GB2394034A

GB2394034A - Air-conditioning for underground tube trains

Info

Publication number: GB2394034A
Application number: GB0328215A
Authority: GB
Inventors: Brian Stapleton Stratford
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-07-21
Filing date: 2003-12-05
Publication date: 2004-04-14
Anticipated expiration: 2023-12-05
Also published as: GB0328215D0; GB0316925D0; GB2394034B

Abstract

An air-conditioning system for an underground tube train uses spherical pellets of ice 3 held in an ice box 4 for cooling the air. The ice is replenished at each station without delaying the train by delivering it through a pipe loop 2 in a carrier flow of water from the front end of the platform. Air from inside the railway coaches is cooled by the ice 3. This air is then mixed with air taken from outside the coach, either from the tunnel or from a station. The air taken will to a degree be heated. Ice enters the box 4 through an entry 5. When the box is full, bolts 6 close off the entry 5 and the water level is then lowered to the level of entry 5. The inlet air arrives at entry 7 and passes through a perforated plate 9. After travelling directly through the ice to be cooled, the air passes through a perforated plate 10 and an exit 8, and then on to various personal nozzles located in the railway coach. The ice box is below floor level. The rising air ducts each include a water trap to prevent water being sprayed into the coach. The ice may be covered by a flexible sheet.

Description

Air-conditioning for underground tube trains The present invention

concerns the air-conditioning of underground tube trains.

On the 1 G'h July 2003, it was reported - as for example, on page 4 of the Financial limes of that date - that London Underground was inviting proposals for a method of air-conditioning their tube trains.

Underground tube trains in long established transport systems can be rather small because of the large expense of constructing the tunnels. In comparison, the passenger flow dunug rush-hours can be very large. In addition, the heat generated by the trains arid the people can sometimes cause the air in the tunnels and at the stations to become very warm. Now if there were conventional air-conditioners in each train they would rely on 'heat pumps' and heat exchangers transfering heat to the air outside the train. Such a system in the circumstances indicated above would not readily fit into the small amount of space that could be made available. That background appears to be the explanation of the London Underground invitation.

Immediately below is given a slightly edited version of the writer's submission, followed by further discussion.

"A. Intermediate objectives (de, "Strategy") 1. Cool the air in the coaches.

2. Cool and improve the air in the tunnels and stations, including reducing the heat generated by the trains.

3. Change the air in the coaches-and then reconsider the need for item 1., above.

B. Proposals - listed under the above objectives 1. Cool the air in the coaches.

Cont'd

Proposal 1: Air coolers based on ice cubes Circulate the air of each coach through boxes of ice cubes. The air would be both cooled and, to some extent, purified, especially as gases are more soluble, I think, in cold water than in warm. The cooled air is then further improved, by mixing into the exit flow l'rom the ice cubes a small amount of the dry warm air from the tunnels.

The exit air passing to the passengers in the coach is then slightly warmed, it is cool rather than cold, and its relative humidity can be made an optimum, presumably below 1 00%.

The melt hom the ice would flow offinto another container, in order to allow continued passage of the airflow.

Replenishment of the ice cubes could occur at each station when the train stops. The replenishment should be completed within the ordinary stopping time of the train and should cause no delay. A pipe or duct, with suitable joints between the coaches, could run the length of the train on both sides, in a loop. Valves would operate automatically to make and break the loop, and rapidly acting connectors would be operated, or would operate automatically, so that, on whichever side the platform is located, cold inlet water carrying the ice cubes flows rapidly around the loop, and both delivers the ice cubes and returns the carrier water.

At awkward junctions in the delivery loop a divergence of the pipe or duct could be inserted in order to reduce the chance of the ice jamming. The divergence would be correctly orientated, I think, whatever the direction ot'the train, if the valves were arranged so that the flow were always clockwise or always anticlockwise. At very awkward junctions it may be necessary to install a rotating helix. Jamming would be more likely if the ice cubes were somewhat below freezing temperature, as then the water close to where two ice cubes were touching each other would tend to freeze and lock them together. Consequently it would be important to supply the ice cubes at very close to freezing temperature, such as by monitoring the manufacture and then keeping them mixed with water for some time before supply to the train.

When the ice replenishment were finished at each station the water level in the ice boxes would be arranged to tall so that the air from the coach could pass through the ice - at fairly high speed.

