3 ms·

Please see my comments on the first two posts

aurizon 6y ago
More intense acceleration as well as more intense braking produce heat. Steel on steel is efficient, thus energy lost on braking is on the order of 50% of that used for acceleration. This is moderated by the top speed, grade etc and gain/loss in height. So the cases are complex. I do not have data on the mass of the train as well as the live load, or the HP of the motors and what acceleration in fractional g is involved. In any event to move more people/unit time, higher acceleration, top speed and braking all increase the passengers/hour. It may well be the major culprit is this move to more people/hour via higher speed/acceleration/deceleration/efficiency etc, all of which are additive.
- CalvinBarrows 6y ago
  I agree that all these things will make a difference but I'd be really interested in your explanation as to how it makes such a difference in the summer but not in the winter, and also why it does not seem to make much difference on underground only networks compared to mixed under/overground networks?
  - aurizon 6y ago
    I think the total underground temperature is less, compared to surface routes because the earth mass has a large moderating effect. Only as the surface warms does it gradually warm the depper levels, as we are seeing. Train that go up and down from the heated summer air to the averaged undergound get a net warming from that exposure. It needs a detailed study to nail these all down
    - CalvinBarrows 6y ago
      Indeed, I agree that it needs more study and in my first paper I cover this - see link below. The first point that London Underground, and other similar metro networks, needed to establish/confirm was that my findings that "the train gains more heat on the surface than it does underground" is essential. However, for some reason they have, and still are, refusing to engage. They continue to think that the unsuccessful path they have been going down for the past 15 years is suddenly going to reap benefits! (https://www.railjournal.com/in_depth/cooling-the-tube https://www.railjournal.com/in_depth/cooling-the-tube). Is your interest in this as a passenger or a railway man. If as a passenger I would like to encourage you to do some of your own simple temperature monitoring, both under and overground!
      - aurizon 6y ago
        Calvin, I am retired Chemical Engineer in Toronto, Canada. I live on the Toronto islands and occasionally use the subway or surface public system. The original subway through the core of Toronto was 'cut and cover', as they reach the outskirts they go to open cuts. Toronto is smaller than London, so the maxmimum underground path is small by comparison. I agree with your paper. The cars integrate the net exposure and in the summer they transport heat into the underground clay, and from there is spreads away, with only a tiny increase in the underground temperature. I am sure a time chart of clay depth versus temperature along a time axis will show thermal waves that go deeper, and decrease to the mean clay temperature, At some depth the clay will become invariant and reflect the gradient from the deep earth to the surface. This is all well known. In the summer the trains will gain more heat overground than underground. In the winter they will act as a heat export path from the underground to the surface. This will vary with day/night, cloudy or not, I suspect that the train speed will ensure max turbulent heat transfer to/from the air. As for the refusal to engage, out here in Canada we have fossils in the ground, in your area they are employed in the London underground - twas ever thus... These people are either incompetent or are conflicted in some manner that prevents them from confirming your cpnclusions. It could be their own studies confim your data, but this requires a large expenditure to remedy. The only way to remedy this is to add a 2 inch layer of foam insulation to the exterior, with a suitable fire proof metal shell. This is best done by integrating into the design when the cars are built. It would be hard to add an insulated shell to a finished car, but your reflective paint would help. This will decouple the mass of the train from the air. This will reduce the heat/cool energy needed and also reduce the heat carried underground in the summer, or exported in winter. The exterior surface, as you suggested, should be reflective, but unless cleaned daily by an automatic barn shower as they are stabled at dusk, they will soon lose much of their reflectivity.
        CalvinBarrows 6y ago
        Interesting. Do you know much about Montreal's metro. For Toronto what is the proportion of open cut to covered? I was led to believe by someone who should know better that it was all underground! This may explain the reluctance to accept they are not on the right track: https://www.brainyquote.com/quotes/upton_sinclair_138285 https://www.brainyquote.com/quotes/upton_sinclair_138285

