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Old July 5th, 2008, 11:00 AM   #2581
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Originally Posted by pricemazda View Post
Is Boris right when he says that with the increase in frequency of trains will create a lot of kinetic energy and then air conditioning will be essential?

Yeah 'cos the air con won't generate any heat at all...

...He seriously worries me sometimes!
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Old July 5th, 2008, 12:35 PM   #2582
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Quote:
Originally Posted by Tubeman View Post
I wrote a huge response to the question yesterday complete with diagrams, and got '505 Internal server error' and lost it... I could have cried.
Next time use Firefox browser and hit the Back button when it happens and you should see your text again. Or write longer texts in an editor and copy them into the SSC form.
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Old July 5th, 2008, 01:33 PM   #2583
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Originally Posted by pricemazda View Post
Is Boris right when he says that with the increase in frequency of trains will create a lot of kinetic energy and then air conditioning will be essential?
Basically, yes - although he doesn't put it very well.

Every train represents hundreds of tonnes of metal plus the weight of its passengers. To accelerate those trains to the linespeed, requires energy that is supplied in the form of electrical energy from the National Grid. That energy is converted in the traction motors into kinetic energy - the movement of the train and heat (as electric motors are not 100% efficient).

When the train brakes, that kinetic energy is converted into heat in the brake pads.

All this goes toward heating the air in the tunnels and stations.

In addition to all this, more trains will inevitably result in more passengers and, as the temperature of the human body is above that of the air in the tube tunnels (due to the chemical energy we consume in the food that we eat and the air we breathe), we all contribute to heating the air in the tunnels.

So more trains will mean higher temperatures in the tube tunnels.

As iampuking says, trains moving about will create draughts and anyone caught in those draughts will feel pleasantly cool but that does not reduce the air temperature in the tunnels.

If you put a fan into a hot room, people in the line of the air current will feel cooler but that is because, when the air is static, our body heat warms up the air in contact with our skin. As the air gets warmer, the difference in temperature between our bodies and the surrounding air reduces and we cool down more slowly - so we begin to heat up and feel uncomfortable. When a fan blows that hot air away from us, we cool down, even though the air is no cooler than the ambient air temperature in the room. That is the same thing as wind chill.

In fact, putting a fan into a room makes the room marginally warmer as it absorbs electrical energy and converts it into the kinetic energy of the air, which ends up as heat energy.

The only way in which train movement would be beneficial in reducing air temperature would be in sub-surface lines such as the Metropolitan, where trains would push a slug of hot air in front of them to the open air stretches, where the hot air would rise by natural convection and be replaced by cooler air that would be pushed into the tunnels. In the enclosed systems of the deep level tube lines, there is little scope for that effect.

Air conditioning would reduce temperatures in the deep level tube tunnels but only if the hot air had somewhere to escape to. Basically, an air conditioner is a combination of a fan and refrigeration system. The refrigeration cools the air which is moved around by the fan. However, refrigeration is just a means of pumping heat from one place to another (think of the hot grills at the rear of a domestic refrigerator) and, as Tubeman says, it requires energy to power it and so produces more heat. The solution is to have a link to the cooler external air where the heat can be dissipated but this will inevitably result in some heavy construction work.
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Old July 5th, 2008, 11:56 PM   #2584
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As we all know, energy can neither be created nor destroyed, only stored or transferred. With a train, the only places it can be stored are as kinetic energy (but this is lost as soon as the train stops) and gravitational potential energy (if the train is going uphill, but this is lost as soon as it goes downhill again). If the energy isn't being stored on the train, then it must be being transferred into the tunnels, and the only way it can do that is as heat. Every single watt of power used by the system ultimately becomes heat in the tunnels.

Metro systems use a lot of electricity, and lines with a more frequent service intuitively use more power. More trains may draw extra cool air into the system to negate the heat they produce, but the effect is probably negligible.

(what's the Boris quote that prompted this, btw?)
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Old July 6th, 2008, 03:28 AM   #2585
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For in depth info on the efforts going on to cool the tube, see:
http://www.freewebs.com/going_underg...sits.co.uk.doc
and an alternative write up about the same talk
http://www.freewebs.com/going_underg...ogspot.com.doc

Last edited by Acemcbuller; July 8th, 2008 at 03:59 PM.
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Old July 6th, 2008, 04:41 PM   #2586
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Quote:
Originally Posted by Acemcbuller View Post
For in depth info on the efforts going on to cool the tube, see: http://thelondoneer.blogspot.com/search?q=cooling
and an alternative write up about the same talk http://www.freewebs.com/going_underg...ogspot.com.doc
Interesting articles there Acemcbuller. Thanks for posting.

I don't know what Boris has actually said, but if he is advocating putting air conditioning in trains without catering for the exhaust heat, then he needs a few physics lessons.