I'art way bctwccn stations the ice in any one box would be partly used and would not fill its box. Consequently there would be an air space above the ice. If the air passed vertically through the ice the cooling would be less thorough than when the box were full, but may perhaps be satisfactory. If the air passed horizontally through the box it would tend to bypass the ice by travelling through the air space. That could be prevented and adequate cooling achieved if the ice were covered with a flexible sheet weighed down by say an inch of water. The air entry and exit would need to be under the level of the fixings of the sheet.

Should there be an occasional jam of the ice cubes in the supply loop it could be freed quickly by temporarily switching the supply from ice and cold water to hot water.

Proposal 2: A boosted conventional cooler Proposal 2 has been edited and is considered in the "further discussion", later.

Proposal 3: "Regenerative braking" Introduce "regenerative braking", for routine braking at least, if you do not already have it. I believe that, in principle, regenerative braking is easily accomplished, by altering your wiring and switching slightly - although I guess that in practice it's easier said than done. I think at least one of the main car manufacturers already does it, on their special, partly electrical, 'green' cars.

Proposal 4: Modify the airflow in the tunnels: modify the aerodynamics, the air supply quantities, the supply temperatures, and the tunnel cleaning I'm sorry that I do not know the arrangement of the airflow in the stations and tunnels. To what extent does a train act as a piston in a tube and to what extent does it act like a train in the open air? Are there any existing side or top openings from the tunnels, openings which are at present closed but which could be set open, and which would allow an easier piston type flow path and so reduce the aerodynamic drag? Would streamlined Airings at the front and back of the train, designed to take into account the tunnel type flow, reduce the drag? Could changes to the supply of the air to the stations and tunnels reduce the aerodynamic drag? Could changes, such as increases in the flow supply quantities, improve the quality of the air as regards temperature and cleanliness? Could cosmetic changes be made to the tunnels and their equipment in order to make them suitable for frequent and semi-automatic cleaning, and would frequent cleaning in the tunnels improve the quality of the air? Proposal 5: Reduce the aerodynamic drag on the wheels and lower structure Examine whether, conceivably, a close fitting 'spat' over the upper part of each wheel is practicable, as that could reduce the aerodynamic dissipation of the wheel where it is greatest. The reduction is provided by the spat splitting the velocity difference between the airflow and the top of the wheel into 2 parts, with the drag from each part being proportional to the square of the velocity difference in that part.

Might any other changes to the wheel layout, or wheel geometry, or bogey, or lower main structure, reduce the total aerodynamic dissipation'? Proposal 6: Smooth the upper external surfaces of the trains

Could smoothing the upper external surfaces of the trains, at passenger level, reduce drag? Smoothing is now standard around car windows and doors, so could LIJ use it? Perhaps it already does. Also, might there be an advantage in using the flexible ['airings that, aerodynamically, completely fill the slot between adjacent coaches and are common on high speed trains? Proposal 7: Reduce the rolling resistance Examine the contributions to the rolling resistance and consider whether any of them can reasonably be reduced.

Proposal 8: Capture the heat dissipation from the main motors Use the ice cube technique of'Proposal 1' to capture the heat in the flow that cools the main motors. The arrangement would need to be able to accommodate failure of the ice cube cooling without it affecting the motor.

3. Change the air in the carriages Proposal 9: Use air from the tunnel and stations to change the air in the carriages The above proposals 1, and 3 to 8, could in total give a large improvement in the temperature and quality of the air of the tunnels and stations. Consequently the tunnel and station air could be used more freely for changing the air in the carriages.

Individual nozzles would be desirable, rather as on aircraft and in road coaches, but with additional nozzles for standing passengers. It could then be that, when the train is running in tunnels, the use of ice or refrigeration for the cooling of the air for the passengers within the coaches would scarcely be required. The individual nozzles could then merely control the inflow of the cool tunnel air. However, the additional internal cooling would still sometimes be required for when the train is running in the open. Conventional air conditioning, perhaps as boosted in proposal 2, could maybe be adequate for the additional cooling. That could be so particularly if it is automatically switched off in the tunnels, as, with it old the hot exhaust from conventional air conditioning would also be off in the tunnels."

Further discussion is given on the f allowing pages.

F,ffcct of cooling the tunnel air on the additional cooling required inside the coaches In the Proposal 9 of the submission it is suggested that cooling of the tunnel air by the means discussed could be sufficient to allow there to be no additional internal cooling when the trains are in the tunnel, while, when the trains are in the open, a boosted conventional cooler could be adequate. This type of argument may need to be considered if there is complete success in cooling the tunnel air. At present, however, the discussion will treat the tunnel air as still too warm for there to be no additional internal cooling in the trains when they are in the tunnel.

