Who invented the car radiator?

Type of heat exchanger; radiant body through water or other liquids

This article is about radiators in automobiles, buildings, and electronics. For other uses, see Radiator (disambiguation)

Water-air convective cooling radiator, made from aluminum, from a 21st-century car

A radiator is a heat exchanger used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in cars, buildings, and electronics.

A radiator is always a source of heat to its environment, although this may be for either the purpose of heating an environment, or for cooling the fluid or coolant supplied to it, as for automotive engine cooling and HVAC dry cooling towers. Despite the name, most radiators transfer the bulk of their heat via convection instead of thermal radiation.[citation needed]

History

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The Roman hypocaust is an early example of a type of radiator for building space heating. Franz San Galli, a Prussian-born Russian businessman living in St. Petersburg, is credited with inventing the heating radiator around 1855,[1][2] having received a radiator patent in 1857,[3] but American Joseph Nason developed a primitive radiator in 1841[4] and received a number of U.S. patents for hot water and steam heating.[4]

Radiation and convection

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A cast iron convector radiator from 1904

Heat transfer from a radiator occurs by two mechanisms: thermal radiation and convection into flowing air or liquid. Conduction is not normally a major source of heat transfer in radiators.. A radiator may even transfer heat by phase change, for example, drying a pair of socks. In practice, the term "radiator" refers to any of a number of devices in which a liquid circulates through exposed pipes (often with fins or other means of increasing surface area). The term "convector" refers to a class of devices in which the source of heat is not directly exposed.

To increase the surface area available for heat exchange with the surroundings, a radiator will have multiple fins, in contact with the tube carrying liquid pumped through the radiator. Air (or other exterior fluid) in contact with the fins carries off heat. If air flow is obstructed by dirt or damage to the fins, that portion of the radiator is ineffective at heat transfer.

Heating

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A panel convector radiator, typical of a standard central heating system in the UK

Radiators are commonly used to heat buildings on the European continent. In a radiative central heating system, hot water or sometimes steam is generated in a central boiler and circulated by pumps through radiators within the building, where this heat is transferred to the surroundings.

In some countries, portable radiators are common to heat a single room, as a safer alternative to space heater and fan heater.

Heating, ventilation, and air conditioning

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Radiators are used in dry cooling towers and closed-loop cooling towers for cooling buildings using liquid-cooled chillers for heating, ventilation, and air conditioning (HVAC) while keeping the chiller coolant isolated from the surroundings.

Engine cooling

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Car engine bay, with radiator in front Auto radiators with double grids of tubes: staggered grids on the left, parallel grids on the right

Radiators are used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plants and other places where heat engines are used (watercrafts, having an unlimited supply of a relatively cool water outside, usually use the liquid-liquid heat exchangers instead).

To cool down the heat engine, a coolant is passed through the engine block, where it absorbs heat from the engine. The hot coolant is then fed into the inlet tank of the radiator (located either on the top of the radiator, or along one side), from which it is distributed across the radiator core through tubes to another tank on the opposite end of the radiator. As the coolant passes through the radiator tubes on its way to the opposite tank, it transfers much of its heat to the tubes which, in turn, transfer the heat to the fins that are lodged between each row of tubes. The fins then release the heat to the ambient air. Fins are used to greatly increase the contact surface of the tubes to the air, thus increasing the exchange efficiency. The cooled liquid is fed back to the engine, and the cycle repeats. Normally, the radiator does not reduce the temperature of the coolant back to ambient air temperature, but it is still sufficiently cooled to keep the engine from overheating.

This coolant is usually water-based, with the addition of glycols to prevent freezing and other additives to limit corrosion, erosion and cavitation. However, the coolant may also be an oil. The first engines used thermosiphons to circulate the coolant; today, however, all but the smallest engines use pumps.[5]

Up to the 1980s, radiator cores were often made of copper (for fins) and brass (for tubes, headers, and side-plates, while tanks could also be made of brass or of plastic, often a polyamide). Starting in the 1970s, use of aluminium increased, eventually taking over the vast majority of vehicular radiator applications. The main inducements for aluminium are reduced weight and cost.[citation needed]

Since air has a lower heat capacity and density than liquid coolants, a fairly large volume flow rate (relative to the coolant's) must be blown through the radiator core to capture the heat from the coolant. Radiators often have one or more fans that blow air through the radiator. To save fan power consumption in vehicles, radiators are often behind the grille at the front end of a vehicle. Ram air can give a portion or all of the necessary cooling air flow when the coolant temperature remains below the system's designed maximum temperature, and the fan remains disengaged.[citation needed]

Electronics and computers

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A passive heatsink on a motherboard

As electronic devices become smaller, the problem of dispersing waste heat becomes more difficult. Tiny radiators known as heat sinks are used to convey heat from the electronic components into a cooling air stream. Heatsinks do not use water, rather they conduct the heat from the source. High-performance heat sinks have copper to conduct better. Heat is transferred to the air by conduction and convection; a relatively small proportion of heat is transferred by radiation owing to the low temperature of semiconductor devices compared to their surroundings.

