Heating based on the circulation of hot water - the most common option for arranging a private house. For competent development of the system it is necessary to have preliminary results of the analysis, the so-called hydraulic calculation of the heating system, linking the pressure on all parts of the network with diameters pipes.
This article describes in detail the method of calculation. In order to better understand the algorithm of actions, we reviewed the calculation procedure using a specific example.
Adhering to the described sequence, it will be possible to determine the optimal diameter of the line, the number of heating devices, boiler power and other system parameters necessary for arranging an effective individual heat supply.
The content of the article:
- The concept of hydraulic calculation
- The sequence of calculation steps
- Example Initial Conditions
- How data is collected
- Heat generator power
- Dynamic parameters of the coolant
- Determination of pipe diameter
- Conclusions and useful video on the topic
The concept of hydraulic calculation
The determining factor in the technological development of heating systems has become the usual savings on energy. The desire to save makes you more careful approach to the design, choice of materials, methods of installation and operation of heating for the home.
Therefore, if you decide to create a unique and first of all economical heating system for your apartment or house, then we recommend that you read the rules of calculation and design.
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The operation of the heat network consists in transmitting the calculated amount of heat energy to the devices that transmit heat to the consumer.
The task of the hydraulic calculation is the selection of pipes that ensure minimum heat loss during the passage of coolant through an extensive heating network
The amount of thermal energy transferred to the devices depends on the heat consumption and on the temperature difference during cooling of the coolant. In two-pipe circuits are oriented to the temperature differential in all devices
When performing a hydraulic calculation for a one-pipe scheme, the temperature difference across all risers is taken as a reference point.
The purpose of the calculation is the selection of pipes through which the calculated coolant flow rate can circulate. Pipes are usually picked up according to the presented assortment, therefore there is always some error in the calculations.
The flow rate of the coolant in the production of the calculation is not set in advance, but is determined by linking the pressure parameters in all rings of the system
First of all, calculations are performed on the main circulation ring. It is divided into sections and calculate the flow rate of the coolant and pressure loss, aimed at friction when moving water or steam along the contour
After determining the parameters of the main circulation ring, similar calculations are performed for the secondary rings. According to the results of circulating it in all parts of the system, select the diameter of the pipe to balance the pressure in all components of the network
Autonomous heating network
The complexity of heating systems
Guideline for the calculation of two-pipe systems
Landmark for the calculation of one-pipe systems
Specific calculation for heating
Loopback system
First steps in the calculation
Calculation for secondary rings
Before defining the hydraulic calculation of the system, it is necessary to clearly and clearly understand that the individual system heating of the apartment and the house is conditionally much higher relative to the central heating system of a large building.
Personal heating system is based on a fundamentally different approach to the concepts of heat and energy.
The essence of the hydraulic calculation is that the coolant flow rate is not set in advance with significant approaching the real parameters, and are determined by linking the pipe diameters with the pressure parameters in all system rings
It is enough to make a trivial comparison of these systems according to the following parameters.
- The central heating system (boiler-house-apartment) is based on standard types of energy carrier - coal, gas. In an autonomous system, you can use almost any substance that has a high specific heat of combustion, or a combination of several liquid, solid, granular materials.
- DSP is built on ordinary elements: metal pipes, “clumsy” batteries, stop valves. The individual heating system allows you to combine a variety of elements: multi-section radiators with good heat dissipation, high-tech thermostats, different types of pipes (PVC and copper), taps, plugs, fittings and of course own more economical boilers, circulation pumps.
- If you enter the apartment of a typical panel house, built 20-40 years ago, we see that the heating system comes down to the presence of a 7-section Batteries under the window in each room of the apartment plus a vertical pipe through the entire house (riser), with which you can “communicate” with your neighbors top / bottom. Whether it is an autonomous heating system (ASO) - allows you to build a system of any complexity, taking into account the individual wishes of tenants of the apartment.
- Unlike DSP, a separate heating system takes into account a rather impressive list of parameters that affect transmission, energy consumption and heat loss. Ambient temperature conditions, the required range of temperature in the rooms, the area and volume of the room, the number of windows and doors, the purpose of the rooms, etc.
Thus, the hydraulic calculation of the heating system (GDF) is a conditional set of calculated characteristics of the heating system, which provides comprehensive information on parameters such as pipe diameter number of radiators and valves.
This type of radiator was installed in most panel houses in the post-Soviet space. Saving on materials and the lack of design ideas "on the face"
ГРСО allows to choose the right water ring pump (heating boiler) for transporting hot water to the final elements of the heating system (radiators) and, ultimately, have the most balanced system, which directly affects the financial investments in the heating of the dwelling.
Another type of heating radiator for DSP. This is a more versatile product that can have any number of ribs. So you can increase or decrease the heat exchange area
The sequence of calculation steps
Speaking about the calculation of the heating system, we note that this procedure is the most ambiguous and important in terms of design.
Before performing the calculation, you need to make a preliminary analysis of the future system, for example:
- set the heat balance in all and specifically in each room of the apartment;
- approve temperature controllers, valves and pressure regulators;
- choose radiators, heat transfer surfaces, heat transfer panels;
- identify areas of the system with maximum and minimum heat carrier consumption.
