As soon as the product data is not called - ranging from fire heaters, heat guns, just burners and further: gas calorificates, gas furnaces, Hot (warm) air generators, air heat generators. The most common (faithful) name is the same gas air heaters and, if you look from the side of the air intake installations, the gas sections of heating. This material - this is short review On the topic for ventilation and air conditioning specialists for which gas air heaters are still new.
The main focus is on the supply plants with gas heating.
Direct heating- This is heating the air directly with the flame of the burner. The devices of direct heating (they are also called air heaters of the mixing type) do not have no combustion chambers or heat exchangers.
Modern systems The burning makes it possible to highly burn natural gas, but when designing it is necessary to calculate the dilution of the troubles entering the combustion facility below the MPC. These aggregates are particularly effective at large multicast of air exchange, when the level of harmful to indoors is significantly higher than the level of combustion products from the gas air heaters of direct heating: foundry, welding workshops, etc.
Range of thermal power - 40-1500 (2000) kW.
Due to the smaller metal, mixing gas air heaters are cheaper than recuperative. Large power modulation range. No chimney, combustion products immediately mixed with heating air - no need to think about condensate combustion products when working with negative temperatures Street air.
Widely common in the USA, Canada, Great Britain. There are manufacturers in France, Germany and Holland. In Russia, it is still relatively rarely used, although we have several domestic manufacturers.
With an indirect heating, the air supplied inside the unit with a fan is heated by passing around the combustion chamber and through the heat exchanger. Then the heated air is released either directly into the room, or is supplied through the system of air ducts. Combustion products are derived through chimney.
The devices of indirect heating in turn are divided into air heaters with built-in atmospheric burner (from tubular heat exchanger) (Fig. 2, 3, 4) and heat exchange modules with an additional fan (inflatable, blowing) burner.
Schematic scheme The units of the first type: at the entrance of the atmospheric burner, i.e., working under atmospheric pressure and consisting, as a rule, from several nozzles / injectors (similar as on any home gas stove). Next, after a tubular (lamellar) heat exchanger at the outlet of the chimney fan, thanks to which the products of combustion and pass the heat exchanger.
Dignity- Simple design, and therefore competitive price.
Disadvantages:
a small range of thermal power: 15-150 (200) kW. To ensure greater thermal power, these heat exchange modules are set sequentially and / or in parallel, which leads to an increase in the value of this solution;
difficulties, if necessary, work in the condensation mode of combustion products.
Scheme of an air heater with a fan burner: a fan burner is installed in the combustion chamber of the heat exchange module (i.e. with a fan). Thanks to the pressure generated by the burner, combustion products pass through the combustion chamber and heat exchange tubes (channels).
Range of thermal power - 40-1000 (1200) kW. The more expensive solution compared to the corresponding heat powered by atmospheric burners, but but the more significant range is in power, it is easier to solve the issue with the formation of condensate of combustion products - the possibility of using diesel burners.
Intermediate conclusion: At the moment, due to the small heat range, gas air heaters with an atmospheric burner are advisable to use for small aircraft installations or monoblock (roof - roof top) air conditioners. For large central air conditioners and aircraft installations, more competitive gas air heaters (heat exchange modules) with an additional fan burner. Further in more detail about the embodiment of the gas sections of heating consisting of a heat exchange module (air heater) and a fan (inflatable) burner.
The heat exchange module under the fan burner conventionally consists of a combustion chamber and further heat exchanger.
Most manufacturers use the following materials:
The phenomenon of the formation of condensate products of combustion directly in the heat exchanging module is due to the increased cooling of the latter. With constant nominal air flow, this can be caused by a low temperature of the supply air or a decrease in the thermal power of the burner below 60-65% of the nominal air at work per 100% recycled air.
One way to reduce the condensate of the combustion products inside the heat exchange module is an organization of a bypass line, operating depending on the temperature of combustion products in the chimney.
Fuel for gas air heaters can serve first, liquefied petroleum or hydrocarbon gases (SUG): propane and butane. They are also called heavy hydrocarbons, since they, in contrast to natural gas, heavier than air. With leaks, they are more dangerous, as they do not destroy, but they are spilled by the floor, filling the niche. It is a mixture of propane and butane sold for household needs in cylinders.
Liquefied carbon gases when replacing the nozzle and the corresponding reconfiguration can use almost any burner. However, due to the fact that the Sug is not much cheaper than diesel fuel, for industrial facilities This is a very rare option.