Radiators are also used in liquid cooling loops for rejecting heat.

Spacecraft

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Radiators are found as components of some spacecraft. These radiators work by radiating heat energy away as light (generally infrared given the temperatures at which spacecraft try to operate) because in the vacuum of space neither convection nor conduction can work to transfer heat away. On the International Space Station, these can be seen clearly as large white panels attached to the main truss. They can be found on both crewed and uncrewed craft.[6]

See also

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• Radiatori – small, squat pasta shaped to resemble radiators

References

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Effective cooling of the combustion engine was, and still is, a prerequisite for producing powerful engine output. Vehicle designer Wilhelm Maybach was the first to demonstrate this fact 120 years ago. On 20 September 1900, he took out a patent for the honeycomb radiator design: as the car moved, the airstream was forced through a multitude of tubes mounted side-by-side, similar to a honeycomb when viewed from the front, which efficiently cooled the cooling water – that had been heated by the combustion action in the engine – as it passed through the radiator. The system was constructed as a protruding, vertical radiator and debuted in the Mercedes 35 hp in 1900. Form follows function – and so the high-performance radiator became a central characteristic of the modern car. What’s more: that distinctive heat exchanger at the front of the vehicle became a defining stylistic element for the Stuttgart car manufacturer over the decades, and the front grille remains so today.

The background: The first vehicles after the invention of the car by Carl Benz in 1886 did not have a closed cooling circuit. Instead, the cooling water heated by the engine just evaporated. Refilling the water supply was part of the motoring experience – but, as engine power increased, it was no longer a practical solution.

Taking up the challenge: Wilhelm Maybach (1846 to 1929) was the first car designer to develop a solution, and quickly, at that. As early as 1897, that resourceful engineer, together with Gottlieb Daimler, introduced the tube-based radiator. Maybach himself described it as an “apparatus for cooling the water flowing around the cylinders of internal combustion engines, consisting of a flat vessel traversed by a large number of tubes, whereby a stream of air generated by a suitable ventilation device passes continuously through the tubes and extracts the heat from the cooling water”. The tubes were made of brass because that alloy of copper and zinc has very good thermal conductivity. The new cooling system was first used in September 1898 in the world’s first road vehicle with a four-cylinder engine: the engine of the “Phoenix” horseless carriage initially developed 5.8 kW (8 hp) from a 2.1-litre engine.

The breakthrough: On 20 September 1900, Maybach applied for a patent for the honeycomb radiator design as a “cooling and condensation device based on the cross-flow principle”. From 8 August 1901, German Reich Patent (DRP) number 122 766 came into force to protect the invention, which was a further development of the tube-based radiator. Wilhelm Maybach had a new type of radiator soldered, made up of 8,070 square tubes measuring six by six millimetres in cross-section. The increased inner surface area of the square tubes in comparison to round tubes, combined with the smaller gaps between the individual tubes, increased the cooling effect considerably and made significantly higher engine performance possible.

Better efficiency: Compared to the Phoenix horseless carriage from 1898, the water consumption in the new 26 kW (35 hp) Mercedes engine from 1900 was reduced by half, from 18 litres to nine per 100 kilometres. In other words: for each horsepower, rather than requiring 2.25 litres of water for cooling purposes, only 0.26 litres was needed over that distance. A small fan located behind the radiator additionally improved the cooling effect at low speed. In this way, the new high-performance radiator solved the car cooling problem permanently – to this day, vehicle radiators are based on exactly the same principle.

Première The honeycomb radiator found its first practical application in the Mercedes 35 hp, the epoch-making new high-performance car manufactured by Daimler-Motoren-Gesellschaft (DMG). After the long-legged early motorised, horseless carriages, the design of this, the first modern car in history was trend-setting and triggered a landslide design change: the elongated silhouette, high engine output, honeycomb radiator, low bonnet, long wheelbase, a gear-change gate, inclined steering column, equally sized wheels on both axles and low weight were pioneering core features.

A design feature for decades: The vehicle design of the Mercedes 35 hp was defined to a large extent by the radiator that presented itself to the airstream, which was copied by many manufacturers. Allgemeine Automobil-Zeitung, (issue 51-52/1902), commented on the Mercedes Simplex at the Paris Motor Show: “The honeycomb radiator, which also influences the lines of the vehicle in some respects, was virtually unknown at the last Paris Motor Show, but has since become ‘de rigueur’ for most French construction engineers.” This was followed by the vertical, pointed radiator, also a defining design feature for decades. From the Mercedes-Benz 170 (W 15) model series, from 1931 on, the flat radiator was hidden behind a grille. It was incorporated as part of the bonnet and, with its house-roof shape, resembled the pointed radiator. The chrome-plated grille became the central distinctive feature of the brand. Now flatter, more elongated and redesigned many times over, it still is today.