Design and thermal design of the heating system - a mandatory step in the regeneration of home heating. The main task of computing activities - defining the optimal parameters of the boiler and radiator system.
Agree, at first glance it may seem that the conduct of the calculation of heating only by the engineer. However, not all that difficult. Knowing the sequence of actions, you get to perform the necessary calculations.
The paper presents in detail the procedure for the calculation and provides all the necessary formulas. For a better understanding, we have prepared an example of thermal calculations for a private home.
The content of the article:
- Thermal heating calculation: total order
- Norms temperature modes premises
- Calculation of heat loss in the house
- Determining the boiler output
- Features selection of radiators
- Hydraulic calculation of water supply
- EXAMPLE thermal calculation
- Conclusions and useful videos on the topic
Thermal heating calculation: total order
Classic thermal calculation of the heating system is a consolidated technical document that includes the required standard incremental computation methods.
But before studying these Calculation of key parameters necessary to determine the concept itself of the heating system.
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Calculations and competent design of independent heating circuits are required for the selection of equipment that can heat the house of a certain area
Calculations are made with a guide on the coldest months of the year, ie, for the period of maximum system load
The calculations take into account losses that occur through the window and door openings, as well as across the street associated with the ventilation system
Be sure to take into account thermal performance of building structures, one of the tasks which the heat retention is
Independent heating system private homes must cope with the heat the air coming through the vents during the ventilation and through the open doors
The boiler of an independent heating system must cope with the completion of heat loss. Its capacity should allow to maintain the temperature in the building + 20º C
After determining the optimal capacity of the boiler is selected according to the most appropriate machine efficiency and operating costs
For systems with forced movement of the coolant hydraulic calculations performed to choose an optimal pump and pipe diameter
The purpose of the calculations for heating
Specificity perform calculations heating
Accounting of heat loss through openings
Accounting for thermal insulation
Heat consumption for heating the incoming air
Rules for selection of the boiler heating
productivity of the equipment
The heating circuit is forced type
The heating system is characterized by involuntary forced feed and removal of heat in the room.
The main tasks of calculation and design of the heating system:
- most reliably determine heat loss;
- determine the amount and conditions of use of the coolant;
- to accurately select the elements generating recoil movement and heat.
During the construction heating systems you must initially make a collection of various data about the room / building in which the heating system will be used. After doing the calculation of thermal parameters of the system, analyze the results of arithmetic operations.
podobirayut components of the heating system with subsequent purchase on the basis of the data obtained, the installation and commissioning.
Heating - a multi-component system for ensuring the approved temperature in the room / building. It is a separate part of the complex communication of modern housing facilities
It is remarkable that this method allows the calculation of heat sufficient to accurately calculate a large number of variables, which specifically describe future heating system.
As a result, thermal calculation will be available the following information:
- number of heat losses, power boiler;
- number and type of heat sink for each room separately;
- hydraulic characteristics of the pipeline;
- volume, the flow rate Heat pump power.
Thermal calculation - it is not a theoretical outline, but quite accurate and valid results, which are recommended to be used in practice in the selection of heating system components.
Norms temperature modes premises
Before carrying out any calculations of the system settings, you must at least know the order of the expected results, as well as keep in available standardized characteristics of some table values to be substituted into the formula or orientate on them.
Performing the parameter calculation with these constants can be sure of the reliability of the desired dynamic or permanent system parameter.
For rooms for various applications, there are reference standards for temperature conditions of residential and non-residential premises. These rules are enshrined in the so-called GOSTs
For heating one such global parameter is the temperature of the room, which should be constant regardless of the time of year and the ambient conditions.
According to the regulations of sanitary norms and rules there are differences in temperature with respect to the summer and winter period of the year. For room temperature regime in the summer air-conditioning system meets the principle of its calculation is set out in detail in this article.
But the room air temperature in winter is provided with heating. So we are interesting range of temperatures and their tolerance deviations for the winter season.
Most regulations stipulate the following temperature ranges that allow a person to be comfortable in the room.