Secondly, the fuel for the burner can be liquefied natural gas (LNG), that is, liquefied methane. It is cheaper than Sugh, but in Russia with its developed network of gas pipelines its use is exotic.
Finally, the third and most common option: Natural gas - methane.
Gas pipelines for natural gas are divided into low (up to 0.05 kgf / cm2), medium (from 0.05 to 3 kgf / cm²) and high (from 3 kgf / cm²) pressure.
Atmospheric burners and premix burners are designed for low - 20 mbar - the inlet pressure of the gas, when connecting them to the gas pipeline, as a rule, additional reduction gearboxes should be used.
Inlet pressure The fan burners (Fig. 7) may be different depending on the gas ramp used (Multible) (Fig. 7). The lower limit depends on the characteristics of the ramp and the heat exchange module. The top threshold in the burners is usually fixed: 100, 360 or 500 mbar. Thus, fan burners can work in low and medium pressure networks.
It should be said that the composition of gas heat generators can be diesel burners. In addition, exist combined burnersworking on gas and on diesel fuel. But such a solution is quite expensive, so if necessary, the diesel burner is first put at objects, and then gas is bought.
When using diesel burners, it should be avoided in the condensation mode of combustion products.
Depending on the task of the burner can be:
Single-stage - work on one fixed power;
Two-stage - operate on two pre-installed power values \u200b\u200b(low and high);
Modulating - its power can smoothly vary from MIN values \u200b\u200bto MAX.
The selection of burners is carried out by the power of the heat generator and the oppression created in the combustion chamber; In addition, it is necessary to consider the length of the nozzle burner. The length of the burner nozzle must be in the range specified by the manufacturer of heat exchange modules.
Air heaters (heat exchange modules) are equipped with a thermostat unit that provide internal logic of the operation and the safety of the heating section, but do not control the temperature in heated and / or ventilated room. Automation for temperature control indoors (in the air duct) is a separate question depending on the task and the burner used.
The placement of gas heating intake installations inside the heated premises is regulated by the NPB document 252-98 "Thermogenerating devices operating on different types Fuel. Fire safety requirements. "
If the air heater is placed in the ventilation chamber (Fig. 9), then the norms of SNIP II 35-76 * "boiler installations" should be viewed here.
The easiest option in terms of coordination and regulatory documents - Street accommodation. At the same time, you should not forget about maintenance in the fresh air.
Standard European floor heater heat generators (air heaters) of street performance are designed for operation at temperatures to -15 (20) ° C. The burner automatics allows it to be turned on at a temperature not lower than -15 ° C. Usually, the burner and the electric shield are simply covered with a casing of sandwich panels (
In most cases, this is enough, since the burner is warming up and the surrounding space. There are examples when these measures allow the burner to normally serve in the Russian conditions for more than one year.
In fig. 11 You can see an example of a more thorough execution of the gas air heater section: section with a burner is isolated from all sides, lattices are made for ventilation section.
In the regions where the temperature in the winter falls below -30 ° C, the section with a burner must be heated. Most often, an additional electric heater is installed for this, sometimes warm air from heated room or ventilation channel.
In general, the gas air heater (inlet installation with the heating gas section) is more expensive by capital expenditures of a similar installation with water (electric) heating, but, on the other hand, the gas air heater is always cheaper than boiler room + water supply installation of similar thermal power.
Accordingly, gas air heaters are most competitive when there is no parallel large boiler house (heating mains), and a small boiler room is used, let's say on some small ABC (office center) and / or DHW
That is, a single system is built on the basis of gas air heaters air heating and ventilation: industrial premises, warehouse, shopping complex, cinema or gym. As a rule, in this case, mixing chambers (air heaters) are provided for mixing chambers for simultaneous operation with supply and recycled air. It is possible to damn and / or ventilate particularly fire-hazardous premises due to the supply of superheated 100% supply air, but such installations are more expensive and complex. Initially, the main purpose of gas air heaters is air heating.
A gas air heater in a clean supply installation mode, solving only the ventilation problem, is used for rooms heated by gas infrared heaters (radiant heating) or mounted gas air heaters (gas AVO).