Advantage of the ice system compared with conventional air conditioning I'he ice system has only one main heat exchanger and in that one there is direct contact between the air and the ice, ie without any intermediate structural wall. There will in fact tend to be a film of melt and condensate water on the ice, but, the stronger the airflow the more rapidly would that film be blown away. A strong airflow would give a very intense heat transfer. 'I'he price to be paid for there being only one main exchanger is that the first heat exchange has to be carried out offsite and the ice transported.

Manufacture of the ice-cubes The ice-cubes could be manufactured in a machine close to the end of the platform. The refrigerator and freezer could have its heat output eased compared with a domestic type of system by spraying water into air prom ambient and passing the mixture at fairly high speed onto the outlet heat exchanger. The water spray and air mixture would be expected to drop in temperature to close to the ambient dew point and the combination should give a good heat sink. The exhaust flow would preferably be ducted to the open air above the station. Ideally the heat to be absorbed from the refrigerator and freezer would be absorbed as "moist heat", ie, by heating the air while keeping it saturated. The effective heat capacity of the air is then several times greater than for dry heating of air, so that the outlet sink would remain correspondingly cooler and the refrigerator and freezer correspondingly more effective.

Alternatively the ice-cubes could be maufactured in an ice factory and transported to the station platform. If the factory were close to the sea, it would be able to use the sea water at depth as the outlet heat sink, provided acceptable precautions were taken.

The ice "cubes" would probably be spherical, in order to give a more reliable now path through the interstices, for the air flow.

Transfer of the ice-cubes from the platform to the coaches of the train In the submission the transfer is by water as a carrier, with possibly a helical screw rotor at difficult positions.

A helical screw rotor could instead be used for the full length of the train, with flexible joints as required. The helical screw rotor may be the easier method, but, potentially, the water carrier could perhaps be quieter and faster.

s

A previous mention of ice for air-conditioning In a recent patent application concerned with "Buoyant Ducts" and power generation the writer discusses the use of cool water from the buoyant duct being used for air-conditioning. The water would probably have had a frozen content.

Boosting of a conventional air-conditioning system One possibility lor boosting a conventional air-conditioning system could be to carry on the train a small amount of water, perhaps replenished at each station rather as discussed for the ice cubes in the submission, and to spray the water into the cooling air taken from the tunnels and platforms rather as discussed above for the manufacture of the ice cubes.

The present invention According to the present invention there is provided an air-conditioning system for underground tube trains comprising means for controlling airflows, means for reducing the heat released by the trains into the tunnels and stations, and an ice system for cooling the air inside the trains.

Example

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure I shows an ice box filled with ice cubes, the supply pipe for the ice, and the air flows.

The example is of a tube train with air-conditioning by means of ice cubes. All the suggestions for cooling and cleaning the air in the tunnels and stations as listed in proposals 3 to 8 of the main submission above are in place, but not shown in the drawing. The air quality has been improved accordingly. However, additional conditioning of the air takes place inside the coaches by means of ice cubes. The details are given below, but, first, the general arrangement is that say 70 % of the air flow supplied to the passengers consists of conditioned and recirculated air taken from inside the coaches. This conditioned and recirculated air is conditioned first by passing it through the ice boxes. That cools the flow and condenses out much of its moisture. Some of the impurities will also be removed. The say 70% is then mixed with the other (say) 30% of the flow. The 30% is taken from outside the coach, ie from the tunnels and platforms. There will be some heat in the tunnel air as a result of the dissipation from the trains, even with the regenerative braking and the other improvements. The dissipation heat from the trains will be dry heat. Consequently the 70% and 30% mix supplied to the passengers will be close to both optimum temperature and optimum humidity. In fact the "say 70%" is a controllable proportion, as is the rate of flow, with the various flows and proportions determined by various valves set automatically according to humidity and temperature monitors, as well as by the respective passenger at each nozzle. The various monitors and controls are not shown. The 30% flow passes through a frequently cleaned filter - also not shown.

In Figure I items I are ice pellets being carried by water in pipe 2 to replenish the ice pellets 3 in ice boxes such as 4. There are 8 such ice boxes distributed in each coach, with all the ice boxes on the train supplied by the pipe 2, as it goes around the train in a loop.

