Usage
Oil cooling is commonly used to cool high-performance motorcycle engines that are not liquid-cooled. Typically, the cylinder is kept air-cooled in a traditional motorcycle fashion, but the cylinder head benefits from the additional cooling. Since there is already an oil circulation system available for lubrication, this oil is also piped to the cylinder head and used as a liquid coolant. Oil cooling requires additional oil capacity, a larger pump flow, and an oil cooler (or a larger cooler than normal) compared to an oil system used only for lubrication.
If air cooling proves sufficient for most of the operating time (such as an aero engine in flight or a motorcycle in motion), then oil cooling is the ideal way to cope with those times when additional cooling is needed (such as an aero engine taxiing before takeoff, or a motorcycle in an urban traffic jam). However, if the engine is a racing engine that always generates a lot of heat, then water cooling or liquid cooling may be preferable.
Air-cooled aero-engines may experience "shock cooling" as they descend from cruising altitude before landing. During descent, very little power is required, so the engine is throttled down, thus generating much less heat than if it had maintained altitude. During descent, the airspeed of the aircraft rises, greatly increasing the air cooling rate of the engine. These factors can cause cylinder head cracking; However, the adoption of an oil-cooled cylinder head can significantly reduce or eliminate this problem because the cylinder head is now "oil-heated".
Splash lubrication is the basic form of oil cooling. Some slow-turning early engines would have a "splash spoon" below the big end of the connecting rod. This spoon will dip into the oil pan oil and then pour the oil out, hoping to cool and lubricate the underside of the piston.
Advantages of oil cooling
Oil has a higher boiling point than water, so it can be used to cool items at temperatures of 100 °C or higher. However, pressurized water cooling can also exceed 100°C.
Oil is an electrical insulator, so it can be used inside or in direct contact with electrical equipment such as transformers.
The oil already exists as a lubricant, so there is no need for additional coolant tanks, pumps, or radiators (although all of these projects may need to be larger than others).
Cooling water can be corrosive to the engine and must contain corrosion inhibitors/rust inhibitors, while oil naturally helps to prevent corrosion.
Disadvantages of oil cooling
Cooling oil may be limited to cooling objects at about 200-300 °C, otherwise the oil may degrade or even leave ash deposits.
Pure water may evaporate or boil, but it will not degrade, although it may become contaminated and sour.
If coolant needs to be added to the system, water can usually be used, but oil may not be necessary.
Unlike water, oil can be flammable.
The specific heat of water or water/glycol is about twice that of oil, so a given volume of water may absorb more engine heat than the same volume of oil.
Therefore, if the engine continues to produce a lot of heat, water may be a better coolant, making it more suitable for high-performance or racing engines.
The oil cooler can make the two fluid media with a certain temperature difference realize heat exchange, so as to reduce the oil temperature and ensure the normal operation of the system. Heat exchangers transfer part of the heat of hot fluid to cold fluid equipment, also known as heat exchangers.
Oil cooler is a very commonly used oil cooling equipment in hydraulic system and lubrication system, its working principle is to achieve heat exchange between two fluid media with a certain temperature difference, so as to achieve the purpose of reducing the oil temperature, in order to ensure the normal operation of the system.
The cooler is a class of heat exchange equipment, including water or air as coolant to remove heat equipment. Therefore, the oil cooler is only one kind of heat exchanger, a large class, a small class, just like a fan, an air conditioning fan.
Among the many types of heat exchangers on the market, coolers occupy an important position. Because the cooler can play an important role in different operating environments and different working conditions such as condensation, heating, evaporation, and waste heat recovery. It is worth mentioning that oil coolers are usually divided into air-cooled oil coolers and water-cooled oil coolers.
First, air cooling heat dissipation
Air-cooled heat dissipation is cooled by the wind brought by the vehicle. The air-cooled cylinder will design a large heat sink, and the cylinder head will design a fan hot plate and air duct. Now, many air-cooled heat dissipation are single-cylinder machines or v2 machines with low speed and high torque. Air cooling is the standard of the daily scooter, the cooling system zero failure engine cost is low, as long as the proper maintenance is not a high temperature problem, but the water cooled car high temperature more. In short, single-cylinder low-speed car air cooling is fully sufficient, do not worry about long-distance problems.
Air cooling advantage
Zero fault cooling system (natural cooling) Air-cooled engines cost less and take up less space.
Air cooling defect
Air cooling is slower than other heat dissipation methods, and is limited by the form of the engine, for example, he rarely uses air cooling in the middle of the 4-cylinder can not effectively dissipate heat, so air cooling is only suitable for 2-cylinder engines.
The specific difference between oil and water cooling:
1, cooling time: because the cooling speed of oil is slower than that of water, the cooling time of oil cooling is longer than that of water cooling.
2, quenching hardness: water-cooled high, oil-cooled low.
3, quenching deformation: water cooling, oil cooling is small.
4, quenching cracking tendency: water cooling, oil cooling is small.
5, the depth of the hardening layer: water cold deep, oil cold shallow.
6, environmental pollution: water is basically not polluted, waste oil is polluted and oil smoke is also polluted, and there may be burning safety hazards.
7, the method of heat dissipation is different: the oil-cooled car uses its own oil inside the engine, connects to the outside of the engine through the pipeline, and then flows back to the inside of the engine after the cooling of the oil-cooled radiator, the process is driven by the oil pump inside the engine. This design is simpler than the water-cooled engine, without the design of water jacket.
Water to cool the engine, which is a more common design at present, has been widely used in cars/motorcycles. The principle of water-cooled heat dissipation is to design a water jacket around the engine cylinder, and the liquid flows to the radiator of the water tank to dissipate heat through the drive of the water pump, and the cooled liquid flows back to the water jacket to reduce the temperature around the cylinder.
8, the cost and occupy space is different: the cost of water cooling is high, because the external water tank occupies a large space. Oil cooling has limits on the amount of engine oil required, and the oil radiator cannot be too large.