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Coefficient of leakage(consumption) in a single-pipe heating system

Let us consider the problem of calculating the coefficients of leakage. Find the actual and nominal values of the leakage coefficients.

Coefficient of leakage(consumption) – this is a very important parameter as an indicator of the quality of the work of a single-pipe heating system! Due to this parameter, we can accurately calculate a more reliable single-pipe heating system!

Consider the following questions:

 ```- How to calculate the coefficient of leakage into the radiator in a single-pipe system? - Calculation of the coefficient of leakage? What should it be equal for the radiator? - how the bypass diameter affects the leakage coefficient? - How does the thermostatic valve affect the leakage factor? - How to choose the diameters, valves and tees to set the required coefficient of leakage? - What happens if the actual value does not match the nominal value of the leakage coefficient? - How to calculate the coefficient of leakage through the parameters of tees? For example, we calculate the tee PP25x20x20. ```

More details about the schemes: Hydraulic meaning of chains

How to calculate the coefficient of leakage into the radiator in a single-pipe system?

Gобщ – total flow (riser), м3/час

Кзат - Coefficient of leakage:

Где:

Gобщ – total consumption, м3/час

Gб – bypass consumption, м3/час

Sрад – hydraulic characteristic of a branch of a radiator, Па/(л/ч)2

Sб – hydraulic characteristic of the bypass branch, Па/(л/ч)2

What is Kv written here: What is Kvs?

0.1 this is a translation (from liter in cubic meter) and (from pascal to meter of water column).

If the bandwidth of the branches (radiator and bypass) is known, then one can find the leakage coefficient (Kзат) in the radiator:

how the bypass diameter affects the leakage coefficient?

Reducing the bypass diameter increases the coefficient of leakage into the radiator.

Increasing the bypass diameter reduces the coefficient of leakage into the radiator.

If the total flow (riser) is 2 m3/hour, and the coefficient of leakage into the radiator is 0.1 then the flow rate in the radiator will be equal to

Calculation of the nominal coefficient of leakage?

That is, we calculate the nominal value of the leakage coefficient. The calculation of the actual value will be considered below.

The term nominal should be understood as the recommended value.

For example, it is necessary to choose diameters and valves in order to establish the necessary value of the leakage coefficient. And how do you know what this value should be 0.1 or 0.2 or 0.3?

The nominal coefficient of leakage should be equal to:

Количество радиаторов - this is the number of radiators

If the power of the radiators is different:

For example, we have 2 radiators of different power: 1 kW and 3 kW. The sum of the power of the two radiators is 4 kW.

That is, we have a single-tube system with a certain number of radiators. It is necessary to divide the unit by the number of radiators for one single-pipe system. Or divide the coefficient of leakage according to the power of each radiator. More details about systems and schemes: Hydraulic senses of chains

It is very important not to strive to increase the temperature difference between the feed and the return of the radiators. The larger the radiator drop, the colder the last radiator will be. To reduce the temperature drop, it is necessary to increase the total flow of the main pipe of a single-pipe heating system.

Problem: We have 2 radiators. System flow rate = 0.2 m3/h. Find the value of the coefficient of leakage into the radiator.

Roughly speaking, you need to divide the flow of the common main pipe evenly into all the radiators. If the power of the radiators is very different, then calculate according to the power per radiator (the calculation is described above).

How to choose the diameters, valves and tees to set the required leakage factor?

In order to find the actual leakage coefficient, it is necessary to solve the inverse problem of hydraulics in calculating the head losses in the pipeline when the coolant moves. How to find the head loss in the pipeline?

Automatically solves the inverse problem of the software: http://gidroraschet.ru/kurs/gidravlika/prog/present2.htm

That is, it is necessary to find the costs of two branches: the radiator branches and the bypass branch.

If costs are known, then it is easy to find the coefficient of leakage by the formula:

Calculation of actual wicking factor

Consider the problem of how to find the actual value of the leakage coefficient in a single-pipe heating system.

Problem: We have a single-pipe heating system with diameters, see figure:

Pipes made of polypropylene. Tees PP25x20x20 are used.

The coefficient of leakage will depend on the ratio of the hydraulic resistance of the branches: the radiator branches and the bypass branch.

Tees will also affect the leakage coefficient. And the coefficient of leakage will also depend on the motion of the coolant with the rotation. For example, see the diagram:

Reducing the bypass diameter will lead to an increase in the leakage coefficient.

Find the actual costs of the radiator and bypass branches easier in this program:

The nominal coefficient of leakage should be equal to 0.5.

Diameters and valves should be selected so that the actual value coincides with the nominal value.

That is, to calculate the actual leakage rate, you need to find the actual costs. And to find costs, including all hydraulic resistance, the software will help: http://gidroraschet.ru/kurs/gidravlika/prog/present2.htm

Let's calculate the difference in the coefficients of leakage at different motions of the coolant in the tee.

What happens if the actual value does not match the nominal value of the leakage factor?

If there is a big difference between the actual and nominal value, we will not get an efficient allocation of costs in the system between the radiators. Roughly speaking, it is not economically profitable. For example, the pump will use excess work to pump the coolant through the main pipeline. Or for example, in the first minutes of the start, the radiators will warm up less evenly. And if the heating is not uniform, we will get a strong temperature deviation between the first and last radiators.

If the actual leakage ratio is higher than the nominal one, , when the system starts up for the first time, the heating of the radiators will be less uniform. That is, the first radiators will certainly receive more advantages in heating than the latter. A strong deviation of the values ??will lead to an increase in the temperature difference between the first and last radiator. That is, the last radiators will be colder. If the actual coefficient of leakage is equal to the nominal, the heating will be more uniform and the temperature deviation will be minimal.

If the actual coefficient of leakage is below the nominal , then for good warming up of the radiators it is necessary to start excess flow through the main pipeline. That is, a lack of value will result in a reduction in the flow in the radiator. And if you increase the flow, we get an extra - useless expense in the main pipeline. This leads to economically unprofitable use of the circulation pump. If we do not increase the flow rate, we will get high drops in the radiators, which will cause the radiators to produce less heat. That is, it turns out that we bought the extra power of the radiator, which we do not use.

How does the thermostatic valve affect the leakage factor?

The thermostatic valve greatly reduces the leakage coefficient. This can also lead to inefficient use of the radiator. That is, the efficiency of the radiator can be lower.

In conclusion, I'll ask the plumbers:

- Who of the plumbers and engineers takes into account the coefficient of leakage? The overwhelming majority of plumbers, including myself, created schemes and chose diameters, not understanding the depth of the leakage factor when calculating single-pipe heating systems.

And in this article I wrote what will happen if you do not follow the rule: The actual value of the leakage coefficient should coincide with the nominal coefficient of leakage. This rule of the economy must be observed otherwise your entire economy is a waste of money and extra energy.