Steel tubes for water are the most popular in the rolled metal wide application. Besides its use for the construction of communications in accordance with the title, they successfully perform the function of heating devices. From the pipes manufactured AIV smooth and ribbed different configuration registers, which are not inferior to the heat transfer efficiency of modern radiators. They are ideal for transporting coolant in natural circulation systems, while simultaneously engaging in space heating.
Installing steel water and gas pipes for heating, it is very important to know their basic characteristics. Foremost among them are the weight and the heat transfer coefficient. Carefully performing preliminary calculations, you will save yourself from unexpected difficulties during installation and to ensure the desired effect during operation.
Range of water and gas pipes
Water and gas pipes are manufactured in accordance with the requirements of State Standard - GOST 3262-75. It operates more than 40 years and regulates all sizes and technical requirements.
The assortment stands out 3 varieties of pipes:
- Lungs;
- conventional;
- Reinforced.
Tube type is determined by the wall thickness. It may vary for different diameters from 1.8 to 5.5 mm. Strengthening the walls allows products to withstand more pressure and provides a longer service life. This, of course, increases the consumption of metal to manufacture, cost and weight.
The information in Table GOST weight steel water-gas pipes to determine the weight per unit length 1 m, depending on the type and diameter.
Important! Mass defined in the table, a theoretical actual value may vary by 4-8%, which is significantly for large batches. Galvanized products are always heavier than about 3-5%.
As seen from the table, the steel pipe water and gas may have a nominal diameter of 6 to 150 mm, which corresponds to the range from ¼ to 6 inches. Inch sizes are often used for marking the fittings and shut-off and regulating valves. Therefore it is very important to handle these units of measurement at a complete system.
On a note: If the hand is not a table, it is possible to conduct recalculation of their own diameter. It's enough to know that English 1 inch corresponds to the average thickness of the thumb of an adult male and is equal to 25.4 mm. All gauges are readily determined by dividing the value of orifice 25, rounded to the nearest standard value.
Mass pipe can also be found manually by using simple geometry and physics of the formulas represented below. When large volumes of calculations it is convenient to use a special online calculatorThat allows you to automate the process.
In the figure the following symbols:
d - diameter of the inner tube;
D - outside diameter;
b - wall thickness;
S - a metal cross-sectional area;
V - volume of metal;
m - mass of the product;
ρ - specific gravity became equal to 7.85 g / cm3.
Important! Note that the internal diameter and the nominal diameter - this is not the same thing. Pipes with different wall thicknesses have different inner diameters with the same conditional pass. Under nominal bore understand certain standard value in the line gauge which is only approximately equal to the value d. Bringing the pipe to various types of one nominal size greatly simplifies the selection of shaped elements, and other components.
It is necessary to note the high strength characteristics of steel pipes. They have a stiffness characteristic of the metal rod of the same diameter. At the same time a lot easier and cheaper. Thus, the product of the heavy type will weigh 30-40% less than the all-metal rolling.
Due to this, water and gas pipes are widely used not only for transporting various environments of any temperature, but also in construction and mechanical engineering for the construction of a variety of structures.
Types of heating registers
Steel heating registers are for water or welded tubes which are connected by welding in appliances for space heating. They may be of different configurations. In accordance with the form of the instrument are the following varieties:
- Coil;
- Sectional.
The figure shows some variations of their design.
Sectional in turn are divided into types depending on the way the compound: string or column. In the former case the heated fluid passes sequentially on each tube, moving along the device as in the coil. The second - the coolant enters each subsequent tube with two parallel sides, as shown above.
Sometimes used similar structures of metal profiles of rectangular or square section. They are more expensive than round, but may be suitable for individual processing in the presence of starting material.
Despite the unappealing appearance, steel registers are quite popular in the areas of technical designation. They are often found in garages, workshops, manufacturing plants, and sometimes in public buildings. Some homeowners prefer it registers of the pipes due to the relative cheapness of the product and the possibility of producing their own hands the instrument desired length and shape.
By the ability to give off heat such devices are somewhat inferior to the radiators of the same length, but are of lower cost. An important advantage of a smooth pipe registers is easy to care for them. It is the convenience of regular cleansing causes their frequent use in hospitals.
