And the heat won’t go anywhere Choosing a heat exchanger for a sauna stove
Heat exchanger is a special device for transferring heat energy from the heat source, usually a furnace or boiler, to the liquid heat carrier.
The heat carrier in the heat exchanger was water, as well as any other liquid. Once heated, the unit was used for domestic, industrial, or other needs.
Heat exchanger for sauna stove
The way our grandfathers used to bathe in a bathhouse? A large vat for water was built into the stove. While the heater was heating, the water in the tub was heating, and its volume (about 50 liters) was enough for the whole family. Cold water was taken from another container. The people bathed in the same room, which was not very convenient. It was hard to wash in an overheated and overflowing steam room.
It is not very comfortable to take a steam bath and wash at the same time
Not surprisingly, nowadays, owners of baths want to increase the comfort of taking water procedures and divide the process of steaming and washing in different rooms.
Separate from the shower room, the steam room is aesthetically pleasing and comfortable
There are two ways to solve warm water issues: with a separately installed electric boiler and with a heat exchanger that takes heat from the stove. We will not consider the first method, there is nothing interesting and complicated in it. In addition, to heat a large amount of water consumes a significant amount of electrical energy, and its cost is constantly increasing nowadays.
Let’s talk about heat exchangers, give step-by-step instructions for the construction of some of them and practical advice on engineering problems of heat exchangers.
The device of the furnace with a heat exchanger is so well proven that there are different variants of the design of heat extraction, with varying degrees of efficiency. The most common:
- Classic coil.
- Integrated flat heat exchanger (resembling two hollow plates connected to each other).
- Samovar heat exchanger installed on the chimney.
The water jacket surrounding the furnace chamber is extremely rare and found in only 1-2 factory-made furnace models.
Meanwhile, bath stoves with a heat exchanger have become a topic of discussion for consumers. Some argue that the use is not practical, others, on the contrary, point to the convenience and comfort during operation.
What gives a built-in or samovar-type heat extraction device?
- The heat exchanger in a sauna stove is needed to obtain hot water for bathing. This was the primary objective of the design.
- The possibility of heating in the bath from the furnace with a water loop. in fact, the metal furnace becomes a kind of heating boiler. During the firing enough heat is released for heating the coolant and heating the required volume of DHW.
The principle of operation depends on the device used. The efficiency is determined by several parameters:
By design, it is possible to divide all water heating devices into built-in and superstructure (samovar type).
Stoves for baths with a water loop for heating and hot water heating needs began to appear after the good reviews received conventional water heat generators. In terms of its device, furnace equipment with an integrated water heating circuit is divided into several classes:
- Coil. the simplest device used in classic solid fuel boilers. Inside the structure is a bent metal tube. The form is different and depends on the features of the internal design of the furnace. The coil is positioned so that the flame does not affect it directly, and heating is carried out by the flue gases.
- Flat heat exchanger. a more complex device compared to the previous. Flat heat exchanger for sauna stoves, looks like two hollow plates connected to each other. In terms of thermal efficiency, the design is superior to the coil, used in modern models of furnace equipment.
The principle of the integrated heat exchanger in the sauna stove is as follows. The coil or plate is heated by the flue gases, which reaches a temperature of 450-500 ° C. When heated, pressure is generated, forcing the coolant to circulate in the heating system. In schemes where a boiler of indirect heating is used, DHW is heated at the expense of the heat of heating.
Pressure heat exchanger of the samovar type
Installing a heat exchanger on the sauna stove. a budget solution to the problem of DHW and heating. Water heating device is made in two ways:
- Coil. a coil of aluminum or copper is installed on the chimney. For systems with natural circulation, up to the storage tank or water distribution taps, the size of the coil should not exceed 3 m. Optimal coil sizes with forced circulation, 5 m.
- Design of a samovar-type heat exchanger. specialists agree that this design is best suited for the bath. Hot water for the shower is prepared gradually, boiling of the liquid is prevented.
Water movement in the heat exchanger of the samovar type occurs according to natural physical laws. The heated liquid rises upwards, the pressure is created in the tank.
The optimum volume of the heat exchanger of the samovar type is chosen so that the water reaches the required temperature, after 2-3 hours of intensive combustion. The design is optimal for hot water supply.
No possibility to buy equipment? You can make a heat exchanger for heating a private home with your own hands
Living in a private home in the fall and winter is impossible without a heating system. Only it creates a favorable microclimate in the room.
Not the last place in its design takes the heat exchanger. In a private home, you can not do without it. Thanks to the device, heat is supplied even to remote rooms. There are several types of this device, each of which has weak and strong points.
