Hydraulic arrow for heating: purpose + installation diagram + parameter calculations

Heating systems in their modern form are complex structures equipped with various equipment.Their efficient operation is accompanied by optimal balancing of all their constituent elements. The hydraulic arrow for heating is designed to provide balance. It’s worth understanding its operating principle, don’t you agree?

We will talk about how a hydraulic separator works and what advantages a heating circuit equipped with it has. The article we presented describes the installation and connection rules. Helpful operating instructions are provided.

Hydraulic flow separation

The hydraulic arrow for heating is more often called a hydraulic separator. From this it becomes clear that this system is intended for implementation in heating circuits.

In heating, it is assumed that several circuits are used, for example, such as:

• lines with groups of radiators;
• underfloor heating system;
• hot water supply through a boiler.

In the absence of a hydraulic arrow for such a heating system, you will either have to make a carefully calculated design for each circuit, or equip each circuit individually circulation pump.

But even in these cases there is no complete certainty of achieving the optimal balance.

The classic design of hydraulic separators made on the basis of round or rectangular pipes can be considered approximately this way. A simple but effective solution that radically changes the state of the heating system involving the boiler

Meanwhile, the problem is solved simply.You just need to use a hydraulic separator in the circuit - a hydraulic arrow. Thus, all circuits included in the system will be optimally separated without the risk of hydraulic losses in each of them.

Hydroarrow – the name is “everyday”. The correct name corresponds to the definition - “hydraulic separator”. From a constructive point of view, the device looks like a piece of an ordinary hollow pipe (round, rectangular cross-section).

Both end sections of the pipe are plugged with metal plates, and on different sides of the body there are inlet/outlet pipes (a pair on each side).

The natural appearance of the products is hydraulic switches made from rectangular and round pipes. Both options show high efficiency. However, hydraulic guns based on round pipes are still considered a more preferable option

Traditionally, the completion of installation work on heating system design is the beginning of the next process - testing. The created plumbing design is filled with water (T = 5 - 15°C), after which the heating boiler is started.

Until the coolant is heated to the required temperature (set by the boiler program), the water flow is “spinned” by the primary circuit circulation pump. Circulation pumps of secondary circuits are not connected. The coolant is directed along the hydraulic arrow from the hot side to the cold side (Q1 > Q2).

Subject to achievement coolant the set temperature, the secondary circuits of the heating system are activated. The coolant flows of the main and secondary circuits are equalized. In such conditions, the hydraulic arrow functions only as a filter and air vent (Q1 = Q2).

Functional diagram of the operation of a classic hydraulic switch for three different boiler operating modes. The diagram clearly indicates the distribution of heat flows for each individual operating mode of boiler equipment

If any part (for example, a heated floor circuit) of the heating system reaches a predetermined heating point, the selection of coolant by the secondary circuit temporarily stops. The circulation pump is turned off automatically, and the water flow is directed through the hydraulic arrow from the cold side to the hot side (Q1 < Q2).

Design parameters of the hydraulic arrow

The main reference parameter for the calculation is the coolant speed in the section of vertical movement inside the hydraulic arrow. Typically the recommended value is no more than 0.1 m/s, under either of two conditions (Q1 = Q2 or Q1 < Q2).

The low speed is due to quite reasonable conclusions. At this speed, debris contained in the water flow (sludge, sand, limestone, etc.) manages to settle to the bottom of the hydraulic arrow pipe. In addition, due to the low speed, the required temperature pressure has time to form.

There are two design types of hydraulic arrows, for which calculations are usually carried out: 1 – for three diameters; 2 – by alternating pipes. Regardless of the adoption of one or another technique, the basic calculation parameters are always typical - coolant flow through the circuits and the speed parameter

The low transfer rate of the coolant promotes better separation of air from water for subsequent removal through the air vent of the hydraulic separation system. In general, the standard parameter is selected taking into account all significant factors.

For calculations, the so-called method of three diameters and alternating pipes is often used.Here the final calculated parameter is the value of the separator diameter.

Based on the obtained value, all other required values ​​are calculated. However, to find out the size of the hydraulic separator diameter, you need the following data:

• by flow on the primary circuit (Q1);
• by flow on the secondary circuit (Q2);
• the speed of the vertical flow of water along the hydraulic arrow (V).

In fact, this data is always available for calculation.

For example, the flow rate in the primary circuit is 50 l/min. (from the technical specifications of pump 1). The flow rate on the second circuit is 100 l/min. (from the technical specifications of pump 2). The diameter of the hydraulic needle is calculated by the formula:

Formula for calculating the diameter of the hydraulic arrow pipe depending on the coolant flow parameters (flow according to the pump characteristics) and the vertical flow rate

where: Q – difference between costs Q1 and Q2; V is the velocity of the vertical flow inside the arrow (0.1 m/sec), π is a constant value of 3.14.

Meanwhile, the diameter of the hydraulic separator (conditional) can be selected using a table of approximate standard values.

The height parameter for the heat flow separation device is not critical. In fact, any pipe height can be taken, but taking into account the supply levels of incoming/outgoing pipelines.

