Steam locomotive condensing apparatus

Steam locomotive condensing apparatus

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A steam locomotive condensing apparatus differs in purpose from the usual closed cycle steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

 condenser
Condenser (heat transfer)
In systems involving heat transfer, a condenser is a device or unit used to condense a substance from its gaseous to its liquid state, typically by cooling it. In so doing, the latent heat is given up by the substance, and will transfer to the condenser coolant...

, in that its function is primarily either to recover water, or to avoid excessive emissions to the atmosphere, rather than maintaining a vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...

 to improve both efficiency
Energy conversion efficiency
Energy conversion efficiency is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The useful output may be electric power, mechanical work, or heat.-Overview:...

 and power
Power (physics)
In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...

. It takes the form of a series of pipes, valves and other ancillary equipment usually attached to an otherwise conventional steam locomotive
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...

. The apparatus takes the exhaust steam that would normally be lost up the funnel and routes it through a heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...

, into the normal water tanks. Installations vary depending on the purpose, design and the type of locomotive to which it is fitted.

Purpose


Unlike the surface condenser often used on a steam turbine
Steam turbine
A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....

, the condensing apparatus on a steam locomotive does not normally increase the power output. In fact it may reduce it considerably. Whilst more power is potentially available by expanding down to a vacuum, the corresponding low density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

 (high specific volume
Specific volume
In thermodynamics, the specific volume of a substance is the ratio of the substance's volume to its mass. It is the reciprocal of density:In thermodynamics, the specific volume of a substance is the ratio of the substance's volume to its mass...

) implies extremely bulky low pressure cylinders or a turbine would be needed to actually extract it. So with a more practical volume ratio the condenser pressure would be near atmospheric rather than at a more typical low pressure, and the temperature would be correspondingly higher. In exhausting hot steam to the condenser, the temperature gradient between the exhaust steam and the cooling water is greater, so that a smaller heat exchange surface area is needed than would be required for typical stationary or ship-based steam plant of similar power. However none of the energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 in the hot steam is available to do mechanical work. The potential improvement in thermal efficiency
Thermal efficiency
In thermodynamics, the thermal efficiency is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, a boiler, a furnace, or a refrigerator for example.-Overview:...

 expected from including the condenser in the cycle is therefore not usually realised within the space constraints of a typical locomotive, indeed losses due to viscous friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...

 in the condenser piping is likely to reduce the power output over what was achievable from simply venting to atmosphere. There are two usual reasons for fitting such equipment, reducing exhaust emissions
Exhaust gas
Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline/petrol, diesel fuel, fuel oil or coal. According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack or propelling nozzle.It often disperses...

 and increasing range.

Underground railways



Originally developed for the Metropolitan Railway
Metropolitan railway
Metropolitan Railway can refer to:* Metropolitan line, part of the London Underground* Metropolitan Railway, the first underground railway to be built in London...

 to allow their locomotives to work the tunnels of the London Underground
London Underground
The London Underground is a rapid transit system serving a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex in England...

. This system was devised by Daniel Gooch
Daniel Gooch
Sir Daniel Gooch, 1st Baronet was an English railway and transatlantic cable engineer and Conservative politician who sat in the House of Commons from 1865 to 1885...

 and developed by Beyer Peacock. Steam is diverted from the exhaust steam pipes into the water tanks via condensing pipes within the same tanks. The water in the tanks could quickly heat up near boiling point
Boiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....

, reducing the condensing effect on the exhaust steam. It was not unknown for the tanks to be emptied and refilled with cold water on a regular basis. Ordinary injector
Injector
ʎ̩An injector, ejector, steam ejector, steam injector, eductor-jet pump or thermocompressor is a pump-like device that uses the Venturi effect of a converging-diverging nozzle to convert the pressure energy of a motive fluid to velocity energy which creates a low pressure zone that dɯaws in and...

s will not work with hot water (until hot-water injectors were developed) so condensing locomotives were usually fitted with axle
Axle
An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to its surroundings, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle...

-driven boiler feedwater pump
Boiler feedwater pump
A boiler feedwater pump is a specific type of pump used to pump feedwater into a steam boiler. The water may be freshly supplied or returning condensate produced as a result of the condensation of the steam produced by the boiler...

s. When not working in tunnels, the steam was directed to the blast pipe and up the funnel in the usual way.

Roadside tramways


In Britain, locomotives working on roadside steam tramways were required by law to have condensers. Water tank condensers (as above) were sometimes used but air-condensers were more common. A steam tram engine
Tram engine
A tram engine is a locomotive specially built, or modified, to work on a street, or roadside, tramway.-Steam tram engines:In the steam locomotive era, tram engines had to comply with certain legal requirements, although these varied from country to country:* The engine must be governed to a maximum...

 usually had a full-length roof and this was surmounted by a nest of air-cooled copper tubes in which the exhaust steam was condensed. Kitson & Co.
Kitson & Co.
Kitson and Company was a locomotive manufacturer based in Hunslet, Leeds, West Yorkshire, England.-Early history:The company started as James Kitson at the Airedale Foundry, off Pearson Street, Hunslet in 1835 with Charles Todd as a partner...

 made many engines of this type. The system was satisfactory for tram engines (which were very low-powered) but would not have worked for larger railway locomotives.

Increased range


Generally this was a more sophisticated installation that used forced air cooling to condense the exhaust steam. The system was intended to reduce the problems of getting enough water to steam locomotives running through desert and very arid areas.

Locomotives fitted with a condensing apparatus

  • Metropolitan Railway A Class
    Metropolitan Railway A Class
    The Metropolitan Railway A Class were 4-4-0T steam locomotives built to work the first of the London Underground lines. They were built by Beyer, Peacock and Company from 1864....

     4-4-0T
  • Metropolitan Railway B Class 4-4-0T
  • Great Northern Railway (later LNER) Class N2
    GNR Class N2
    The Great Northern Railway Class N2 is an 0-6-2T side tank steam locomotive designed by Nigel Gresley and introduced in 1920. Further batches were built by the London and North Eastern Railway from 1925...

     0-6-2T
  • GWR 9700 Class 0-6-0PT (a variation on the 5700 Class)
  • Mersey Railway
    Mersey Railway
    The Mersey Railway connected Liverpool and Birkenhead, England, via the Mersey Railway Tunnel under the River Mersey. Opened in 1886, it was the second oldest urban underground railway network in the world. The railway contained the first tunnel built under the River Mersey. It was constructed by...

     0-6-4T No.5 "Cecil Raikes" (preserved at the Museum of Liverpool)
  • South African Class 20 2-10-2
    South African Class 20 2-10-2
    In 1935 the South African Railways placed one Class 20 steam locomotive with a Santa Fe wheel arrangement in service. In 1950 it was modified to an experimental condensing locomotive.-Design:...

  • South African Class 25 4-8-4
    South African Class 25 4-8-4
    Between 1953 and 1955 the South African Railways placed ninety Class 25 condensing steam locomotives with a 4-8-4 Northern wheel arrangement in service...


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