Good point about the heating of the London clay on the deep level lines. With todays level of crowding, it would have been absolutely unbearable for people in Edwardian dress to have travelled on those lines but clearly, the tunnels themselves have heated up since those days.

I remember when the Merseyrail underground first opened in the late 70s, the stations were very cold. It would be interesting to compare the temperature nowadays with that of thirty years ago.
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Old July 6th, 2008, 08:44 PM   #2587
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Quote:
Originally Posted by Tubeman View Post
...He seriously worries me sometimes!
It's OK, his sort of worship's worried others in other towns.
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Old July 6th, 2008, 10:19 PM   #2588
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Quote:
Originally Posted by Martin S View Post
Basically, yes - although he doesn't put it very well.

Every train represents hundreds of tonnes of metal plus the weight of its passengers. To accelerate those trains to the linespeed, requires energy that is supplied in the form of electrical energy from the National Grid. That energy is converted in the traction motors into kinetic energy - the movement of the train and heat (as electric motors are not 100% efficient).

When the train brakes, that kinetic energy is converted into heat in the brake pads.

All this goes toward heating the air in the tunnels and stations.

In addition to all this, more trains will inevitably result in more passengers and, as the temperature of the human body is above that of the air in the tube tunnels (due to the chemical energy we consume in the food that we eat and the air we breathe), we all contribute to heating the air in the tunnels.

So more trains will mean higher temperatures in the tube tunnels.

As iampuking says, trains moving about will create draughts and anyone caught in those draughts will feel pleasantly cool but that does not reduce the air temperature in the tunnels.

If you put a fan into a hot room, people in the line of the air current will feel cooler but that is because, when the air is static, our body heat warms up the air in contact with our skin. As the air gets warmer, the difference in temperature between our bodies and the surrounding air reduces and we cool down more slowly - so we begin to heat up and feel uncomfortable. When a fan blows that hot air away from us, we cool down, even though the air is no cooler than the ambient air temperature in the room. That is the same thing as wind chill.

In fact, putting a fan into a room makes the room marginally warmer as it absorbs electrical energy and converts it into the kinetic energy of the air, which ends up as heat energy.

The only way in which train movement would be beneficial in reducing air temperature would be in sub-surface lines such as the Metropolitan, where trains would push a slug of hot air in front of them to the open air stretches, where the hot air would rise by natural convection and be replaced by cooler air that would be pushed into the tunnels. In the enclosed systems of the deep level tube lines, there is little scope for that effect.

Air conditioning would reduce temperatures in the deep level tube tunnels but only if the hot air had somewhere to escape to. Basically, an air conditioner is a combination of a fan and refrigeration system. The refrigeration cools the air which is moved around by the fan. However, refrigeration is just a means of pumping heat from one place to another (think of the hot grills at the rear of a domestic refrigerator) and, as Tubeman says, it requires energy to power it and so produces more heat. The solution is to have a link to the cooler external air where the heat can be dissipated but this will inevitably result in some heavy construction work.
Fair enough... But will 5 more trains really make that much of a difference?
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Old July 7th, 2008, 12:29 AM   #2589
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Quote:
Originally Posted by iampuking View Post
Fair enough... But will 5 more trains really make that much of a difference?
I think the problem is that the Tube is just about at the limit of what is tolerable in terms of ambient temperatures. I noticed when I returned to London last year after a gap of some seven years that the Victoria Line seemed significantly hotter than how I remembered it. Even travelling in the evenings when the trains were relatively empty could be hot enough to cause sweating.

OK, that's subjective and may just be me getting older but I think that the conditions that people would experience who were stuck in a crowded Tube train at rush hour for an extended length of time (as does happen fairly frequently) would be so bad that there could be serious problems.

I'm sure there must be some legislation on just what is acceptable on a public transport network and maybe the Tube is now at that point that some serious investigation into a method of cooling must take place before any further capacity is introduced.

I've read people on SSC who say that they prefer to use the Metropolitan and Circle lines during the summer months because they are so much cooler due to their different construction. That's ironic because when those lines were first constructed they used steam trains and the smoke pollution was so bad that people were often taken ill when they travelled on them.
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Old July 7th, 2008, 07:06 PM   #2590
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in february i had to get off a jubillee line train and get on a met one as i was simply too hot.
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Old July 7th, 2008, 10:13 PM   #2591
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Everyone who has been on the Underground in summer knows how hot it is... What I was pondering was whether or not the increase in train frequencies will make a difference.
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Old July 7th, 2008, 10:43 PM   #2592
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Quote:
Originally Posted by iampuking View Post
Everyone who has been on the Underground in summer knows how hot it is... What I was pondering was whether or not the increase in train frequencies will make a difference.