For residential premises office type area 100 m2:
- 22-24 ° C - optimum temperature;
- 1 ° C - Permissible variation.
Improvement for office-type area of 100 m2 the temperature is 21-23 ° C. For non-residential buildings such as industrial temperature ranges differ depending on the destination premises and established safety standards.
Comfortable room temperature for each person "their own". Someone who likes to was very warm in the room, someone comfortable when it is cool in the room - it's all quite individual
With regards to the residential premises: apartments, private houses, mansions, etc... there are certain ranges of temperature that can be adjusted depending on the wishes of the residents.
And yet we have for the specific premises apartments and houses:
- 20-22 ° C - residential, including a children's room, a tolerance of ± 2 ° C -
- 19-21 ° C - kitchen, toilet, tolerance ± 2 ° C;
- 24-26 ° C - bathroom, shower, swimming pool, tolerance ± 1 ° C;
- 16-18 ° C - corridors, hallways, stairways, storage, tolerance of + 3 ° C
It is important to note that there are several key parameters that affect the temperature in the room and that need to be guided in the calculation Heating system: humidity (40-60%), the concentration of oxygen and carbon dioxide in the air (250: 1), the speed of air movement (0.13-0.25 m / s) and m. p.
Calculation of heat loss in the house
According to the second law of thermodynamics (School Physics) there is no spontaneous transfer of energy from a less heated to a more heated mini or macro lens. A particular case of this law is the "desire" to create a thermal equilibrium between the two thermodynamic systems.
For example, the first system - environment with a temperature of -20 ° C, the second system - a building with an internal temperature of + 20 ° C. This misleading according to the law, the two systems will tend to equilibrate through energy exchange. This will occur via the heat losses from the second cooling system and the first.
We can say that the ambient temperature depends on the latitude on which the private home. A difference in temperature affects the amount of heat loss from the building (+)
Under the heat losses meant an involuntary release of heat (energy) from an object (house, apartment). For an ordinary apartment, this process is not as "visible" in comparison with the private home because the apartment located inside the building and "adjacent" to other apartments.
In a private house through exterior walls, floor, roof, windows and doors in varying degrees "out" heat.
Knowing the amount of heat for the most adverse weather conditions and the characteristics of these conditions, it is possible to accurately calculate the heating power.
Thus, the amount of heat loss from a building is calculated using the following formula:
Q = Qfloor+ Qwall+ Qwindow+ Qroof+ QDoor+... + Qiwhere
Qi - the amount of heat loss from the uniform appearance of the building envelope.
Each component of the formula is calculated as:
Q = S * ΔT / Rwhere
- Q - heat leak, V;
- S - the area of the particular type of construction, q. m;
- ΔT - ambient air temperature difference and the indoor environment, ° C;
- R - thermal resistance of a particular design type, m2* ° C / Watt.
The value itself of the thermal resistance for the actually existing materials recommended to take from the supporting tables.
Furthermore, the thermal resistance can be obtained using the following relationship:
R = d / kwhere
- R - thermal resistance (m2* K) / W;
- k - thermal conduction coefficient of the material (W / m2*TO);
- d - thickness of the material, m.
In older houses with damp roof structure heat leakage occurring through the upper part of the building, namely the roof and loft. Implementation of measures to ceiling insulation or insulation of mansard roof solve this problem.
If warm attic space and roof, the total heat loss from the house can be significantly reduced
In the house there are several types of heat loss through the cracks in structures, ventilation, kitchen hood, opening doors and windows. But take into account their volume does not make sense, because they are no more than 5% of the total number of major heat loss.
Determining the boiler output
In support of the difference in temperature between the environment and the temperature inside the house requires an autonomous heating system that maintains the desired temperature in each room of a private house.
The basis of the heating system are the different types of boilers: Liquids or solid fuel, electric or gas.
The boiler - a central heating unit that generates heat. The main characteristic is its capacity boiler, namely the conversion rate of heat quantity per unit time.
The calculation of the thermal load on the heating obtain the required nominal output of the boiler.
