Introduction

Don't you think that the term "liquid cooling" is suggestive of cars? In fact, liquid cooling has been an integral part of the conventional internal combustion engine for almost 100 years. This immediately begs the question: why is it the preferred method of cooling expensive car engines? Why is liquid cooling so great?

To find out, we have to compare it to air cooling. When comparing the effectiveness of these cooling methods, two of the most important properties must be taken into account: thermal conductivity and specific heat capacity.

Thermal conductivity is a physical quantity that shows how well a substance transfers heat. The thermal conductivity of water is almost 25 times greater than that of air. Obviously, this gives water cooling a huge advantage over air cooling, as it allows heat to be transferred from a hot engine to the radiator much faster.

Specific heat capacity is another physical quantity, which is defined as the amount of heat required to raise the temperature of one kilogram of a substance by one kelvin (degree Celsius). The specific heat capacity of water is almost four times that of air. This means that it takes four times as much energy to heat water as it does to heat air. Again, the ability of water to absorb much more heat energy without raising its own temperature is a huge advantage.

So, we have indisputable facts that liquid cooling is more efficient than air. However, this is not necessarily the best method for cooling PC components. Let's figure it out.

PC Liquid Cooling

Despite the very good qualities of water in terms of heat dissipation, there are several good reasons not to put water in a computer. The most important of these reasons is the electrical conductivity of the coolant.

If you accidentally spilled a glass of water on a gasoline engine while filling the radiator, then nothing terrible would happen; water would not damage the engine. But if you poured a glass of water on the motherboard of your computer, it would be very bad. Therefore, there is a certain risk associated with the use of water to cool computer components.

The next factor is the complexity of maintenance. Air-cooled systems are easier and cheaper to manufacture and repair than water-cooled systems, and the radiators require no maintenance other than dust removal. Water cooling systems are much more difficult to work with. They are more difficult to install and often require maintenance, albeit a minor one.

Thirdly, PC water cooling components cost much more than air cooling components. If a set of high-quality heatsinks and air-cooling fans for a processor, video card, and motherboard will most likely cost around $150, then the cost of a liquid cooling system for the same components can easily reach up to $500.

With so many drawbacks, water cooling systems, it would seem, should not be in demand. But in fact, they remove heat so well that their property justifies all the shortcomings.

On the market, you can find completely ready-to-install liquid cooling systems that are no longer a set of spare parts that enthusiasts had to deal with in the past. Ready-made systems are assembled, tested and quite reliable. In addition, water cooling is not as dangerous as it seems: of course, there is always a big risk when using liquids in a PC, but if you are careful, this risk is significantly reduced. In terms of maintenance, modern refrigerants need to be replaced quite infrequently, maybe once a year. In terms of price, any high-performance hardware is always more expensive than usual, whether it's a Ferrari in your garage or a water-cooling system for your computer. There is a price to pay for high performance.

Let's assume that you are attracted to this cooling method, or at least you would like to know how it works, what is involved with it, and what are its advantages.

General principles of water cooling

The purpose of any cooling system in a PC is to remove heat from the computer's components.

A traditional CPU air cooler transfers heat from the CPU to the heatsink. The fan actively pushes air through the heatsink fins, and as the air passes by, it picks up heat. The air from the computer case is removed by another fan or even several. As you can see, air makes many movements.

In water-cooled systems, water is used instead of air to remove heat. Water exits the tank through a tube, flowing where it is needed. The water cooling unit can either be a separate unit outside of the PC case, or it can be built into the case. In the diagram, the chiller unit is external.

Heat is transferred from the processor to the cooling head (water block), which is a hollow heatsink with coolant inlet and outlet. As water passes through the head, it takes heat with it. Heat transfer due to water is much more efficient than due to air.

The heated liquid is then pumped into the reservoir. From the tank, it flows into the heat exchanger, where it gives off heat to the radiator, and that to the surrounding air, usually with the help of a fan. After that, water enters the head again, and the cycle begins again.

Now that we have a good understanding of the basics of liquid PC cooling, let's talk about what systems are available on the market.

Choice of water cooling system

There are three main types of water cooling systems: internal, external and built-in. The main difference between them is where, in relation to the computer case, their main components are located: the heatsink/heat exchanger, the pump, and the reservoir.

As the name implies, the built-in cooling system is an integral part of the PC case, that is, it is built into the case and sold with it. Since the entire water cooling system is mounted in the case, this option is probably the easiest to handle, because there is more space inside the case and there are no bulky structures outside. The downside, of course, is that if you decide to upgrade to such a system, the old PC case will be useless.

If you love your PC case and don't want to part with it, then internal and external water cooling systems are probably more attractive. The components of the internal system are placed inside the PC case. Since most cases are not designed to accommodate such a cooling system, it becomes quite crowded inside. However, the installation of such systems will allow you to save your favorite case, as well as transfer it without any special obstacles.