To increase the heat transfer fins are used the steel pipe of the plates. They significantly increase the area of contact with the ambient air, besides improving convection. The efficiency of such heating devices about 3 times higher than the smooth pipe. A disadvantage with fins registers only in the complexity of removing dust which accumulates between the plates.
There are also more sophisticated, modern design of the vertical registers. They can be both direct and bow-shaped in plan, repeating the outlines of the most complex architectural forms. Variants of columns in one or two rows. These registers are very convenient for large high spaces and give freedom a bold design solutions.
Determination of heat transfer
For proper selection of the size of the registers for space heating according to the heat loss is necessary to know the value of the heat transfer tube 1 meter long. This value depends on the diameter and the difference in coolant temperature and the environment. Temperature difference is given by:
Δt = 0,5 · (t1+ t2) - tto,
Where t1 and t2 - temperature at the boiler inlet and outlet thereof, respectively;
tto - the temperature in the heated room.
Quickly determine the approximate value of the amount of heat received from the register table will heat the steel pipe 1 m. Despite the fact that the result is very approximate, this method is the most convenient and does not require complicated calculations.
For reference: 1 BTU / hr · ft2 ·oF = 5,678 W / m2K = 4,882 kcal / h · m2 ·oC.
The table shows what will be the heat transfer tube of steel in air at certain temperatures. For intermediate values of the temperature difference calculations are performed by interpolation.
For a more accurate determination of the amount of heat which gives the steel pipe should use the classic formula:
Q = K · F · Δt,
wherein: Q - heat transfer coefficient, W;
K - heat transfer coefficient, W / (m2·0FROM);
F - surface area, m2;
Δt - temperature difference, 0FROM.
The principle of Δt has been described above, and the value of F is the formula for a simple geometrical surface of the cylinder: F = π·d · l,
Where π = 3.14, and dandl - the diameter and the length of the tube, respectively, m.
When calculating portion 1 m long formula takes the form Q = 3,14·K·d·Δt.
On a note: the determination of a single tube of heat sufficient to substitute the reference value of heat transfer coefficient for the steel during heat transfer from water to the air, which is 11.3 W / (m2·0FROM). For the heater K value depends not only on the material from which pipes are made, but also on their diameter and number of threads, since they affect each other.
The average values of heat transfer coefficients for the most popular types of heating appliances listed in the table.
Important! Substituting the values in the formula should be closely monitored units. All the values must have dimensions that are coordinated among themselves. Thus, the heat transfer coefficient is found in Kcal / (h· m2 ·0C) necessary to transfer in W / (m2·0C), considering that 1 kcal / h = 1,163 watts.
Of course, the table heat of steel pipes allows you to get results more quickly than the calculation formulas, but if accuracy is important, have a little trouble.
To determine the appropriate size of the register, required thermal power must be divided by heat meter 1 with rounding to the nearest integer. A guide can take the average data for the insulated space in height and 3 m 1 m register with a diameter of 60 mm is able to heat a 1 m2 premises.
On a note: As seen from the table, the coefficient K for steel pipes may vary from 8 to 12.5 Kcal / (h· m2 ·0FROM). Increasing the diameter and number of threads results in a reduction of heat transfer efficiency. In this regard, to increase heat transfer register should be favored increasing length elements.
You must also take into account that the pipes require large high volume of water in the system, which creates an additional load on the boiler. The recommended distance between the thread diameter of the pipe be equal to plus 50 mm.
If the system is not filled with water and antifreeze, it significantly affects the heat sensitive and requires an increase in its size after additional calculations. This is especially true when using devices with heating elements and oil as a coolant.
conclusion
The steel pipe is relatively strong, durable product with good heat dissipation. Registers plain tubes can have various configurations, it is very easy to maintain and do not require periodic cleaning. This allows them to compete successfully with light bimetal and aluminum radiators, as well as the traditional "unkillable" cast iron radiators.
Water and gas pipes are widely used in outdoor heating networks with open laying due to high rigidity and durability. The feasibility of using steel pipes for heating is determined by the operating conditions, financial opportunities and aesthetic taste of the owners. The application registers the most justified in industrial and technical areas, but in other cases, they will have their own advantages.
Author (Expert Site): Irina Chernetskaya
