Waterless antifreeze, is it really an IQ tax?

February 15, 2024

Waterless antifreeze, is it really an IQ tax?

When the gasoline engine is working, it will produce a lot of heat, which will cause damage to the engine if it is not cooled in time. Therefore, modern engines require coolant to cool the engine. At present, the coolant commonly used in the engine is a mixture of water and ethylene glycol, and then through additives to increase its anti-corrosion, anti-rust and other properties. In recent years, waterless cooling liquid has gradually appeared in the automotive aftermarket. Due to the lack of water, the water-free cooling liquid can achieve no scale, low vapor pressure, fast heating and other characteristics, and its main component propylene glycol has low toxicity and easy degradation, which is more environmentally friendly than glycol in the traditional coolant.

Previously, because the water-free cooling liquid can completely eliminate the pitting and cavitation of the wet cylinder liner of the engine, it is mostly used in heavy-duty diesel engines, racing cars and high-performance vehicles. Some foreign countries have banned the use of ethylene glycol for environmental protection considerations, and propylene glycol anhydrous cooling liquid has been used for many years in the field of home vehicles. In China, the use of waterless cooling liquid is not common, there is no Oems in the factory vehicles originally equipped with waterless cooling liquid, only love Wen and other brands in the post-market promotion. Then, the applicability of using propylene glycol waterless cooling solution for vehicles originally loaded with glycol coolant is studied.

1. Introduction to typical coolant

At present, the common coolants are divided into three categories: water, water and ethylene glycol in proportion to the water-containing coolant and propylene glycol as the main component of the water-free cooling solution. The physical properties of purified water, 50% glycol coolant, and NPG+ waterless cooling liquid of Aiwen brand are shown in Table 1.

Table 1 Comparison of physical properties of common coolants

It can be seen from the physical properties of all kinds of common coolants that pure water is easy to "open the pot" in summer due to its low boiling point and high freezing point, and it is easy to freeze in winter leading to cylinder block rupture, which is rarely used at present. The boiling point of NPG+ is as high as 191 ° C, about 60 ° C higher than glycol coolant and about 90 ° C higher than pure water, and opening the coolant cover at high temperature of the engine will not cause steam eruption, nor will it cause loss of coolant due to high temperature steam. Its freezing point of -40 ° C is also lower than the traditional coolant, which can meet the requirements of use in cold regions. At the same time, its higher boiling point determines that the water-free cooling liquid can work under the conditions of no pressure on the tank cover, and even work under high altitude and low pressure.

But the water-free cooling liquid has many advantages, but also has the problem of high viscosity and small specific heat capacity. At 10℃, the dynamic viscosity of the traditional coolant is 5.0Pa·s×10-3, but the viscosity of the water-free cooling liquid is as high as 58Pa·s×10-3, which is more than 10 times that of the traditional coolant and nearly 50 times that of pure water. At 100℃, the dynamic viscosity of the water-free cooling liquid is also more than 3 times the viscosity of the traditional coolant.

In terms of specific heat capacity, at 100℃, the specific heat capacity of the water-free cooling liquid is 80% of that of the traditional coolant, and there is a risk of insufficient heat dissipation capacity under high load conditions.

2. The effect of no water cooling liquid on the engine

2.1 Impact on cold start performance

When the engine is cold started, it needs to heat up quickly to reach the working temperature as soon as possible, and the engine makes the coolant circulate through the closed thermostat, so as to achieve the rapid rise of the water temperature. After replacing the water-free cooling liquid, because its specific heat capacity is lower than that of the traditional coolant, when absorbing the same amount of heat, the temperature rises higher, so the temperature rises faster. At the same time, due to the greater viscosity of the water-free cooling liquid, the poor fluidity at low temperature further shortens its heating time.

Therefore, the water-free cooling liquid can shorten the engine heating process and allow the engine to enter the working temperature faster.

2.2 Influence on engine operating temperature

When the engine reaches the operating temperature, the thermostat will open and the coolant will enter the large circulation. When the vehicle is running hot, because the specific heat capacity of the water-free cooling liquid is lower than that of the traditional coolant, the heat dissipation capacity will be lower than that of the traditional engine, so the temperature of the coolant and the cylinder block will also use the traditional coolant engine. The advantage of this difference is that due to the higher temperature of the coolant, heat loss can be reduced to a certain extent, improve the thermal efficiency of the engine, and theoretically reduce fuel consumption.