Currently, several types of aggregates with gas heating are presented on the market. The first type is floor heater heat generators (gas air heaters). Such devices consist, as a rule, only from the heat exchange module and the fan sections. The second is the monoblock roofing conditioners (in English they are called ROOF TOP), which, in addition to the cooling section, can have a heating section on water, electricity or gas. Finally, the third is custom-made supplies and supply and exhaust installations with the gas section of heating.
It is clear that the use of standard solutions is lower capital costs, but sometimes the only acceptable option is custom installations, equipped, for example, by the recovery section, humidification and other additional equipment.
We consider the topic on this topic. Some nuances are better clarified by a specific task by contacting the profile.
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Recuperative air heater with atmospheric burner |
Section of gas heating with atmospheric burner |
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Air heater with fan burner |
Heating section with bypass |
 Fan hot chuck gas Rampa
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An example of an object with gas supplies |
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Execution of the section under the burner with street accommodation |
For comfortable stay in the house or in the apartment, it is important for both cold and warm water. In order to heat the water, the instruments are in demand. of different typesUsing different sources of energy for their work. Since natural gas is one of the available energy resources, boilers operating on such fuel are quite common.
It is a gas boiler much more than electrical models.
The main element of the gas boiler is a gas burner located in the combustion chamber under water tank. From her through a boiler tank passes a pipe, which disks combustion products. Heat is transferred to water in the tank and from the burner itself, and from this pipe.
The power of the burner directly affects the productivity and power of the boiler.In the wall aggregates, gas installations are usually used with a capacity of up to 5 kW, and in the outdoor - over 6 kW.
The outer corps and the tank of most modern gas boilers are made of metal. It can be both stainless steel and a different metal with an enameled coating. From the inside the wall of the drive is often treated with a coating that impede corrosion - glass-ceramic, titanium or other.
There is a thermal insulating layer between the water tank and the outer corps in gas boilers. Its function is to preserve the water temperature, which was heated in the boiler, for some time after heating. From above on the housing there is a control unit.
Water is supplied inside the gas boiler tank over the inlet nozzle, and is selected from the top of the apparatus along the outgoing pipe associated with the cerave of hot water.
In our previous article we told you about , His characteristics and construction. Like all boilers for heating, it only works in a tandem with a stationary heating system. Today we will tell you about gas heaters for the house that neither the pipes nor the heat carrier do not need, nothing but a cylinder with propane. There are several types of such aggregates. These include infrared, catalytic and convection gas heater for giving. Feedback from people who used them for heating their homes are reduced to one: conveniently, but somewhat dangerous, the gas is still, you should be extremely prudent and be sure to air the room.
Gas heaters are equally well operating on natural gas and propane.
Let's start with the fact that gas heaters can work regardless of the availability of any communications and networks. So, it does not require a water supply with sewage, no electricity. Even the central supply of natural gas is not needed. All that will be needed is a cylinder with liquefied gas. In this case, the gas heater for the cottage, according to reviews, it can work on that gas that comes on the gas pipeline is centrally, that is, from natural gas.
Based on this, it turns out that the gas heater for the house can be used anywhere, even in a deaf taiga, at least in the apartment high-rise buildings, even in a tent on the top of Everest. By the way, it is not necessary to forget that in the mountains at high height pressure is not like on the plain, so you need to use special cylinders. Gas heater for the apartment is a very mobile device. They are different depending on the heating method, despite the fact that everyone uses the same type of fuel - natural or gas liances.
On the principle of operation, two groups of instruments are distinguished:
Gas heaters for apartments that warm objects work on the principle of all known, electrical infrared heaters "UFO". If the item is in the radiation range, then it is heated, and if not, it remains cold until the heat reaches the indirect paths, which we will tell a little later. In the case of heating, the air is quite simple and understandable.
In different situations, one or another gas heater is used. The need for heating can occur both indoors and on the street. Based on this, you can highlight the following classification of gas heaters for giving with a cylinder:
Below will look at the main types of gas heaters for giving with a balloon individually, their characteristics, as well as the scope of application.
One of the modifications of the infrared heater per gas.
An infrared gas heater for the house does not heat the air, it affects only objects. For greater efficiency, the heater is better to place higher, so that the range of infrared radiation is wider. Infrared Heater Design:
The heater dimensions can be different: from mini-models for tents, to more solid devices for garages warming up and large premises.
Gas infrared heater For giving should be at some distance from the cylinder, since the principle of its work implies the presence of a flame from burning.
