Heaters have high performance, so with their help, even very large rooms can be heated in a relatively short time. Many models of these devices working on the basis of different heat carriers come into the market.
To choose the best option, you need to calculate the heater, which can be performed either manually or using an online calculator. With the question of calculations, we will help you to understand - in this article we will give an example of calculations that will be needed when choosing a suitable instrument for heating the air.
And also consider the design features of various types of heaters, the advantages and disadvantages of a heating system using such devices.
The content of the article:
- Pros and cons of heating with heater
- Classification of devices for air heating
Design of heaters of different types
- View # 1 - Smooth Pipe Heaters
- View # 2 - Finned Air Heaters
- View # 3 - bimetallic heaters with fins
What to look at when choosing?
- Calculator required calculations
- Recommendations for choosing an electrical model
- Conclusions and useful video on the topic
Pros and cons of heating with heater
The heating system of the house, based on the supply of air heated to the set temperature directly to the house, is of particular interest to the owners of their own homes.
This design of the heating system consists of the following important components:
- a heater that acts as a heat generator that warms the air;
- channels (ducts) through which heated air flows into the house;
- the fan directing well heated air on all volume of the room.
The advantages of this type of system are many. These include both high efficiency and the absence of auxiliary elements for heat exchange in the form of radiators, pipes, and the possibility combine it with the climate system, and low inertia, with the result that the heating of large volumes is very quickly.
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Air heater - heating device intended only for processing the air flow without changing the humidity of the treated mass
Heaters are equipped with air heating and air conditioning systems, which mix the fresh portion of air from the street to the circulating flow.
In air heating systems, the air heated by the heater is forced into the room by means of a fan
A weighty advantage of the use of heaters is their ability to heat large premises in space and volume, including shops, malls, warehouses, as quickly as possible.
Air heating equipment
Air conditioning system with heater
Air heating with heater
Fast heating of large areas
For many homeowners, the disadvantage is that the installation of the system is possible only simultaneously with the construction of the house itself and then its further modernization is impossible.
The downside is such a nuance as the mandatory availability of backup power and the need for regular maintenance.
The heater is easy to install and operate, affordable, but most importantly, it is an effective device for heating the room. Pictured water heater mounted in the system
Our site has more detailed materials on the device of air heating in the house and cottage. We recommend that you familiarize yourself with them:
- Do-it-yourself air heating: everything about air heating systems
- How to arrange air heating of a country house: the rules and schemes of construction
- Calculation of air heating: basic principles + example calculation
Classification of devices for air heating
Heaters are included in the design of the heating system for heating the air. The following groups of these devices exist by the type of heat carrier used: water, electric, steam, fire.
It makes sense to use electrical devices for premises of no more than 100 m². For buildings with large areas a more rational choice would be water heaters, which function only with a heat source.
The most popular are steam and water heaters. Both the first and second surfaces are divided into 2 subspecies: ribbed and smooth pipe. The finned heaters on the geometry of the fins are plate-like and spiral-wavy.
Capacity of the heaters working on such a coolant as steam, is regulated by means of special valves installed on the inlet pipe
According to the constructional design, these devices can be one-way, when the coolant in them moves through the tubes, adhering to constant direction and multi-pass, in the covers of which there are partitions, as a result of which the direction of movement of the coolant is constantly is changing.
4 models of water heaters and steam heaters are sold, differing in the heating surface area:
- CM - the smallest with one row of pipes;
- M - small with two rows of pipes;
- WITH - average with pipes in 3 rows;
- B - large, having 4 rows of pipes.
During operation, water heaters withstand large temperature fluctuations - 70-110⁰. For good performance of this type of heater, the water circulating in the system must be heated to a maximum of 180⁰. In the warm season, the heater can serve as a fan.
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According to the type of coolant used in the heating, the heaters are divided into water, steam, fire and electric
In the heating of private, commercial and industrial facilities, steam and water heaters are most often used.
Electric air heaters - the easiest option to install, connect and maintain, but not very rational from an economic point of view
Steam heaters are divided into smooth-tube models and finned devices. Ribbed are divided into spiral-wavy and lamellar
Water heater in the production room
Steam heater on the glazed terrace
Compact electric air heater
Spiral wound model
Design of heaters of different types
The heating water heater consists of a body made of metal, a heat exchanger placed in it in the form of a series of tubes and a fan. At the end of the unit there are inlet pipes through which it is connected to a boiler or a centralized heating system.
As a rule, the fan is in the back of the device. His task - to drive the air through the heat exchanger.
After heating, through the grate located on the front of the heater, the air returns to the room.
Most often the body is made in the shape of a rectangle, but there are models designed for round ventilation ducts. On the supply line install two- or 3-way valves to adjust the power of the unit.
The fan blows tubes located in the body of the heater. Heated water moves through the pipes from the heating system, and the fan distributes evenly warm air around the room.
Different heaters and the method of installation - they are ceiling and wall. Models of the first type are placed behind the false ceiling, only the lattice looks beyond it. Wall appliances are more popular.
