Climax boiler

The large industrial boiler known as the Climax was one of the first of this overall type. It was invented by Thomas F. Morrin and Walter W. Scott of New Jersey and was patented in 1884. The water-tubes were single-turn loops aligned diagonally and arranged into horizontal tiers. The upper tube entry is vertically above the lower entry of the adjacent tube. In the original patent, tubes are hairpin-shaped with radial straight sections. Later designs used a larger outer radius and "pear-shaped" tubes,finally a tube shape that was almost the radius of the outer casing. Reducing the curvature of tubes like this reduces the effects of expansion due to heating and the risk of leakage at the tube entries. The water level of these boilers was around 3/4 of the height of the tube tiers, so that the upper tubes were filled with steam rather than water. Above the tube banks a single flat spiral tube was used as an economiser or feedwater heater.

The furnace used to fire these large boilers was annular, often with four or more separate firedoors. The boiler was also successfully fired with bagasse, plant waste or refuse. Where they were used for continual high-power production, such as for electricity generation, some were also used with early automatic stokers. One advantage of these boilers was the rapidity with which they could be constructed. A factor in this was their pre-fabricated steel casings that were bolted together in sections. Although their potential for high pressure was not made use of, they did gain a reputation for reliability and long service between overhaul.

These boilers were developed by Morrin & Scott at the "Clonbrook Steam-Boiler Works" and have no connection with either the Climax Locomotive Works or their logging locomotives. They were licensed for production to the "Clonbrook Steam-Boiler Co.", but in 1896, their previous manager Thomas J. Lawler began production of a competing boiler at the "Columbian Steam-Boiler Works" and Morrin & Scott successfully sued them for infringement of the Climax patents.

Flued boiler

An early proponent of the cylindrical form, was the American engineer, Oliver Evans who rightly recognised that the cylindrical form was the best from the point of view of mechanical resistance and towards the end of the 18th Century began to incorporate it into his projects. Probably inspired by the writings on Leupold’s “high-pressure” engine scheme that appeared in encyclopaedic works from 1725, Evans favoured “strong steam” i.e. non condensing engines in which the steam pressure alone drove the piston and was then exhausted to atmosphere. The advantage of strong steam as he saw it was that more work could be done by smaller volumes of steam; this enabled all the components to be reduced in size and engines could be adapted to transport and small installations. To this end he developed a long cylindrical wrought iron horizontal boiler into which was incorporated a single fire tube, at one end of which was placed the fire grate. The gas flow was then reversed into a passage or flue beneath the boiler barrel, then divided to return through side flues to join again at the chimney (Columbian engine boiler). Evans incorporated his cylindrical boiler into several engines, both stationary and mobile. Due to space and weight considerations the latter were one-pass exhausting directly from fire tube to chimney. Another proponent of “strong steam” at that time was the Cornishman, Richard Trevithick. His boilers worked at 40–50 psi (276–345 kPa) and were at first of hemispherical then cylindrical form. From 1804 onwards Trevithick produced a small two-pass or return flue boiler for semi-portable and locomotive engines. The Cornish boiler developed around 1812 by Richard Trevithick was both stronger and more efficient than the simple boilers which preceded it. It consisted of a cylindrical water tank around 27 feet (8.2 m) long and 7 feet (2.1 m) in diameter, and had a coal fire grate placed at one end of a single cylindrical tube about three feet wide which passed longitudinally inside the tank. The fire was tended from one end and the hot gases from it travelled along the tube and out of the other end, to be circulated back along flues running along the outside then a third time beneath the boiler barrel before being expelled into a chimney. This was later improved upon by another 3-pass boiler, the Lancashire boiler which had a pair of furnaces in separate tubes side-by-side. This was an important improvement since each furnace could be stoked at different times, allowing one to be cleaned while the other was operating.

Multi Tube Boilers

A significant step forward came in France in 1828 when Marc Seguin devised a two-pass boiler of which the second pass was formed by a bundle of multiple tubes. A similar design with natural induction used for marine purposes was the popular “Scotch” marine boiler.

Prior to the Rainhill trials of 1829 Henry Booth, treasurer of the Liverpool and Manchester Railway suggested to George Stephenson, a scheme for a multi-tube one-pass horizontal boiler made up of two units: a firebox surrounded by water spaces and a boiler barrel consisting of two telescopic rings inside which were mounted 25 copper tubes; the tube bundle occupied much of the water space in the barrel and vastly improved heat transfer. Old George immediately communicated the scheme to his son Robert and this was the boiler used on Stephenson's Rocket, outright winner of the trial. The design was and formed the basis for all subsequent Stephensonian-built locomotives, being immediately taken up by other constructors; this pattern of fire-tube boiler has been built ever since.

steam generator

A boiler or steam generator is a device used to create steam by applying heat energy to water. Although the definitions are somewhat flexible, it can be said that older steam generators were commonly termed boilers and worked at low to medium pressure, but at pressures above this it is more usual to speak of a steam generator

A boiler or steam generator is used wherever a source of steam is required. The form and size depends on the application: mobile steam engines such as steam locomotives, portable engines and steam-powered road vehicles typically use a smaller boiler that forms an integral part of the vehicle; stationary steam engines, industrial installations and power stations will usually have a larger separate steam generating facility connected to the point-of-use by piping. A notable exception is the steam-powered fireless locomotive, where separately-generated steam is transferred to a receiver (tank) on the locomotive.

Solar water heaters

Increasingly, solar powered water heaters are being used. Their solar collectors are installed outside dwellings, typically on the roof or walls or nearby. Many models are the direct-gain type, consisting of flat panels in which water circulates. Heating water itself directly is inherently more efficient than heating it indirectly via antifreeze and heat exchangers. However with hard water supplies, direct solar heaters may need limescale control.

Another type of solar collector is the evacuated tube. It has a row of glass tubes containing heat conducting rods, typically copper which as heating elements in a circulating loop of antifreeze. The captured heat is transferred into the domestic hot water system via a heat exchanger. Usefully, this design is smaller and more efficient than traditional flat plate collectors, and works well in very cold climates. The evacuated description refers to air having been removed from the glass tubes to create a vacuum. This results in very low heat loss, once the inside coating has absorbed solar radiation. So the antifreeze, if pressurised, can be heated to well over 100C if required. Vacuum tubes can be deployed successfully in homes where suitable roof space is a limiting factor: where there is typically less than 1 sqm of sunny roof per person. Other types of solar collector may use solar concentrator dish or trough mirrors to concentrate sunlight on a collector tube filled with water, brine or other heat transfer fluid.

A storage vessel/container is placed indoors or out. Circulation is ideally zero carbon, caused by either natural convection thermosyphon or by a small solar electric pump. However it can also be low carbon circulation, typically, when higher power mains electric powered pumps are used, for example to cope with viscous antifreeze based circuits in cold climates. At night, or when insufficient sunlight is present, circulation through the panel can be stopped by closing a motorised valve and/or stopping the circulating pump, to keep hot water in the storage tank from cooling. Depending on local climate, freeze protection (e.g. via freeze-tolerant silicone rubber water channels, draining the system down or the use of antifreeze), as well as prevention of overheating, must be addressed in their design, installation, and operation.