Kirchweger condenser

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The purpose of the Kirchweger condenser (German: Kirchweger-Kondensationseinrichtung or Kirchwegersche Abdampfkondensation) was to preheat feedwater in a steam locomotive using the exhaust steam from the engine. It was invented in 1850 by Heinrich Kirchweger. A similar system was developed by Rohrbeck.

Steam locomotive railway locomotive that produces its pulling power through a steam engine

A steam locomotive is a type of railway locomotive that produces its pulling power through a steam engine. These locomotives are fueled by burning combustible material – usually coal, wood, or oil – to produce steam in a boiler. The steam moves reciprocating pistons which are mechanically connected to the locomotive's main wheels (drivers). Both fuel and water supplies are carried with the locomotive, either on the locomotive itself or in wagons (tenders) pulled behind.

Johann Gottfried Heinrich Kirchweger was a German railway engineer. Heinrich Kirchweger was born on 12 June 1809 in Stettin, then part of Germany, now Szczecin in Poland. After attending the trade school in Berlin, Kirchweger worked with the industrialist Georg Henschel in Kassel.

Contents

Overview

Exhaust steam was extracted from the steam chest and fed through a 100 mm diameter pipe under the locomotive to the tender. There the steam was fed directly into the feedwater, which thus heated up to boiling point. The remaining steam was allowed to escape to atmosphere through a second chimney on the tender. The quantity of steam could be regulated using a cock on the tender. The Rohrbeck system differed in detail from the Kirchweger condenser. Here steam was removed at the blast pipe and led away along the top of the boiler. It was regulated by a throttle valve on the blast pipe.

Tender (rail) vehicle for carrying a steam locomotives supply of fuel and water

A tender or coal-car is a special rail vehicle hauled by a steam locomotive containing its fuel and water. Steam locomotives consume large quantities of water compared to the quantity of fuel, so their tenders are necessary to keep them running over long distances. A locomotive that pulls a tender is called a tender locomotive. Locomotives that do not have tenders and carry all their fuel and water on board the locomotive (itself) instead are called tank locomotives.

Boiler closed vessel in which water or other fluid is heated

A boiler is a closed vessel in which fluid is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central heating, boiler-based power generation, cooking, and sanitation.

Fuel savings

Using such a system fuel savings of between 10 and 20% were possible depending on the operating conditions, in some circumstances even as much as 30% could be saved. The Lower Silesian-Märkisch Railway (Niederschlesisch-Märkische Eisenbahn) put this saving at 7.5% on its locomotives.

Contamination

However the contamination of boiler feedwater with foreign bodies was a problem. Old sources report erosion of the boiler plates which was caused by fatty acids contained in the lubricant accompanying the exhaust steam. On the other hand, the formation of scale in the boiler was delayed because a proportion of the boiler scale constituents had already been left behind in the tender.

Boiler feedwater

Boiler feedwater is an essential part of boiler operations. The feed water is put into the steam drum from a feed pump. In the steam drum the feed water is then turned into steam from the heat. After the steam is used it is then dumped to the main condenser. From the condenser it is then pumped to the deaerated feed tank. From this tank it then goes back to the steam drum to complete its cycle. The feed water is never open to the atmosphere. This cycle is known as a closed system or Rankine cycle.

Withdrawal

On the introduction of injectors for boiler feeding the exhaust steam condensers were taken out of use from the 1860s, because injectors could only handle cold water. By about 1880 around 900 German locomotives had been fitted with condensing apparatus.

Injector type of pump

A steam injector is typically used to deliver cold water to a boiler against its own pressure using its own live or exhaust steam, replacing any mechanical pump. This was the purpose for which it was originally invented in 1858 by Henri Giffard. Its operation was from the start intriguing since it seemed paradoxical, almost like perpetual motion, but its operation was later explained using thermodynamics. Other types of injector may use other pressurised motive fluids such as air.

See also

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Surface condenser Steam engine component which condenses excess steam for reuse as water

A surface condenser is a commonly used term for a water-cooled shell and tube heat exchanger installed on the exhaust steam from a steam turbine in thermal power stations. These condensers are heat exchangers which convert steam from its gaseous to its liquid state at a pressure below atmospheric pressure. Where cooling water is in short supply, an air-cooled condenser is often used. An air-cooled condenser is however, significantly more expensive and cannot achieve as low a steam turbine exhaust pressure as a water-cooled surface condenser.

Condensing steam locomotive

A condensing steam locomotive is a type of locomotive designed to recover exhaust steam, either in order to improve range between taking on boiler water, or to reduce emission of steam inside enclosed spaces. The apparatus takes the exhaust steam that would normally be used to produce a draft for the firebox, and routes it through a heat exchanger, into the boiler water tanks. Installations vary depending on the purpose, design and the type of locomotive to which it is fitted. It differs from the usual closed cycle condensing steam engine, in that the function of the condenser is primarily either to recover water, or to avoid excessive emissions to the atmosphere, rather than maintaining a vacuum to improve both efficiency and power.

Steam-electric power station power plant, wherein the thermal energy is exploited by steam in a steam turbine

The steam-electric power station is a power station in which the electric generator is steam driven. Water is heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser. The greatest variation in the design of steam-electric power plants is due to the different fuel sources.

Franco-Crosti boiler

The Franco–Crosti boiler is a type of boiler used for steam locomotives. It was designed in the 1930s by Attilio Franco and Dr Piero Crosti. The main difference between it and conventional feedwater heaters widely used on the continent is that the Franco-Crosti boiler uses both exhaust steam and exhaust gases from the firebox. Conventional feedwater heaters only use exhaust steam.

A deaerating feed tank (DFT), often found in steam plants that propel ships, is located after the main condensate pump and before the main feed booster pump. It has these three purposes:

  1. Remove dissolved oxygen (“air”) from the condensate
  2. Pre-heat the feedwater
  3. Provide a storage/surge volume

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Kirchweger is a German surname. Notable people with the surname include:

South African Class 25 4-8-4 class of 90 South African 4-8-4 locomotives with condensing tenders

The South African Railways Class 25 4-8-4 of 1953 was a condensing steam locomotive.

High-pressure steam locomotive

A high-pressure steam locomotive is a steam locomotive with a boiler that operates at pressures well above what would be considered normal. In the later years of steam, boiler pressures were typically 200 to 250 psi. High-pressure locomotives can be considered to start at 350 psi (2.41 MPa), when special construction techniques become necessary, but some had boilers that operated at over 1,500 psi (10.34 MPa).

Evaporator (marine) Ships equipment used to produce fresh water

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South African type CL tender

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South African type CZ tender class of condensing 5000-imp.gal. locomotive tenders on South African Railways

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References

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