Variants of heating water for washing
If we talk about ready-made metal heaters, which are currently on sale, the function of heating water in them is implemented in 3 ways:
- The simplest. it is a hinged tank, heated directly from the wall of the firebox.
- Integrated steel tank; both steel and brick stoves can be fitted with the same tank.
- Heat exchanger for sauna stoves in the form of a coil.
- Samovar-type heater.
The hinged metal tank is attached to one of the side walls of the unit. Filled via the top lid, emptied via a cock. This option is inexpensive, but the most uncomfortable, because the water in the container quickly heats up and boils. This process must be monitored, emptying the tank in time and filling it with cold water.
The next option. a stainless steel tank, built inside the fuel chamber. For water supply and extraction is welded to it with two threaded nipples on the outside. They are connected with pipes leading to the next room (washing room), where they are connected to a separate storage tank. The latter is placed at a certain height so that water can flow into the shower by gravity. Here it is important to connect the heat exchanger for natural water circulation.
The device removes a considerable amount of heat from the burning wood, which makes the steam room heated for a longer period of time. Stoves with heat exchanger in the form of a pipe bent into a coil are deprived of this drawback. It also connects to a remote tank installed in the next room by means of pipes.
The listed 3 types of heat exchangers have 1 common disadvantage: they can not be used empty, that is, without water. If a hinged tank somehow survive such a situation, the heaters built into the furnace will burn out very quickly.
What is a bath without hot water?? And to heat it, you do not need a boiler. there is a furnace and a fire in the furnace. And the water will be heated by the heat exchanger.But first you need to determine what exactly will be better tank for the bath: on the pipe, remote or built-in, what material it will be made of. in general, what it should be, so that during the operation of the bath it will not have to be replaced by another.
You can, of course, find stoves for baths with a tank, but what to do if you have a stove, and the tank for heating. no? Then you can find custom bath tanks or make them yourself, using a regular welding machine. and that’s it.
- 2 Cast iron, steel or stainless steel?
- 2.1 Cast iron: Hot water all day long
- 2.2 Stainless steel bath tanks: lightweight and durable
- 2.3 Enameled tanks. good with careful handling
Bath tanks can be built-in, external and on a pipe. and each has its own pros and cons. Compare and estimate. which one is suitable for your bath?
To build your own heat exchanger you need sheet metal at least 2.5 mm thick. To equip a sauna stove with such an appliance, you will need the following kit:
It follows that the heat exchanger for a heating device consists of two parts: an upper cylinder and a lower rectangle.
Pre-cutting of the metal blanks, their welding is performed. Try to connect the parts with the smallest possible gap. After making the reservoirs, the assembly of the system is carried out. The choice of pipe diameter depends on the area of the room that will be heated. Equally important is the length of the connection elements. The shorter the pipes, the higher the efficiency will be different heat exchanger for the sauna stove.
Heat Exchanger with Your Own Hands for a Sauna Stove. DIY
The final assembly involves the following steps:
- A tube is welded to the bottom part of the device.
- Water is poured into the tank to be built into the furnace through the air source opening.
- The metal piece is welded to the top of the heat exchanger.
The apparatus is ready. How well performed all the welding work can be checked with high pressure. You need source of compressed air connected to the constructed system. If there are no leaks it means that everything was done correctly. Otherwise it is necessary to get rid of manufacturing defects.
The heat exchanger is a device that can be plugged into the work, if it only carries out the heating of water in the bath. In the case of the full introduction of the unit into the heating system is required to take care of quality insulation of the room.
What you need to know about the design
It will be easiest to buy a built-in heat exchanger in the furnace at the time of construction and laying. But not everyone is so forward-thinking, and many people simply do not encounter such a need. But it is worth understanding that if the furnace is already functioning, nothing prevents you from finding the right coil. Installation is not considered complicated, although it requires following some rules.
According to how heat exchangers work, you can divide them into three main groups:
- The heat exchanger inside the furnace;
- Outdoor structures, which is a tank at the wall of the furnace;
- External pipe circuit, which is heated by exhaust gases.
The internal heat exchanger can be made in the form of a coil or tank. the principle is the same here. In any case the heating element is installed directly in the fuel box. It must be mounted so that the part is not exposed to fire, and it is not exposed to the highest temperatures. But at the same time it is made in the way of gas escape. If the structure will be installed correctly, it will last a long time, it will not melt. But call it an effective option can not be called, because the coil takes the heat directly from the furnace, that is lowers its performance. That’s why the efficiency is only 50%.
The outer tank hangs to one of the walls of the furnace. You can not find an easier installation, but that is practically the end of the advantages. Requires the constant addition of cold liquid, and the heat flowing through the walls is insufficient to heat the steam room.