For normal-bedroom apartment boiler output is calculated through the area and power density:
Rboiler= (Sroom*Rspecific)/10where
- Sroom- Total area of heated space;
- Rudellnaya- power density with respect to climatic conditions.
But this formula does not take into account the heat loss, which is enough in a private home.
There is a different ratio, which takes into account this parameter:
Rboiler= (Qloss* S) / 100where
- Rboiler- boiler output;
- Qloss- heat loss;
- S - heated area.
The estimated power of the boiler must be increased. The stock is needed if you plan to use the boiler for heating water for the bathroom and kitchen.
Most private houses heating is recommended to be sure to use an expansion tank in which the supply of the coolant to be stored. Each private house in need of hot water supply
In order to provide power supply of the boiler in the last formula it is necessary to add a safety factor K:
Rboiler= (Qloss* S * K) / 100where
TO - will be equal to 1.25, that is, the calculated boiler capacity will be increased by 25%.
Thus, the power of the boiler provides the ability to maintain the air temperature in the regulatory building rooms, and have an initial and additional volume of hot water in the building.
Features selection of radiators
Standard components provide indoor heat radiators are, panel system "warm" floor, convectors and the like. D. The most common parts of the heating system have radiators.
Heat sink - a special hollow design of the modular type of alloy with high emissivity. It is made from steel, aluminum, cast iron, ceramics, and other alloys. actions radiator principle is reduced to energy radiation from the coolant in the space of the room through the "petals".
Aluminum and bimetal radiator replaced the massive cast-iron batteries. Ease of production, high heat, successful design and design made it a popular and common tool for heat radiation in the room
There are several techniques calculating radiators in the room. The below list of ways to be sorted in order of increasing precision.
Variants of computing:
- by area. N = (S * 100) / C, where N - number of sections, S - Area (m2), C - a heat transfer radiator sections (W, taken from the passport or a certificate in the product), 100 W - the number of the heat flow required for heating 1m2 (Empirical value). The question arises: how to take into account the height of the ceiling of the room?
- by volume. N = (S * H * 41) / C, where N, S, C - similarly. H - height of the room 41 W - the number of the heat flow required for heating 1m3 (Empirical value).
- from the coefficients. N = (100 * S * k1 * k2 * k3 k4 * * * k5 k6 k7 *) / C, where N, S, C, and 100 - similarly. K1 - accounting of the number of cameras in the pane window of the room, k2 - thermal insulation of walls, K3 - the ratio of the area of windows to floor area, K4 - average minus the temperature in the coldest week of winter, K5 - the number of the outer walls of the room (which is "out" on the street), K6 - the type of top facilities, K7 - height ceiling.
This is the most accurate version of calculating the number of sections. Naturally, the rounding of fractional calculation results is always carried out to the next whole number.
Hydraulic calculation of water supply
Of course, "painting" the calculation of heat for heating may not be complete without calculating the characteristics such as volume and coolant velocity. In most cases, the coolant performs regular water in liquid or gaseous aggregate state.
The actual volume of coolant is recommended to count through the summation of all the cavities in the heating system. When using single-circuit of the boiler - it is the best option. In the application of double-boiler heating system it is necessary to consider the costs of hot water for sanitary and other domestic purposes
Calculation of the volume of water heated boiler dual-circuit to provide occupants with hot water and heating the coolant, It is made by adding the internal volume of the heating circuit and the real needs of users in the heated water.
The volume of hot water in the heating system is calculated by the formula:
W = k * Pwhere
- W - volume of heat carrier;
- P - the heating power of the boiler;
- k - power ratio (number of gallons per unit of power is equal to 13.5, range - 10-15 L).
As a result, the final formula is as follows:
W = 13.5 * P
coolant velocity - Final dynamic estimation heating system that characterizes the rate of fluid circulation in the system.
This value helps to assess the type and diameter of the pipeline:
V = (0.86 * P * μ) / ΔTwhere
- P - boiler output;
- μ - the efficiency of the boiler;
- ΔT - the temperature difference between the supplied water and water return flow.
Using the above methods hydraulic calculationIt is able to get the real parameters, which are the "foundation" of the future of the heating system.
