On 23 July, 16:17, "Recliner" wrote:
"Peter Masson" wrote in message



"Tom Barry" wrote

And without Boris trumpeting them as meeting a manifesto commitment,
to boot. *If they'd only had aircon...

Among the problems with aircon on the tube lines is - where do you
dump the heat? Presumably on, say, the Central or Piccadilly lines it
would be possible to devise a system whereby the heat was retained on
the train until it got to the open air, and then dumped, but Victoria
Line trains stay underground all the time they are in service. No use
cooling the trains if you just heat the tunnels even more.

That's why the plan is to cool the stations, not the trains, but of
course there's less to see with that approach.

And the regenerative braking on the new 2009 stock will also mean less
heat released into the stations and tunnels in the first place.

On Jul 23, 4:57*pm, Andy wrote:

And the regenerative braking on the new 2009 stock will also mean less
heat released into the stations and tunnels in the first place.


Ummm thats not strictly true. Overall you might be generating less
heat directly from braking, true, but the type of train, with AC
motors, will itself create more heat to be released, including
indirectly from braking.

Go back to the NR southern third rail zone power upgrade for Mk.1
stock replacement. What was that all about. All the new trains coming
in had AC motors, replacing DC motors under the Mk.1s. The big issue
was heating effect.

AC motor characterisitics are such that it draws a higher constant
current - this means the heating effect in lineside traction equipment
is much increased - because heat dissipated is I^2*R [I-squared-R].
When the trains are regenerating, the heating effect in lineside eqpt
is still I^2*R, it still is still being heated, it does not cool
because it is reversed, and it does not cool because t gets no respite
(like it does when a friction brake train brakes). A non regen braked
train using friction brakes disspates the heat transformed from
mechanical energy at the brake shoes/pads - wheel rim/disc interface.
A regen braked train convert mechanical energy to electrical, which
while contributing a useful energy saving does nonetheless heats
lineside gear in doing so.

1967 stock Crompton/Brush LT115 DC traction motors are 53 kW cont.
rating.
2009 stock Bombardier Mitrac AC traction motors are 75 kW cont.
rating.

1967 stock 8-car trains are MTTMMTTM - 16 motors per train = 16 x 53
kW = 848 kW per train
2009 stock 8-car train are MTMMMMTM - 24 motors per train = 24 x 75
kW = 1800 kW per train

All those motrs and traction packs get hot.

A 2009 stock train draws over twice the traction load of 1967 stock,
and thats before you look at DC v. AC, and before you look at
auxiliary loads. All this air-con draws a load that was not there with
1967. Thats never put back into regen braking.

Further, the service frequency will be increased, and there are more
trains in service at any one time. True they will all regenerate, but
there are more of them to accelerate in the first place, and
accelerating at a higher rate.

It all adds up - I bet one would not be far wrong to say current draw
on the whole line with full TPH with 2009 stock may well be 3 times
that of 1967 stock at the same voltage. Offset this by increasing
from 630 V to 750 V which is a 30% current drop, so overall load
doubled.

All that heat has to go somehwere. And Peter is quite right, there is
nowhere to dump the air-con load.

NR southern zone has trackside power distrbution cables everywhere, LU
does not, so at east not heating tunels that way.

There is a substantial uplift in heating effect from the new trains.
Unless my sums are seriously flawed, there'd have to be some seriously
hefty cooling gear to cool stations. Gear that itself draws power ...
maybe more than the entire train regenerated power is taken up by air-
con ?


--
Nick

"D7666" wrote

There is a substantial uplift in heating effect from the new trains.
Unless my sums are seriously flawed, there'd have to be some seriously
hefty cooling gear to cool stations. Gear that itself draws power ...
maybe more than the entire train regenerated power is taken up by air-
con ?

Add to that the congestion relief works at Victoria and the more frequent
service, there'll be more passengers pumping kilowatts into the system.

Perhaps the Victoria Line needs to be extended into the open air, at least
so the piston effect of trains can add ventilation into the tunnels, and
ideally so that the next generation (49 stock) can have aircon that takes
heat out of the system and dumps it in the open air. Take over Chingford
from National Rail? Quadruple Northumberland Park to Cheshunt, with a
extended Victoria Line running the local service?

Peter

Peter Masson wrote:

Perhaps the Victoria Line needs to be extended into the open air, at
least so the piston effect of trains can add ventilation into the
tunnels, and ideally so that the next generation (49 stock) can have
aircon that takes heat out of the system and dumps it in the open
air. Take over Chingford from National Rail? Quadruple Northumberland
Park to Cheshunt, with a extended Victoria Line running the local
service?

A few years ago, a significant proportion of trains went to Northumberland
Park anyway - is that still true? I always wondered why - maybe it is to
cool the line.