The most effective constructions are considered to be those for heat takeoff from gases. They increase the heat from the fuel by 60% and do not affect the performance of the stove in any way. Here the tank is mounted directly at the outlet of the chimney. Many modern types of furnaces, such as Ermak and Termofor, are made according to this principle. To such a tank can be connected spigots with remote, additional capacity.
Heat exchanger for a sauna stove with their own hands
The heat exchanger is a special device for transferring heat energy from the heat source, usually a furnace or boiler, to the liquid heat carrier.
The coolant in the heat exchanger is water, as well as any other liquid. After heating, the unit is used for domestic, industrial, or other needs.
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 tin. In this case the furnace design must be taken into account. If it provides for afterburning of flue gases, and the temperature of smoke at the outlet of the furnace does not exceed 200 degrees, you can use any material for the manufacture of the heat exchanger.
In simple ovens without a smoke turnover smoke temperature value at the outlet can reach 500 degrees Celsius. In this case it is necessary to use stainless steel, as the zinc coating when heated strongly emits harmful substances.
Most often heat exchangers of this type are installed on the sauna stove and used as a water heater for DHW. The tank is equipped with nipples at the top and bottom of it, they are connected to the pipes brought into the system. The hot water tank in this case is installed in the shower or steam room. You can use such a system and for heating the utility room or garage.
Heat exchangers for industrial furnaces are sold with some modifications, when installing a new furnace, you can pick up a suitable model with a ready-made water circuit. You can also make a heat exchanger on the chimney with your own hands. For its manufacture the following materials are required:
- pieces of stainless steel pipe of different diameters with a wall thickness of 1.5-2 mm, sheet steel;
- Two 1-inch or ¾-inch fittings to connect to the system;
- tank made of stainless steel or galvanized steel with the volume of 50 to 100 liters;
- copper or steel pipes or flexible piping for DHW;
- ball valve for draining the coolant.
Sequence of fabrication for a sauna stove or wood-burning stove:
- Start by preparing a blueprint. The dimensions of the tank to be installed on the chimney, depending on the diameter of the pipe and the type of furnace. Stoves of simple design with a straight chimney has a high temperature of flue gases at the outlet, so the size of the heat exchanger can be quite large: up to 0.5 m high.
- The diameter of the inner walls of the tank should ensure a tight fit of the heat exchanger on the chimney. The diameter of the outer walls of the tank can be 1.5-2.5 times the diameter of the inner. Such dimensions will ensure rapid heating and good circulation of the coolant. Furnaces with a low flue gas temperature is better to equip the tank, which has a small size, to accelerate its heating and avoid the formation of condensation and reduced draught.
- Use a welding inverter to connect the parts of the workpiece, making sure the seams are tight. At the bottom and top of the tank weld on nipples for water supply and withdrawal.
- The tank is installed on the oven chimney fitting snugly, blotting the connecting seam with a heat-resistant silicate sealant. On top of the tank heat exchanger similarly put adapter from uninsulated pipe to insulated pipe and take the chimney from the room through the ceiling or wall.
- Connect the heat exchanger to the system and the storage tank. While maintaining the required degree of slope: cold water supply pipe connected to the bottom nozzle should have an angle of at least 1-2 degrees relative to the horizontal plane, the supply pipe heated water is connected to the top nozzle and with a slope of at least 30 degrees lead to the storage tank. The storage tank must be above the level of the heat exchanger.
- At the lowest point of the system set the drain cock. In the bath it can be combined with a tap of warm water for the steam room.
- Before you start using the system must be filled with water, otherwise the metal will overheat, and it will hang, which can lead to leakage and weld sealing failure.
- The water supply to the storage tank can be made either manually or automatically by means of a float valve. When manually filling it is recommended to take out on its outer wall of a transparent tube to control the level of water in the tank, so as not to run the system dry.
Heat exchanger-water heater, made with his own hands, shown in the video.
How to calculate the area of the heat exchanger?
All calculations of heat exchanger dimensions are always approximate. For example, to heat an ordinary sauna room needs about 5kW. that is how much energy the system should give the furnace with a heat exchanger. And 1 square meter of heat exchanger area is about 8-9 kW during the furnace.
Of course, much depends on the location of the boiler in the furnace and the intensity of fuel combustion, but in any case, the power of the boiler at the end of the furnace quickly drops by 5-10 times. That is why the surface area of the heat exchanger should be calculated with multiple reserves. only in this way you can create a system that can maintain a comfortable temperature in all rooms of the bath for single or double firing.
The shape of the boiler itself of the sauna stove with a heat exchanger can be very different. The most common option. from stainless steel pipes, but today increasingly popular are manifolds made of two channels and samples of plate type.