The third option is an external water cooling system. It is also for those who wish to leave the old case of their PC. In this case, the heatsink, reservoir, and water pump are placed in a separate unit outside the computer case. Water is pumped through the tubes into the PC case, to the cooling head, and the heated liquid is pumped out of the case into the tank through the return tube. The advantage of an external system is that it can be used with any enclosure. It also allows for a larger radiator and may have better cooling capacity than the average built-in setup. The disadvantage is that a computer with an external cooling system is not as mobile as with internal or built-in cooling systems.

In our case, mobility is not a big deal, but we would like to keep our "native" PC case. In addition, we were attracted by the increased cooling efficiency of the external radiator. Therefore, for the review, we chose an external cooling system. Koolance has kindly provided us with a great sample, the EXOS-2 system.

External water cooling system Koolance EXOS-2.

EXOS-2 is a powerful external water cooling system with a cooling capacity of over 700W. This does not mean that the system consumes 700 watts - it consumes only a small fraction of that. This means that the system can efficiently handle 700W of heat output while maintaining a temperature of 55 degrees Celsius at 25 degrees ambient.

EXOS-2 comes with all necessary pipes and accessories, except for cooling heads (waterblocks). The user will have to buy suitable heads, depending on which PC components he wants to cool.

Cooling multiple components

One of the advantages of most liquid cooling systems is that they are expandable and can cool other components as well as the CPU. Even after passing through the CPU cooling head, the water is still able to cool, for example, the motherboard chipset and graphics card. This is basic, but you can add even more components if you wish, such as a hard drive. To do this, each component that will be cooled will need its own water block. Of course, you will have to do some planning to make sure that the coolant flows well.

Why is it beneficial to combine all three components - CPU, chipset and graphics card - with a good water cooling system?

Most users understand the need for CPU cooling. The CPU gets very hot inside the PC case, and the stable operation of the computer depends on keeping the CPU temperature low. The CPU is one of the most expensive parts of a computer, and the lower the temperature is maintained, the longer the CPU will last. Finally, processor cooling is especially important during overclocking.

CPU water block and assembly accessories.

The idea of ​​cooling the motherboard chipset (northbridge, to be more precise) may not be familiar to everyone. But keep in mind that a computer is only as stable as its chipset. In many cases, additional chipset cooling can contribute to system stability, especially when overclocked.

Chipset waterblock and assembly accessories.

The third component is very important for those who have a higher-end graphics card and use a PC for games. In many cases, the graphics processor in a video card generates more heat than the rest of the computer. Again, the better the cooling of the GPU, the longer it will last, the higher the stability and the more opportunities for overclocking.

Of course, for those users who do not intend to use their computer for games and have a low-power graphics card, water cooling will be overkill. But for today's powerful and very hot video cards, water cooling can be a profitable purchase.

We are going to install a cooling system on our Radeon X1900 XTX video card. Although this video card is not the newest and most powerful, it is still anywhere, and besides, it gets very hot. In the case of this model, Koolance offers not only a water block for the GPU / memory, but also a separate cooling head for the voltage regulator.

GPU waterblock and assembly accessories.

If air-cooling systems can keep the GPU temperature within acceptable limits, then we are not aware of similar systems that can handle the extremely high temperature of the voltage regulators on the X1900, which can easily reach 100 degrees Celsius under loads. I wonder how the waterblock for the voltage regulator will affect the X1900 graphics card.

Waterblock for video card voltage regulator and assembly accessories.

These are the main components that are cooled with water. As mentioned above, there are other components that can be cooled in this way. For example, Koolance offers a 1200W liquid-cooled PSU. All electronic components of the power supply are immersed in a non-conductive fluid that is pumped through its own external heatsink. This is a special example of alternative liquid cooling, but it does the job just fine.

Koolance: 1200W liquid-cooled power supply.

Now you can start installation.

Planning and installation

Unlike air-cooled systems, installing a liquid-cooled system requires some planning. Liquid cooling has several limitations that the user must take into account.

First, during installation, you should always remember about convenience. The water pipes must be free to pass inside the case and between the components. In addition, the cooling system must leave free space so that later work with it and components does not cause difficulties.

Secondly, the flow of fluid should not be restricted by anything. It should also be remembered that the coolant heats up as it passes through each waterblock. If we designed the system in such a way that water enters each subsequent water block in the following sequence: first to the processor, then to the chipset, to the video card, and finally to the video card voltage regulator, then water heated by all previous components of the system. Such a scenario is not ideal for the last component.

To somehow mitigate this problem, it would be nice to let the coolant through separate, parallel paths. If this is done correctly, the water flow will be less loaded, and the water blocks of each component will receive water that is not heated by other components.

