How did our grandfathers wash in the bathhouse? A large vat for water was built into the oven. While the heater was heating, water was heated in the vat; its volume (about 50 liters) was enough for the whole family. Cold water was taken from another container. People steamed and then washed in the same room, which was not very convenient. It was difficult to wash in the overheated and steamy steam room.

It is not surprising that nowadays bathhouse owners want to increase the comfort of taking water procedures and divide the process of steaming and washing into different rooms.

Issues with warm water are solved in two ways: using a separately installed electric boiler and using a heat exchanger that takes heat from the stove. We will not consider the first method; there is nothing interesting or complicated in it. In addition, heating a large amount of water requires a significant amount of electrical energy, and its cost is currently constantly increasing.

Let's talk about heat exchangers, give step-by-step instructions for building some of them and practical advice on engineering problems of heat exchangers.

The generally accepted classification of technical units divides all products into types, which in turn have their own subtypes. There can be a huge number of subtypes of heat exchangers; each bathhouse owner, by making minor changes to the design or manufacturing materials, can create his own personal subtypes. And according to the main design features, heat exchangers are divided into the following types:

At the location of the warm water tank

Tanks can be placed in a steam room, shower room or in the attic. Each location has its advantages and disadvantages.

The first option is a tank in the steam room. Advantages - the length of water pipes is significantly reduced, and this has a great positive effect on the rate of heating of water. We will talk about these and many other features of the functioning of heat exchangers and the design requirements for their devices at the end of the article. The disadvantage is that an already small room “shrinks” even more.

The second option is a tank in the shower. In our opinion, the most optimal option, the disadvantage is that the length of the pipelines increases slightly.

Water tank in the shower - diagram

A common problem for the first two options is low water pressure. The fact is that the height of the bathhouse rarely exceeds two meters. If we subtract the height of the water tank from this value (approximately 50 centimeters), then the maximum height of the water intake pipe is reduced to 1.5 meters. What does it mean? This means that it is impossible to install a stationary shower; you will only have to wash with a flexible hose. And then do not raise it above 1.5 meters. Even less, more or less tolerable water pressure will only be with a height difference of at least 10 centimeters.

These problems are being solved moving the container for warm water to the attic of the bathhouse (option three).

But in this case, problems arise - the length of the pipelines increases and heat losses increase; the tank must be insulated. But that’s not all – there is a problem with adding water to the container. Not every bathhouse owner wants to carry buckets up the stairs. But running water does not exist everywhere. It is impossible to give universal advice to all readers on the location of the water tank; everyone must independently navigate, taking into account their own individual characteristics of the structure, the presence of utility networks, the climatic zone of residence and the maximum number of people washing at the same time.

According to the location of the heat exchanger

There are two options for placing the heat exchanger - in the stove or near the chimney (the chimney in this case should be made of metal pipes). Both options are workable, but have their own characteristics.

The first option, that is internal heat exchanger, allows you to heat water relatively quickly, but there is a high risk of it boiling.

In addition, there are great difficulties in carrying out periodic maintenance or replacement of heat exchangers.

There is generally a problem with replacement - you will have to disassemble the stove. As for maintenance, they can be done, but at the cost of considerable effort. The fact is that water forms scale inside the heat exchangers; one millimeter of scale reduces heat transfer by 10%, which is a significant loss. In many regions of our country, the water is solid (has a large amount of Ca ions), which is good for drinking water, but bad for all types of heat exchangers.

For scale to form, it is not necessary for the water to boil throughout the entire volume. A small layer of water constantly boils near the overheated walls of the heat exchanger; the entire volume does not boil due to its continuous mixing by convective currents, but the calcium on the walls turns to stone. In some cases, after just a few years of using the sauna, the scale will reach such a thickness that this will noticeably affect the rate of its heating. The heat exchanger can only be cleaned with a concentrated solution of hydrochloric acid; commercially available special products are not very effective. Working with hydrochloric acid in violation of safety regulations has a negative impact on health.

Heat exchanger near the chimney does not have these disadvantages, the pipe temperature is not so high that the water near the walls of the heat exchanger boils. This advantage causes disadvantages - the heating time of water in the container increases significantly.

Sometimes there is another option for placing a heat exchanger - heaters under the stones. You can, of course, place a heat exchanger there, but why then would there be stones in the steam room? Just look at them? The fact is that with this arrangement of the heat exchanger, the heating temperature of the stones will be insufficient for the formation of steam. And steam in a Russian bath plays a decisive role, and not only for warming up the body. Real lovers of Russian baths add an infusion of medicinal or fragrant herbs to the water for watering the stones. And if you add a little natural kvass or beer to the water (only natural, and not “churned up” from alcohol and paint), then the air in the steam room will be filled with the indescribable aroma of fresh bread. If you install a heat exchanger under the stones, you will deprive yourself of many pleasures.

We have found out the general characteristics of heat exchangers and containers for warm water; now we can move on to a detailed consideration of the technology of their manufacture and installation. This topic is very large, it is worth breaking it into several parts. Let us consider separately the options for manufacturing containers, heat exchangers and methods of their installation.

Heat exchanger prices

heat exchangers

Making containers for warm water

There are several options for containers - from expensive stainless steel to cheap store-bought plastic ones. We will not consider these options; we will focus on the most successful, from our point of view, metal made from sheet iron. Its advantages are not only its relatively low cost (although this is important), but also the ability to make a tank that is ideally suited in terms of linear parameters to each room of the bathhouse. As for appearance, there is a large selection of durable paints; surfaces can be painted in any color or covered with self-adhesive decorative polyethylene film.

Table. Calculation of tank volume

Stage	Description	Scheme
Find the volume of your tank	Multiply length (l), width (w) and height (h)
Calculate filled volume (d)	For rectangular tanks, the filled volume is the same length and width, but less height. The new height is the filling height of the tank.

Table. Making a tank

Step, No.	Description of work
Step 1. Prepare materials.	You will need sheet iron with a thickness of at least 0.5 mm. We suggest making a rectangular tank, length 80 centimeters, height 40 centimeters, width 20 centimeters. The tank holds 64 liters of water, but you need to fill no more than 60 liters. You need to weld three metal pipes with threads into the tank; they are sold in stores. It is better to take the nominal diameter of the pipes at least 3/4 inch. This is the most commonly used diameter of pipelines and ensures normal natural circulation of water. To fully install the heat exchanger, you will need to have additional plumbing fixtures and fittings; we will talk about this below when considering installation issues.
Step 2. Mark the tank on a metal sheet.	You will need two plates 80x60 cm, two 40x20 cm and one 80x20 cm. We specially made the tank rectangular. The fact is that the distance between the inlet and outlet pipes should be increased as much as possible. This will allow warm water not to immediately mix with cold water; a significant difference in their temperatures will be achieved, which has a decisive influence on the speed of water flow in the pipelines. And not only the efficiency, but also the safety of using the heat exchanger largely depends on this criterion.
Step 3. Cut the blanks to size.	You need to use a grinder; when working with this tool, strictly follow the safety rules - it is very dangerous. Try to keep the cut as even as possible. Check the quality of cutting of each edge on a flat surface, eliminate large flaws.
Step 4. Assemble all the parts of the tank in pairs, making them absolutely identical.	Pay special attention to the corners, they should only be rectangular.
Step 5. Place the front part of the tank on a flat surface, and weld the side of the tank in several places with a short seam.	Do the same operation on the other side. Check their position; they will definitely move as the seam cools.
Step 6. Place the second large part on the welded sidewalls, check its position, and adjust the sidewalls if necessary.	Grab the elements. Make sure that the gap between the individual parts does not exceed 2–3 millimeters, otherwise during welding you will have to put wire in them, and this is undesirable.
Step 7. Place the structures upside down and grab the bottom.	Check and correct its position.
Step 8. If everything is fine, weld all the elements.	Monitor the quality of the seam; omissions are strictly excluded. You can “cheat” a little on the thickness of the weld seam; the container does not carry significant loads, but omissions are prohibited.
Step 9. Weld metal pipes into the bottom.	We have already said that the input and output should be removed from each other as much as possible. It is better to place the water intake pipe for the shower not in the middle, but closer to the drain; the water intake will speed up the circulation in the tank.
Step 10. Burn holes for the pipes.	For the pipes, you must first burn holes in the bottom of the tank; this can be done more conveniently by electric welding.
Step 11. Come up with a way to attach the tank to the wall.	You can weld special brackets to the back wall or install it on a stand. If you have the desire and the material, make a removable lid.
Step 12. Using a cylindrical grinder, clean all seams, pour water and check their tightness.	Seal holes if necessary.
Step 13. Prepare the front surfaces of the container for finishing.