View # 1 - Smooth Pipe Heaters
The smooth tube construction consists of heating elements in the form of hollow thin tubes with a diameter of from 20 to 32 mm, spaced 0.5 cm in relation to each other. Coolant circulates through them. The air, washing the heated surfaces of the tubes, heats up due to the convective exchange of heat.
The tubes in the heater are placed in a staggered or corridor order. Their ends are welded into the collectors - upper and lower. The coolant enters the junction box through the inlet, then, after passing through the tubes and heating them, goes through the outlet in the form of condensate or cooled water.
Stable heat transfer devices provide a staggered arrangement of tubes, but the resistance to air flow is higher. It is necessary to perform the calculation of the power of the unit in order to know the real capabilities of the device.
There are certain requirements for air - there should be no fibers, suspended particles, sticky substances. Permissible dust content is less than 0.5 mg / mᶾ. The inlet temperature is at least 20.
One-way and 3-way air heaters. 1 - inlet pipe through which the coolant flows, 2 - junction box, 3 - tube, 4 - outlet pipe, 5 - partition
Thermal characteristics of smooth tube heaters are not very high. Their use is advisable when not required a significant flow of air and its heating to a high temperature.
View # 2 - Finned Air Heaters
The ribbed tubes have a ribbed surface, therefore, the heat transfer from them is greater. With a smaller number of pipes, their thermal performance is higher than that of smooth-tube air heaters.
Lamellar heaters include tubes with plates mounted on them - rectangular or round.
The first type of plates is placed on a group of pipes. The coolant passes to the junction box of the device through the nozzle, warms the air passing from considerable speed through channels of small diameter, and then out of the team box goes through choke.
Heaters of this type are compact, easy to maintain and install.
One-way lamellar devices designate: KFB KFS KVB STD3009V KZPP K4P, and multi-pass - KVB, K4VP, KZVP, KVS, KMS, STDZOYUG, KMB. The average model has the designation KFS, and the large one - KSE.
Steel corrugated tape 1 cm wide and 0.4 mm thick is wound on the tubes of these heaters. The heat carrier for them can be both steam and water.
Water heaters should not be connected with metal-plastic or polymer pipes. they are not designed for heat transfer temperature. Need steel pipes and better galvanized to eliminate corrosion
The first is equipped with three rows of tubes, and the second with four. The plates of the average model have a thickness of 0.5 mm and dimensions of 11.7 x 13.6 cm. Plates of a large model of the same thickness and width are longer - 17.5 cm.
The plates are located at a distance of 0.5 cm from each other and have a zigzag arrangement, whereas in the models of the middle type, the plates are arranged along the corridor principle.
Air heaters with STD marking have 5 numbers (5, 7, 8, 9, 14). In heaters STD4009V steam is a heat carrier, and in STD3010G it is water. The first installation is performed with a vertical orientation of the tubes, the second - from the horizontal.
View # 3 - bimetallic heaters with fins
In heating systems with air heating, models of bimetallic heaters KP3-SK, KP4-SK, KSK-3 and 4 with a special type of fins - spiral-rolling are often used. The heat carrier for KP3-SK, KP4-SK heaters is hot water with the highest pressure of 1.2 MPa and a maximum temperature of 180⁰.
For the operation of the two other air heaters, steam with the same working pressure as for the former, but with a slightly higher temperature — 190 is required. Manufacturers must carry out acceptance tests. Testing devices and tightness.
The heat exchanger of the KSK heater consists of tubes made of steel and having aluminum fins. Connect their tube sheets
There are 2 lines of bimetallic heaters - KSK3, KPZ, with 3 rows of tubes, refer to the middle, and KSK4, KP4 with 4 rows of tubes - to the big models. The components of these devices are bimetallic heat exchange elements, side shields, tube grids, covers with partitions.
The heat exchanger element consists of 2 tubes - with an inner diameter of 1.6 cm, made of steel and aluminum aluminum mounted on it with fins. The transverse interval between the heat transfer tubes is 4.15 cm, and the longitudinal interval is 3.6 cm.
What to look at when choosing?
In the design of a heating system with one or a group of heaters, as well as in the calculations should follow a number of rules. Consider them in more detail in the photo selection below.
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The connection diagram of a group of heaters can be parallel or sequential. For steam units, only the parallel version is applicable. All devices in a heating installation must be of the same model and power.
If the heaters are used in systems that take in outside air in order to move it to the bulk, calculations are carried out taking into account the lowest temperature outside
Adjust the quality characteristics of the steam unit is impossible. Only quantitative adjustment of the coolant is available, for the implementation of which double bypass valves are placed in front of the heater
Calculations and design of heating systems are carried out in such a way that there is a minimum of devices in the group, there is an armature allowing to disconnect one unit or row, and also to regulate the heat transfer
Parallel connection of a group of heaters
Operation of heaters in the cold
Control valves at the entrance to the device
Ribbed Steam Air Heater
Calculator required calculations
To calculate the power of a water or steam heater, the following initial parameters are needed:
- The performance of the system or in other words - the amount of air distilled in an hour. The unit of measurement of the volumetric flow rate is m / h., The mass kg / h. Symbol - L.