In addition, it is necessary to determine the general scheme of coolant transportation: a full and small circuit, single pipe system or twin pipe.
As a result of the hydraulic calculation, we obtain several important characteristics of the hydraulic system, which provide answers to the following questions:
- what should be the power of the heating source;
- what is the flow rate and speed of the coolant;
- What is the diameter of the main pipeline of the heat pipeline?
- what are the possible losses of heat and the mass of the coolant.
Another important aspect of the hydraulic calculation is the procedure of balancing (linking) all parts (branches) of the system during extreme thermal conditions using control devices.
There are several main types of heating products: cast-iron and aluminum multisection, steel panel, bimetallic radiators and covectors. But the most common are aluminum multi-section radiators.
The estimated area of a pipeline main is a section with a constant diameter of the main line itself, as well as a constant flow of hot water, which is determined by the formula for the heat balance of the rooms. The enumeration of design zones starts from the pump or heat source.
Example Initial Conditions
For a more specific explanation of all the details of the hydraulic miscalculation, we take a concrete example of the usual housing space. We have a classic 2-bedroom apartment of a panel house with a total area of 65.54 m^{2}which includes two rooms, a kitchen, separate toilet and bathroom, a double corridor, a twin balcony.
After commissioning received the following information regarding the readiness of the apartment. The described apartment includes walls with monolithic reinforced concrete structures treated with plaster and primer. double-glazed windows with profile, brick-pressed interior doors, ceramic tiles on the floor the bathroom.
A typical panel 9-storey house with four entrances. On each floor there are 3 apartments: one 2-bedroom and two 3-bedroom. The apartment is located on the fifth floor
In addition, the presented housing is already equipped with copper wiring, distributors and a separate guard, gas stove, bathroom, sink, toilet, towel warmer, sink.
And most importantly in the living rooms, bathroom and kitchen there are already aluminum heating radiators. The question regarding the pipes and the boiler remains open.
How data is collected
The hydraulic calculation of the system is mostly based on calculations related to the calculation of heating over the area of the room.
Therefore it is necessary to have the following information:
- the area of each individual room;
- dimensions of window and door connectors (internal doors have practically no effect on heat loss);
- climatic conditions, features of the region.
We will proceed from the following data. Common room area - 18.83 m^{2}bedroom - 14.86 m^{2}kitchen - 10.46 m^{2}, balcony - 7.83 m^{2} (sum), corridor - 9.72 m^{2} (amount) bathroom - 3.60 m^{2}, toilet - 1.5 m^{2}. Entrance doors - 2.20 m^{2}, window showcase of the common room - 8.1 m^{2}bedroom window - 1.96 m^{2}kitchen window - 1.96 m^{2}.
The height of the walls of the apartment is 2 meters 70 cm. The outer walls are made of concrete class B7 plus interior plaster, 300 mm thick. Internal walls and partitions - bearing 120 mm, ordinary - 80 mm. The floor and, accordingly, the ceiling of concrete slabs class B15, thickness 200 mm.
The layout of this apartment provides the opportunity to create one single branch of heating, passing through the kitchen, bedroom and living room, which will provide an average temperature of 20-22⁰C in rooms (+)
What about the environment? The apartment is located in the house, which is located in the middle of the microdistrict of a small city. The city is located in a certain lowland, the height above sea level is 130-150 m. The climate is moderately continental with cool winters and rather warm summers.
Average annual temperature + 7.6 ° C. The average January temperature is -6.6 ° C, July + 18.7 ° C. The wind is 3.5 m / s, the average humidity is 74%, and the amount of precipitation is 569 mm.
Analyzing the climatic conditions of the region, it should be noted that we are dealing with a large range of temperatures, which in turn affects the special requirement for adjusting the apartment's heating system.
Heat generator power
One of the main components of the heating system is the boiler: electric, gas, combined - at this stage it does not matter. Since its main characteristic is important to us - power, that is, the amount of energy per unit of time that will be spent on heating.
The power of the boiler itself is determined by the formula below:
Wotla = (room) W / 10,
Where:
- Room - the sum of the areas of all the rooms that require heating;
- Woode - specific power, taking into account the climatic conditions of the location (this is why it was necessary to know the climate of the region).
That is characteristic, for different climatic zones we have the following data:
- northern areas - 1.5 - 2 kW / m^{2};
- central zone - 1 - 1.5 kW / m^{2};
- southern regions - 0.6 - 1 kW / m^{2}.
These figures are fairly arbitrary, but nonetheless give a clear numerical answer regarding the influence of the environment on the apartment's heating system.
This map shows climatic zones with different temperatures. From the location of the housing relative to the zone and it depends on how much you need to spend on heating a square meter of energy (+)
The total area of the apartment that needs to be heated is equal to the total area of the apartment and is equal, that is, 65.54-1.80-6.03 = 57.71 m2 (minus the balcony). The specific power of the boiler for the central region with a cold winter is 1.4 kW / m2. Thus, in our example, the calculated power of the heating boiler is equivalent to 8.08 kW.