Video - Making a water tank (welding)

Video - Making a stainless steel tank

That's it with the water tank, you can install it in any room in the bathhouse. Now let's talk in more detail about heat exchangers.

Heat exchangers - manufacturing features

The most important elements, the comfort of washing largely depends on their correct design and effective functioning. We will consider several options for heat exchangers and express our comments; the final decision is yours. One of the main problems of all types of heat exchangers is the inability to regulate the water heating temperature. The water in the tank may not be warm enough or too hot. You have to manually dilute hot water with cold water. But that’s not all – the risks of water boiling in the heat exchanger are very high. The system will not suffer much from steam, it is an open type, but for the heat exchanger such situations will not be “in vain”. What to do if the water in the heat exchanger boils? Putting out the fire in the stove? How can you regulate the water temperature at least a little? Constantly put one log into the firebox and take half a log out of it? We will answer these questions at the end of the article.

Let's start with simple heat exchangers and end with more complex ones.

Heat exchangers near the chimney

The simplest, but very effective heat exchanger made of copper tube.

Depending on the diameter of the chimney, you need to purchase 1.5÷2.0 meters of copper pipe with a diameter of approximately 10 millimeters. The smaller the diameter of the tube, the larger the surface of its direct contact with the pipe, the faster the water heats up. But, on the other hand, the small diameter of the tube significantly reduces the speed of water flow, and this can cause it to boil. Taking into account both factors, we recommend taking a tube with a diameter of 10 mm.

Adapters should be put on the ends of the tube and flared. There are special devices for flaring.

Steel pipes can be connected to the ends of the tubes. Fittings are screwed to the nuts Fittings. The cone of the fitting should fit snugly against the flared end of the tube

Do the flaring carefully; the plane of the flared end must be even and smooth, otherwise there will be leaks at the junctions of the pipelines.

Prices for copper tubes

copper tubes

Video - Bending copper tubes

A more difficult to manufacture heat exchanger can be made from two metal pipes. The diameter of the first should be slightly larger than the diameter of the chimney, and the diameter of the second should be 5–10 cm larger than the first. How to make such a heat exchanger?

Step 1. Use a grinder to cut two pieces of pipe of different diameters, 20÷30 centimeters long. The ends of the pipes must lie in the same plane, be even and neat.

Step 2. Cut two circles from sheet steel with the diameter of the larger pipe. In these circles, cut holes exactly in the middle with the diameter of a smaller pipe.

Step 3. Insert pipe sections into the holes and weld them. Weld carefully, do not skip a seam.

Step 4. At the top and bottom of the structure, weld metal pipes with threads at the ends; a hole must be made for each pipe. Check the heat exchanger for leaks.

The structure is ready, you can install it on the chimney and install pipes. It is advisable to insulate both heat exchangers with mineral wool with a top covering of aluminum foil. This will greatly reduce unproductive heat losses and speed up water heating.

With the help of such heat exchangers, the water will heat up much faster. Heat exchangers in a furnace can be made of tubes in the form of various geometric designs or be ordinary flat. The efficiency of flat-plate heat exchangers is lower. But they are much more durable and easier to manufacture.

Heat exchangers must be installed simultaneously with the laying of the furnace. Taking into account the parameters of the firebox, the dimensions of the heat exchangers are selected. The pipe outlets can be either on one side of the furnace or on both. The option of cold water entering from below and exiting from above the plane of the furnace is allowed. In a word, there are a great many options both in terms of the heat exchanger material, type, geometry, linear dimensions and design features. It is impossible to give unambiguous universal advice; you must make your own decision, taking into account the characteristics of the sauna stove and the modes of use of the shower and steam room.

To make a heat exchanger, choose durable, high-quality materials; welding seams must be made in accordance with the rules and characteristics of the materials. Keep in mind that in many cases it is impossible to fix a damaged heat exchanger in a furnace without disassembling it. It’s not worth explaining what it means to disassemble and reassemble a stove.

The easiest option is to purchase a factory-made metal sauna stove with a built-in heat exchanger. But such furnaces have one drawback - the low efficiency of the heat exchanger.

Pipeline installation

We have already mentioned that for pipelines it is better to use pipes with a diameter of 3/4″; this diameter is most often used in all heating systems and is suitable in all respects for a bathhouse heat exchanger.

Pipes can be metal or plastic. You can also use flexible corrugated hoses, but you need to keep in mind that they have a significantly smaller nominal diameter, and this negatively affects the speed of water flow.

Let's give some tips on installing pipelines.

1. Try to reduce the length of the pipelines as much as possible; do not make many turns or bends in the pipe. Your task is to create the most favorable conditions for water circulation.

   

2. When using plastic pipes, do not allow them to overheat at the junction with the heat exchangers. The presence of water inside will prevent their complete breakthrough due to loss of strength caused by heating, but deformation is possible.

   

3. Don't forget to place the drain valve in the lowest place. If the bathhouse is not used for a long time, then in winter you need to drain all the water from the system.

   

4. When connecting pipelines, provide for the possibility of dismantling them to perform repair or routine maintenance work.
5. Try to keep the length of horizontal sections of the pipeline to a minimum. Install all such sections at an angle of at least 10°. Such measures have a positive effect on the speed of water flow.

Prices for flexible corrugated stainless steel tube

flexible corrugated stainless steel tube

When using heat exchangers, some problems arise that can “spoil your mood.” What are these problems and how can they be solved?

You need to “catch” the moment when it will be acceptable, but such a “moment” is almost impossible to catch. The fact is that while taking a shower, the stove continues to burn, and accordingly, the water temperature constantly rises. What to do? Putting out the fire in the stove? This, of course, is not an option.

We suggest solving the problem using a mixer. If there is a water pipe in the bathhouse, great; it will help not only create a comfortable temperature, but also, using simple automation, make filling the water container automatic. It will be possible to wash without saving water, and the risk of it boiling in the heat exchanger will be somewhat reduced. If there is no water supply, we recommend installing an additional container for cold water next to the warm water tank. It must be connected to the shower through a mixer.

This happens especially often during installation of the heat exchanger directly in the furnace firebox. We guarantee that you will never be able to calculate the parameters of the heat exchanger in such a way as to completely eliminate such a phenomenon. The calculations are too complex and there are too many unknown and unregulated indicators. Calculations based on the speed of water flow can only be performed by a qualified design engineer who has an excellent knowledge of the laws of heat engineering, hydraulic engineering and installation. But the most important unknown quantity is the flame in the furnace.

