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Engine cooling
Dec 29, 2018

Auto radiators with a double grid of tubes: staggered grids on the left, parallel grids on the right

Radiators are used to cool internal combustion engines, mainly for automobiles, but also for piston engines, railway locomotives, motorcycles, stationary power plants and other places where such engines are used.

To cool the engine, coolant passes through the engine block and absorbs heat from the engine block. The hot coolant is then fed into the inlet box of the radiator (on the top of the radiator or along one side), from the radiator core of the radiator to the other tank on the other side of the radiator. As the coolant passes through the radiator tube on the way to the opposite tank, it transfers most of the heat to the tube, which in turn transfers heat to the fins between each row of tubes. The heat sink then releases heat into the surrounding air. The fins are used to greatly increase the contact surface of the tube with the air, thereby improving the exchange efficiency. The cooled coolant is sent back to the engine and the cycle repeats. Typically, the heat sink does not reduce the temperature of the coolant back to ambient air temperature, but it is still sufficiently cooled to prevent the engine from overheating.

This coolant is typically water based and glycol is added to prevent freezing and other additives to limit corrosion, corrosion and cavitation. However, the coolant can also be an oil. The first engine uses a thermosiphon to circulate the coolant; however, today, all engines except the smallest one make

Until the 1980s, radiator cores were usually made of copper (for fins) and brass (for tubes, headers and side panels), while tanks could also be made of brass or plastic, usually poly Amide. Since the 1970s, the use of aluminum has increased, eventually accounting for the vast majority of automotive radiator applications. The main incentives for aluminum are weight reduction and cost reduction.

Since air has a lower heat capacity and density than liquid coolant, a substantial volume flow (relative to the coolant) must be blown through the radiator core to capture heat from the coolant. The heat sink typically has one or more fans that blow air through the heat sink. To save fan power consumption in the vehicle, the radiator is usually located behind the grille at the front of the vehicle. When the coolant temperature remains below the maximum temperature of the system design, the ram air may provide some or all of the necessary cooling air flow and the fan remains detached.

Electronics

As electronic devices become smaller, the problem of dissipating waste heat becomes more difficult. A miniature heat sink, called a heat sink, is used to transfer heat from the electronic components into the cooling air stream. Instead of using water, the heat sink conducts heat from the source (high-performance heat sinks give copper better thermal conductivity). Heat is transferred to the air by conduction and convection; a relatively small proportion of heat is transferred through the radiation due to the low temperature of the semiconductor device compared to the surrounding environment.

Spacecraft

Radiators were found to be part of some spacecraft. These heat sinks work by using thermal energy as light (usually infrared at temperatures at which the spacecraft is trying to operate) because convection and conduction do not transfer heat away in a vacuum in space. On the International Space Station, these can be clearly seen as large white panels attached to the main truss. They can be found on both manned and unmanned aircraft.

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