Strictly speaking, the term "liquid cooling" is not entirely correct, since the liquid in the cooling system is just an intermediate heat carrier that penetrates into the thickness of the cylinder block walls. The role of the diverting agent in the system is played by the air blowing over the radiator, therefore the cooling modern car it would be more correct to call it hybrid.

Liquid cooling system device

The liquid engine cooling system consists of several elements. The most difficult one is called "cooling jacket". This is a branched network of channels in the thickness of the cylinder block and. In addition to the jacket, the system includes a radiator for the cooling system, an expansion tank, a water pump, a thermostat, metal and rubber connecting pipes, sensors and control devices.

Propylene Glycol is a coolant (antifreeze) base and veterinarian-approved dietary supplement for dogs

The system is based on the principle of forced circulation, which is provided by a water pump. Due to the constant outflow of the heated fluid, the engine is cooled evenly. This explains the use of the system in the vast majority of modern cars.

Having passed through the channels in the walls of the block, the liquid heats up and enters the radiator, where it is cooled by the air flow. When the car is moving, natural airflow is sufficient for cooling, and when the car is at a standstill, airflow occurs due to an electric fan, which is activated by a signal from a temperature sensor.

Details on the key elements of water cooling

Cooling radiator

The radiator is a panel made of small diameter metal tubes covered with aluminum or copper "plumage" to increase the heat transfer area. In essence, the plumage is a repeatedly folded ribbon of metal. The total total area of ​​the tape is large enough, which means that it can release a lot of heat into the atmosphere per unit time.

The most vulnerable element of the engine design is the turbocharger (turbine), which operates at extremely high speeds. When overheated, destruction of the impeller and shaft bearings is almost inevitable.

Thus, the heated liquid inside the radiator circulates at once through all the numerous thin tubes and is cooled quite intensively. A safety valve is provided in the radiator filler cap that removes vapors and excess liquid that expands when heated.

Depending on the operating mode of the internal combustion engine, the cycle of movement of the coolant in the system may vary. The volume of fluid circulating in each circle directly depends on the degree to which the main and additional thermostat valves are open. This circuit provides automatic maintenance of the optimum temperature regime for the engine.

Advantages and Disadvantages of a Liquid Cooling System

The main advantage of liquid cooling is that the engine is cooled more evenly than if the unit is blown with an air stream. This is due to the higher heat capacity of the coolant compared to air.

The liquid cooling system can significantly reduce the noise from the engine running due to the thicker block walls.

The inertia of the system does not allow the engine to cool down quickly after shutdown. Preheated vehicle fluid and for preheating the combustible mixture.

Along with this, the liquid cooling system has several disadvantages.

The main disadvantage is the complexity of the system and the fact that it operates under pressure after the fluid has warmed up. A pressurized fluid places high demands on the tightness of all joints. The situation is complicated by the fact that the operation of the system implies a constant repetition of the heating-cooling cycle. It is harmful to joints and rubber pipes. When heated, the rubber expands and then contracts when it cools, causing leaks.

In addition, the complexity and a large number of elements in itself serve as a potential cause of "man-made disasters", accompanied by "boiling" of the engine in the event of failure of one of the key parts, for example, the thermostat.

Many motorists know why a car needs a cooling system and a fluid that circulates through it. But not everyone knows how the process of the flow of antifreeze through the pipes in the system takes place. If you are interested, then we propose to find out what the coolant circulation scheme looks like and how the whole process takes place.

The cooling system is needed to cool the parts of the motor that become hot during operation. This is the simplest answer. But we will take a deeper look and first find out what functions the cooling system (hereinafter referred to as CO) performs, except for the most important:

• heats the air flow in heating and ventilation systems;
• heats the oil in the lubrication system;
• cools waste gases;
• cools transmission fluid(in the case of automatic transmission).

The circulation of coolant (coolant) is necessary for any car, and if there are malfunctions in the CO, this will affect the operation of the car as a whole. Depending on the type of cooling, several types of systems can be distinguished:

• closed CO (liquid);
• open CO (air);
• combined.