No one will ever be able to say exactly how much heat a stove produces in each individual unit of time. It is impossible to quickly increase or decrease the flame intensity depending on the water temperature. We propose to solve the problem of boiling water using ordinary single-phase water pumps for heating systems. They are built directly into the pipeline, the power of the devices is 100÷300 W. Installing a circulation pump not only eliminates the risk of boiling, but also significantly speeds up the water heating time.

We hope that our information will be useful for bathhouse owners and will make it possible not to solve problems with heat exchangers, but to prevent their occurrence at the stage of manufacturing and installation.

Circulation pump prices

circulation pump

Video - How a universal heat exchanger works in a sauna stove

With stove heating, the thermal energy is not completely used to heat the room: part of it is spent on heating the chimney pipe, and part goes outside. To optimize the operation of the heating system and use excess heat profitably, a metal heat exchanger is installed on the chimney of the stove pipe - a device that allows you to increase the efficiency of the stove and retain heat without allowing heated air to escape outside.

A heat exchanger is a device designed to exchange energy between various parts of a system through which coolant circulates. Installing a heat exchanger has several purposes:

• using excess thermal energy to heat water in circuits connected to heating (for example, in a hot water supply system);
• chimney thermal insulation.

When installing stove heating, installing a heat exchanger is a rational solution. By connecting it to the circuit of the hot water supply system in the house (provided that the stove heating is powerful enough), you can save on electricity or solid fuel, and also avoid installing a separate boiler for DHW operation.

Types of device and principle of operation

There is a basic classification of heat exchangers - according to the type of coolant, which divides them into water and air.

Water heat exchangers

Water heat exchangers are the simplest and most common type of equipment. Their work is based on the basic laws of physics: when heated, a liquid expands and its density decreases. Under the pressure of denser cold water located in the lower part of the circuit, the heated liquid enters the expansion tank, and from there back to the heat exchanger, moving in a vicious circle.

Heating devices that use fuel combustion to produce heat cannot function without a smoke exhaust duct. The device removes toxic combustion products that can be dangerous to humans. However, the flue gases escaping through the pipe into the atmosphere literally take away with them a large amount of heat that could be used to heat the room. To correct this drawback, you can install a heat exchanger on the chimney. The device allows you to significantly increase the efficiency of the heating device.

Operating principle and design of the heat exchanger

There are several different models of heat exchangers. Their design, as well as the principle of operation, are generally similar. The heat exchanger has a hollow body equipped with outlet and inlet pipes. A so-called braking device designed for flue gases is installed inside the housing. Most often this is a system of dampers with cutouts mounted on axles. The elements have the ability to rotate, creating a zigzag flue of various lengths. Adjusting the position of the dampers allows you to select the optimal ratio of heat exchange efficiency and draft in the smoke exhaust duct, without violating the standards of safe operation. There are also simpler options without a system of adjustable dampers.

Heat exchanger device for the Bulleryan furnace. Cold air enters the structure through holes in the bottom of the device, is heated by combustion products passing through the chimney, and exits outside

Through the holes located in the lower part of the device, colder air is drawn in using the principle of convection. It passes through the internal space, where flue gases passing through the flue heat it. Through the upper openings, heated air is discharged into the heated room. In this way, it is possible to increase the efficiency of the heating device and significantly reduce the amount of fuel it consumes. Experiments were conducted that showed that the fuel consumption of a potbelly stove with a heat exchanger installed on the chimney decreased by three times.

However, in order to achieve this effect, you must choose the right device. Do not forget that, giving up their heat in the flue, the combustion products cool down quite quickly. This leads to a decrease in the temperature difference in the chimney and, accordingly, a drop in draft in the system. To prevent this unpleasant effect from occurring, damper adjustments are used or the optimal dimensions of the structure are selected.

How to make such a heat exchanger yourself?

Home craftsmen can make a heat exchanger for the chimney with their own hands. The technology for its manufacture is quite simple. Let's look at it using the example of a design for a potbelly stove. To work you will need:

• sheet metal measuring 350x350 mm, two pieces;
• eight pieces of pipe with a diameter of 32 mm or 1.25 inches, a length of 300 mm;
• pipe with a diameter of 57 mm or 2.25 inches, 300 mm long;
• metal bucket with a volume of 20 liters.

We begin work by making end caps. To do this, take sheet metal and cut out two circles with a radius of 150 mm. We mark holes for the pipes on them. In the center of each part there should be the largest pipe with a diameter of 57 mm, at an equal distance from it in a circle we place eight elements with a diameter of 32 mm. The distance from the center of the plug to the center of each of the eight pipes should be 100 mm. We check the markings and make holes.

To ensure accurate assembly of the heat exchanger, a template should be made from 20 mm thick plywood. By installing the parts into it, it will be much easier to assemble the device

For assembly accuracy, it is recommended to make a template; it is made of 20 mm thick plywood. We insert the pipe sections one by one into the prepared holes and weld them securely to the flat part. First we work with one plug, then we turn the structure over and repeat the operation with the other. As a result, we obtain the “core” of the heat exchanger, prepared for installation in the housing.

Pipe fragments are welded to the plugs. The result is a “core” of the heat exchanger, ready for installation in the housing

For the heat exchanger body, you can use a steel bucket, in which technical liquids are sold. It must be thoroughly cleaned of any remaining contents. In this case, it is best to burn the bucket and carefully walk along the walls with a wire brush. We cut out the bottom with an angle grinder. Now you need to connect the outlet and inlet pipes. These are fragments of an ordinary chimney pipe purchased in a store.

On the body we mark a place for the inlet pipe. It should be located in the center of the side of the structure. Use metal scissors to cut out a hole. Let's try on the pipe. We make notches on the bottom of the chimney. We insert the pipe prepared in this way into the body blank and use a hammer to bend the notches, securing the part in place. From the outside we fasten the part to the base using welding tacks. Installation of the inlet pipe is complete. The weekend installation is carried out in the same way. It should be located on the opposite side of the housing.

We insert the prepared “core” of the heat exchanger into the housing, secure it by welding and be sure to seal all seams with fireproof sealant. We paint the dried structure with special paint

We install the heat exchanger into the prepared housing and securely fix it with welding tacks. We carefully coat all seams with a special fire-resistant sealant. Leave the product to dry for a day. Now the finished heat exchanger can be painted with special paint or stove varnish. We install the finished device on the chimney of the potbelly stove. To enhance the effect, you can install a fan near the heat exchanger, which will increase air circulation. The device can be portable or permanently mounted on the device body. The second option is more practical and convenient.

To improve air circulation in the device, a conventional fan is used. It can be portable. As in the photo, but it is much more convenient to mount the device using brackets directly on the heat exchanger

Well, as they say, it’s better to see once. Therefore, we invite you to watch a video with an example of creating a similar design:

An air heat exchanger for a chimney is an extremely useful design that makes it possible to seriously increase the efficiency of using heating appliances. The increased efficiency of the system allows you to reduce fuel consumption and, accordingly, save on heating. You can make a heat exchanger yourself, but this is quite a complex and painstaking job that only fairly experienced home craftsmen can handle.

Any private house, cottage, bathhouse and sometimes even a garage require heating in the winter season. But any prudent owner is faced with the question of how to reduce fuel costs and use the heating device more efficiently. One of the modern promising directions for increasing efficiency is the use of heat from hot exhaust gases.

I welcome my dear reader and bring to your attention an article about what a heat exchanger for a chimney pipe is and how to make it yourself.

Heat exchanger is a device for transferring heat from a heated medium to a colder one. One principle, many designs. A heat exchanger for a chimney allows you to select part of the energy of the exhaust gases and use it to heat an adjacent room or heat hot water.

Devices for extracting heat from flue gases for a chimney can only be used if the pipe is made of steel. It is not possible to install a heat exchanger on modern ceramic and sandwich structures, since the outer surface of the insulated pipe is cold.