The ice enters the box through the entry 5. The size of the entry 5 varies around the loop and is set so that all the boxes on the loop fill at about an equal rate. The required distribution of size of the entry 5 will be different between the 2 directions of the train. The 2 different distributions are obtained by automatic adjustment of the set of pointed rod plungers 6. If the type of entry 5 shown in Figure I gives an inadequate rate of ice cubes entering the box, the geometry is adjusted (not shown) towards a "ram scoop" form, rather than a "flush".

When the ice box is fully replenished, the bolts 6 close off the entry 5 and the water level is lowered to the level of 5. Bolts 6 are sufficient to prevent full size cubes falling through, but small pieces are encouraged to fall through in order to reduce the blockage of the interstices of the good cubes. The air is then turned on.

The inlet air arrives at entry 7 and enters the icebox by the perforated plate 9. It flows through the interstices of the ice cubes 3, it is cooled to a temperature not much higher than the ice, and leaves the ice box by the perforated plater O. The cold air leaves at the exit 8 and goes to the various personal nozzles in that local part of the coach - but via the water trap discussed below.

Care is taken in the design of the pipes and junctions to avoid stagnant puddles of water, that might cause problems with health infections such as legionnaires' disease.

In order to avoid spraying the passengers with icy water during the ice replenishment the icebox is below floor level and the rising air ducts each include a water trap (not shown) before reaching the floor. Firstly there is a valve which is closed before turning on the water, with a monitor on each valve and possibly an over-ride to the water supply. The pipes then each rise to an injection pump, still below floor level. If, then, water has somehow still got past a valve, then a build-up of water in the pipe between floor and ceiling under the maximum available water pressure would drive out all the water through the side entry to the injection pump, that entry being open to atmosphere, (preferably without restriction from a blocked air filter) without any water being able to flow through the nozzle to the passenger. In ordinary operation a chosen small amount of tunnel and platform air enters through the side entrance of the injection pump, slightly warming the cold air flow from the ice box and reducing its relative humidity.

The ice 3 in the ice-box 4 is covered by a flexible sheet 11. The sheet 11 descends to a position such as I I B when the ice has been partially used. It is weighed down on to the ice by a layer of water 12, which enters through the port 13. The depth of the water could be rather greater than the inch of the submission. The flexible sheet forces the air to travel through the ice, rather than bypassing it through the air space above it.

The installation of supply pipes and ice-box would have a light heat insulation (not shown) where it is below the floor.

Acknowledgement The writer is pleased to acknowledge a very helpful discussion with Helen Carrington, his daughter, but does not wish to blame her for his mistakes. Helen is a member of the London Underground.

Claims

1. An air-conditioning system for underground tube trains comprising means for controlling airflows, means tor reducing the heat released by the trains into the tunnels End stations, and an ice system for cooling the air inside the trains.

2. An air-conditioning system for underground tube trains as in Claim l wherein means are provided for loading the ice without delaying the train.

3. An air-conditioning system for underground tube trains as in Claim 2 wherein the ice is in the form of pieces and is delivered to iceboxes in the coaches by a piped carrier flow of water.

4. An air-conditioning system for underground tube trains as in Claim 3 wherein a flexible sheet is pressed down onto the top of the ice.

5. An air-conditioning system for underground tube trains as in any preceding claim wherein the water level of the ice carrying system is lowered when the replenishment of the ice is finished.

6. An air-conditioning system for underground tube trains as in Claim 5 wherein bolts partly close the ice entrance immediately before said lowering of the water level.

7. An air-conditioning system for underground tube trains as in any preceding claim wherein the airflow pipes are fitted with water traps consisting of valves and injection pumps near the bottom of rising pipes.

8. An air-conditioning system for underground tube trains as in any preceding claim wherein the ice is in the form of spherical pieces, or lumps.

9. An air-conditioning system for underground tube trains as in any preceding claim wherein the ice is manufactured in ice machines near the end of station platforms.

l O. An air-conditioning system for underground tube trains as in any preceding claim wherein the ice is delivered to the whole train from a single pipe connection at the end of the platform.

11. An air-conditioning system for underground tube trains as in any preceding claim wherein improvements are made to reduce the heat released by the trains into the tunnels and stations.

12. An air-conditioning system for underground tube trains as in Claim 11 wherein the improvements include regenerative routine braking.

l 3. An air-conditioning system for underground tube trains substantially as descibed herein with reference to the accompanying Figure 1.