In liquid operation, heat from hot engine parts is removed by means of a coolant flow. In an open CO, the air flow performs the cooling function, and in a combined CO, the first two types of systems are combined.

But today we are interested in exactly how the refrigerant circulates, so we will talk about it.

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How does the coolant circulate?

The systems themselves in gasoline and diesel cars are similar, there are no fundamental differences in their design and operation. They include many components and controls are used to regulate them. To understand how antifreeze circulates, consider the main components of CO:

The main components of CO
Radiator	It is necessary for cooling the hot coolant with an air stream.
Oil radiator	Cools the engine oil.
Heater heat exchanger	Serves to heat the air flow that passes through this element. In order for the component to function more efficiently, it is installed at the place where the hot antifreeze exits from the motor.
Expansion tank for liquid	Through it, the system is filled with a consumable, and its purpose is to compensate for the change in coolant volume from the temperature in CO.
Centrifugal pump or pump	With its help, the direct process of circulation of liquid through CO is carried out. Depending on the design of the engine, an additional pump can be installed on it.
Thermostat	Provides the optimum CO temperature by regulating the coolant flow through the radiator.
Coolant temperature sensor	If it increases above the norm, it signals the driver about this using the electronic control unit.

The direct functioning of the CO is provided by the motor control system. In modern motors, the principle of operation is based on a mathematical model that takes into account many parameters and determines the normal conditions for the activation and operation of all components.

It is clear that "Tosol" cannot pass through the CO by itself, therefore its flow is provided by a centrifugal pump. The coolant is circulated through the "cooling jacket". As a result, the motor vehicle is cooled, and "Tosol" heats up. The very course of movement of the coolant in the unit can occur either from the first cylinder to the last, or from the exhaust manifold to the intake.

Let's consider the coolant circuit process in more detail:

During the operation of the motor, approximately one temperature must always be maintained, which determines its functioning. Conventionally, it is 90 degrees. This temperature allows the engine to reach a good speed and provides an acceptable gas mileage. That is why the refrigerant for CO is so complex and divided into several circles so that the motor can sooner enter this operating mode.

Circulation scheme

We invite you to see the refrigerant flow diagram with your own eyes. Large and small circles are presented.

• a) small circle circle;
• b) a large circle.

1. cooling radiator;
2. refrigerant flow tube;
3. expansion tank;
4. thermostat;
5. centrifugal pump;
6. engine block cooling device;
7. block head cooling device;
8. radiator heater with fan;
9. radiator tap;
10. hole for draining antifreeze from the block;
11. a hole for draining the refrigerant directly from the radiator;
12. fan.

Video from Ramil Abdullin "Engine cooling system"

This video describes in detail the process of cooling the engine with antifreeze, and also discusses the CO device.

Was this material useful to you? Maybe you have something to add? Tell us about it!

Let us recall a little more about this cooling system.

V liquid cooling system special coolants are used - antifreezes of various brands with a thickening temperature of 40 ° C and below. Antifreezes contain anti-corrosion and anti-foaming additives that prevent the formation of scale. They are highly poisonous and must be handled with care. Compared to water, antifreezes have a lower heat capacity and therefore remove heat from the cylinder walls of the engine less intensively.

So, when cooled with antifreeze, the temperature of the cylinder walls is 15 ... 20 ° C higher than when cooled with water. This speeds up engine warm-up and reduces cylinder wear, but may overheat the engine in summer.

The optimal temperature regime of the engine with a liquid cooling system is considered to be one at which the temperature of the coolant in the engine is 80 ... 100 ° C at all engine operating modes.

Used in car engines closed(sealed) liquid cooling system forced circulation coolant.

The internal cavity of a closed cooling system does not have a constant connection with the environment, and communication is carried out through special valves (at a certain pressure or vacuum) located in the plugs of the radiator or expansion tank of the system. The coolant in such a system boils at 110 ... 120 ° C. Forced circulation of coolant in the system is provided by a liquid pump.