The Koolance EXOS-2 kit we chose for this article is designed primarily to work with 3/8" tubing, and the CPU waterblock is designed with 3/8" compression connectors. However, Koolance's chipset and graphics card cooling heads are designed to work with smaller 1/4" connecting tubes. This forces the user to use a splitter that splits the 3/8" tube into two 1/4" tubes. This scheme works well when we split the flow into two parallel paths. One of these 1/4" tubes will cool the motherboard chipset, and the other - the video card. After the water has taken heat from these components, the two 1/4" tubes will reconnect to form one 3/8" tube, through which the heated water will flow from the PC case back into the heatsink for cooling.

The whole process is shown in the following diagram.

Planned configuration of the cooling system.

When planning the layout of your own water cooling system, we recommend that you draw a simple diagram. This will help install the system correctly. Having drawn a plan on paper, you can proceed to the actual assembly and installation.

To begin with, you can lay out all the details of the system on the table and estimate the required length of the tubes. Don't cut too short, leave a margin; then you can always cut off the excess.

After the preparatory work, you can proceed to the installation of water blocks. The Koolance cooling head for the CPU we are using requires a metal mounting bracket on the back of the motherboard behind the CPU. And what's good, this mounting bracket comes with a plastic spacer to prevent shorting to the motherboard. First, we took the motherboard out of the case and installed the mounting bracket.

Then you can remove the heat sink, which is attached to the north bridge of the motherboard. We used the Biostar 965PT motherboard, where the chipset is cooled by a passive heatsink attached with plastic clips.

Motherboard chipset without heatsink. Ready to install water block.

Once the chipset heatsink is removed, the chipset waterblock mounting hardware should be attached.

During installation, we noticed that the chipset water block mounting hardware, specifically the plastic spacer, was pressing against the resistor on the back of the motherboard. This must be carefully monitored during installation. Over-tightening the bolts can cause irreparable damage to the motherboard, so be careful and careful!

After installing the fastening elements for the processor and chipset cooling heads, you can return the motherboard to the PC case and think about connecting water blocks to the processor and chipset. Be sure to remove the old thermal paste from the processor and chipset before applying a new thin layer.

Processor with fasteners for a water block.

You may want to connect the water pipes to the waterblocks before you install them on the motherboard. But be careful: you can not calculate the pressure and force that, when the tubes are bent, will be applied to the fragile chipset and processor. The main thing is to leave a sufficient length of the tubes, because you can cut them to size later.

Now you can carefully install the waterblocks on the processor and chipset using the provided fasteners. Remember that you do not need to press them hard: just install them well on the processor and chipset. Using force can damage components.

After installing water blocks on the processor and chipset, you can switch your attention to the video card. We remove the existing radiator on it and replace it with a water block. In our case, we also removed the voltage regulator heatsink and installed a second water block on the card. After the water blocks are installed on the video card, you can connect the tubes. After that, the video card can be inserted into the PCI Express slot.

After installing all the water blocks, connect the remaining pipes. The last thing you need to connect the tube, which leads to an external water cooling unit. Make sure that the direction of water flow is correct: the coolant must enter the processor water block first.

The moment has come when you can pour water into the tank. Fill the reservoir only to the level specified in the manufacturer's instructions. As the tank fills, water will slowly flow into the tubes. Pay special attention to all fasteners and have a towel handy in case of unexpected fluid leakage. At the slightest sign of a leak, fix the problem immediately.

When all components are assembled together, you can fill in the coolant.

If you did everything carefully, and there were no leaks in the system, then you need to pump the coolant to remove air bubbles. In the case of the Koolance EXOS-2, this is achieved by shorting the pins on the ATX power supply to power the water pump but not power the motherboard.

Let the system work in this mode, and at this time you slowly and carefully tilt the computer to one side and the other so that air bubbles come out of the water blocks. When all the bubbles are out, you will most likely find that coolant needs to be added to the system. This is fine. Approximately 10 minutes after pouring, no air bubbles should be visible in the tubes. If you are convinced that there are no more air bubbles and the possibility of leakage is excluded, then you can start the system for real.

Test configuration and tests

All assembly and installation worries behind. It's time to see what benefits the water cooling system provides.

Hardware
CPU	Intel Core 2 Duo e4300, 1.8 GHz (overclocked to 2250 MHz), 2 MB L2 cache
Platform	Biostar T-Force 965PT (Socket 775), Intel 965 chipset, BIOS vP96CA103BS
RAM	Patriot Signature Line, 1x 1024MB PC2-6400 (CL5-5-5-16)
HDD	Western Digital WD1200JB, 120 GB, 7200 rpm, 8 MB cache, UltraATA/100
Net	Built-in 1 Gbps Ethernet adapter
video card	ATI X1900 XTX (PCIe), 512 MB GDDR3
Power Supply	Koolance 1200W
System Software and Drivers
OS	Microsoft Windows XP Professional 5.10.2600, Service Pack 2
DirectX Version	9.0c (4.09.0000.0904)
Graphics driver	ATI Catalyst 7.2

In our test configuration, we used the Core 2 Duo platform because the E4300 processor is very easy to overclock. Overclocking allowed us to see how high temperatures would rise, and how the standard air-cooling system and our new water-cooling system would handle it.

