How to make a heat exchanger on the chimney with your own hands: tips from the master

In the last decade, it has become very fashionable to introduce man to nature. Our compatriots began to get out on picnics and outings more and more often, to build summer cottages and country houses. But a resident of a modern metropolis is not accustomed to living in uncomfortable conditions and, with passion and ingenuity inherent only to our person, he began to equip his home with electricity, plumbing and heating systems.

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The main source of heat in a suburban building, of course, is an ordinary stove or fireplace, which “devours” solid fuel in incredible quantities as fuel. For smaller and cheaper buildings, our people most often use a potbelly stove and all its derivatives. A feature of the bourgeoisie is a simple and fairly fire hazardous design, and low efficiency. Common for space heating through a stove, fireplace, potbelly stove is a fairly high temperature of exhaust gases released into the atmosphere and the fact that such devices can only heat the room in which they are installed.

Comparing these two shortcomings, our man came up with a device that allows you to turn them into a solid advantage, namely, he invented a heat exchanger for a chimney pipe.

Purpose and features of the device

This design is designed to take heat from a heated chimney and transfer it to the coolant circulating in the heat exchanger. The very design of such a device depends on the shape and section of the chimney, the material from which it is made, the power of the heating device and the coolant, which can be air, water, oil and various non-freezing liquids.

According to the coolant circulating inside the device, all heat exchangers can be classified into air and liquid. Air — easier to manufacture, but do not have the highest efficiency. For example, to heat a second room, a dressing room or an attic, it is necessary to run an air duct there, and if such a room is located far enough from the stove, then a fan must be installed to create a forced air flow.

Heat exchangers with a liquid heat carrier are more demanding in terms of workmanship and material, but have greater efficiency. For example, a chimney with a heat exchanger through which water circulates can serve as a full-fledged water heating system for a small country house, if you connect the supply and return to one or two radiators to the inlet and outlet of the device.

The design of the liquid heat exchanger for the chimney

The standard heat exchanger is a coil and metal, with a high coefficient of thermal conductivity, which is in direct contact with the surface of the chimney pipe. For safety and better heat transfer, the coil is installed in a metal casing and carefully insulated from the inside with non-combustible types of insulation. Basalt wool is best suited for this.

The entire structure is installed on the section of the chimney pipe. The ends of the coil are led out through the casing and connected to the heating system, at the highest point of which an expansion tank is installed, which serves as a container for the liquid that has expanded under heating. Annealed copper pipe is the best material for the coil. The heat exchanger from the copper tube to the chimney will be 7 times smaller than from steel, due to the high coefficient of thermal conductivity.

Water is heated in a coil. Expanding, it rises along the coil, after which it enters the heating radiator by gravity through the pipe. When hot water enters the radiator, it pushes out cold water, which, when it enters the coil, heats up. This is how the natural circulation of the heat exchanger through the system occurs. But, this is just the physics of the process. To create water movement in the system, it is necessary to accurately calculate the diameter and length of the coil, observe the angles of inclination of the supply and return, provide for the degree of expansion of the coolant when heated to a certain temperature, and many more factors.

The importance of calculations cannot be underestimated: a non-working design is not as scary as the consequences of a water hammer when the coolant boils.

Such, at first glance, a useful device has a number of disadvantages: complexity in calculations and manufacture, constant monitoring of the coolant temperature and pressure in the system, high water consumption associated with the evaporation of liquid from the expansion tank. If water is used as a heat carrier, then it must be drained when the system is not used in the winter. In addition, the heat exchanger significantly reduces the temperature of the gases discharged from the chimney, which can lead to a decrease in thrust and incomplete combustion of the fuel.

Despite all the shortcomings, it is possible to make such a heat exchanger for a chimney with your own hands by almost any person who has school knowledge of physics and knows how to hold a tool in his hands.

Air heat exchanger for potbelly stove

Such a device, as a rule, consists of a hollow metal body with several inlet and outlet nozzles installed in it. The whole structure is mounted on the chimney of the potbelly stove. The principle of operation of such a device is quite simple.

From below, according to the principle of convection, colder air enters the nozzles, where, when heated, it is ejected from the upper part of the structure directly into the room. It is this principle that can significantly increase the efficiency of the potbelly stove and reduce fuel consumption by two to three times.

Making an air heat exchanger for a chimney with your own hands is quite simple, if you have a welding machine, metal pipes of different diameters, a grinder, for cutting pipes and a great desire.

Material:

• A piece of metal sheet, 1 mm thick and 35 cm x 35 cm in size.
• Steel pipe, 1 ¼» in diameter, 2.4 m long.
• A piece of pipe with a diameter of 57-60 mm.
• Metal tank. A bucket of engine oil with a volume of 20 liters is suitable.

Manufacturing:

1. We make the end parts of the structure. To do this, cut circles from a metal sheet. The diameter of the plugs should be the same as that of a tank or bucket prepared in advance.
2. In the center, a hole should be cut for the central pipe (57-60 mm).

3. Along the edges, evenly mark and cut holes for the 1 ¼ pipe.

   Two such preparations should be made.

4. Using a grinder, cut a 1 ¼ pipe into eight identical pieces of 30 cm each.
5. Weld a piece of pipe with a diameter of 60 mm and a length of 300 mm to the central hole of the plugs.
6. Circumferentially weld eight 1 ¼ inch pieces to the plug holes.

This is how the design should look like.

The next step will be the manufacture of the heat exchanger housing from a bucket. For this you need:

• Bulgarian cut off the bottom of the bucket.
• From the sides (in the center) of the casing, cut holes along the diameter of the chimney.
• Weld pipes of the required diameter to the side holes in the casing.

Now the prepared «core» should be inserted into the body and the plugs should be carefully fixed by welding. The finished heat exchanger should be painted with heat-resistant paint for furnaces.

It remains to install the finished heat exchanger on the chimney of the potbelly stove and enjoy. If the effect does not suit you, then enhance it by creating a directed air flow with a fan.

You can create an air heat exchanger “and on your knees”, using improvised means for this. If you decide to create a full-fledged water heating using a chimney heat exchanger, then it is best to contact specialists for help in calculating and creating a device.