يعمل سائل التبريد على تبريد محرك الاحتراق الداخلي للوصول إلى درجة حرارة التشغيل المناسبة. يمكن استخدام الحرارة المنقولة من المحرك إلى سائل التبريد في تدفئة مقصورة الركاب. ... فخطر التجمد يزداد عندما تكون نسبة تركيز سائل التبريد منخفضة للغاية ومرتفعة للغاية.
#Antigel
#Liquide_de_refroidissement
قطع غيار السيارات - معلومات و نصائح هي قناة خاصة، مغربية تقدم معلومات جد مهمة في مجال قطع غيار
السيارات من طرف خبير في المجال.
#قطع_غيار_السيارات
#pièces_de_rechange_automobile
An antifreeze is an additive which lowers the freezing point of a water-based liquid. An antifreeze mixture is used to achieve freezing-point depression for cold environments. Common antifreezes also increase the boiling point of the liquid, allowing higher coolant temperature.[1] However, all common antifreeze additives also have lower heat capacities than water, and do reduce water's ability to act as a coolant when added to it.[2]
Because water has good properties as a coolant, water plus antifreeze is used in internal combustion engines and other heat transfer applications, such as HVAC chillers and solar water heaters. The purpose of antifreeze is to prevent a rigid enclosure from bursting due to expansion when water freezes. Commercially, both the additive (pure concentrate) and the mixture (diluted solution) are called antifreeze, depending on the context. Careful selection of an antifreeze can enable a wide temperature range in which the mixture remains in the liquid phase, which is critical to efficient heat transfer and the proper functioning of heat exchangers. Secondarily but not less importantly, most if not all commercial antifreeze formulations intended for use in heat transfer applications include different kinds of anti-corrosion and anti-cavitation agents that protect the hydraulic circuit from progressive wear.
Automotive and internal combustion engine use
Fluorescent green-dyed antifreeze is visible in the radiator header tank when car radiator cap is removed
Most automotive engines are "water"-cooled to remove waste heat, although the "water" is actually antifreeze/water mixture and not plain water. The term engine coolant is widely used in the automotive industry, which covers its primary function of convective heat transfer for internal combustion engines. When used in an automotive context, corrosion inhibitors are added to help protect vehicles' radiators, which often contain a range of electrochemically incompatible metals (aluminum, cast iron, copper, brass, solder, et cetera). Water pump seal lubricant is also added.
Antifreeze was developed to overcome the shortcomings of water as a heat transfer fluid.
On the other hand, if the engine coolant gets too hot, it might boil while inside the engine, causing voids (pockets of steam), leading to localized hot spots and the catastrophic failure of the engine. If plain water were to be used as an engine coolant in northern climates freezing would occur, causing significant internal engine damage. Also, plain water would increase the prevalence of galvanic corrosion. Proper engine coolant and a pressurized coolant system obviate these shortcomings of water. With proper antifreeze, a wide temperature range can be tolerated by the engine coolant, such as −34 °F (−37 °C) to +265 °F (129 °C) for 50% (by volume) propylene glycol diluted with water and a 15 psi pressurized coolant system.[3][4]
Early engine coolant antifreeze was methanol (methyl alcohol). Ethylene glycol was developed because its higher boiling point was more compatible with heating systems.
The most common water-based antifreeze solutions used in electronics cooling are mixtures of water and either ethylene glycol (EGW) or propylene glycol (PGW). The use of ethylene glycol has a longer history, especially in the automotive industry. However, EGW solutions formulated for the automotive industry often have silicate based rust inhibitors that can coat and/or clog heat exchanger surfaces. Ethylene glycol is listed as a toxic chemical requiring care in handling and disposal.
Ethylene glycol has desirable thermal properties, including a high boiling point, low freezing point, stability over a wide range of temperatures, and high specific heat and thermal conductivity. It also has a low viscosity and, therefore, reduced pumping requirements. Although EGW has more desirable physical properties than PGW, the latter coolant is used in applications where toxicity might be a concern. PGW is generally recognized as safe for use in food or food processing applications, and can also be used in enclosed spaces.
Similar mixtures are commonly used in HVAC and industrial heating or cooling systems as a high-capacity heat transfer medium. Many formulations have corrosion inhibitors, and it is expected that these chemicals will be replenished (manually or under automatic control) to keep expensive piping and equipment from corroding.
16 дек 2021