The gases coming from modern gas and pellet boilers are not hot – about 200 °C, so you won’t be able to get a lot of heat from the chimney. Solid fuel boilers emit hotter gases - up to 600 °C, and the recuperator allows you to obtain a fairly significant amount of heat for heating or heating water.

The maximum amount of heat from exhaust gases can be obtained by using not very modern traditional stoves, fireplaces, and homemade potbelly stoves. The efficiency of these heating devices is low, the temperature of the flue gases is high, so a considerable part of the wasted heat can be captured using a heat sink. The use of heat collectors on the chimney of a homemade potbelly stove allows you to capture up to 30-40% additional energy.

The main reason for installing a heat exchanger is that it allows you to maximize the use of fuel combustion energy and save on heating costs. In addition, sometimes when heating small houses it is not economically feasible to purchase a heating device with a heat exchanger and install a heating system.

A modern fireplace or stove heats well houses with an area of ​​up to 70 m² and even more; only some rooms need heating - bathrooms or back bedrooms, second floor rooms or attics, so for their heating you can use the heat from the recuperator for the chimney. Sometimes a chimney heat exchanger is used to heat water.

Principle of operation

The operating principle of a heat exchanger for chimneys is heat recovery through a heat-conducting wall. In this case, the coolants move in one or different directions. In a counterflow design, coolants move in opposite or perpendicular directions, in a direct flow design - in parallel.

Types and designs

Heat exchangers are primarily divided according to the coolant into air and liquid (water). In principle, it is allowed to fill in oil and antifreeze, but not in homemade designs, since antifreeze is poisonous and expensive, and the oil can catch fire if leaks occur.

By design, water devices are usually made in the form of a coil or register (pipe) with water (water jacket); air ones are a cap with warm air removal or a wide insert into the chimney with welded transverse elements.

When deciding how to remove the residual heat of flue gases, you should keep in mind that condensation may fall on the heated walls of the chimney. This drawback is especially noticeable in gas boilers, in which the temperature of the exhaust gases is low. But on inexpensive homemade stoves you can ignore condensation.

Water

The advantage of water for recovery is that it has a high heat capacity and more efficiently removes the heat from the flue gases. But water recuperators require higher quality manufacturing - the system cannot leak; When operating it, it is necessary to ensure that there is no overheating, since boiling water can rupture the pipeline.

If water structures are used in a garage, workshop, “weekend cottage,” or a free-standing bathhouse, the water will have to be drained in the winter, since frozen liquid can also rupture the pipeline.

A circuit with water is heated through the metal walls of the chimney; when heated, the water rises up, then into the batteries, cools, falls down in the battery, goes into the return line and is sucked back into the heat exchanger.

To optimize the operation of the system, an expansion tank is included in it - this reduces the possibility of boiling. Some craftsmen install a pump, which creates a complete small heating system.

Water systems are used for heating using radiators or hot water supply. A serious drawback is the inability to regulate the heating temperature of the water; if it overheats, it simply has to be drained. It is impossible to pour cold water into the system while the heating unit is running - the water can boil, rupture the pipes and damage the chimney, while condensation settles on the inner walls of the chimney pipe.

• Homemade coil

The easiest design to make. The coil is usually made from a tube that is wound in a spiral around a steel chimney. Tubes use copper, ordinary steel, stainless steel, and aluminum. Aluminum should not be used for solid fuel boilers - its melting point is 660 °C, and the temperature of the exhaust gases of solid fuel heating devices reaches 600 °C.

When winding (bending), the pipe should be filled with sand and sealed on both sides - this will avoid defects (kinks, folds, kinks). To improve the heating of the coil, there should be a small distance between the turns - up to 1 diameter.

But it is not the most durable coil material (especially galvanized carbon steel).

• Register

Register - a casing with a larger diameter than the chimney. The register is placed on top of the chimney body and welded, the ends are welded with plates with cut holes corresponding to the diameter of the chimney. A pipe is welded or screwed in at the bottom for water supply, and at the top for discharging warm water. Otherwise it is used in the same way as a coil. The casings are made not only round, but also square.

Air

This option is more suitable for local heating of premises - one room, bathroom, dressing room. Air structures are easier to assemble. Sometimes a coil or register is used, sometimes a Kuznetsov or bell-type heat exchanger is used. The coil has too much resistance from the pipe walls; it should not be too long. Because of these difficulties, it is rarely used. Air recuperators cool the chimney less, so there is less chance of condensation forming on its walls.

Sometimes they do not build complex structures, but use available materials - they weld ribs from corners or bent strips to the chimney, pipes open on both sides, attach “skirts” or strips (aluminum or thin steel) bent into a corrugated structure.

• Kuznetsov heat exchanger

The Kuznetsov heat exchanger is an expanded cylinder, across which pipes are welded. The cylinder is mounted in the chimney, hot flue gases flow through the inside and heat the transverse elements. The air from the cavities exits into the room and heats it or is collected in an air duct and enters the adjacent room.

• Bell type

If a small house does not have a heating system and there is a need to heat a room in the attic or second floor, a bell-type heat exchanger is used. A cylinder is installed around the chimney, open at the bottom; at the top, air from the cylinder enters pipes going to the second floor. Warm air is released in the lower part of the room on the second floor - this way the hot air is better distributed in the room and heats it as much as possible.

Sometimes, instead of a cylinder above the stove, a hood is installed under the ceiling; air heated by the stove rises into it and flows through pipes into the room on the second floor. You can install a fan, in which case it is easier to heat the room on the same floor with the stove with warm air.

Which type is better

Which type is better is determined by what exactly needs to be heated and in what way. The efficiency is better for water recuperators - 50-60% (for a register parameter it is higher, for a coil it is lower). Air devices have lower efficiency.

For hot water supply or radiator heating systems, it is better to install water heat exchangers. Air heaters are more suitable for heating closely spaced individual rooms.

Power calculations

Independently calculate the power of the recuperator in the absence of initial data (furnace power, temperature and amount of exhaust gases per unit of time, contact area of ​​the heat exchanger and the metal of the chimney, speed of passage of air or water through the device) almost impossible. You can measure the power of an already installed heat exchanger.

Roughly, you should expect that the heat exchanger on the chimney of a solid fuel stove or fireplace will warm up a couple of small radiators, increase the temperature in the garage, or make a room in the attic or a dressing room in a bathhouse warmer.

Buy or make it yourself

If you want to increase the heat transfer from an expensive purchased boiler, it is better to buy ready-made high-quality devices - the industry produces them in a sufficient range. But if you want to modernize either your garage or increase the efficiency of a fireplace with a steel pipe in your country house, you can save a lot of money by making and installing a heat exchanger on the chimney yourself. Installing a heat exchanger by a hired specialist will cost the same as the structure itself.

The simplest option - a coil - can easily be made by a home hobbyist even without much experience, but a home craftsman with at least some welding skills can handle more complex designs.

approximate price

The cost of industrially manufactured chimney heat exchangers varies depending on the design and manufacturer.

Running heat exchanger tanks for a chimney with a diameter of 115 mm and a capacity of 6 liters cost rubles; those with a capacity of 12 liters cost rubles.

How to make your own device

It’s easy to make a simple coil yourself from a copper tube. For a chimney with a diameter of 100 mm, a copper pipe with a diameter of ¼ inch and a length of 3-4 m is suitable. Threaded fittings should be soldered to the ends of the pipe. Then the tube is filled with fine sand, twisted and wrapped around the chimney.

It is advisable to leave a small distance between the turns - then the pipe from the chimney will be heated by both heat transfer and infrared radiation. It is convenient to do this work with an assistant. The sand is then washed out of the pipe with water under pressure. Connect the pipes leading to the radiators and expansion tank.