The technique is simple: overclock the E4300 with stock air cooling, then overclock it with water cooling and compare the results. As it turns out, the E4300 is capable of more. We increased the processor frequency from the declared 1800 MHz to 2250 MHz. At the same time, the E4300 easily handled the added 450 MHz without increasing the voltage or any other problems. However, the standard cooler didn't do the job, as under load the CPU temperature rose to an undesirable 62 degrees Celsius. Although the core could be overclocked further, further temperature rise could become dangerous, so we stopped, recorded the result and installed a water cooling system.

Before looking at CPU temperatures under load, let's take a look at system idle temperatures.

In idle mode, water cooling gives a decent reduction in processor temperature, by about 10 degrees. However, this is not such a great achievement, considering that the processor's own cooler is low-end, and a high-quality air cooler could be more efficient. However, it is worth remembering that water cooling cannot reduce the temperature so that it is lower than the ambient temperature, which in our case was about 22 degrees Celsius.

With the system under load - a ten-minute run of the Orthos stress test - the water-cooling setup really showed what it was capable of.

Now this is really interesting. The stock air cooler can't even keep the CPU below an undesirably high 60 degrees, and the water cooling system has dropped the temperature down to 49 degrees at the lowest fan speed. In addition to lowering the temperature, the water cooling system is much quieter than the stock CPU cooler.

At the maximum speed of the fans in the water cooling system, the temperature of the processor drops below 40 degrees! This is 24 degrees lower than with the stock cooler under load, and almost as much as the own cooler gives out when idle. The result is impressive, although at high fan speeds, the water cooling system makes more noise than we would like. However, the fan speed is adjustable on a 10-point scale, and it is unlikely that in everyday use you will need to set it to full power. Orthos stresses the processor more than other tests, and we were quite interested to see what the water cooling system is capable of.

In conclusion, pay attention to the results obtained for the video card. Usually X1900 XTX gets very hot, but we had one of the best air coolers at our disposal - Thermalright HR-03. Let's see what advantages water cooling has over this cooler after 10 minutes of Atitool's stress test in artifact testing mode.

The temperature maintained by the stock cooler is terrible: 89 degrees on the GPU and over 100 degrees on the voltage regulator! The Thermalright HR-03 cooler did an amazing job cooling the GPU down to 65 degrees, but the temperature of the voltage regulators is still too high - 97 degrees!

The water cooling system reduced the temperature of the GPU to 59 degrees. That's 30 degrees better than the stock cooler and only 6 degrees better than the HR-03, further highlighting its effectiveness.

A separate water block for the voltage regulator shows excellent results. The HR-03 has no means to cool the voltage stabilizer, and the waterblock lowered the temperature to 77 degrees, which is 25 degrees better than with the stock cooler. This is a very good result.

Conclusion

The results obtained when testing with a water cooling system are quite obvious: liquid cooling is much more effective than air cooling.

Water cooling is now available not only to a limited circle of professionals, but also to ordinary users. In addition, modern water cooling systems such as the EXOS-2 are very easy to install and operate on a plug and play basis, unlike older systems that required assembly. In addition, modern water cooling kits with illuminated and stylized cases look very nice.

If you are an enthusiast and have tried all air-cooled systems, then liquid cooling is the next logical step for you. Of course, there is a risk, and water-cooled equipment will cost more than air-cooled equipment, but the benefit is clear.

Editor's opinion

For a long time, I avoided water cooling, as I was afraid that it would be more trouble than good. But now I can say with confidence that my opinion has changed: water cooling systems are much easier to install than I thought, and the cooling results speak for themselves. I would also like to express my gratitude to Koolance for providing us with the EXOS-2 kit, which was a pleasure to work with.

The engine cooling system serves to maintain the normal thermal operation of engines by intensively removing heat from hot engine parts and transferring this heat to the environment.

The heat removed consists of a part of the heat released in the engine cylinders, which is not converted into work and is not carried away with the exhaust gases, and from the heat of the friction work that occurs during the movement of engine parts.

Most of the heat is removed to the environment by the cooling system, a smaller part - by the lubrication system and directly from the outer surfaces of the engine.

Forced heat removal is necessary because at high temperatures of gases in the engine cylinders (during the combustion process 1800–2400 °C, the average gas temperature for the operating cycle at full load is 600–1000 °C), natural heat transfer to the environment is insufficient.

Violation of proper heat dissipation causes deterioration of lubrication of rubbing surfaces, oil burnout and overheating of engine parts. The latter leads to a sharp drop in the strength of the material of the parts and even their burning (for example, exhaust valves). When the engine is severely overheated, the normal clearances between its parts are violated, which usually leads to increased wear, seizing, and even breakdown. Overheating of the engine is also harmful because it causes a decrease in the filling factor, and in gasoline engines, in addition, detonation combustion and self-ignition of the working mixture.