On 24/7/09 21:55, in article , "Peter
Masson" wrote:



"D7666" wrote

There is a substantial uplift in heating effect from the new trains.
Unless my sums are seriously flawed, there'd have to be some seriously
hefty cooling gear to cool stations. Gear that itself draws power ...
maybe more than the entire train regenerated power is taken up by air-
con ?

Add to that the congestion relief works at Victoria and the more frequent
service, there'll be more passengers pumping kilowatts into the system.

Perhaps the Victoria Line needs to be extended into the open air, at least
so the piston effect of trains can add ventilation into the tunnels, and
ideally so that the next generation (49 stock) can have aircon that takes
heat out of the system and dumps it in the open air. Take over Chingford
from National Rail? Quadruple Northumberland Park to Cheshunt, with a
extended Victoria Line running the local service?

It was at one time intended to come to the surface beyond Hoe Street, as it
then was, and to terminate at Wood Street, with platforms alongside the BR
ones. I don't know when this was dropped from the plans.

On Fri, 24 Jul 2009, Peter Masson wrote:

"D7666" wrote

There is a substantial uplift in heating effect from the new trains.
Unless my sums are seriously flawed, there'd have to be some seriously
hefty cooling gear to cool stations. Gear that itself draws power ...
maybe more than the entire train regenerated power is taken up by air-
con ?

Add to that the congestion relief works at Victoria and the more frequent
service, there'll be more passengers pumping kilowatts into the system.

Perhaps the Victoria Line needs to be extended into the open air, at least so
the piston effect of trains can add ventilation into the tunnels, and ideally
so that the next generation (49 stock) can have aircon that takes heat out of
the system and dumps it in the open air.

How about putting in some crossovers at Finsbury Park and running some
trains from Cockfosters into the Vic core? It's probably too far from the
Picc portal to Finsbury Park for this to really help.

Could you get a piston effect with some more ventilation shafts with
valves attached? Shafts would come in pairs, with a one-way valve on each,
so passing trains would push up one and suck it down the other. Integrate
some of the shafts with the Lea and New River for water-cooling of the
incoming air.

tom

--
Miscellaneous Terrorists: Ducks | Bird Flu | Avian flu | Jimbo Wales |
Backstreet Boys | The Al Queda Network | Tesco -- Uncyclopedia

Tom Anderson wrote:
On Fri, 24 Jul 2009, Peter Masson wrote:

"D7666" wrote

There is a substantial uplift in heating effect from the new trains.
Unless my sums are seriously flawed, there'd have to be some
seriously hefty cooling gear to cool stations. Gear that itself draws
power ... maybe more than the entire train regenerated power is taken
up by air- con ?

Add to that the congestion relief works at Victoria and the more
frequent service, there'll be more passengers pumping kilowatts into
the system.

Perhaps the Victoria Line needs to be extended into the open air, at
least so the piston effect of trains can add ventilation into the
tunnels, and ideally so that the next generation (49 stock) can have
aircon that takes heat out of the system and dumps it in the open air.

How about putting in some crossovers at Finsbury Park and running some
trains from Cockfosters into the Vic core? It's probably too far from
the Picc portal to Finsbury Park for this to really help.

Could you get a piston effect with some more ventilation shafts with
valves attached? Shafts would come in pairs, with a one-way valve on
each, so passing trains would push up one and suck it down the other.
Integrate some of the shafts with the Lea and New River for
water-cooling of the incoming air.

tom


Different signalling and train-operating systems between the two lines
would make that difficult.

Peter Masson wrote:


"D7666" wrote

There is a substantial uplift in heating effect from the new trains.
Unless my sums are seriously flawed, there'd have to be some seriously
hefty cooling gear to cool stations. Gear that itself draws power ...
maybe more than the entire train regenerated power is taken up by air-
con ?

Add to that the congestion relief works at Victoria and the more
frequent service, there'll be more passengers pumping kilowatts into the
system.

Perhaps the Victoria Line needs to be extended into the open air, at
least so the piston effect of trains can add ventilation into the
tunnels, and ideally so that the next generation (49 stock) can have
aircon that takes heat out of the system and dumps it in the open air.
Take over Chingford from National Rail? Quadruple Northumberland Park to
Cheshunt, with a extended Victoria Line running the local service?

Peter

Wasn't there talk about building a station around Northumberland Park?

On Jul 24, 6:19*pm, D7666 wrote:
On Jul 23, 4:57*pm, Andy wrote:

And the regenerative braking on the new 2009 stock will also mean less
heat released into the stations and tunnels in the first place.

Ummm thats not strictly true. Overall you might be generating less
heat directly from braking, true, but the type of train, with AC
motors, will itself create more heat to be released, including
indirectly from braking.