More intense acceleration as well as more intense braking produce heat. Steel on steel is efficient, thus energy lost on braking is on the order of 50% of that used for acceleration. This is moderated by the top speed, grade etc and gain/loss in height. So the cases are complex. I do not have data on the mass of the train as well as the live load, or the HP of the motors and what acceleration in fractional g is involved. In any event to move more people/unit time, higher acceleration, top speed and braking all increase the passengers/hour. It may well be the major culprit is this move to more people/hour via higher speed/acceleration/deceleration/efficiency etc, all of which are additive.

CalvinBarrows 6y ago
I agree that all these things will make a difference but I'd be really interested in your explanation as to how it makes such a difference in the summer but not in the winter, and also why it does not seem to make much difference on underground only networks compared to mixed under/overground networks?
- aurizon 6y ago
  I think the total underground temperature is less, compared to surface routes because the earth mass has a large moderating effect. Only as the surface warms does it gradually warm the depper levels, as we are seeing. Train that go up and down from the heated summer air to the averaged undergound get a net warming from that exposure. It needs a detailed study to nail these all down
  - CalvinBarrows 6y ago
    Indeed, I agree that it needs more study and in my first paper I cover this - see link below. The first point that London Underground, and other similar metro networks, needed to establish/confirm was that my findings that "the train gains more heat on the surface than it does underground" is essential. However, for some reason they have, and still are, refusing to engage. They continue to think that the unsuccessful path they have been going down for the past 15 years is suddenly going to reap benefits! (https://www.railjournal.com/in_depth/cooling-the-tube https://www.railjournal.com/in_depth/cooling-the-tube). Is your interest in this as a passenger or a railway man. If as a passenger I would like to encourage you to do some of your own simple temperature monitoring, both under and overground!
    - aurizon 6y ago
      Calvin, I am retired Chemical Engineer in Toronto, Canada. I live on the Toronto islands and occasionally use the subway or surface public system. The original subway through the core of Toronto was 'cut and cover', as they reach the outskirts they go to open cuts. Toronto is smaller than London, so the maxmimum underground path is small by comparison. I agree with your paper. The cars integrate the net exposure and in the summer they transport heat into the underground clay, and from there is spreads away, with only a tiny increase in the underground temperature. I am sure a time chart of clay depth versus temperature along a time axis will show thermal waves that go deeper, and decrease to the mean clay temperature, At some depth the clay will become invariant and reflect the gradient from the deep earth to the surface. This is all well known. In the summer the trains will gain more heat overground than underground. In the winter they will act as a heat export path from the underground to the surface. This will vary with day/night, cloudy or not, I suspect that the train speed will ensure max turbulent heat transfer to/from the air. As for the refusal to engage, out here in Canada we have fossils in the ground, in your area they are employed in the London underground - twas ever thus... These people are either incompetent or are conflicted in some manner that prevents them from confirming your cpnclusions. It could be their own studies confim your data, but this requires a large expenditure to remedy. The only way to remedy this is to add a 2 inch layer of foam insulation to the exterior, with a suitable fire proof metal shell. This is best done by integrating into the design when the cars are built. It would be hard to add an insulated shell to a finished car, but your reflective paint would help. This will decouple the mass of the train from the air. This will reduce the heat/cool energy needed and also reduce the heat carried underground in the summer, or exported in winter. The exterior surface, as you suggested, should be reflective, but unless cleaned daily by an automatic barn shower as they are stabled at dusk, they will soon lose much of their reflectivity.
      - CalvinBarrows 6y ago
        Interesting. Do you know much about Montreal's metro. For Toronto what is the proportion of open cut to covered? I was led to believe by someone who should know better that it was all underground! This may explain the reluctance to accept they are not on the right track: https://www.brainyquote.com/quotes/upton_sinclair_138285 https://www.brainyquote.com/quotes/upton_sinclair_138285