Schematic solution for shifting pipes

The classic version of a hydraulic separator involves the creation of pipes symmetrically located relative to one another. However, a circuit version of a slightly different configuration is also practiced, where the pipes are located asymmetrically. What does this give?

Manufacturing diagram of a hydraulic separator in which the secondary circuit pipes are slightly offset relative to the primary circuit pipes. According to the inventors (and proven by practice), this option seems to be more productive in filtering particles and separating air

As the practical application of asymmetrical circuits shows, in this case more efficient air separation occurs, and better filtration (sediment) of suspended particles present in the coolant is achieved.

Number of connections on the hydraulic switch

Classic circuit design determines the supply of four pipelines to the hydraulic separator structure. This inevitably raises the question of the possibility of increasing the number of inputs/outputs. In principle, such a constructive approach is not excluded. However, the efficiency of the circuit decreases with increasing number of inputs/outputs.

Let's consider a possible option with a large number of pipes, in contrast to the classics, and analyze the operation of the hydraulic separation system for such installation conditions.

Scheme of a multi-channel heat flow distribution separator. This option allows you to service larger systems, but if the number of pipes increases beyond four, the efficiency of the system as a whole decreases sharply

In this case, heat flow Q1 is completely absorbed by heat flow Q2 for the state of the system when the flow rate for these flows is actually equivalent:

Q1=Q2.

In the same state of the system, heat flow Q3 in temperature value is approximately equal to the average values ​​of Tav. flowing through the return lines (Q6, Q7, Q8). At the same time, there is a slight temperature difference in the lines with Q3 and Q4.

If the heat flow Q1 becomes equal in thermal component Q2 + Q3, the distribution of temperature pressure is noted in the following relationship:

T1=T2, T4=T5,

whereas

T3= T1+T5/2.

If the heat flow Q1 becomes equal to the sum of the heat of all other flows Q2, Q3, Q4, in this state all four temperature pressures are equalized (T1=T2=T3=T4).

Multi-channel separation system with four inputs/four outputs, quite often used in practice. For servicing private heating systems, this solution is quite satisfactory in terms of technological parameters and stabilization of boiler operation

In this state of affairs on multi-channel systems (more than four), the following factors are noted that have a negative impact on the operation of the device as a whole:

• natural convection inside the hydraulic separator is reduced;
• the effect of natural mixing of supply and return is reduced;
• the overall efficiency of the system tends to zero.

It turns out that a departure from the classical scheme with an increase in the number of outlet pipes almost completely eliminates the working properties that a gyro shooter should have.

Hydraulic separator without filter

The design of the arrow, which excludes the presence of the functions of an air separator and a sediment filter, also deviates somewhat from the accepted standard. Meanwhile, with such a design it is possible to obtain two flows with different speeds (dynamically independent circuits).

A non-standard design solution for the manufacture of hydraulic arrows. It differs from the classics in that there are no filtration or air removal functions. In addition, the distribution of heat flows has a perpendicular transport pattern, which achieves speed decoupling

For example, there is a heat flow of the boiler circuit and a heat flow of the circuit heating devices (radiators). With a non-standard design, where the direction of flow is perpendicular, the flow rate of the secondary circuit with heating devices increases significantly.

On the contrary, movement along the contour of the boiler is slower. True, this is a purely theoretical view. It is practically necessary to test under specific conditions.

How is a hydraulic arrow useful?

The need to use the classic hydraulic separator design is obvious. Moreover, on systems with boilers, the implementation of this element becomes a mandatory action.

Installing a hydraulic valve in the system served by the boiler ensures stable flows (coolant flow). As a result, the risk of water hammer and temperature fluctuations.

Examples of hydraulic arrows in a classic simple design based on plastic pipelines. Now such structures can be found even more often than metal ones. The operating efficiency is almost the same as that of metal ones, but the fact of savings on the device and implementation in the system

For any ordinary water heating systemmade without a hydraulic separator, shutting off part of the lines is inevitably accompanied by a sharp rise in the temperature of the boiler circuit due to low flow. At the same time, the highly cooled return flow takes place.

There is a risk of water hammer formation. Such phenomena are fraught with rapid failure of the boiler and significantly reduce the service life of the equipment.

In most cases, plastic structures are well suited for household systems. This application option seems to be more economical to install.

In addition, the use of fittings makes it possible to install polymer pipe systems and connecting plastic hydraulic arrows without welding.From a maintenance point of view, such solutions are also welcome, since the hydraulic separator installed on the fittings can be easily removed at any time.

Conclusions and useful video on the topic

Video about practical application: when there is a need to install a hydraulic arrow, and when it is not needed.

The importance of the hydraulic arrow in the distribution of heat flows is difficult to overestimate. This is truly necessary equipment that should be installed on every individual heating and hot water system.

The main thing is to correctly calculate, design, and manufacture the device - a hydraulic separator. It is accurate calculation that allows you to achieve maximum efficiency from the device.

Please write comments in the block below, post photos related to the topic of the article, and ask questions. Tell us about how you equipped the heating system with a hydraulic arrow. Describe how the operation of the network changed after its installation, what advantages the system acquired after including this device in the circuit.