- Initial or outdoor temperature is tul.
- The final air temperature is tcon.
- The density and heat capacity of air at a certain temperature - the data are taken from the tables.
First, calculate the cross-sectional area along the front of the air heater. Knowing this value, get the preliminary dimensions of the unit with a margin.
For calculation use the formula:
Af = Lρ / 3600 (ϑρ),
Where L - air volume flow or capacity in m³ / h, ρ - outside air density measured in kg / m³ ϑρ - mass air velocity in the calculated section, measured in kg / (cm²).
After receiving this parameter, for further calculations, we take the typical size of the heater, the closest in size. With a large final value of the area, set in parallel several identical units, the area of which in sum is equal to the value obtained.
Heaters are called not only devices for heat exchange, but also air coolers operating on the basis of cold water, which are much less popular.
To determine the required power for heating a specific air volume, you need to know the total flow rate of heated air in kg per 1 hour by the formula:
G = L x p,
Where R - air density at medium temperature conditions. It is determined by summing the temperature at the entrance and exit of the unit, then divided by 2. Density indicators are taken from the table.
From this table, you can take data on the density and specific heat of air at a certain temperature to calculate the power of the device
Now you can calculate the heat consumption for heating the air, for which the following formula is used:
Q (W) = G x c x (t con. - t beg.),
Where G - mass air flow in kg / h. When calculating, the specific heat capacity of air measured in J / (kg x K) is taken into account. It depends on the temperature of the incoming air, and its values are in the table above. The temperature at the entrance to the device and at the exit from it is indicated t beg. and t con. respectively.
Suppose you need to pick up a heater with a capacity of 10,000 mᶾ / hour so that it heats the air up to 20⁰ at an outside temperature of -30⁰. The heat carrier is water having an outlet temperature of 95⁰ and 50⁰ at the outlet.
Mass flow of air mass: G = 10 000 mᶾ / h. x 1,318 kg / mᶾ = 13,180 kg / h.
Density value: ρ = (-30 + 20) = -10, while dividing this result in half, we got -5. From the table selected, corresponding to the average temperature, density.
Substituting the result in the formula, get the heat consumption: Q = 13,180 / 3600 x 1013 x 20 - (-30) = 185 435 W. Here, 1013 is the specific heat capacity selected from the table at a temperature of –30⁰ J / (kg x K). To the calculated power of the heater add from 10 to 15% of the stock.
The reason is that the tabular parameters often differ from the real ones in the direction of reduction, and the thermal performance of the unit, due to clogging of the tubes, decreases with time. Excess inventory is undesirable.
With a significant increase in the heating surface, hypothermia can occur, and even defrosting in extreme cold.
In the steam heater, the coolant is supplied from above, and the water resulting from the condensation of the exhaust steam is removed from below. On the photo - the steam calorifier piping scheme
The power of steam heaters calculated in the same way as water. Only the calculation formula for the coolant differs:
G = Q / r,
Where r - specific heat, which is released during the condensation of steam, measured in kJ / kg.
Recommendations for choosing an electrical model
Manufacturers in the catalogs of electric heaters often indicate the installed power and air flow, which greatly simplifies the selection. The main thing is that the parameters should not be smaller than those indicated in the passport, otherwise it will quickly be out of order.
The design of the heater includes several special electric heating elements, the area of which is increased due to the pressing on of the fins.
Power devices can be very large, sometimes it is hundreds of kilowatts. Up to 3.5 kW, the heater can be powered from a 220 V outlet, and at voltages above this, a connection should be made with a separate cable directly to the panel. If there is a need to use a heater with a capacity higher than 7 kW, a power of 380 V. will be required.
These devices have small dimensions and weight, they are completely autonomous, for them the presence of centralized hot water supply or steam is not necessary.
A significant disadvantage is that low power is not sufficient for using them on large areas. The second drawback is high power consumption.
From the calculation of the heater, it follows that the result of using the device is a tangible saving of energy resources. Sometimes this unit is combined with a recuperator and then the air intake occurs not from the outside, but from the room.
To find out what current consumes a heater, you can use the formula:
I = p / u,
Where P - power, U - supply voltage.
With a single-phase connection of the heater, U is assumed to be 220 V. With 3-phase - 660 V.
The temperature to which the heater of a certain power heats the air mass is determined by the formula:
T = 2.98 x P / L,
Where L - system performance. The optimal values of the power of the heater for the house from 1 to 5 kW, and for offices - from 5 to 50 kW.
Conclusions and useful video on the topic
What is the density of air to take in the calculation, described in this video:
Video on how the heater works in the heating system:
When choosing a specific type of heater, you should proceed from considerations of expediency and operational characteristics of the house.
For small areas, an electric heater will be a good acquisition, and for heating a large house it is better to choose another option. In any case, can not do without prior calculation.
Are you familiar with the choice and calculation of the heater? Perhaps you want to share useful recommendations on the choice of the heater or point out an error or inaccuracy in the calculations in the material discussed above? Leave your comment under this article - your opinion can be useful to people who choose the right heater for their home.