At present, many diesel generator sets on the market are made of aluminum water tanks. We all know that the thermal conductivity of aluminum water tanks is inferior to that of copper water tanks, so which one has the longest service life? Will the low melting point of aluminum affect the service life? This article will bring you an analysis. Of course, the water tank of the generator set is naturally inseparable from the help of many systems and other components. I will also explain them one by one.
The cooling water tank is also called a radiator and is made of two materials: copper water tank and aluminum water tank. According to the classification of radiator structure, there are two types of engine cooling system radiators: tube-band type and plate-fin type. Common radiators on the market include copper tube strips, aluminum tube strips and aluminum plate fins.
At present, many generators on the market are matched with aluminum radiators. We all know that aluminum radiators are not as thermally conductive as copper. So which one is longer in service life? Does the low melting point of aluminum affect the service life? The melting point of copper is 1084.4°C, and that of aluminum is 660.4°C. However, because the diesel generator contains overheating protection devices, it will not reach this temperature at all. On the contrary, high temperature water determines the radiator life. The water in our daily life is not pure water. It contains various ions, especially the concentration of chloride ions. When copper comes into contact with active ions such as Cl- and SO42- in the water, it will locally produce the active ions containing these active ions. The reaction product and water generate acid. The SO2, CO2, and H2S in the air dissolved in water will also reduce the local PH value. Intrusion into copper will accelerate the corrosion of copper and cause pitting corrosion in the copper radiator and copper hot water pipe.
The aluminum radiator cannot avoid the erosion of water, and Cl- will destroy the protective film of aluminum. Cl- penetrates into the protective film through the pores or defects on the aluminum surface, so that the protective film on the aluminum surface is colloidal and dispersed. The Al2O3 protective film undergoes hydration and becomes a hydrated oxide, which reduces the protective effect. Moreover, the Cu2+ generated after the copper parts are corroded will accelerate the pitting corrosion of aluminum. In addition, SO2 in the air is adsorbed by the water film on the aluminum surface, dissolving to generate H2SO3 (sulfurous acid) and reacting with oxygen to generate H2SO4 to corrode the aluminum surface. When Cl- with strong diffusion and penetrating power destroys the aluminum protective film, SO2- contacts with the aluminum matrix again, and corrosion occurs. This cycle increases the corrosion of aluminum. As the corrosion potential sequence of aluminum is much higher than that of copper, under the action of electrolytes such as water, when aluminum contacts these metals, a galvanic couple is formed. Aluminum is the anode. Galvanic corrosion will aggravate the corrosion of aluminum more quickly. Therefore, the life of the aluminum radiator is still not as long as that of the copper radiator.
Advantages of copper and aluminum water tanks:
The copper pipe has a water tank, which conducts heat quickly and has good heat dissipation performance. Antifreeze liquid can be directly replaced with aluminum water tanks. The overall price is cheaper than copper water tanks. It is suitable for large-area radiators. Aluminum plate-fin water tanks have good reliability and durability.
Copper and aluminum water tank price comparison:
Starting from raw materials, copper is more expensive than aluminum, so copper water tanks must be more expensive than aluminum water tanks.
Aluminum water tank weight comparison:
The radiator is an important part of the diesel engine cooling system. Reducing the weight of the radiator can reduce the total mass of the engine cooling system unit. Aluminum is much lighter than copper.
Comparison of durability and reliability of copper and aluminum water tanks: Copper has better durability than aluminum because its oxide layer is denser than aluminum and its corrosion resistance is higher than aluminum. In a slightly corrosive environment (such as natural water, weak acid and weak alkali), aluminum will continue to be corroded until the rust penetrates. The oxide layer of copper is more corrosion-resistant and durable.
The corrosion resistance of copper water tanks is relatively balanced. Strictly speaking, they are relatively afraid of acids but not alkali, while aluminum water tanks are quite sensitive to alkaline corrosion. Usually the PH value of the engine antifreeze we use is greater than 7, which means it is alkaline and relies on the anti-corrosion agent inside to protect aluminum products.
Comparison of thermal conductivity of copper and aluminum water tanks:
Thermal conductivity: aluminum 237, copper 401. For the same water temperature and air temperature difference, area and thickness of the water tank wall, the heat dissipation rate of copper is 401/237=1.7 times that of aluminum. Therefore, copper water tanks have advantages over aluminum water tanks in terms of heat dissipation efficiency.
When it comes to radiators, it is natural that the cooling system cannot be separated. Let’s talk about the cooling system.
Basic components of the cooling system (degassing cooling system)
The function and principle of cooling system
Timely dissipate the heat transferred to the coolant during the engine combustion process to prevent engine parts from being damaged due to overheating.
Under the action of the water pump, the coolant with a higher temperature (generally higher than 83°C) flows from the engine water outlet through the radiator through the thermostat;
- If the water temperature is lower than 83°C, the thermostat will close the external circulation to ensure that the engine water temperature is not too low;
Under the action of the fan, cool air blows through the radiator, taking away the heat of the coolant and reducing the coolant temperature;
The water pump sucks the cooled coolant back into the engine to cool the engine cylinder liner and other heat dissipation components.
Then there are the requirements for cooling system installation
Cooling system installation requirements
- The cooling system must ensure that the engine water outlet temperature does not exceed the limit value in the engine parameter table when the unit is operating at the highest ambient temperature;
- The cooling system must ensure that the engine water outlet temperature is not lower than the limit value in the engine parameter table when the unit is operating at the lowest ambient temperature;
- At rated water pump flow, the resistance of the cooling system (including radiator and pipes) must be lower than the limit value in the engine parameter table;
Water tank pressure cap:
- The type and opening pressure of the water tank pressure cap must meet the specified values in the engine parameter table;