An additional five trains per hour will mean an additional five thousand passengers travelling in each direction on the deep level tubes, which means more heat load in addition to the heat produced by the trains themselves.

Of course you can argue that more frequent trains will reduce the overall length of time that people will spend in the underground system and so the level of discomfort felt. Also, more capacity should reduce crowding at station platforms but, with the system working at capacity, I doubt that latter advantage will last very long.

Londoners always seem to put up with the discomfort of rush hour Tube train travel and see it as all part of life in the Capital but there must be a limit even for them.
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Old July 8th, 2008, 12:12 AM   #2593
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I think its embarrassing that we cant solve this problem quickly and easily.

This ice solution does look promising though.
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Old July 8th, 2008, 07:52 AM   #2594
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Most other cities seem to manage to air-condition their metro-trains. Is it problematic to do London's because the tunnels are so small?
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Old July 8th, 2008, 03:54 PM   #2595
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Most other cities seem to manage to air-condition their metro-trains. Is it problematic to do London's because the tunnels are so small?
Read the write-ups on my links above.
The tunnels not well ventilated enough to carry away the existing heat, let alone the extra that would be created by air-con units.
Plus the tunnels are too small to allow air-con units to be addded to the trains (at least not without taking up what is currently space for passengers I suppose).
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Old July 9th, 2008, 11:59 PM   #2596
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The idea I pondered was chiller trains, that could have a high specific latent heat capacity substance chilled down on the surface during running hours and then trundle through the tunnels durring the engineering hours to help reduce the temperature for the next day.

The long term solution has got to be a lot more vents with chiller units, that might actually solve it - at great expense.

I cycle, and I get less sweaty than I would on the equivalent tube journey (and it takes half the time, and is free).
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Old July 15th, 2008, 02:30 AM   #2597
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Mr. Tubeman, sir. This is my first time on this website. I am a former New Yorker living in Pennsylvania with my Hendon born wife. Here's the question. Did you ever get the opportunity to operate any experimental tube stock in your operational career? I have seen some very cool units from 1986 in blue, red and green. They intrigue me so. Also, how in the world do those white cars stay so clean? NYMTA cars are all that dull stainless steel finish and they are such a snorefest. Very boring. My wife and I are saving up for a trip across to London next year. We will only have two weeks to cover everything she plans to show me. Can't wait. Thank you.
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Old July 15th, 2008, 03:33 PM   #2598
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I have seen some very cool units from 1986 in blue, red and green. They intrigue me so.
Cool. I didn't know about the 1982 prototype stock. It says the public liked the blue design but the red design most closely resemebes the resulting 1992 stock.
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Old July 15th, 2008, 08:37 PM   #2599
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Mr. Tubeman, sir. This is my first time on this website. I am a former New Yorker living in Pennsylvania with my Hendon born wife. Here's the question. Did you ever get the opportunity to operate any experimental tube stock in your operational career? I have seen some very cool units from 1986 in blue, red and green. They intrigue me so. Also, how in the world do those white cars stay so clean? NYMTA cars are all that dull stainless steel finish and they are such a snorefest. Very boring. My wife and I are saving up for a trip across to London next year. We will only have two weeks to cover everything she plans to show me. Can't wait. Thank you.
Hello! And welcome to SSC

I never had the chance to drive any of those prototypes, that honour would have been bestowed upon the dedicated Test train drivers. I've driven a few stocks in my time though, some now gone:

1956 Stock (1959 Stock prototype)*
1959 Stock (originally Piccadilly Line but later moved to Northern)*
1962 Stock (originally Central Line but later moved to Northern)*
1967 Stock (Victoria Line, tenuous... I've pushed the buttons to start the ATO)
C69 Stock (District Line)
1972 Mk I Stock (Northern Line)*
1972 Mk II Stock (Bakerloo Line)
C77 Stock (District Line)
D78 Stock (District Line)

Those marked with * are now scrapped

The painted finish to (now) all LU trains was a response to graffiti... The bare aluminium bodies used to carry stains of graffiti which couldn't be buffed off. They are kept clean simply though running through a car wash, but as trains can outstable at locations without a wash they can get very dirty if they outstable at one of these locations for several nights consecutively. An example is the Bakerloo, where trains stable at either Elephant & Castle Sidings, London Road Depot (near Lambeth North), or Stonebridge Park Depot. Only the latter has a car wash, so if a train stables at Elephant & castle or London Road for several consecutive nights it can get very dirty. This is avoided by the timetable, but if a train has its number changed (is 'reformed') due to service disruption it could easily miss its 'turn' to stable at Stonebridge and get dirty.
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Old July 16th, 2008, 11:35 AM   #2600
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Thats alot of trains!
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