Engine cooling system consists from:

• cooling jacket for the head and cylinder block;
• radiator;
• pump;
• thermostat;
• fan;
• expansion tank;
• connecting pipelines and drain taps.

In addition, the cooling system includes a heater for the car's interior.

How the cooling system works

I propose to first consider the schematic diagram of the cooling system.

1 - heater; 2 - engine; 3 - thermostat; 4 - pump; 5 - radiator; 6 - cork; 7 - fan; 8 - expansion tank;
A - a small circle of circulation (the thermostat is closed);
A + B - a large circle of circulation (the thermostat is open)

The circulation of the liquid in the cooling system is carried out in two circles:

1. Small circle- the liquid circulates when starting a cold engine, providing it quick warm-up.

2.Large circle- movement circulates when the engine is warm.

Simply put, the small circle is the circulation of the coolant WITHOUT the radiator, and the large circle is the circulation of the coolant THROUGH the radiator.

The design of the cooling system differs in its design depending on the car model, however, the principle of operation is the same.

The principle of operation of this system can be seen in the following videos:

I propose to disassemble the system device according to the sequence of work. So, the beginning of the operation of the cooling system occurs when the heart of this system - the liquid pump - starts up.

1. Liquid pump (water pump)

The liquid pump provides forced circulation of liquid in the engine cooling system. Vane pumps of the centrifugal type are used on car engines.

Look for our liquid pump or water pump on the front of the engine (the front is the one that is closer to the radiator and where the belt / chain is located).

The liquid pump is connected by a belt to the crankshaft and generator. Therefore, to find our pump, it is enough to find the crankshaft and find the generator. We'll talk about the generator later, but for now I'll just show you what to look for. The generator looks like a cylinder attached to the engine body:

1 - generator; 2 - liquid pump; 3 - crankshaft

So, we figured out the location. Now let's take a look at its structure. Recall that the structure of the entire system and its parts is different, but the principle of operation of this system is the same.

1 - pump cover;2 - The persistent sealing ring of the stuffing box.
3 - an epiploon; 4 - Pump shaft bearing.
5 - the hub of the fan pulley;6 - Locking screw.
7 - pump roller;8 - pump casing;9 - Pump impeller.
10 - Suction branch pipe.

The work of the pump is as follows: the pump is driven from the crankshaft through a belt. The belt turns the pump pulley, rotating the pump pulley hub (5). That, in turn, drives the pump shaft (7) into rotation, at the end of which there is an impeller (9). The coolant enters the pump casing (8) through the inlet (10), and the impeller moves it into the cooling jacket (through a window in the casing, as seen in the figure, the direction of movement from the pump is shown by an arrow).

Thus, the pump is driven by the crankshaft, the liquid enters it through the inlet pipe and goes into the cooling jacket.

The operation of the liquid pump can be seen in this video (1:48):

Let's now see, where does the liquid come from to the pump? And the liquid enters through a very important part - the thermostat. It is the thermostat that is responsible for the temperature regime.

2. Thermostat

The thermostat automatically adjusts the water temperature to speed up engine warm-up after starting. It is the operation of the thermostat that determines which circle (large or small) the coolant will go.

This unit looks like this in reality:

How the thermostat works very simple: the thermostat has a sensitive element, inside of which there is a solid filler. At a certain temperature, it begins to melt and opens the main valve, and the additional valve, on the contrary, closes.

Thermostat device:

1, 6, 11 - branch pipes; 2, 8 - valves; 3, 7 - springs; 4 - balloon; 5 - diaphragm; 9 - stock; 10 - filler

The operation of the thermostat is simple, you can see it here:

The thermostat has two inlets 1 and 11, outlet 6, two valves (main 8, additional 2) and a sensitive element. The thermostat is installed in front of the inlet to the coolant pump and is connected to it through branch pipe 6.

