Technological progress in the segment of heating equipment is developing in different directions. Some manufacturers are betting on improving the operational characteristics of the component base of the units, others are promoting the latest automatic control devices, while others are also at the basic level involved in the optimization of designs. The last group of developments includes a bithermic heat exchanger. What it is? In fact, this is a heating chamber, capable of performing two different tasks - to prepare water directly for heating, and for the needs of hot water supply, that is, for domestic consumption.
Bithermic Heat Exchanger Overview
Classic heat exchangers for boilers provide for the separation of heating chambers. That is, one chamber is intended for servicing heating circuits - as a rule, the main one, and for domestic hot water - a secondary radiator. This design has many advantages, however, against the background of the combined heating chambers, its weaknesses become apparent. In this case, it will be wrong to assume that in the second case the water is mixed - a bithermic heat exchanger also does not allow this principle. What is this in terms of an approach to water service? This is the same radiator equipment, but with a common case, which encloses both chambers for heating the coolant and compartments for the preparation of household water. In bithermic systems, the principle of separation of service areas of different environments also applies, but this applies specifically to the internal delimitation of cameras. Whereas a standard split heat exchanger initially contains two different chambers.
Construction device
Now it’s worthwhile to understand the design features of bithermic radiators, which allow it to separately carry out heating of different media. Specialists characterize such constructions with the concept of “pipe in pipe” or “section in section”. If in a conventional heat exchanger it is assumed a set of pipes that have a hollow niche, then the bithermic device is distinguished by internal division into several segments - these are zones in which water circulates for domestic hot water and heating without mixing. And already according to the classical scheme, copper fins-plates are also attached to the pipes, which increase the heat transfer coefficient. Obviously, depending on the method of integration already in the target equipment, other design features of the radiator will be provided. In particular, the device of the bithermic heat exchanger of a gas boiler is oriented toward heating by a burner, therefore, the housing may provide additional layers of protection. Mandatory for all heat exchangers are provided and means of ensuring safety against short circuit of electric current. Since the circuits can be interfaced with other utility lines, grounding and the presence of fuses in the boiler stations are also mandatory.
How does a bithermic heat exchanger work?
Operating modes for heating and hot water supply have several differences. In the first case, standard water heating occurs during the gas combustion process - if we are talking about the same gas boilers, for example. That is, in heating mode, direct heating of the coolant occurs, which then circulates along its circuit. As for the operating mode in the DHW format, this function is in some way secondary. Also, primary heating of the coolant occurs, and heat is transferred from the sections with water intended for hot water supply from it. In this case, the heat exchangers for heating do not distribute the water for heating along the respective circuits - it remains in its section. For almost all bithermic boilers, one rule applies - only one of the two circuits can operate at the same time. Simultaneous circulation of water for heating and domestic hot water is unacceptable.
Bithermal heat exchanger boilers
The use of bithermic radiators in boiler plants is becoming increasingly common. Often, large manufacturers themselves develop model designs on their own components, including heat exchangers. One of the leaders in the segment is Immergas, which offers boilers with 6 tubes heat exchangers. This design provides a plus over 4 and 5-tube heat exchangers, since the expanded section can be located close to the flame of the burner. However, it is necessary to take into account the thermal power that the 6-tubular heat exchanger of the boiler will provide. The bithermic principle of operation in this case is capable of delivering about 24 kW and this may be redundant for private houses and large country cottages. The development of bithermic units is also carried out by Vaillant, Navien, Protherm. The products of these manufacturers are distinguished not only by modern design, but also by functionality. Engineers strive to provide models with the ability to smoothly control the flame, the option of cooling the heat exchanger, etc.
The advantages of bithermic units
The advantages of heat exchangers with a single unit extend to the heating efficiency as such, and to the convenience of control, not to mention the higher reliability of the units. As for efficiency, bithermic radiators operate with a lower coefficient of heat loss. If in a system divided into two blocks, heating of two blocks is required, then in this case the filling of one case is serviced - accordingly, the amount of heat generated increases. In terms of control, a bithermic heat exchanger is more profitable for the same reason. Thermostats are guided by indicators of one whole unit, which affects the accuracy of the data received. Reliability, in turn, is achieved by minimizing the connecting infrastructure - in fact, only a bundle between the heat exchanger and the supply channels is required.
Design flaws
The main disadvantage of the bithermic design is the limitation when working with liquids saturated with salts. In this context, one can note the imperfection of the monoblock case and coaxial circuits inside, which are quickly covered with scale. In addition, the bithermic heat exchanger is not able to provide the same performance as in the case of split radiators. This applies specifically to hot water supply, since the design itself involves a smaller volume of water served for such tasks.
Consumer Reviews
Users themselves mainly emphasize the energy efficiency of this solution. Owners of boilers and boilers that previously dealt with traditional split heat exchangers indicate both high heat transfer and low gas consumption. But this applies to cases where the gas supply infrastructure is used, into which boilers with a bithermic heat exchanger are introduced. Reviews of owners who rarely use the heating function - on the contrary, indicate the disadvantage of such units. The fact is that boilers with split heating allow you to work purposefully for one of the tasks - heating or hot water, which is more economical.
Operation Nuances
Manufacturers of bithermal equipment note that it is possible to prevent rapid wear of the heating filling by observing several operating rules. These include, in particular, ignoring preventive circuit checks. Most often, a bithermic heat exchanger for a heating system and hot water supply is installed with the expectation of long-term and regular operation. In intensive operation, even relatively clean water can adversely affect the condition of the radiator pipes. Accordingly, periodically cleaning the surfaces of the sections.
It is not recommended to sharply increase the temperature of heating. Unlike split heat exchangers, monoblock systems require more time to prepare hot water. When heat exchangers are used for heating, it is almost imperceptible, because for such tasks the water warms up quickly. But liquid for domestic needs, as already noted, is heated in the second place.
Conclusion
The choice in favor of a bithermic boiler should be made only after a clear analysis of the needs for water and heating. This option justifies itself in situations when it is planned to use approximately the same volumes of heating and hot water. Of course, in the summer, the bithermic heat exchanger will noticeably lose in energy efficiency to classic radiators, but over the long winter period this difference is leveled in favor of the first option. In addition, the advantages of the combined heating units include the compact design. Usually these are small boilers that do not take up much space and are easily interfaced with control thermostats.