearing of bearing surfaces represents an energy loss. However, the energy lost in this way, which can be calculated by the science of tribology, is really minute, and nobody would bother. In any case, it is already accounted for in the figure for friction loss. Ratbone 121.221.7.194 (talk) 03:52, 29 November 2012 (UTC)[reply]

My interpretation of the OP is that it asked what percentage of the waste heat was dissipated by various means. That is, he is excluding the actual work done by the engine by the moving cylinders. Thus, the percentage of waste heat going to the exhaust is 44%, but the percentage of the total energy going to the exhaust would be less. StuRat (talk) 04:01, 29 November 2012 (UTC)[reply]

Well, only the OP can really say what he had in mind, however he /she accurately quoted from the Wikipedia article. The OP and the article says "..percentage of heat generated..", not percentage of waste heat generated - so the article is talking about the combustion heat, not the waste heat. The article could have been better worded, but the meaning is never the less clear - to an engine man at any rate. However, the OP used the phrase "waste heat" in the last sentence of his question, and that implies he misunderstood the data. Using the waste heat as a base, for my example above, the figures are:-

Combustion heat:........686 kW

Brake power output:....265 kW

"Wasted heat" is 686 - 265 = 421 kW

Exhaust heat:............233 kW i.e., 55% of wasted heat. (34% of combustion heat as given in my previous post)

55% is not 34% and for a typical air cooled gasoline engine the descrepancy will be about as bad. I can't think why you would want to calculate in this way. In any case, the reference for the Wiki article on this aspect, http://www.avweb.com/news/maint/182883-1.html, makes it very clear they meant 44% of the combustion heat, not the wasted heat. The answer to the OP's question, "where does the remaining 36% go", is of course the indicated power output (the mechanical effort to the pistons). Most of this ends up as the mechanical (i.e., brake) power output (typically about 25% of the total heat in an ordinary gasoline engine), the rest is lost in bearing and piston ring friction, valve gear and oil pumping loses. Ratbone 121.215.61.79 (talk) 12:26, 29 November 2012 (UTC)[reply]

^ Olah, G. A. (2001). "Hydrogen Fluoride–Antimony(V) Fluoride". In Paquette, L. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X.rh037m. {{cite encyclopedia}}: Unknown parameter |coauthor= ignored (|author= suggested) (help)

[Olah-1] Olah, G. A. (2001). "Hydrogen Fluoride–Antimony(V) Fluoride". In Paquette, L. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X.rh037m. {{cite encyclopedia}}: Unknown parameter |coauthor= ignored (|author= suggested) (help)

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Wikipedia:Reference desk/Archives/Science/2012 November 28

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