Compound:

Acrossbranch pipe 1 connects Withengine cooling jacket,

Across branch pipe 11- with bottom diverting radiator reservoir.

The sensing element of the thermostat consists of a balloon 4, a rubber diaphragm 5 and a stem 9. Inside the balloon, between its wall and the rubber diaphragm, there is a solid filler 10 (fine crystalline wax), which has a high coefficient of volumetric expansion.

The main valve 8 of the thermostat with a spring 7 begins to open when the coolant temperature is more than 80 ° C. At temperatures less than 80 ° C, the main valve closes the liquid outlet from the radiator, and it enters the pump from the engine, passing through the open additional valve 2 of the thermostat with a spring 3.

When the temperature of the coolant rises above 80 ° C, a solid filler melts in the sensitive element, and its volume increases. As a result, the rod 9 comes out of the cylinder 4, and the cylinder moves upward. At the same time, additional valve 2 begins to close and, at a temperature of more than 94 ° C, blocks the passage of the coolant from the engine to the pump. In this case, the main valve 8 opens completely and the coolant circulates through the radiator.

The operation of the valve is clearly and visually shown in the figure below:

A - small circle, the main valve is closed, the bypass valve is closed. B - a large circle, the main valve is open, the bypass valve is closed.

1 - Inlet pipe (from the radiator); 2 - Main valve;
3 - Thermostat housing; 4 - Bypass valve.
5 - Branch pipe of the bypass hose.
6 - Branch pipe for supplying coolant to the pump.
7 - Thermostat cover; 8 - Piston.

So, we have dealt with the small circle. Disassembled the device of the pump and thermostat, connected to each other. Now let's move on to the large circle and the key element of the large circle - the radiator.

3. Radiator (radiator / cooler)

Radiator provides heat removal from the coolant to the environment. On the passenger cars tubular-plate radiators are used.

So, there are 2 types of radiators: collapsible and non-collapsible.

Below is their description:

I want to say again about the expansion tank (expansion Tank)

A fan is installed next to the radiator or on it. Let's now move on to the design of this very fan.

4. Fan (fan)

The fan increases the speed and amount of air passing through the radiator. Four- and six-blade fans are installed on car engines.

If a mechanical fan is used,

The fan includes six or four blades (3) riveted to a crosspiece (2). The latter is screwed to the pulley of the liquid pump (1), which is driven by the crankshaft using a belt drive (5).

As we said earlier, the generator (4) is also engaged.

If an electric fan is used,

then the fan consists of an electric motor 6 and a fan 5. The fan is four-bladed, mounted on the shaft of the electric motor. The blades on the fan hub are located unevenly and at an angle to the plane of its rotation. This increases the fan flow and reduces the fan noise. For more efficient operation, the electric fan is located in the casing 7, which is attached to the radiator. The electric fan is attached to the casing with three rubber bushings. The electric fan is switched on and off automatically by sensor 3, depending on the temperature of the coolant.

So let's summarize. Let's not be unfounded and summarize by some picture. You should not focus on a specific device, but you need to understand the principle of operation, because it is the same in all systems, no matter how different their device is.

When the engine is started, the crankshaft begins to rotate. Through the belt drive (let me remind you that the generator is also located on it) rotation is transmitted to the pulley of the liquid pump (13). It drives the shaft with the impeller in rotation inside the housing of the liquid pump (16). The coolant flows into the engine cooling jacket (7). Then, through the outlet (4), the coolant returns to the liquid pump through the thermostat (18). At this time, the bypass valve is open in the thermostat, but the main one is closed. Therefore, the liquid circulates through the engine jacket without the involvement of the radiator (9). This allows the engine to warm up quickly. After the coolant heats up, the thermostat main valve opens and the bypass valve closes. Now the liquid cannot flow through the thermostat bypass pipe (3) and is forced to flow through the inlet pipe (5) into the radiator (9). There, the liquid is cooled and flows back to the liquid pump (16) through the thermostat (18).