Visually it is unnoticed, but it is still present, although there is alternative options. A ceramic plate is a ceramic plate as a heat exchanger. To connect a gas heater for giving enough to fasten the hose from the cylinder on the nozzle of the machine.
Principle of operation:
Thus, the total temperature in the room also grows, but only very slowly, since air heating is not carried out from the flame itself, but in several intermediary stages. In addition to the traditional combustion of fuel in a ceramic heat exchanger, fluid (catalytic) burning is used in such gas heaters for the house. Its essence we will explain below, but besides the differences in technological process, There is also a difference in the temperature of the heat exchanger.
In conventional burning with the presence of a flame, ceramic elements are heated to a temperature of 800-1000 degrees. This so-called high-temperature appliances, in which the heat exchanger besides heat emits light. When catalytic combustion, the temperature of the ceramic heat exchanger does not exceed 600 degrees, with no light. In addition to the heating function, the infrared gas heater can serve as a stove for cooking.
Such devices can be used both indoors (necessarily well ventilated) and outside. There are special gas outdoor heaters for giving. On the street, infrared devices work no worse than indoors, and heat losses are reduced only to the cooling of heated items. The aggregate itself has a similar efficiency, regardless of the situation.
In a catalytic heater with back side There is a niche for a cylinder, although it can stand separately.
Catalytic gas heater from the balloon for the home difference with infrared the fact that:
Catalytic combustion is a flameless combustion in which gas is experiencing deep oxidation to CO2 and H2O due to the effects of catalysts. Two metal can be used as a catalyst: platinum or palladium, as well as several metal oxides, such as:
In catalytic gas heaters for the heating of a private house, the heat exchanger is made of fiberglass, and then a catalyst is applied, more often than platinum. When the gas interacts with a platinum coating, a chemical reaction begins with abundant heat release, with the smoke and fuel combustion products. Catalytic combustion occurs with the minimum amount of oxygen, in contrast to infrared gas heaters for the room. Catalytic gas heaters can be equipped with additional electric tanks and fans. In this case, the device becomes energy-dependent.
Convectors need chimney by which smoke will go and enter the air into the combustion chamber.
Convector heaters for home are used not so long ago. These units cannot boast of mobility and belong to stationary equipment. The fact is that the heating of the house with a gas heater of convector type is possible only if there is a convector, like a catalytic heater, heats the air, but it has an open flame, as in gas boiler For heating. Through coaxial chimney The oxygen required for burning is coming, and the smoke is derived to the street. It turns out that the device does not burn the air at all indoors.
Air heating is carried out not directly from the flame, but through a metal heat exchanger. Burning chamber in the convector hermetic, by analogy with . Principle of operation:
In the case there are holes through which circulation (convection) is carried out. At the bottom of the heater installed a fan. It turns on with the button on the housing and contributes to more active air convection. The convector heater can operate both on natural gas and propane-butane.
The device is equipped with a control unit and a thermostat, thanks to which you can set the required temperature in the room. The intensity of operation is regulated by a combined valve that controls pressure and gas supply to the combustion chamber. When problems appear with the device or any negative consequences His works, automatics work and the heater is turned off.
There is still such kind of heater as a gas gun. This is, in fact, also convector, only more powerful action. It works from electricity, there is no chimney in it and it is impossible to use it for the heating of residential premises.
In the heat guns there are openings of the flame source, heat from which is blown by a powerful fan. They are very burned with oxygen, therefore can only be used in open spaces. By the way, such guns are used when the stretch ceilings are mounted.
What gas heater is better for giving? When choosing a gas heater for the house initially you must decide which heating method for you is preferable: air heating or items. In the first case, the temperature will gradually rise throughout the room, and in the second, it is assumed instant heating of objects to which infrared radiation falls. In addition, there are portable and stationary types of gas heaters for home, and the price is also different. Cheaper will cost a portable infrared gas heater. The cost of catalytic aggregates is higher due to the high cost of the catalyst components. Convector gas heater is the most expensive and needs a stationary setting and have of chimney. Only infrared heaters are suitable for the street.
If you wondered how to choose a gas heater for cottages, video below will clarify you a situation in the market of heating devices:
In addition to all listed advantages, the compensation air heater is the most economical means of heating the room. How is it possible? It is really very simple.
The system of direct heating gives 100% of its heat into the airflow. System S. indirect heating Always have an exhaust or ventilation pipe, which takes hot gaseous combustion products from the building into the atmosphere.
The air heating device has the original peak level of efficiency of about 56%, since approximately 20% of the fuel is lost in the oscillation gases, and the additional fuel is lost in the heat exchanger, which is about 70% of the effectiveness of the new device. The heat exchanger over time fails, and the level of efficiency may fall up to 40 - 50% of all efficiency.
The air heating device is not only ineffective, it cannot provide a homogeneous temperature, because it depends on the infiltration of cold air for combustion. The combustion process requires approximately 10 parts of atmospheric air to 1 part of natural gas. On one cubic foot of natural gas, approximately 1000 British thermal units (BTO). A typical building can lose about 3,000,000 BTU / h in conventional heat losses. This means that heating devices will consume 3,000 cubic feet of air for combustion every hour. This leakage air for the combustion process should be heated, therefore, it increases the usual infiltration load of the room. The cost of alone air for burning in heating devices is about $ 0.95 / h.
Unlike air-heating devices, the compensation air heater does not bring cold air to the building for combustion. It also does not pull the heated air. In a compressed atmosphere, the temperature is much more homogeneous. The compensation air heater does not use the heat exchanger, it does not pull and serves cold air to the enterprise. Gas-burner It works in accordance with the need, and its effectiveness is approaching 100%. All heat obtained as a result of fuel combustion comes directly to the room. Natural gas contains 8% water. During burning natural gas generates "explicit / physical" heat, which increases the temperature in the room. Present in gas water generates "Latent Heat", providing moisture in the enterprise. When using an air heating device, the latent heat is lost in the exhaust pipe.
Without the compensation air heater, the natural strength of the wind is connected to the mechanical drawing of the building and creates a situation in which the cold air enters the room, and warm leaves it. Cold air accumulates at the floor, and warm rises to the ceiling. Lost energy is going at the ceiling, while the workers are freezing legs. All burners react to covers of cold air at the floor level with more intense burning to compensate for the penetration of cold air.
Positive pressure from the compensatory air heater provides ventilation with controlled embroidery. The building is still breathing, but now the air indoors are more fresh, and the temperature is flat. Fresh air from the compensation air heater pushes outward air and pollutants. The volume of the dumping air is controlled. Exhaust systems in washes and vulcanization furnaces operate on specified volumes, without annoying rustling of burners or reverse thrust.
The occurrence of the aerodynamic tube passing through the equipment, which can occur in air heating devices, is excluded. The cost of 20-40% is lower than with indirect air heating heating.
Infiltration causes strong temperature stratification. The floor is very cold, especially near the doors and on sites, poorly insulated outside. Air heating devices that are often used for heating the room will work constantly, but will never increase the temperature in cold areas to an acceptable level. Air heating devices get their air to combustion from cracks in the walls of the building. Since the cold air penetrates through the cracks constantly, there is no possibility that this room warms up. Heated air from an air heating device rises to the ceiling together with heat generated by vulcanization furnaces and washing. The temperature of the floor may be about 45 ° F, while the ceiling is about 120 ° F (5 ° - 49 ° C) and above. The air heating device continues to operate in a vain force to increase the temperature of the floor at the floor level to a comfortable value. Cold air continues to penetrate, British thermal units are consumed and lost as the temperature and cold air infiltration increases.
Thus, the compensation air heater with direct heating is more efficient than the air heating device. The combustion air enters the heater, heats up to a predetermined value and is injected into the room for efficient energy transmission. Since the air in the building is compressed, heat spreads much more evenly. Those 120 ° F air, which were lost under the ceiling, now extend throughout the enterprise, increasing the overall comfort. Unlike an air-heating device, which allows the cold air to constantly penetrate the room, the compensation air heater takes only the number of outdoor air, which is necessary to meet the needs of the room, increases the temperature to a given value and distributes it evenly throughout the building. The burner modulates to develop only what is needed, not more and no less.
Air heating systems
In general, some cases can significantly reduce capital and operating costs, providing autonomous heating of premises with warm air based on the use of heat generators operating on gas or liquid fuel. In such aggregates, not water heats up, and the air? Fresh trimming, recycling or mixed. This method is especially effective to ensure autonomous heating industrial premises, exhibition pavilions, workshops, garages, stations maintenance, car miles, film studios, warehouses, public buildings, gyms, supermarkets, greenhouses, greenhouses, livestock complexes, poultry farms, etc. .
Advantages of air heating
Advantages of airborne heating in front of traditional water in large rooms in terms of rooms, we will list only the main:
1. Efficiency.
Heat is carried out directly in the heated room and is practically consumable for its intended purpose. Thanks to the direct combustion of fuel without intermediate coolant, a high thermal efficiency of the entire heating system is achieved: 90-94% for recovery heaters and almost 100% for direct heating systems. The use of programmable thermostats provides the possibility of additional savings from 5 to 25% of thermal energy due to the function of the duty regime automatic maintenance Indoor temperatures at no time at + 5-7ºС.
2. The ability to "enable" inflow ventilation.It's no secret that today at most enterprises, the supply ventilation does not work properly, which significantly worsens the working conditions of people and affects productivity. Heat generators or direct heating systems warm the air to ΔT to 90 ° C of this, it is quite enough to "force" the supply ventilation even in the conditions of the Far North. Thus, air heating implies not only economic efficiency, but also an improvement in the environmental situation and working conditions.
3. Small inertia. The units of air heating systems in a matter of minutes go to the working mode, and at the expense of high air turnover, the room is fully heated in just a few hours. This makes it possible to quickly and flexibly maneuver when changing the needs of heat.
4. No intermediate coolantit allows you to abandon construction and content ineffective for large premises of the water heating system, boiler, heating mains and water treatment station. Losses in the heating and their repair are excluded, which allows dramatically to reduce operating costs. IN winter time There is no risk of defrosting the calorificates and the heating system in the event of a continuous disconnection of the system. Cooling even to a deep "minus" does not lead to defrosting the system.
5. High degree of automationallows you to produce exactly the amount of heat in which there is a need. In combination with high reliability gas equipment This significantly increases the safety of the heating system, and for its operation it is quite a minimum of the service personnel.
6. Small costs.The method of heating large premises with the help of heat generators is one of the cheapest and rapidly implemented. Capital Costs for Construction or Reconstruction air systemis usually significantly lower than the cost of organizing water or radiant heating. The payback period of capital expenditures usually does not exceed one or two heating seasons. Depending on the tasks being solved, heaters of various types can be used in air heaters. In this article, we will consider only aggregates working without the use of intermediate coolant recovery air heaters (with a heat exchanger and the tension of combustion products outside) and the direct heating system (gas mixing air heaters).
Recovery air heaters
In the aggregates of this type, the fuel mixed with the necessary amount of air is supplied to the burner into the combustion chamber. The resulting combustion products pass through a two- or three-way heat exchanger. The heat obtained during the combustion of the fuel is transmitted to the heated air through the walls of the heat exchanger, and the flue gases through the chimney are allocated to the outside (Fig. 1) that is why they are called the heat generators of "indirect heating". Recovery air heaters can be used not only directly for heating, but also in the system of supply ventilation, as well as for process heating of air. Nominal thermal power of such systems from 3 kW to 2 MW. The supply of heated air into the room is carried out through a built-in or remote injection fan, which makes it possible to use the aggregates for both direct heating of air with the issuance of it through the lolome grilles and with air ducts. Washing the combustion chamber and heat exchanger, the air heats up and heads either directly into the heated room through the lolous air distribution lattices located in the upper part, or is distributed through the air duct system. On the front of the heat generator there is an automated block burner (Fig. 2)
The heat exchangers of modern air heaters are usually made of stainless steel (heat-resistant steel firing) and serve from 5 to 25 years, after which they can be repaired or replaced. Kpd. modern models reaches 90-96%. The main advantage of recovery air heaters their versatility. They can work on natural or liquefied gas, diesel fuel, oil, fuel oil or spent oil is only worth changing the burner. There is the possibility of working with fresh air, with an internal and in full recirculation mode. Such a system allows some libations, for example, changing the flow of heated air, "on the go" to redistribute the streams of heated air into different branches of air ducts using special valves. The regenerative air heaters can operate in ventilation mode. Units are mounted both in vertical and horizontal position, on the floor, wall, or embedded in a sectional ventka meter as a heater section. Recuperative air heaters can be used even for heating the premises of a high category of comfort, if the unit itself is deposited beyond the location of the direct service area.
Basic Disadvantages:
1. A large and complex heat exchanger increases the cost and weight of the system, compared with mixing type air heaters;
2. Need chimney pipe and condensate discharge.
Direct air heating systems
Modern technologies have made it possible to achieve such a purity of the burning of natural gas, which appeared the possibility of not to remove the combustion products to "into the pipe", but use them for direct heating of air in the supply ventilation systems. Gas coming to burning, completely burns in the stream of heated air and, mixing with him, gives it all warm. This principle was implemented in a number of similar designs of the ramp burner in the United States, England, France and Russia and successfully used since the 60s of the XX century at many enterprises of Russia and abroad. Based on the principle of ultrapure combustion of natural gas directly in the stream of heated air Gas mixing air heaters of type STV (Starveine "Star Wind") are made with a nominal thermal power from 150 kW to 21 MW. The technology of combustion organization itself, as well as the high degree of dilution of combustion products, allow you to obtain clean warm air in installations in accordance with all current norms, practically inconsistent impurities (not more than 30% of the MPC). The air heaters STV (Fig. 3) consist of a modular burner block located inside the housing (duct section), Dungs gas line (Germany) and automation systems. The case is usually equipped with Hermeodore for convenience of service. The burner block, depending on the required thermal power, is composed of the required number of burner sections of different configurations. The heater automation provides a smooth automatic start of a cyclogram, monitoring the parameters of safe operation and the possibility of smooth control of thermal power (1: 4), which allows you to automatically maintain the necessary air temperature in the heated room.
The use of gas mixing air heaters
Their main purpose is the direct heating of fresh supply air supplied to industrial premises For compensation exhaust ventilation And improvements, thus, the working conditions of people. For premises with high multiple air exchange, the expediency of combining the system of supply ventilation and heating system - in this regard, there are no competitors in the ratio of price / quality in the ratio of direct heating. Gas mixing air heaters are designed for:
· Autonomous air heating of premises various destination with a large air exchange (to 1.5);
air heating in air-thermal curtains of a shut-off type, possibly combined with heating systems and supply ventilation;
preheating systems of car engines on unheated parking;
heating and defrosting of wagons, tanks, cars, bulk materials, heating and drying products before painting or other types of processing;
direct heating of atmospheric air or drying agent in various installations of technological heating and drying, such as drying grain, herbs, paper, textiles, wood; Applications in coloring chambers and drying after painting, etc.
Accommodation
Mixing heaters can be built into the air channels of the supply ventilation systems and thermal curtains, into the air ducts of drying installations both on horizontal and vertical sites. Can be mounted on the floor or platform, under the ceiling or on the wall. Placed, asked, in the supply and ventilation chambers, but it is possible to install them and directly in the heated room (in accordance with the category). For additional equipment The corresponding elements can serve the rooms of categories A and B. Recycling of internal air through mixing air heaters is undesirable to a significant decrease in the level of oxygen in the room.
Strengths of straight heating systems
Simplicity and reliability, low cost and efficiency, the possibility of heating to high temperatures, high degree of automation, smooth regulation, do not need a chimney device. Direct heating is the most economical method - the efficiency of the system is 99.96%. The level of specific capital expenditures on the heating system based on the installation of direct heating combined with the supply ventilation is the lowest at the highest degree of automation. All types of air heaters are equipped with a security and control system, providing smooth start, maintaining the heating mode and shutdown in case of emergency situations. For the purpose of energy saving, it is possible to equip the adjustment automation air heaters, taking into account the outer and control of the internal temperatures, the functions of daily and weekly heating programming modes. It is also possible to enable the parameters of the heating system consisting of many heating units, to the system of centralized management and dispatching. In this case, the dispatcher operator will have operational information on the operation and the state of heating units, visually displayed on the computer monitor, and also manage their operation mode directly from the remote control center.
Mobile heat generators I. heat guns
Designed for temporary use - at construction sites, for heating in offseason periods, technological heating. Mobile heat generators and thermal guns work on propane (liquefied balloon gas), diesel fuel or kerosene. There can be both direct heating and with a discharge of combustion products.
Types of autonomous air heating systems
For autonomous heat supply of various premises, various types of air heating systems are used - with centralized heat distribution and decentralized; Systems operating completely on the influx of fresh air, or with full / partial recirculation of internal air. In decentralized air heating systems, heating and air circulation indoors are carried out by autonomous heat generators located in various sections or work areas - on the floor, wall and under the roof. Air from heaters is supplied directly to the work area of \u200b\u200bthe room. Sometimes, for a better distribution of thermal flows, heat generators are equipped with small (local) air duct systems. For aggregates in this version, the minimum power of the fan electric motor is characterized, so decentralized systems are more economical in terms of electricity consumption. It is also possible to use air-thermal curtains as part of the air heating system or supply ventilation. The possibility of local regulation and use of heat generators as needed by zones, at different times it makes it possible to significantly reduce fuel costs. However, the capital costs for the implementation of this method are somewhat higher. In systems with centralized heat distribution, air-heating aggregates are used; We produce warm air enters the working areas on the system of air ducts. Installations, as a rule, are embedded in existing vents, but it is allowed to place them directly in the heated room on the floor or on the site.
Application and accommodation, selection of equipment
Each types of the above heating units have their indisputable advantages. And there is no ready-made recipe, in which one more expedient it depends on many factors: the values \u200b\u200bof air exchange in correlation with the size of heat loss, room category, availability free space To accommodate equipment, from financial capabilities. We will try to form the most general principles Calculating equipment selection.
1. Systems of heating for rooms with a small air exchange (Conducting ≤0.5-1)
The total thermal power of heat generators in this case is taken almost equal to the amount of heat required to compensate for the heat loss of the room, the ventilation is relatively small, therefore it is advisable to use the heating system based on indirect heating heat generators with full or partial recirculation of indoor indoor air. Ventilation in such premises may be natural or with a stroke air bench for recycling. In the second case, the power of heaters increases by a value sufficient to heat the fresh supply air. Such a heating system may be local, with outdoor or wall heat generators. If it is impossible to place the installation in a heated room or with the organization of servicing several rooms, you can apply a centralized type system: heat generators to locate in the ventkamera (attachment, on the mezzanine, in the adjacent room), and heat through the air ducts. During the working hours, heat generators can operate in partial recirculation mode, along the way heating the mixed aircraft air, while you can turn off some of them, and the remaining translate to the economical duty mode + 2-5 ° C with full recycling.
2. Systems of heating for premises with a high multiple of air exchange, constantly needed in the supply of large volumes of fresh air (Conducting\u003e 2)
In this case, the amount of heat needed to heat the supply air may already several times higher than the heat required to compensate for heat loss. Here is the most advisable and economically combining the air heating system with the supply ventilation system. The heating system can be based on the direct heating of air, or on the basis of the use of recovery heat generators performed with an increased heating degree. The total thermal power of heaters should be equal to the sum of the thermal need for heating of the supply air and heat required to compensate for heat loss. In direct heating systems, 100% outdoor air is heated, providing the supply of the required volume of supply air. During the working time, they heat the air from the street to the estimated temperature of + 16-40ºС (taking into account overheating to ensure the heat loss). In order to save, inoperative time, part of the heaters can be turned off to reduce the consumption of supply air, and the remaining translate to the duty mode of maintenance of + 2-5ºС. Recurative heat generators in standby mode allow you to provide additional savings due to the transfer of them to the full recycling mode. The smallest capital costs in organizing the heating systems of a centralized type with the use of as large heaters as possible. Capital costs for Gas mixing air heaters STV can range from 300 to 600 rubles / kW installed thermal power.
3. Combined air heating systems
Optimal option For premises with a significant air exchange during working hours, with a single-shift mode of operation, or the intermittent working cycle - when the difference in the need for supply air and heat during the day is significant. In this case, it is advisable to separate the operation of two systems: duty heating and supply ventilation combined with heating system (firing). At the same time, recuperative heat generators are installed in a heated room or in vents to maintain only the duty regime with full recycling (with calculated outer temperature). The system of supply ventilation combined with the heating system provides heating of the required volume of fresh supply air to + 16-30ºС and fitting the room to the required operating temperature and in order to save only during working hours. It is built or on the basis of recovery heat generators (with an increased heating degree), or on the basis of powerful direct heating systems (which is cheaper by 2-4 times). It is possible to combine the supply system of the fever with an existing water heating system (may remain duty), the option is also applicable to the stadium modernization of the existing heating and ventilation system. With this method, operating costs will be the smallest. Thus, applying air heaters different types In various combinations, you can solve both problems and heating, and supply ventilation. Examples of the use of air heating systems are very much and the possibility of combinations is extremely diverse. In each case it is necessary to hold heat calculations, take into account all the conditions of application and perform several options for selecting equipment by comparing them by appropriateness, the magnitude of capital expenditures and operating costs.