However, the lower specific heat capacity will lead to the engine under high load conditions, the cooling capacity of the coolant is lower than the heat of the engine, the coolant return port temperature, the engine exhaust temperature, the oil temperature will rise, the overall heat load of the engine will also rise, if the engine design reserve is insufficient, it may lead to component damage. Previously, there were cases of rubber parts being damaged at high temperatures using waterless cooling liquid and cases of engine high temperature alarm.

2.3 Influence on oil temperature

However, while having advantages, due to the low cooling capacity of the cooling liquid, the use of water-free cooling liquid will cause the oil temperature to rise by 5-10 ° C. This oil temperature rise will lead to an increase in the heat dissipation pressure of the oil, and the viscosity decreases with the rise in temperature, taking a brand of 5W-30 oil as an example, if the oil temperature rises from 110 ° C to 120 ° C, its kinematic viscosity will drop from 8.592mm2/s to 7.171mm2/s, and the viscosity will decrease by 16%. Too low a viscosity may result in poor lubrication. At the same time, the increase of oil temperature will also lead to the reduction of oil pump flow under the same speed and pressure. Coupled with the heating of the engine block itself, three factors work together, which may lead to increased engine wear.

2.4 Impact on fuel consumption

Experiments have proved that the use of water-free cooling liquid has the effect of reducing fuel consumption of diesel engines [3], but in the field of household gasoline vehicles, especially in the field of high-end vehicles with complex thermal management systems, there is no experiment to prove its fuel saving effect.

Although the higher working temperature can improve the thermal efficiency to a certain extent, due to the higher temperature of the coolant, the radiator electronic fan will start working earlier, and the viscosity of the water-free cooling liquid is larger, the operation resistance of the pump is larger, and multiple factors are about each other, the fuel consumption will not decrease significantly, and may even rise.

2.5 Anti-corrosive effects

The liquid phase of anhydrous cooling has greater advantages in corrosion resistance than pure water and early glycol coolant, but there is no significant difference in corrosion resistance compared with the long-acting glycol coolant with organic acids. The current more advanced glycol coolant can also achieve a life of more than 100,000 kilometers, and even achieve lifelong maintenance free.

2.6 Influence on boiling temperature

The boiling point of the water-free cooling liquid can reach more than 190 ° C, which can realize the cooling system to work at low pressure and prevent the coolant from "boiling". But to a certain extent, "boiling" itself is a cooling system cooling capacity is insufficient fault state, the use of water-free cooling liquid, if similar failures occur, although the coolant will not boil, but the temperature of the engine block will still rise, serious may lead to oil failure, burning tile holding shaft, and even lead to the overall engine scrap.

2.7 Impact on engines with advanced thermal management systems

The early engine can only control the engine water temperature by opening and closing the thermostat and controlling the speed of the radiator fan, after the thermostat is designed, the working temperature of the coolant will not change greatly. Many vehicles now have relatively complex thermal management systems, such as some cars are equipped with electronic water pumps, some cars are equipped with electronic thermostat, and some cars are equipped with the function of closing the cylinder coolant circulation. For vehicles equipped with these advanced thermal management systems, the engine coolant can work at different temperatures, and when it is necessary to improve the thermal efficiency of the engine to reduce fuel consumption, the coolant operating temperature can be increased by increasing the opening temperature of the electronic thermostat. At this time, if the non-water-cooled liquid engine thermal management system is changed, the coolant water temperature will still be controlled near the calibration temperature, at this time there may be insufficient heat dissipation, and fuel consumption can not reach the optimal.

2.8 Impact on vehicles equipped with water-cooled air conditioners and water-cooled intercoolers

At present, the air conditioning condenser of most vehicles is an air-cooled condenser, and the turbocharged intercooler is also mostly air-cooled. However, the current vehicles of high-end brands such as BMW have gradually begun to be equipped with water-cooled air conditioning condensers and water-cooled supercharged intercoolers. The air conditioning refrigerant and pressurized air intake of these vehicles do not dissipate heat directly through blowing, but heat exchange with the coolant to achieve indirect cooling.

If you change the water-free cooling liquid, it may destroy the working temperature designed by the original factory, thus affecting the work of the air conditioning system, and may also make the intake air temperature rise.

3. Conclusion

Although the water-free cooling liquid has the advantage of high boiling point, the engine of the current domestic car on the market is matched with glycol coolant in the original design, and in the absence of special design and matching, the replacement of the water-free cooling liquid by itself has no obvious advantages, and may destroy the thermal balance of the original car design. In addition, the current water-free cooling liquid is expensive, complex to replace, no special requirements, should be carefully replaced and used.

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