Dynamic parameters of the coolant
We proceed to the next stage of calculations - analysis of the coolant consumption. In most cases, the apartment heating system is different from other systems - this is due to the number of heating panels and the length of the pipeline. Pressure is used as an additional “driving force” flow vertically through the system.
In private single and multi-storey buildings, old panel apartment buildings, high pressure heating systems are used, which allows transport heat to all parts of a branched, multi-ring heating system and raise the water to its full height (up to the 14th floor) building.
In contrast, a typical 2- or 3-room apartment with independent heating does not have such a variety of rings and branches of the system, it includes no more than three circuits.
This means that the transportation of the coolant occurs through the natural process of the flow of water. But you can also use circulation pumps, heating is provided by a gas / electric boiler.
We recommend using a circulating pump for space heating more than 100 m^{2}. It is possible to mount the pump both before and after the boiler, but usually it is put on the “return” - the carrier temperature is lower, the airflow is less, the pump life is longer
Experts in the field of design and installation of heating systems define two main approaches in terms of calculating the volume of coolant:
- According to the actual capacity of the system. All volumes of cavities, without exception, are summed up where the flow of hot water will flow: the sum of individual sections of pipes, sections of radiators, etc. But this is quite a time-consuming option.
- By boiler power. Here the opinions of experts diverged very strongly, some say 10, the other 15 liters per unit of boiler power.
From a pragmatic point of view, it is necessary to take into account, the fact that probably the heating system will not only serve hot water for the room, but also to heat the water for the bath / shower, washbasin, sink and dryer, and maybe for hydromassage or jacuzzi. This option is easier.
Therefore, in this case, we recommend installing 13.5 liters per unit of power. Multiplying this number by the power of the boiler (8.08 kW), we obtain the calculated volume of water mass - 109.08 liters.
The calculated velocity of the coolant in the system is the very parameter that allows you to select a specific pipe diameter for the heating system.
It is calculated by the following formula:
V = (0.86 * W * k) / t-to,
Where:
- W - boiler power;
- t - temperature of the water supplied;
- to - water temperature in the return circuit;
- k - boiler efficiency (0.95 for a gas boiler).
Substituting the calculated data into the formula, we have: (0.86 * 8080 * 0.95) / 80-60 = 6601.36 / 20 = 330 kg / h. Thus, in one hour, 330 l of coolant (water) is moved in the system, and the capacity of the system is about 110 l.
Determination of pipe diameter
For the final determination of the diameter and thickness of the heating pipes, it remains to discuss the issue of heat loss.
The maximum amount of heat leaves the room through the walls - up to 40%, through the windows - 15%, the floor - 10%, everything else through the ceiling / roof. For an apartment, losses are mainly characterized through windows and balcony modules.
There are several types of heat loss in heated premises:
- Pressure loss flow in the pipe. This parameter is directly proportional to the product of the specific friction loss inside the pipe (provided by the manufacturer) and the total pipe length. But given the current task, such losses can be ignored.
- Head Loss on Local Pipe Resistances - the cost of heat at the fittings and inside the equipment. But given the conditions of the problem, a small number of fittings and the number of radiators, such losses can be neglected.
- Heat loss based on the location of the apartment. There is another type of thermal costs, but they are more related to the location of the room relative to the rest of the building. For an ordinary apartment, which is located in the middle of the house and is adjacent to the left / right / top / bottom with other apartments, heat losses through the side walls, the ceiling and the floor are almost equal to “0”.
It is only possible to take into account losses through the front part of the apartment - the balcony and the central window of the common room. But this question is closed by the addition of 2-3 sections to each of the radiators.
The value of the diameter of the pipe is selected according to the flow rate of the coolant and the speed of its circulation in the heating line
Analyzing the above information, it is worth noting that for the calculated speed of hot water in the heating system known tabular speed of movement of water particles relative to the pipe wall in a horizontal position of 0.3-0.7 m / s.
To help the master, we present the so-called checklist for performing calculations for a typical hydraulic calculation of a heating system:
- data collection and calculation of boiler power;
- volume and velocity of the coolant;
- heat loss and pipe diameter.
Sometimes during miscalculation, you can get a sufficiently large pipe diameter to cover the calculated volume of the coolant. This problem can be solved by increasing the displacement of the boiler or adding an additional expansion tank.
On our site there is a block of articles devoted to the calculation of the heating system, we advise you to read:
- Thermal calculation of the heating system: how to correctly calculate the load on the system
- Calculation of water heating: formulas, rules, examples of implementation
- Thermal engineering calculation of a building: specificity and formulas for performing calculations + practical examples
Conclusions and useful video on the topic
Features, advantages and disadvantages of natural and forced coolant circulation systems for heating systems:
Summarizing the total hydraulic calculations, the result was specific physical characteristics of the future heating system.
Naturally, this is a simplified calculation scheme, which gives approximate data regarding the hydraulic calculation for the heating system of a typical two-room apartment.
Trying to independently carry out the hydraulic calculation of the heating system? Or maybe they do not agree with the stated material? We are waiting for your comments and questions - the block for feedback is located below.