Types of pipes for thermal systems.
The heat pipe is a hermetic construction capable of transferring heat. The principle of its operation consists in a closed cycle of the process of evaporation and condensation of the liquid and the transfer of heat to external sources. Those. A closed metal container, which has a high degree of thermal conductivity and is filled with water, will evaporate when heated from one side. When moving to a cold surface, the steam again becomes liquid and drains to its original location. This generates heat, which is radiated from the surface of the metal container. 
The very design of the heat pipe consists of:
- Metal housing with good thermal conductivity;
- Filling liquid;
- Liquid wick
The body is made of materials such as glass, ceramics, and also metal alloys. Inside, it is filled with a liquid that has the physical ability to transfer their liquid state to gaseous. This fluid is the source of thermal energy.
The wick is a porous substance capable of moving liquid through its capillaries from one end of the device to the other.
The functionality of such a device depends on the materials used, the operating dimensions and the technical characteristics of the parts and is the efficiency of the transfer of thermal energy. 
In addition to conventional heat pipes, there are its improved analogs - contour pipes.
This product is a non-flexile version of the pipe, where the contour tube, replacing capillaries, but with a larger diameter, performs the function of the wick.
And these tubes have a number of advantages:
- A sufficiently high degree of heat transfer;
- Simplicity of design;
- Durability and reliability in work;
- Resistance to environmental influences;
- High wear resistance due to the immobility of its constituent elements;
To date, contour pipes can be attributed to the number of the best conductors of thermal energy.
Where are heat pipes used?
This kind of product is so multi-functional that it is used in a variety of areas: 
- In microelectronics;
- When installing heating systems;
- In refrigeration units;
- In the space industry;
- Pharmacology and Medicine;
- When equipping greenhouses.
And this is not a complete list of industries, including nanotechnology, using heat pipe networks.
Heating by heat pipes.
Pipes that radiate heat can also be used for heating houses. Most of all for this purpose, suitable structures from zinc steel, cermet or asbestos cement. It is also possible an alloy of metals - bimetal. 
The most popular material is asbestos-cement, which has many positive qualities:
- Resistance to corrosion attack;
- Ability to use at a temperature of +130 0С;
- Acceptable cost;
- Low percentage of heat loss;
- Ease of installation.
But with all the positive aspects, there are also negative ones, namely, fragility.
As for bimetallic pipes, they consist of steel coated with other metals that have anticorrosive properties. The thickness of this layer sometimes reaches up to 15-20% of the thickness of the pipe itself. Advantages of such pipes are:
- Corrosion resistance;
- Durability;
- Low heat loss.
The main disadvantage is a fairly high cost.
To reduce heat loss in heating communications, modern construction markets offer a huge selection of insulation materials.
And today two types of insulation are used:
- Polymer-reinforced fiberglass or mineral wool. This option is more for outdoor heating systems;
- Pipe with a layer of polymer embedded in it during production.
In heating systems, steel pipes coated with zinc are also used. But this is only possible if the water temperature does not rise above +70 degrees.
Pig-iron pipes become popular for heating network equipment. Their unusual spherical structure provides high strength and long service life. In addition, they are quite cheap.
However, their high thermal conductivity has become their biggest drawback.