EXAMPLE thermal calculation
As an example, the thermal calculation of stock is an ordinary one-storey house with four living rooms, kitchen, bathroom, a "winter garden" and storeroom.
Fundam of monolithic reinforced concrete slab (20 cm), outer walls - concrete (25 cm) of plaster, cement - the overlap of the wooden beams, roof - metal and mineral wool (10 cm)
We denote the initial parameters of the house, necessary for the calculations.
Building dimensions:
- floor height - 3 m;
- A small box front and back of the building in 1470 * 1420mm;
- large window facade 2080 * 1420mm;
- entrance door 2000 * 900 mm;
- the back of the door (access to the terrace) 2000 * 1400 (700 + 700) mm.
The total width of 9.5 meters of construction2, Length 16 m2. Will only be heated living rooms (4 pcs.), A bathroom and a kitchen.
For an accurate calculation of the heat loss to the walls of the area of the external walls is necessary to subtract the area of windows and doors - is a different type with its thermal resistance of the material
We start with the calculation of the area of homogeneous material:
- floor area - 152 m2;
- Roof area - 180 m2Taking into account the height of the attic 1.3 m and width of the run - 4 m;
- Window area - 3 * 1.47 * 1.42 + 2.08 * 1.42 = 9.22 m2;
- Door area - 2 * 0.9 + 2 * 2 * 1.4 = 7.4 m2.
The area of the exterior walls will be equal to 51 * 3-9.22-7.4 = 136.38 m2.
We turn to the calculation of heat losses in each material:
- Qfloor= S * ΔT * k / d = 152 * 20 * 0.2 / 1.7 = 357.65 W;
- Qroof= 180 * 40 * 0.1 / 0.05 = 14400 W;
- Qwindow= 9.22 * 40 * 0.36 / 0.5 = 265.54 W;
- Qdoors= 7.4 * 40 * 0.15 / 0.75 = 59.2 Watts;
And Qwall equivalent to 136.38 * 40 * 0.25 / 0.3 = 4546. The sum of all heat loss will be 19628.4 watts.
As a result, we calculate the heat output: Pboiler= Qloss* Sotapliv_komnat* K / 100 = 19628.4 * (10.4 + 10.4 + 13.5 + 27.9 + 14.1 + 7.4) * 1.25 / 100 = 19628.4 * 83.7 * 1.25 / 100 = 20536.2 = 21 kW.
Calculating the number of radiators proizvedom sections for one of the rooms. For all other computations are similar. For example, a room corner (left bottom corner of circuit) area of 10.4 m2.
Hence, N = (100 * k1 * k2 * k3 k4 * * * k5 k6 k7 *) / C = (100 * 10.4 * 1.0 * 1.0 * 0.9 * 1.3 * 1.2 * 1.0 * 1.05) /180=8.5176=9.
To this room heating radiator 9 need to heat transfer sections 180 watts.
We proceed to the calculation amount in the coolant system - W = 13.5 * P = 13.5 * 21 = 283.5 liters. Hence, the flow velocity will be: V = (0.86 * P * μ) / ΔT = (0.86 * 21000 * 0.9) /20=812.7 l.
As a result, a complete revolution of all the coolant volume in the system will be equivalent to 2.87 times in one hour.
Selection of articles on thermal calculations will help determine the exact parameters of the elements of the heating system:
- Calculation of the heating system of a private house: rules and calculation examples
- Thermal calculation of the building: and specificity of formula performing computations + practical examples
Conclusions and useful videos on the topic
Simple calculation of the heating system for private homes is presented in the following overview:
All the subtleties and common methods miscalculation heat buildings are shown below:
Another option for calculating the heat leakage in a typical private house:
This video tells about the features of the circulation of energy carrier for heating homes:
Thermal calculation of the heating system is individual, it is necessary to perform competently and accurately. The more precise calculation to be made, the less will have to pay the owners of a country house in operation.
You have experience in thermal design of the heating system? Or have questions on the subject? Please share your opinion and leave comments. the feedback unit is located below.