Excessive cooling of the engine is also undesirable, since it entails the condensation of fuel particles on the cylinder walls, deterioration of mixture formation and flammability of the working mixture, a decrease in its combustion rate and, as a result, a decrease in engine power and efficiency.

Classification of cooling systems

In automobile and tractor engines, depending on the working fluid, systems are used liquid and air cooling. The most widely used liquid cooling.

With liquid cooling, the liquid circulating in the engine cooling system receives heat from the cylinder walls and combustion chambers and then transfers this heat to the environment using a radiator.

According to the principle of heat removal to the environment, cooling systems can be closed and open (flowing).

Liquid cooling systems of autotractor engines have a closed cooling system, i.e. a constant amount of liquid circulates in the system. In a flow-through cooling system, the heated liquid, after passing through it, is released into the environment, and a new one is taken in to be fed into the engine. The use of such systems is limited to marine and stationary engines.

Air cooling systems are open. The cooling air after passing through the cooling system is discharged into the environment.

The classification of cooling systems is shown in fig. 3.1.

According to the method of circulating the liquid of the cooling system, there can be:

forced in which circulation is provided by a special pump located on the engine (or in the power plant), or pressure, under which the liquid is supplied to the power plant from the external environment;

thermosiphon, in which the circulation of the liquid occurs due to the difference in gravitational forces resulting from the different density of the liquid heated near the surfaces of engine parts and cooled in the cooler;

combined, in which the most heated parts (cylinder heads, pistons) are forced to cool, and cylinder blocks - according to the thermosyphon principle .

Rice. 3.1. Classification of cooling systems

Liquid cooling systems can be open or closed.

open systems- systems that communicate with the environment using a vapor tube.

Most automotive and tractor engines currently use closed systems cooling, i.e., systems separated from the environment by a steam-air valve installed in the radiator cap.

The pressure and, accordingly, the allowable temperature of the coolant (100–105 °С) in these systems is higher than in open systems (90–95 °С), as a result of which the difference between the temperatures of the liquid and the air sucked through the radiator and the heat transfer of the radiator increase. This allows you to reduce the size of the radiator and the power consumption for driving the fan and water pump. In closed systems, there is almost no evaporation of water through the steam outlet pipe and its boiling when the engine is running in high mountain conditions.

Liquid cooling system

On fig. 3.2 shows a diagram of a liquid cooling system with forced circulation of the coolant.

Cylinder Block Cooling Jacket 2 and block heads 3, the radiator and pipes are filled with coolant through the filler neck. The liquid washes the walls of the cylinders and combustion chambers of a running engine and, heating up, cools them. Centrifugal pump 1 pumps liquid into the cylinder block jacket, from which the heated liquid enters the block head jacket and then is forced out into the radiator through the upper pipe. The liquid cooled in the radiator returns to the pump through the lower pipe.

Rice. 3.2. Liquid cooling system diagram

Fluid circulation depending on the thermal state of the engine is changed using a thermostat 4. When the coolant temperature is below 70–75 °C, the main thermostat valve is closed. In this case, the liquid does not enter the radiator 5 , but circulates along a small circuit through a branch pipe 6, which contributes to the rapid heating of the engine to the optimum thermal regime. When the temperature-sensitive element of the thermostat is heated to 70-75 ° C, the main valve of the thermostat begins to open and let water into the radiator, where it is cooled. The thermostat opens completely at 83–90 °C. From this point on, water circulates through the radiator, i.e., large circuit. The temperature regime of the engine is also regulated with the help of rotary shutters, by changing the air flow created by the fan 7 and passing through the radiator.

In recent years, the most effective and rational way to automatically control the temperature regime of the engine is to change the performance of the fan itself.

Elements of the fluid system

Thermostat designed to provide automatic control of the coolant temperature during engine operation.

To quickly warm up the engine when it is started, a thermostat is installed in the outlet pipe of the cylinder head jacket. It maintains the desired temperature of the coolant by changing the intensity of its circulation through the radiator.

On fig. 3.3 shows a bellows-type thermostat. It consists of a body 2, corrugated cylinder (bellows), valve 1 and a stem connecting the bellows to the valve . The bellows is made of thin brass and is filled with a volatile liquid (eg ether or a mixture of ethyl alcohol and water). Windows located in the thermostat housing 3 depending on the temperature of the coolant, they can either remain open or be closed valves .

When the temperature of the coolant washing the bellows is below 70 ° C, the valve 1 closed and windows 3 open. As a result, the coolant does not enter the radiator, but circulates inside the engine jacket. When the temperature of the coolant rises above 70 ° C, the bellows, under the vapor pressure of the liquid evaporating in it, lengthens and begins to open the valve 1 and gradually cover the windows with valves 3. At a coolant temperature above 80-85 ° C, the valve 1 fully opens, the windows are completely closed, as a result of which all the coolant circulates through the radiator. Currently, this type of thermostats is used very rarely.