Ok, so how much more heat would be generated if the trains were not
regenerating?


Go back to the NR southern third rail zone power upgrade for Mk.1
stock replacement. What was that all about. All the new trains coming
in had AC motors, replacing DC motors under the Mk.1s. The big issue
was heating effect.


And how much of the extra power requirement came from the trains being
heavier.

AC motor characterisitics are such that it draws a higher constant
current - this means the heating effect in lineside traction equipment
is much increased - because heat dissipated is I^2*R [I-squared-R].
When the trains are regenerating, the heating effect in lineside eqpt
is still I^2*R, it still is still being heated, it does not cool
because it is reversed, and it does not cool because t gets no respite
(like it does when a friction brake train brakes). A non regen braked
train using friction brakes disspates the heat transformed from
mechanical energy at the brake shoes/pads - wheel rim/disc interface.
A regen braked train convert mechanical energy to electrical, which
while contributing a useful energy saving does nonetheless heats
lineside gear in doing so.

But much of the regenerated energy should be going into powering other
trains, sure you need hefty lineside kit in case everything all brakes
at the same time, but the Victoria line should be ideal for reusing
the energy. Also isn't the peak current draw less with AC than DC. The
AC motors will be warming up fairly constantly during the whole of the
acceleration (and deccelaration) phases and so their heat production
will be spread out. The old DC motors will warm up much more quickly
at the start as that is the point of peak current draw and, of course,
this is will be in the stations.


1967 stock Crompton/Brush LT115 DC traction motors are 53 kW cont.
rating.
2009 stock Bombardier Mitrac AC traction motors are 75 kW cont.
rating.

1967 stock 8-car trains are MTTMMTTM - 16 motors per train = 16 x 53
kW = 848 kW per train
2009 stock 8-car train are MTMMMMTM - 24 motors per train = 24 x 75
kW = 1800 kW per train

All those motrs and traction packs get hot.


Piers Connor (in his series The Underground Electric Train in
Underground News, June 2007) say the following:

"In order to make use of the additional throughput capability of the
new signalling, the
2009 Stock has a higher performance than the current stock. The
existing 1967
Tube Stock draws about 2,700 amps maximum, while the 2009 Tube Stock
will draw
3,500 and is capable of drawing up to 4,500 amps."

This looks like well under double the peak current draw.


A 2009 stock train draws over twice the traction load of 1967 stock,
and thats before you look at DC v. AC, and before you look at
auxiliary loads. All this air-con draws a load that was not there with
1967. Thats never put back into regen braking.

Further, the service frequency will be increased, and there are more
trains in service at any one time. True they will all regenerate, but
there are more of them to accelerate in the first place, and
accelerating at a higher rate.

It all adds up - I bet one would not be far wrong to say current draw
on the whole line with full TPH with 2009 stock may well be 3 times
that of 1967 stock at the same voltage. Offset this by *increasing
from 630 V to 750 V which is a 30% current drop, so overall load
doubled.

All that heat has to go somehwere. And Peter is quite right, there is
nowhere to dump the air-con load.


Lineside equipment will be MUCH easier to cool, as it is in fixed
locations which should already be ventilated.

NR southern zone has trackside power distrbution cables everywhere, LU
does not, so at east not heating tunels that way.

There is a substantial uplift in heating effect from the new trains.
Unless my sums are seriously flawed, there'd have to be some seriously
hefty cooling gear to cool stations. Gear that itself draws power ...
maybe more than the entire train regenerated power is taken up by air-
con ?


Just to be clear, I wasn't arguing for air conditioning to be fitted,
but I still think you are mis-estimating the effect of regeneration on
the total energy consumption and heating for the new trains. The whole
point of regeneration is to reuse the energy which used to be 'wasted'
in resistor banks on the trains (with the original rheostatic train
brakes). My understanding is that little of the recovered energy goes
back to the lineside equipment, if the current rails are not
receptive, then the spare energy goes to resistors, like in older
stock. The extra big lineside equipment is purely because more current
is needed in the first place.

Andy wrote:

Just to be clear, I wasn't arguing for air conditioning to be fitted,
but I still think you are mis-estimating the effect of regeneration on
the total energy consumption and heating for the new trains. The whole
point of regeneration is to reuse the energy which used to be 'wasted'
in resistor banks on the trains (with the original rheostatic train
brakes). My understanding is that little of the recovered energy goes
back to the lineside equipment, if the current rails are not
receptive, then the spare energy goes to resistors, like in older
stock. The extra big lineside equipment is purely because more current
is needed in the first place.

What happened to the test of trackside rotating cylinders designed to store
the energy from regenerative braking?