It is worth noting that some of the coolant enters the heater from the engine cooling jacket through port 2 and returns from the heater through port 1. But we will talk about this in the next chapter.

Hopefully, the system will now become clear to you. After reading this article, I hope it will be possible to navigate in another cooling system, having understood the principle of operation of this one.

I also suggest that you familiarize yourself with the following article:

Since we have touched on the heating system, my next article will be about this system.

Cooling system

The cooling system is designed to maintain normal thermal conditions of the engine.

When the engine is running, the temperature in the engine cylinders periodically rises above 2000 degrees, and the average temperature is 800–900 ° C!

If you do not remove heat from the engine, then in a few tens of seconds after starting it will no longer be cold, but hopelessly hot. The next time you can start your cold engine only after a major overhaul.

The cooling system is necessary to remove heat from the mechanisms and engine parts, but this is only half of its purpose, however, more than half.

It is also important to warm up the cold engine faster to ensure normal operation. And this is the second part of the cooling system.

As a rule, cars use a closed-type liquid cooling system with forced circulation of liquid and an expansion tank (Fig. 29).

The cooling system consists of:

cooling jacket of the block and cylinder head,

centrifugal pump,

thermostat,

radiator with expansion tank,

fan,

connecting pipes and hoses.

In fig. 29 you can easily distinguish between the two circles of coolant circulation.

Rice. 29. Scheme of the engine cooling system: 1 - radiator; 2 - branch pipe for circulation of coolant; 3 - expansion tank; 4 - thermostat; 5 - water pump; 6 - cooling jacket of the cylinder block; 7 - cooling jacket of the block head; 8 - heater radiator with electric fan; 9 - heater radiator tap; 10 – a plug for draining the coolant from the block; 11 - plug for draining the coolant from the radiator; 12 - fan

A small circle of circulation (red arrows) serves to warm up a cold engine as soon as possible. And when the blue ones join the red arrows, then the already heated liquid begins to circulate in a large circle, cooling in the radiator. This process is controlled by an automatic device - thermostat.

To monitor the operation of the cooling system, there is a coolant temperature gauge on the instrument panel (see Fig. 67). The normal temperature of the coolant when the engine is running should be within 80–90 ° C.

Engine cooling jacket consists of many channels in the block and the cylinder head through which the coolant circulates.

Centrifugal pump forces fluid to move through the engine cooling jacket and the entire system. The pump is driven by a belt drive from the engine crankshaft pulley. The tension of the belt is adjusted by the deflection of the generator housing (see Fig. 63 a) or the tension roller of the drive camshaft engine (see Fig. 11 b).

Thermostat designed to maintain constant optimal thermal conditions of the engine. When starting a cold engine, the thermostat is closed, and all the liquid circulates only in a small circle (Fig. 29 a) for its early warming up. When the temperature in the cooling system rises above 80–85 ° C, the thermostat automatically opens and part of the liquid enters the radiator for cooling. At high temperatures, the thermostat opens completely, and now all the hot liquid is directed along a large circle for its active cooling.

Radiator serves to cool the fluid passing through it due to the air flow that is created when the car is moving or with the help of a fan. The radiator contains many tubes and baffles that provide a large cooling surface area.

Expansion tank It is necessary to compensate for changes in the volume and pressure of the coolant when it is heated and cooled.

Fan is designed to forcibly increase the air flow passing through the radiator of a moving car, as well as to create an air flow when the car is standing still with the engine running.

Two types of fans are used: a permanently on, belt-driven crankshaft pulley and an electric fan that turns on automatically when the coolant temperature reaches approximately 100 ° C.

Connections and hoses serve to connect the cooling jacket to the thermostat, pump, radiator and expansion tank.

The engine cooling system also includes interior heater. Hot coolant flows through heater radiator and heats the air supplied to the vehicle interior.

The air temperature in the passenger compartment is regulated by a special crane, with which the driver increases or decreases the flow of fluid passing through the heater radiator.