Rice. 3.3. Bellows thermostat

Now engines are equipped with thermostats in which the damper 1 opens with the expansion of a solid filler - ceresin (Fig. 3.4). This substance expands when the temperature rises and opens the damper 1 , ensuring the flow of coolant to the radiator.

Rice. 3.4. Solid fill thermostat

Radiator is a heat dissipating device designed to transfer the heat of the coolant to the surrounding air.

The radiators of automobile and tractor engines consist of upper and lower tanks connected to each other by a large number of thin tubes.

To enhance the transfer of heat from the coolant to the air, the fluid flow in the radiator is directed through a series of narrow tubes or channels blown by air. Radiators are made of materials that conduct and give off heat well (brass and aluminum).

Depending on the design of the cooling grille, radiators are divided into tubular, plate and honeycomb.

At present, the most widespread tubular radiators. The cooling grid of such radiators (Fig. 3.5a) consists of vertical tubes of oval or round cross section passing through a series of thin horizontal plates and soldered to the upper and lower radiator reservoirs. The presence of plates improves heat transfer and increases the rigidity of the radiator. Tubes of oval (flat) section are preferable, since with the same jet cross section, their cooling surface is larger than the cooling surface of round tubes; in addition, when water freezes in the radiator, flat tubes do not break, but only change the shape of the cross section.

Rice. 3.5. Radiators

V plate radiators the cooling grid (Fig. 3.5b) is designed so that the coolant circulates in space , formed by each pair of plates soldered together at the edges. The upper and lower ends of the plates are also soldered into the holes of the upper and lower radiator reservoirs. The air cooling the radiator is sucked by the fan through the passages between the soldered plates. To increase the cooling surface, the plates are usually made wavy. Lamellar radiators have a larger cooling surface than tubular ones, but due to a number of disadvantages (rapid contamination, a large number of soldered seams, the need for more thorough maintenance), they are used relatively rarely.

Cellular radiator refers to radiators with air tubes (Fig. 3.5c). In the honeycomb radiator grill, air passes through horizontal, circular tubes, which are washed from the outside with water or coolant. To make it possible to solder the ends of the tubes, their edges are flared so that in cross section they have the shape of a regular hexagon.

The advantage of honeycomb radiators is a larger cooling surface than in other types of radiators. Due to a number of disadvantages, most of which are the same as those of plate radiators, honeycomb radiators are extremely rare today.

A steam valve is installed in the radiator filler cap 2 and air valve 1 , which serve to maintain the pressure within the specified limits (Fig. 3.6).

Rice. 3.6. Radiator cap

Water pump circulates the coolant in the system. As a rule, small-sized single-stage low-pressure centrifugal pumps with a capacity of up to 13 m 3 /h, which create a pressure of 0.05–0.2 MPa, are installed in cooling systems. Such pumps are structurally simple, reliable and provide high performance (Fig. 3.7).

The casing and the impeller of the pumps are cast from magnesium and aluminum alloys, the impeller, in addition, from plastics. In water pumps of automobile engines, semi-closed impellers are usually used, that is, impellers with one disk.

The impellers of centrifugal water pumps are often mounted on the same shaft as the fan. In this case, the pump is installed in the upper front of the engine, it is driven from the crankshaft using a V-belt drive.

Rice. 3.7. Water pump

Belt drive can also be used when installing a centrifugal pump separately from the fan. In some engines of trucks and tractors, the water pump is driven from the crankshaft by a gear transmission. The shaft of a centrifugal water pump is usually mounted on rolling bearings and equipped with simple or self-adjusting seals to seal the working surface.

Fan in liquid cooling systems, they are installed to create an artificial air flow passing through the radiator. Fans of automobile and tractor engines are divided into two types: a) with blades stamped from sheet steel attached to the hub; b) with blades that are cast in one piece with the hub.

The number of fan blades varies between four and six. Increasing the number of blades above six is ​​impractical, since the performance of the fan increases very slightly. Fan blades can be made flat and convex.

= ([Temperature at the hot spot, °C] - [Temperature at the cold point, °C]) / [Dissipated power, W]

This means that if a thermal power of X W is supplied from a hot spot to a cold one, and the thermal resistance is Y cg / W, then the temperature difference will be X * Y cg.

Formula for calculating the cooling of a force element

For the case of calculating the heat removal of an electronic power element, the same can be formulated as follows:

[Power element crystal temperature, GC] = [Ambient temperature, °C] + [Dissipated power, W] *

where [ Total thermal resistance, Hz / W] = + [Thermal resistance between the case and the radiator, Hz / W] + (for the case with a radiator),

or [ Total thermal resistance, Hz / W] = [Thermal resistance between the crystal and the case, Hz / W] + [Thermal resistance between the case and the environment, Hz / W] (for case without heatsink).