The Kuznetsov heat exchanger is made using welding. The simplest option is to make a housing from a gas cylinder or large diameter pipe.

For manufacturing you will need the following materials:

1. Gas cylinder, large diameter pipe (300 mm) for the housing.
2. Pipe with a diameter of 32 mm (it is better to take one piece with a larger diameter - up to 57 mm). The length of the blanks is 300-400 mm, the total quantity should be sufficient for cutting the blanks.
3. Two small pipes of the same diameter as the chimney; It is advisable to use a chimney pipe - if the chimney is prefabricated, then on one side of the structure the pipe will have a socket, which is necessary for installing the heat exchanger.
4. Two pieces of steel sheet, sufficient to cut out the end caps of the housing.

Air heat exchanger manufacturing technology:

1. A large pipe or cylinder is cut to the required size.
2. 9 blanks of the same length are cut from thin pipes.
3. Circles are cut out for the plugs.
4. 9 holes for small diameter pipes are cut in the circles; if one tube of larger diameter is taken, then a hole for it is cut in the center.
5. Thin pipes are inserted into the holes of the plugs, attached by welding, and then welded.

Holes with a diameter equal to the diameter of the chimney are cut in the sides of the body.

A structure of thin tubes and plugs is inserted into the body and welded at the junction of the plugs and the body of a large pipe.

The pipes are inserted into the holes on the sides of the body and also boiled.

Alternative option:

What materials can be used

Perfect option - stainless steel(for example, food grade austenitic stainless steel 08Х18Н10 or AISI 304) or copper. Industrially produced products are sometimes made of titanium. But the price of these materials is quite high. But they are durable, do not rust, are reliable and durable. If you have a potbelly stove in the garage or a homemade heater from scrap materials in the bathhouse, it is quite possible to use ferrous metal (carbon steel).

You can use a high-quality corrugated stainless steel pipe. Galvanized corrugation is an undesirable and short-lived option. Aluminum pipes can also be used for the coil (just not for chimneys of solid fuel stoves).

But it should be borne in mind that during welding work the zinc layer evaporates, and all the advantages of galvanizing (corrosion resistance) come to naught. At temperatures above 400 °C, zinc begins to evaporate (zinc vapor is toxic), so you should not use galvanization for heat exchangers on the chimneys of solid fuel boilers.

Solid or liquid fuel stoves produce a large amount of heat, but a lot of it goes unhindered into the chimney. A heat exchanger for the chimney pipe will help you avoid losing useful energy and stop heating the street. A simple and compact device can increase heat transfer by virtually a third, without reducing the characteristics of the stove itself, but a number of factors should be taken into account, such as maintaining normal draft and the ability to clean the chimney, so as not to get into trouble with the heat exchanger.

Principle of operation

When burning liquid fuel or coal, especially in homemade stoves, the temperature of the gases at the entrance to the chimney reaches 600°C and even higher. Such temperatures are not needed to maintain active traction; they only worsen the situation. Nothing prevents you from taking part of the heat without compromising the functioning of the stove and releasing it to the air in the room or water in the heating or hot water system. So, if you reduce the gas temperature from 600°C to 400°C, then, depending on the quality of the heat exchanger and the volume of flowing gases, the heating power can reach several kilowatts.

The task is to ensure active heat exchange between superheated gases escaping from the stack and the target medium: water or air. The key is the contact area. Placing, for example, air ducts or a water pipe coil inside the chimney is not a good idea; even taking into account all the other features, any objects in the duct will only contribute to the formation of soot and condensation, which will quickly damage the chimney and, accordingly, turn the operation of the stove into a dangerous event for others.

There are three optimal options for heat removal from the chimney:

• Coil around the chimney.
• Water jacket. A larger diameter cylinder is placed over the chimney pipe and filled with coolant. Dividing the chimney channel into a group of channels of smaller diameter allows you to increase the contact area.
• Chimney brake. The chimney channel is formed in the form of a coil, a labyrinth, through which the movement of gases slows down, which increases heat transfer.

The first two options are suitable for forming a water circuit and using heat in a heating or hot water system. The third design is more suitable for local air heating.

All types of heat exchangers have features that should not be ignored. If the heated medium is water, then there is a problem with excessive heat transfer. When the chimney is already hot and the stove is actively heating, the supply of cold water to the heat exchanger causes a sharp drop in the temperature of the chimney walls. This inevitably leads to condensation of moisture from the exhaust gases on the walls of the chimney, and, as a result, the channel quickly fills with smoke and ash. To cope with this, it is necessary to reduce the heat transfer rate and temperature difference.

Air heat exchanger

Along with high performance, durability is very difficult to achieve. On the one hand, an increase in the contact area between the heat exchanger and the chimney increases the heat output, on the other hand, excessive heat intake threatens big problems up to the complete failure of the chimney.

Optimal characteristics of a heat exchanger for a chimney:

1. The water circuit must be supplied with a separate heat storage tank, excluding the supply of cold water directly to the heat exchanger.
2. The heat exchanger design must be easily removable for cleaning and maintenance.
3. The power of the heat exchanger is selected based on the actual performance of the stove and chimney so that the temperature of the gases above the heat exchanger is sufficient to maintain draft.

It is better to choose stainless steel as materials for the heat exchanger, which can withstand sudden temperature changes. The internal surface of the heat exchanger in contact with the smoke should, if possible, be perfectly smooth, so that condensation, even when it appears, falls into the condensate collector without creating unnecessary problems.

Homemade heat exchangers for a chimney are often assembled without taking these requirements into account and without preliminary calculations, which causes a lot of problems, both with heating the water and the condition of the chimney.

With air heat exchangers everything is simpler. If you do not supply a large volume of cold air from the street, but use it to heat the internal volume of the room, then the temperature difference will not be sufficient for active condensation.

For heating

For organizing water heating in a house, a chimney heat exchanger will be an excellent solution, but only if there is a heat storage tank. To heat a house, there is no need to constantly heat cold water; the coolant in the system loses 20-25°C after passing through the circuit and that’s all. Accordingly, the risk of condensation forming on the surface of the chimney is reduced.

The simplest version of the heat exchanger is a coil made of a copper tube, twisted in a spiral around the chimney. The length of the tube should not be too long, even taking into account the route to the boiler and back, and depends on its diameter. If we take, for example, a size of ¼ inch, then it is advisable to limit the length to 3.5-4 meters. This way it will be possible to ensure normal heat exchange with natural circulation of water in the “heat exchanger - storage tank” circuit.

If it is not possible to install the boiler close to the stove, then it is better to use a circulation pump and force water through the heat exchanger, then the length of the tube no longer matters much. There is no need to use soldering or improve the contact between the coil and the chimney in any way. Too good heat transfer will be more detrimental.

Greater heat transfer is achieved by a water jacket, a design in which an external cylinder is installed on top of the chimney section, and water is poured between them. The chimney section can be replaced with an assembly of pipes of smaller diameter, for example 5-6 pieces, so that their total cross-section is equal to the chimney channel or slightly larger than it.

The main difficulty lies in determining the heat transfer power. The actual value is obtained only in practice, and this option will suit few people. It can be approximately calculated based on the temperature of the hot gases at the furnace outlet and the passage of the heat exchanger. The specific heat capacity of the exhaust hot gases is approximately 1.042 kJ/kg*K, slightly higher than air saturated with water vapor. Depending on the temperature difference at the inlet and outlet of the heat exchanger and the contact area, the power is calculated.

The specific heat capacity of water is 4.183 kJ/kg*K. Let’s assume a temperature difference of 150 degrees, then for every kilogram of smoke coming out you can heat a kilogram or liter of water by 38°C. Next comes the calculation of the volume of passing gases and the efficiency of the heat exchanger, which, in fact, does not exceed 60%.