The main malfunctions of the cooling system

Leakage of coolant may result from damage to the radiator, hoses, gaskets and oil seals.

To eliminate the malfunction, it is necessary to tighten the clamps for fastening hoses and pipes, and replace the damaged parts with new ones. In case of damage to the radiator pipes, you can try to patch holes and cracks, but, as a rule, everything ends up replacing the radiator.

Overheating of the engine happens for a reason insufficient level coolant, poor fan belt tension, clogged radiator pipes, and also if the thermostat is malfunctioning.

To eliminate engine overheating, restore the fluid level in the cooling system, adjust the fan belt tension, flush the radiator, and replace the thermostat.

Often, overheating of the engine also occurs with serviceable elements of the cooling system, when the machine is moving at low speed and high loads on the engine. This happens when driving in difficult road conditions, such as country roads and boring city traffic jams. In these cases, you should think about the engine of your car, and about yourself too, arranging periodic, at least short-term "breaks".

Be careful while driving and do not allow emergency operation of the engine! Remember that even a single overheating of the engine violates the metal structure, while the lifespan of the "heart" of the car is significantly reduced.

Cooling system operation

When operating the vehicle, you should periodically look under the hood. A timely noticed malfunction in the cooling system will allow you to avoid major engine overhauls.

If coolant level in the expansion tank if the liquid has dropped or is completely absent, then first you need to top it up, and then you should figure out (on your own or with the help of a specialist) where it went.

During engine operation, the liquid is heated to a temperature close to the boiling point. This means that the water in the coolant will evaporate little by little.

If after six months of daily operation of the car, the level in the tank has dropped slightly, then this is normal. But if yesterday there was a full tank, and today it is only on the bottom, then you need to look for the place of the coolant leak.

Fluid leakage from the system can be easily identified by dark spots on the asphalt or snow after more or less prolonged parking. Opening the hood, you can easily find the leak by comparing the wet marks on the asphalt with the location of the cooling system elements under the hood.

The fluid level in the reservoir must be checked at least once a week. If the level has dropped significantly, then it is necessary to determine and eliminate the cause of its decline. In other words, the cooling system must be put in order, otherwise the engine may become seriously "ill" and require "hospitalization".

Almost all domestic cars as a coolant, a special low-freezing liquid is used with the name Tosol A-40. Number 40 shows the negative temperature at which the liquid begins to freeze (crystallize). In the conditions of the Far North, Antifreeze A-65, and, accordingly, it begins to freeze at a temperature of minus 65 ° C.

Antifreeze is a mixture of water with ethylene glycol and additives. This solution combines a lot of advantages. Firstly, it begins to freeze only after the driver himself has frozen (joke), and secondly, Tosol has anti-corrosion, anti-foaming properties and practically does not form deposits in the form of ordinary scale, since it contains pure distilled water ... So Only distilled water can be added to the cooling system.

When operating a car, it is necessary control not only the tension, but also the condition of the water pump drive belt, as its break on the road is always unpleasant. It is recommended to have a spare belt in the travel kit. If not yourself, then some kind people will help you change it.

Coolant can boil and damage the engine if it fails. fan motor sensor. If the electric fan has not received a command to turn on, then the liquid continues to heat up, approaching the boiling point, without cooling aid.

But the driver has a device with an arrow and a red sector in front of his eyes! Moreover, there is almost always a slight additional noise when the fan is turned on. There would be a desire to control, but there will always be ways.

If on the way (and more often in a "traffic jam") you notice that the coolant temperature is approaching a critical one, and the fan is working, then in this case there is a way out. It is necessary to include in the operation of the cooling system an additional radiator - a radiator for the interior heater. Fully open the heater tap, turn on the heater fan at all revolutions, lower the door windows and sweat to the house or to the nearest car service. But at the same time, continue to closely follow the arrow of the engine temperature gauge. If it does go into the red zone, stop immediately, open the hood and "cool down".