As a result of the calculation, we must obtain such a crystal temperature that it is less than the maximum allowable value indicated in the reference book.

Where can I get the data for the calculation?

Thermal resistance between die and case for power elements is usually given in the reference book. And it is marked like this:

Do not be confused by the fact that the units of measurement K / W or K / W are written in the reference book. This means that this value is given in Kelvin per Watt, in Hz per W it will be exactly the same, that is, X K / W \u003d X Hz / W.

Usually, reference books give the maximum possible value of this value, taking into account the technological spread. We need it, since we must carry out the calculation for the worst case. For example, the maximum possible thermal resistance between the crystal and the case of the power field effect transistor SPW11N80C3 is 0.8 c/W,

Thermal resistance between case and heatsink depends on the case type. Typical maximum values ​​are shown in the table:

TO-3	1.56
TO-3P	1.00
TO-218	1.00
TO-218FP	3.20
TO-220	4.10
TO-225	10.00
TO-247	1.00
DPACK	8.33

Insulating pad. In our experience, a properly selected and installed insulating pad doubles the thermal resistance.

Thermal resistance between case/heatsink and environment. This thermal resistance, with an accuracy acceptable for most devices, is quite simple to calculate.

[Thermal resistance, Hz / W] = [120, (gC * sq. cm) / W] / [The area of ​​the radiator or the metal part of the element body, sq. cm].

This calculation is suitable for conditions where elements and radiators are installed without creating special conditions for natural (convection) or artificial airflow. The coefficient itself is chosen from our practical experience.

The specification of most heatsinks contains the thermal resistance between the heatsink and the environment. So in the calculation it is necessary to use this value. This value should be calculated only if tabular data on the radiator cannot be found. We often use used heatsinks to assemble debug samples, so this formula helps us a lot.

For the case when heat is removed through the contacts of the printed circuit board, the contact area can also be used in the calculation.

For the case when heat is removed through the leads of an electronic element (typically diodes and zener diodes of relatively low power), the area of ​​the leads is calculated based on the diameter and length of the lead.

[Lead area, sq. cm.] = Pi * ([ Length of the right output, see] * [Right outlet diameter, see] + [Length of the left output, see] * [Left outlet diameter, see])

An example of calculating heat removal from a zener diode without a radiator

Let the zener diode have two terminals with a diameter of 1 mm and a length of 1 cm. Let it dissipate 0.5 watts. Then:

The output area will be about 0.6 sq. cm.

The thermal resistance between the case (terminals) and the environment will be 120 / 0.6 = 200.

The thermal resistance between the crystal and the case (terminals) in this case can be neglected, since it is much less than 200.

Let us assume that the maximum temperature at which the device will be operated will be 40 °C. Then the temperature of the crystal = 40 + 200 * 0.5 = 140 °C, which is acceptable for most zener diodes.

Online calculation of heat sink - radiator

Please note that for plate radiators, the area of ​​\u200b\u200bboth sides of the plate must be calculated. For PCB tracks used for heat dissipation, only one side needs to be taken, since the other does not come into contact with the environment. For needle radiators, it is necessary to approximately estimate the area of ​​\u200b\u200bone needle and multiply this area by the number of needles.

Online calculation of heat dissipation without a radiator

Several elements on one radiator.

If several elements are installed on one heat sink, then the calculation looks like this. First, we calculate the temperature of the radiator using the formula:

[Radiator temperature, gc] = [Ambient temperature, °C] + [Thermal resistance between the radiator and the environment, Hz / W] * [Total power, W]

[Crystal temperature, c] = [Radiator temperature, gc] + ([Thermal resistance between the crystal and the body of the element, Hz / W] + [Thermal resistance between the body of the element and the radiator, Hz / W]) * [Power dissipated by the element, W]

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The photo shows a diagram of the Nissan Almera G15 engine cooling system

The cooling system of standard type engines cools its heated parts. In the systems of modern cars, it also performs other functions:

• cools the oil of the lubrication system;
• cools the air circulating in the turbocharging system;
• cools the exhaust gases in their recirculation system;
• cools the working fluid of an automatic transmission;
• heats the air circulating in ventilation, heating and air conditioning systems.

There are several ways to cool the engine, the application of which depends on the type of cooling system used. There are liquid, air and combined systems. Liquid - removes heat from the engine using the fluid flow, and air - air flow. In a combined system, both of these methods are combined.

More often than others, cars use a liquid cooling system. It evenly and effectively cools engine parts and works with less noise than air. Based on the popularity of the liquid system, it is on its example that the principle of operation of car engine cooling systems as a whole will be considered.

Engine cooling system diagram

The photo shows a diagram of the engine cooling system of a VAZ 2110 car with a carburetor and a VAZ 2111 with an injector (equipment for fuel injection).