To heat a small room, one chimney heat exchanger will be sufficient, but it is better to use it as an auxiliary heat source in addition to the main water circuit or hot water boiler, increasing the overall heat output.

In practice, it is easier to heat a small house or a neighboring room using an air heat exchanger for a chimney. It uses the same principle as a water jacket, only gas from the stove is released into the space between the group of pipes, and the structure itself is oriented perpendicular to the chimney. It turns out that the smoke flows around the heat exchanger tubes and heats the air in them; then, through forced ventilation, it is supplied through the air duct to other rooms of the house.

For sauna stove

In a bathhouse, using heat from the chimney is only relevant for hot water supply or using air heating. An air heat exchanger will be relevant primarily for warming up the dressing room and dressing room and other bath rooms, except for the steam room, where there is already enough heat from the heater itself.

The DHW circuit is relevant for a separate bathhouse building. It is enough to install a small container under the ceiling in the room next to the steam room and use a heat exchanger to heat the water in it.

Mounting a heating circuit based on a heat exchanger for a chimney is, to say the least, not relevant. By definition, it is too high to ensure natural circulation, and installing a circulation pump and, accordingly, cooling the chimney walls will affect the draft. Everything depends on the increased heat capacity of any, even the most primitive water heating circuit.

Flaws

The main difficulty with chimney heat exchangers is the lack of adequate power control; there are no well-established ways to stop heating the coolant or hot water while the stove is operating. If you simply shut off the water circuit, the residue in the heat exchanger can boil and rupture the chimney and the body of the device. The liquid must be completely drained.

You can somehow limit the power using dampers, but then the draft and the adjusted operation of the stove itself will suffer. The bypass path, actually a bypass, significantly complicates the design of the chimney and makes it excessively voluminous.

It all comes down to a simple idea. There is no need to put up with the loss of heat that goes into the pipe. But when installing a heat exchanger, it is worth considering that it can only play secondary roles, both in heating and in hot water supply, significantly reducing the load on the main heat source. When choosing the current model, it is necessary to carefully select the power and operating modes so as not to spoil the operating conditions of the stove itself.

udobnovdome.ru

Heat exchanger for chimney for heating from a stove or fireplace

The efficiency of stove heating is not too high anyway. Why allow the heat of the gases removed by the chimney to simply escape into the atmosphere without doing additional necessary work? This is why heat exchange devices were invented.

The stainless steel heat exchanger is manufactured in a factory, but you can make it yourself by welding

Heat exchanger functions in stove heating systems

The principle of the heat exchanger is to remove heat from combustion products leaving through the chimney and return it to the heated space through various designs of steel plates (or pipes).

The heat exchanger also has more radical capabilities - for example, reducing the amount of air required for stable operation of the furnace. In this case, it is called a recuperator and is used to increase the efficiency of solid fuel boilers.

Design and principle of operation of a heat exchanger for a bath: a tank with three fittings and a samovar-type tank

Since combustion products exit through the chimney, it is most advisable to install the heat exchanger there. In the simplest case, it is necessary to manufacture and install a coil of steel pipes, the components of which must be tightly adjacent to the inner surface of the chimney. The smaller the coil pitch and the larger the pipeline diameter, the more efficient the heat exchanger will be.

Readers found these materials useful:

• Do-it-yourself ceramic chimney installation, tips and tricks
• Review of chimneys for stoves made of various materials

Based on the type of coolant used in the secondary circuit, air and water heat exchangers are distinguished.

Since the heat transfer coefficient for water is significantly higher than for air, the efficiency of water heat exchangers is greater.

However, when installing such a device on a chimney, you will have to be satisfied with the second option, since the heat exchanger will have to be mounted outside, and the use of water as a coolant in this case is associated with significant difficulties. Especially if the heat exchanger will be installed independently.

Option for external installation of a heat exchanger based on water as a coolant

Design options and operating principles of heat exchange devices

The choice will depend on whether the furnace is designed with the possibility of subsequent installation of a heat exchanger or whether all work will have to start from scratch. In the first case, it is advisable to use a water heat exchanger installed next to a conventional heating furnace. Such a heat exchanger will include:

• The actual body of the device.
• Storage tank.
• Upper and lower outlets from the furnace working space.
• Heat exchanger and system drain valves.

The principle of operation of a heat exchanger that provides hot water supply and is connected to the stove

The heat exchanger for an air-type chimney will have a completely different structure:

• A housing equipped with inlet and outlet pipes.
• A rotary damper system that will regulate the speed and pressure of exhaust combustion products.
• Elements for fastening the housing in the chimney.

The presence of rotary dampers, although it will require more careful control of the heat exchanger during its operation, will in return increase the efficiency of heat transfer by flue gases due to a targeted change in the paths of their movement along the chimney.

Selection of materials for the heat exchanger

Since the flue gases passing through the chimney have a temperature of up to 300-350°C, the use of ordinary steel for the manufacture of the body is not suitable. Heat exchangers made of stainless steel are durable (the most popular brand is 08Х18Н10 or AISI 304). If financial capabilities do not allow you to make such a choice, you can get by with galvanized steel.

A stainless steel heat exchanger for hot water is connected to a tank placed on the wall

However, at temperatures above 200-250°C, the durability of the housing will begin to decrease. Moreover, with a further increase in temperature, the zinc coating begins to evaporate rapidly and in some cases can be sucked into residential premises, which is very dangerous to health.

At the same time, the second option will be very appropriate if the stove is installed in a country house and is not intended for long-term use.

Methods for installing a heat exchanger in a chimney

The easiest way is to mount the housing to the existing dimensions of the chimney when the stove is not working. A housing is mounted inside the smoke channel, so that the reduction in the passage opening does not exceed 40%. Of course, in this case the thrust increases and heat exchange occurs more intensively, but it will also be much more difficult to control such a process.

You can also attach the heat exchanger to the stove, and then cover it with fire-resistant bricks. Since there are no special loads on the apparatus, bricklaying is usually done “on edge”. The efficiency of the heat exchanger will depend on the walls of the housing - as their thickness increases, the device heats up more slowly, but then operates more stably. In this case, losses due to condensation formation are also reduced.

The heat exchanger installation diagram shows the features of installing pipes and filling the tank with water

DIY heat exchanger installation stages

A coil of thin-walled copper pipes (a less successful option is stainless steel pipes) is laid inside the chimney, through which air will subsequently be pumped. The pitch of the pipes is such that the distance between the axes of adjacent turns is at least four to five pipe diameters. At higher values, unnecessary heat losses occur, and at lower values, the consumption of copper pipes increases and a shielding effect appears, which results in overheating of the pipelines.

The video shows how to make a heat exchanger for a chimney with your own hands

The coil is welded using argon welding. Soldering is not suitable due to elevated (against those usually recommended for brazed structures) operating temperatures of pipes.

Examples of installed heat exchangers in a bathhouse, bathroom, wooden house

Corrugated nozzles are the simplest heat exchanger design

An even more structurally simple (albeit less attractive) heat exchanger for heating purposes can be constructed from corrugated steel pipes. They simply wrap around the outer surface of the chimney, and to subsequently redirect the hot air to other rooms of the house, you can use the existing internal ventilation system. Heat removal will increase if the corrugated nozzles are covered on top with heat-insulating foil material.

A corrugated pipe heat exchanger is applied as close as possible to the chimney and insulated with foil to remove and retain the maximum amount of heat

The presence of a heat exchanger is always beneficial, because it allows the use of stoves or boilers of relatively low power for heating individual houses, and, therefore, with less fuel consumption. In addition, the service life of the chimney will be extended, and it will cool more efficiently.

kamin-maker.ru

Heat exchanger for a chimney pipe, or how not to heat the street

Saving and frugality are qualities inherent only to humans; they are the ones who have been driving technological progress for centuries, creating devices designed not only to make life easier, but also to use all available resources to the maximum.

If we concern the household, or more precisely, the communal sphere, then the costs of heating a house are rightfully considered the highest, but here too, progress and people's ingenuity have found their application.

One of the most affordable ways to save heat in a stove-heated house is a heat exchanger on a chimney pipe, and it is this device that we would like to talk about in this article.

Why is it needed?

The photo above shows that approximately 14% of the heat that could be stored in the house is lost through the chimney. Of course, this is not the largest figure, but if you convert the losses into kilowatts of energy and multiply by the number of days during which heating was carried out, the result is quite significant.

The main purpose of the chimney pipe is, of course, to remove exhaust gases. They are the ones who heat the pipe to enormous temperatures.

If you look at the stove through a thermal imager, you can see that the temperature of the chimney can be the same as in the firebox itself. The problem is that the heat transfer from the chimney is not accumulated in any way, but it can be put to use. And how to do this will be discussed below.

Types of heat exchangers

The main task of the heat exchanger is to transfer the heat emitted by the chimney over a distance, but not to over-cool its surface, as this will lead to increased formation of condensation and, accordingly, the accumulation of soot on the inside of the pipe.

It is maintaining this balance that is the most significant difficulty, especially if you decide to make a heat exchanger for the chimney with your own hands.

According to their design features, heat exchangers can be of two types:

1. Water, when heat is transferred through the natural circulation of liquid in a closed system.
2. Air, when heated air is forcibly transferred in the desired direction.

The choice of design directly depends on the individual characteristics of the house and the stove, as well as on the goals pursued by its installation. But first things first.

Closed type water heat exchanger

The operating principle of all closed heating systems is based on the elementary laws of physics - when heated, the density of water decreases and is pushed from below by colder water, it begins to rise through the pipe, entering the expansion tank, and from there it returns to the heater along the entire circuit.

In this case, the chimney acts as a heater, which with its energy pushes water along the contour of the heating system.

Homemade coil

The design shown in the photo is the most common and simplest way to use heat from a chimney. The upper edge of the tube is connected to the expansion tank, and the lower edge to the heating circuit.

Advice! Copper tube is best suited for the coil. It is easily screwed onto the chimney and has a high thermal conductivity coefficient.

Most often, such a system is used as an auxiliary one. With its help, you can heat small rooms in which heating was not previously provided, but nothing more. It will not be able to act as the main heating, since its design has several significant disadvantages:

• The temperature on the surface of the chimney is an unstable and difficult to control value, as a result, it is impossible to regulate the degree of heating of the coolant.
• Due to the variability of temperature, it is very difficult to calculate the optimal coil length. If it is too short, the water will begin to boil and rupture the tube, and if it is too long, the coolant will not warm up to the desired temperature at all.
• The water from the expansion tank cannot be used for showering or other purposes, and this is not just due to unregulated heating. When the tank is filled with cold water, it will begin to cool the chimney through the coil, resulting in the formation of condensation and accelerating the process of soot formation on the internal walls.
• The temperature to which the chimney heats up is not enough to warm up a long circuit. With conventional heating, water passing through the system loses only 25 degrees; to maintain this figure in this situation, the entire system must be small in size.

Important! Some “traditional craftsmen” come up with the idea that the heat exchanger in the chimney will be much more efficient, because the temperature there is higher. This should not be done under any circumstances; foreign objects inside the pipe prevent the free passage of gases, as a result of which they can enter the room.

Register heat exchanger

To avoid problems with homemade devices, you can purchase a register heat exchanger for the chimney pipe. Of course, the price of such a device will be higher than that of a DIY one. But the quality characteristics cannot be compared.

The principle of operation of such a device is identical to that described above, with the only difference being that all the calculations have already been made to protect the device from boiling. Unfortunately, there is no heating control here either, but there are several significant advantages compared to “homemade” ones:

• The outer casing retains heat inside, allowing the coil to warm up even at low chimney temperatures;
• Copper tubes do not come into close contact with the heating surface, this protects the device from possible boiling.

Important! Each factory heat exchanger comes with detailed installation instructions. To achieve maximum performance and not encounter unexpected problems, you must study it carefully and follow all the manufacturer’s recommendations.

Air heat exchangers

The principle of operation of such a device is that hot gases inside the chimney flow around the heat exchanger tubes, due to which they heat up and release energy outside. In fact, it does not create additional heat, but simply directs hot air into the air in a given direction.

The air heat exchanger for the chimney can be either independent or with forced draft. To speed up the spread of hot air in the room, a regular fan is often used; this is quite enough to circulate the air, and at the same time does not over-cool the chimney.

You can assemble such a heat exchanger yourself, and all stages are shown in the video in this article

Heat exchanger "Kuznetsov"

This is the most optimal chimney heat exchanger for heating a cold attic or attic. Hot gases always tend upward, and since the outlet is located below the inlet level, they first heat the heat exchanger, and after that, when they cool down, they enter the pipe, from where they go outside.

A chimney with a Kuznetsov heat exchanger will not be able to completely heat the room, but it almost completely eliminates heat loss, releasing only cooled gases through the pipe.

fireplace.su

How to install an air or water heat exchanger on a chimney pipe with your own hands

The efficiency of a sauna or heating stove can be increased by equipping it with a water or air heat exchanger. Installing a heat exchanger on a chimney will solve two problems at once: heat water for the heating system or hot water circuit and perform thermal insulation of the chimney.

Principle of operation

The chimney of a metal stove installed in a bathhouse, house or garage becomes very hot when fired. Depending on the design of the stove, its temperature can be from 200 to 500 degrees, which makes it dangerous in terms of fire safety, and accidental touching it can cause a severe burn.

The heat from the chimney can be used for good by placing a heat exchanger on it: a tank or a coil. The coolant in this case is usually water, and in some cases air. When the coolant comes into contact with the heated walls of the chimney, their temperature is equalized: the chimney is cooled, and the water or air in the heat exchanger, on the contrary, is heated.

When heated, warm water rises to the upper part of the heat exchanger, and from there through the outlet fitting and pipe into the system or storage water tank. Instead of heated water, cold water flows through the inlet fitting. As it heats up, circulation continues, as a result of which the water in the storage tank can heat up to a high temperature.

Air heat exchangers operate on a similar principle: cold air is taken from below, and after heating it is supplied through a pipeline to the heated rooms. This way you can heat an attic in a country house or a relaxation room in a bathhouse, which are heated periodically. It is impossible to install water heating in them, since you will have to regularly drain and fill the system with coolant.

Tank with water circuit connection

The heat exchanger in the form of a tank located around the chimney is made of stainless steel or galvanized sheet. In this case, the design of the furnace should be taken into account. If it has a combustion mode for flue gases, and the smoke temperature at the furnace outlet does not exceed 200 degrees, you can use any material to make the heat exchanger.

In simple stoves without smoke circulation, the smoke temperature at the outlet can reach 500 degrees Celsius. In this case, it is necessary to use stainless steel, since the zinc coating releases harmful substances when heated strongly.

Most often, heat exchangers of this type are installed on a sauna stove and used as a water heater for domestic hot water. The tank is equipped with fittings in its upper and lower parts, and pipes leading into the system are connected to them. The hot water tank is installed in the shower or steam room. It is possible to use such a system for heating a utility room or garage.

Making a tank: step-by-step instructions and video

Heat exchangers for industrial furnaces are sold complete with some modifications; when installing a new furnace, you can choose a suitable model with a ready-made water circuit. You can also make a heat exchanger for the chimney with your own hands. To make it you need the following materials:

• pieces of stainless steel pipe of different diameters with a wall thickness of 1.5-2 mm, sheet steel;
• 2 1-inch or ¾-inch fittings for connecting to the system;
• storage tank made of stainless steel or galvanized steel with a volume of 50 to 100 liters;
• copper or steel pipes or flexible connections for hot water supply;
• ball valve for draining coolant.

Manufacturing sequence for a sauna stove or potbelly stove:

1. Work begins with preparing a drawing. The dimensions of the tank installed on the chimney depend on the diameter of the pipe and the type of stove. Furnaces of a simple design with a direct chimney are characterized by a high temperature of the flue gases at the outlet, so the dimensions of the heat exchanger can be quite large: up to 0.5 m in height.

1. The diameter of the inner walls of the tank must ensure a tight fit of the heat exchanger on the smoke pipe. The diameter of the external walls of the tank can exceed the diameter of the internal ones by 1.5-2.5 times. These sizes will ensure quick heating and good coolant circulation. It is better to equip furnaces with low flue gas temperatures with a small tank to speed up its heating and avoid the formation of condensation and deterioration of draft.
2. Using a welding inverter, the parts of the workpiece are connected, ensuring the tightness of the seams. Fittings for supplying and withdrawing water are welded into the lower and upper parts of the tank.
3. The tank is installed tightly onto the smoke fitting of the furnace, coating the connecting seam with heat-resistant silicate sealant. An adapter from a non-insulated pipe to an insulated one is placed on top of the heat exchanger tank in the same way and the chimney is removed from the room through the ceiling or wall.
4. Connect the heat exchanger to the system and storage tank. At the same time, the required degree of inclination is maintained: the cold water supply pipe connected to the lower fitting must have an angle of at least 1-2 degrees relative to the horizontal plane, the heated water supply pipe is connected to the upper fitting and, with a slope of at least 30 degrees, is led to the storage tank. The storage tank must be located above the heat exchanger level.
5. A drain valve is installed at the lowest point of the system. In the bathhouse it can be combined with a tap for drawing warm water for the steam room.
6. Before starting operation, the system must be filled with water, otherwise the metal will overheat and leak, which can lead to poor sealing of welds and leaks.
7. The water supply to the storage tank can be done either manually or automatically using a float valve. When filling manually, it is recommended to place a transparent tube on its outer wall to monitor the water level in the tank, so as not to run the system dry.

For good coolant circulation, it is necessary to use pipes with a diameter of at least ¾ inches, and their total length to the storage tank should not exceed 3 meters!

A do-it-yourself water heater exchanger is shown in the video.

Simple design: coil

Installing a heat exchanger tank on a chimney involves welding work, which not everyone can do. A simpler design is a coil wrapped in a spiral around the chimney. The coil can be made from a copper or aluminum tube - these metals are easy to bend, have high thermal conductivity and are not subject to corrosion.

The diameter of the tube is chosen so that it is convenient to connect it to the fittings of the water storage tank. For bending, pipes with a diameter of no more than 28 mm are more convenient. In any case, the length should not exceed 3 meters - this is a prerequisite for natural coolant circulation. To connect the heating coil to the tank, use a flexible hot water line.

This heat exchanger design can be used to produce hot water, and less often - for heating small rooms. Maximum heating efficiency is achieved if the coil is installed on the chimney of a simple stove such as a potbelly stove with a high temperature of the flue gases.

DIY chimney coil

A pipe heat exchanger is usually installed on the chimney of a metal stove installed in a garage or workshop to produce warm water or heating. It is also possible to install a coil on a sauna stove.

Necessary materials:

• pipe made of copper, aluminum or steel - about 3 meters;
• flexible hose for hot water supply with a diameter of ¾ inches - 2 pieces of the required length;
• a storage tank equipped with a float valve for water supply and a drain valve for its consumption;
• ball valve for draining the system.

Sequence of work:

1. The most difficult thing when making such a heat exchanger is to bend the pipe into a spiral without reducing its cross-section. Copper pipes with a diameter less than 28 mm can be bent using a pipe bender without heating. Steel and aluminum, as well as larger diameter pipes, must be heated with a blowtorch before forming.
2. You can also use this method: fill the pipe with dry sand and tightly plug its ends with wooden plugs. The pipe is bent according to the template - a pipe having the diameter of the chimney, after which the plugs are removed and sand is poured out, the pipe is washed under high pressure of water.
3. Threads are cut at the ends of the pipe and adapters are installed for connection to the system.
4. The pipe is installed on the chimney. To improve heat transfer, you can solder the coil onto the chimney with tin, having previously degreased the soldering areas and removed oxides with phosphoric acid.
5. The tank is hung on the wall or placed on a support above the level of the coil. Connect the heater to the tank using flexible hoses. A drain valve is installed at the lowest point of the system.

When using a coil heat exchanger in closed heating systems, it is necessary to install a circulation pump! The coolant may boil, and if circulation is poor, water hammer can occur, destroying the system elements!

Video: receiving hot water from a coil heat exchanger installed on the chimney

Air tank

You can improve an ordinary potbelly stove or sauna stove with a direct chimney by installing it on an air heat exchanger on the chimney. It is a cylindrical body through which several hollow pipes pass. Air is sucked in from below, heated in the pipe, it leaves the heat exchanger, increasing the efficiency of the furnace by 15-20%. The air ducts can be routed to an adjacent room, thus heating several rooms or sections of the garage from one furnace.

Video: how to make an air heat exchanger for a chimney

Another original design of a stove with an air heat exchanger on a chimney for heating a garage is shown in the video. With the help of such a stove you can heat not only a garage, but also any utility room, including agricultural buildings and greenhouses.

From corrugated pipe

A cheap and simple way to install an air heat exchanger is to use corrugated ventilation pipes for this purpose. They are wrapped around the uninsulated part of the chimney, as a result the air in the corrugation warms up and, due to thermal convection, enters the neighboring rooms. To make the corrugated pipe heat up more efficiently, you can wrap it together with the chimney in several layers of foil.

A system with a corrugated pipe is convenient for heating a garage in which a simple potbelly stove made of rough metal is installed. Such a stove quickly heats the air, but it rises to the ceiling, which is why the temperature at floor level remains low. If you move the air ducts closer to the floor, you can create natural circulation of heated air, and the temperature throughout the garage will become approximately the same.

Bell-type heat exchanger

Heat exchangers in the form of a bell are usually used for heating the attic or second floor. The principle of its operation is that the air heated from the chimney rises to the ceiling, where it is retained by the hood and, gradually cooling, falls down into the room.

The cap can be made of either galvanized metal or fire-resistant plasterboard and lead the air ducts to the desired location. Sometimes the cap is decorated with stones, which, when heated, serve as an additional heat accumulator.

Flaws

Despite many advantages, the installation of a heating element on a chimney pipe also has disadvantages. One of them, the most important, is a sharp decrease in the smoke temperature at the installation site of the heat exchanger. This can lead to deterioration of traction and the formation of condensation, increased soot deposition inside the pipe.

In addition, when connecting a heating system, for example, a garage, you need to calculate the volume of coolant to avoid boiling water and bursting pipes. Welds must be completely sealed.

Any heat exchanger design significantly increases the efficiency of the furnace. For trouble-free operation of the system, it is necessary to carry out a visual inspection of all its elements at least twice a year, and, if necessary, timely repairs, descaling, replacement of gaskets and other necessary maintenance work. In this case, water heating and heating systems will operate flawlessly for a long time.

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