Can cause trouble over time thermostat, if he stops letting fluid through a large circle of circulation. Determining if a thermostat is working is not difficult. The radiator should not heat up (determined by hand) until the arrow of the coolant temperature gauge reaches the middle position (the thermostat is closed). Later, hot liquid will begin to flow into the radiator, quickly heating it, which indicates the timely opening of the thermostat valve. If the radiator continues to be cold, then there are two ways. Knock on the thermostat body, maybe it will open after all, or immediately, morally and financially, prepare for its replacement.

Immediately "surrender" to the mechanic if on the dipstick you see droplets of fluid that has entered the lubrication system from the cooling system. It means that damaged cylinder head gasket and coolant seeps into the oil pan. If you continue to operate the engine with oil, half consisting of Tosol, then the wear of engine parts acquires a catastrophic rate.

Water pump bearing does not break "suddenly". First, there will be a specific whistling sound from under the hood, and if the driver "thinks about the future", he will promptly replace the bearing. Otherwise, it will still have to be changed, but with the consequence of being late to the airport or to a business meeting, because of a "suddenly" broken down car.

Each of the drivers should know and remember that on a hot engine, the cooling system is under pressure!

If the engine of your car is overheated and "boiled", then, of course, you need to stop and open the hood of the car, but you must not open the cap of the radiator or expansion tank. To speed up the engine cooling process, this will practically do nothing, but you can get severe burns.

Everyone knows what an awkwardly open bottle of champagne turns into for smartly dressed guests. In a car, everything is much more serious. If you quickly and thoughtlessly open the stopper of a hot radiator, then a fountain will fly out, but not wine, but boiling Tosol! In this case, not only the driver may be injured, but also pedestrians who are nearby. Therefore, if you ever have to open the cap of a radiator or expansion tank, then you should first take precautions and do it slowly.

When the human circulatory system is divided into two circles of blood circulation, the heart is exposed to less stress than if the body had a common blood supply system. In the pulmonary circulation, blood travels to the lungs and then back thanks to a closed arterial and venous system that connects the heart and lungs. Its path begins in the right ventricle and ends in the left atrium. In the pulmonary circulation, blood with carbon dioxide is carried by arteries, and blood with oxygen is carried by veins.

From the right atrium, blood enters the right ventricle and is then pumped into the lungs through the pulmonary artery. From the right venous blood enters the arteries and lungs, where it gets rid of carbon dioxide, and then is saturated with oxygen. Through the pulmonary veins, blood flows into the atrium, then it enters the systemic circulation and then goes to all organs. Since it is slowly in the capillaries, carbon dioxide has time to enter it, and oxygen has time to penetrate into the cells. Since blood enters the lungs at low pressure, the pulmonary circulation is also called the system low pressure... The time for blood to pass through the pulmonary circulation is 4-5 seconds.

With an increased demand for oxygen, for example, during intense sports, the pressure generated by the heart increases and the blood flow accelerates.

A large circle of blood circulation

The systemic circulation begins from the left ventricle of the heart. Oxygenated blood flows from the lungs into the left atrium and then into the left ventricle. From there, arterial blood enters the arteries and capillaries. Through the walls of the capillaries, the blood transfers oxygen and nutrients into the tissue fluid, taking carbon dioxide and metabolic products. From the capillaries, it enters the small veins that form larger veins. Then, through two venous trunks (superior vena cava and inferior vena cava), it enters the right atrium, ending the systemic circulation. The blood circulation in the systemic circulation is 23-27 seconds.

Blood flows through the superior vena cava from the upper parts of the body, and along the lower - from the lower parts.

The heart has two pairs of valves. One of them is located between the ventricles and the atria. The second pair is located between the ventricles and arteries. These valves provide direction for blood flow and prevent blood from flowing back. Blood is pumped into the lungs under great pressure, and it enters the left atrium under negative pressure. The human heart has an asymmetrical shape: since its left half does more heavy work, it is somewhat thicker than the right.