For gasoline and diesel engines, similar designs of cooling systems are used. Their standard set of elements is as follows:

1. conventional, oil cooler and coolant cooler;
2. radiator fan;
3. centrifugal pump;
4. thermostat;
5. heater heat exchanger;
6. expansion tank;
7. engine cooling jacket;
8. control system.

Let's look at each of these elements individually:

1. Radiators.

1. In a conventional radiator, the heated liquid is cooled by a counterflow of air. To increase its efficiency, a special tubular device is used in the design.
2. The oil cooler is designed to reduce the oil temperature of the lubrication system.
3. To cool the exhaust gases, their recirculation systems use a third type of radiator. It allows you to cool the fuel-air mixture during its combustion, due to which less nitrogen oxides are formed. The additional radiator is equipped with a separate pump, which is also included in the cooling system.

2. . To increase the efficiency of the radiator, it uses a fan, which can have a different drive mechanism:

• hydraulic;
• mechanical (connected on a permanent basis to the crankshaft of the car engine);
• electric (powered by battery current).

The most common electric type of fans, which is controlled within a fairly wide range.

3. Centrifugal pump. With the help of a pump in the cooling system, the circulation of its liquid is ensured. The centrifugal pump can be equipped with various types of drive, for example, belt or gear. In turbocharged engines, in addition to the main one, an additional centrifugal pump can be used for more efficient cooling of the turbocharger and charge air. The engine control unit is used to control the operation of the pumps.

4. Thermostat. The thermostat regulates the amount of fluid entering the radiator. A thermostat is installed in the pipe leading to the radiator from the engine cooling jacket. Thanks to the thermostat, you can control the temperature of the cooling system.

In cars with a powerful engine, a slightly different type can be used - with electric heating. It is able to regulate the temperature regime of the system fluid in a two-stage range with three operating positions.

In the open state, such a thermostat is during maximum engine operation. At the same time, the temperature of the coolant passing through the radiator drops to 90 ° C, thereby reducing the likelihood of engine knocking. In the remaining two operating positions of the thermostat (open and half-open), the liquid temperature will be maintained at around 105 °C.

5. Heat exchanger of the heater. The air entering the heat exchanger is heated for its subsequent use in the car's heating system. To increase the efficiency of the heat exchanger, it is placed directly at the outlet of the coolant that has passed through the engine and has a high temperature.

6. Expansion tank. Due to changes in the temperature of the coolant, its volume also changes. To compensate for it, an expansion tank is built into the cooling system, which maintains the volume of liquid in the system at the same level.

7. Engine cooling jacket. In the design, such a jacket is a fluid channel passing through the engine head and cylinder block.

8. Control system. The following devices can be represented as control elements of the engine cooling system:

1. Temperature sensor of the circulating liquid. The temperature sensor converts the temperature value into the corresponding electrical signal value, which is fed to the control unit. In cases where the cooling system is used for exhaust gas cooling or other tasks, it can be equipped with another temperature sensor installed at the radiator outlet.
2. Control unit on an electronic basis. Receiving electrical signals from the temperature sensor, the control unit automatically responds and performs appropriate actions on other actuating elements of the system. Usually, the control unit has software that performs all the functions of automating the signal processing process and setting up the operation of the cooling system.
3. Also, the following devices and elements can be involved in the control system: a relay for cooling the motor after it stops, an auxiliary pump relay, a thermostatic heater, a radiator fan control unit.

The principle of operation of the engine cooling system in action

The well-established operation of cooling is due to the presence of a control system. In cars with modern engines, its actions are based on a mathematical model, which takes into account various indicators of the system parameters:

• lubricating oil temperature;
• the temperature of the fluid used to cool the engine;
• ambient temperature;
• other important indicators that affect the operation of the system.

The control system, evaluating various parameters and their influence on the operation of the system, compensates for their influence by regulating the operating conditions of the controlled elements.

With the help of a centrifugal pump, forced circulation of the coolant in the system is carried out. Passing through the cooling jacket, the liquid heats up, and once it enters the radiator, it cools down. By heating the liquid, the engine parts themselves cool down. In the cooling jacket, the liquid can circulate both in the longitudinal (along the line of cylinders) and in the transverse direction (from one collector to another).

The circle of its circulation depends on the temperature of the coolant. During the engine start, he and the coolant are cold, and in order to speed up its heating, the liquid is directed to a small circle of circulation, bypassing the radiator. In the future, when the engine is heated, the thermostat heats up and changes its operating position to half-open. As a result, the coolant begins to flow through the radiator.

If the counter air flow of the radiator is not enough to lower the temperature of the liquid to the required value, the fan turns on, generating additional air flow. The cooled liquid enters the cooling jacket again and the cycle repeats.

If the car uses a turbocharger, then it can be equipped with a dual-circuit cooling system. Its first circuit cools the engine itself, and the second - the charge air flow.

Watch an informative video about the principle of operation of the engine cooling system: