DE29723429U1 - Heat distribution system filled with a heat transfer medium - Google Patents

Description

Patent attorneys

Eifert, Bressel and colleagues

European Patent Attorneys

. PAe Effert, Bressel and colleagues · Radickestrasse 48 · D-12489 Berlin .

Dipl.-Ing. Udo Eifert *

Dipl.-Ing. Dr.-Ing. Burkhard Bressel *

Dipl.-Ing. Volker Zucker *

•European Trademark Attorney

Radickestrasse 48 D-12489 Berlin

Telephone 030-670 00 60 Fax 030-670 00 670

18 June 1998

BR/cb

GM00.945.0DE

ECOSOLAR ENERGY TECHNOLOGY GMBH Fuhrtsberg 41 17139 Malchin

Heat distribution system filled with a heat transfer medium

Utility model branch from German patent application 197 31 185.7

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Heat distribution system filled with a heat transfer medium

Description:

The invention relates to a heat distribution system filled with a heat transfer medium.

Various heating systems are known for heating interior spaces in buildings. For example, there are gravity heating systems in which water is used as a heat transport medium. In this case, the water is heated in a heat generator, for example an oil or gas boiler.

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burner. The heated water enters a circuit with radiators, which are located inside the interior. The water releases the heat via the radiators, so that the interior is heated. The water, which is cooled as a result, is returned to the heat generator. This system works essentially at atmospheric pressure, apart from the hydrostatic pressure within the system.

The disadvantage of this system is the inadequate circulation of hot water. Often, poorly located heating pipes do not have enough warm water flowing through them, meaning that sufficient heating power cannot be guaranteed in these areas. Circulation pumps have therefore been used for a long time to support the circulation of the water.
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Such heating systems can be operated with radiators or with underfloor heating. In the latter case, pipes are laid in a meandering pattern in the floor in the interior rooms to be heated.

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The flow temperature for underfloor heating is significantly lower than the flow temperature when using radiators.

Common heat sources are operated by firing and electrical heating. Another option is to generate heat using a heat pump. This involves transporting heat from a colder heat reservoir to the warmer interior rooms. Mechanical work must be used for this. Such systems have also been known for a long time.

The known hot water heating systems have the disadvantage that the flow and return temperatures of the heat transport medium are significantly different, since the heating output is fed exclusively by the increased temperature of the heating medium; the water cools down in the radiators or the heating coils of an underfloor heating system. A significant part of the costs incurred in a hot water heating system are used up by the operation of the circulation pump, since a lot of energy is lost through the transport of the relatively viscous water in the pipe system. This energy is supplied in the form of electrical energy and leads to an additional heating of the heat transport medium. Due to the high electricity costs, this results in increased operating costs.

In contrast, water vapor heating systems have the advantage that the heat to be transferred to the interior is stored in the condensation energy of the water. In this heating system, water vapor is formed in a heat generator by evaporating water that is located in a reservoir. This water vapor is passed through radiators via a suitable pipe system. There, the vapor can partially condense and thus release the heat. The condensate is returned to the heat generator. This heating system can be operated with atmospheric pressure or with negative or positive pressure. This means that

The respective operating temperature can be set by selecting the appropriate boiling temperature of the water in the heater.

Such a steam heating system is described in DE-OS 2027 496. The heat transfer medium should preferably be used in a pressure range that is below atmospheric pressure. It is also mentioned that, for example, a coolant under a certain excess pressure can also be used as a heating medium. This system consists of a heat generator, a steam collector, radiators and a condensate collection vessel. The water vapor passes from the heat generator into the radiators, cools down and condenses there and then returns to the condensate collection vessel via individual pipe strands. A heat exchanger or a burner or an electric heater are proposed as heat generators.

This method also has disadvantages. In particular, it has been found that heating with radiators is less energy efficient than heating with heating coils, which are laid in the floor, for example, because the flow temperature of the heating medium must be significantly higher than the desired room temperature. Furthermore, investigations have also shown that the system described in the disclosure document must be generously designed in terms of pipe diameters in order to ensure that the steam or water is also continuously circulated. The system described in the disclosure document does not have a forced return of the condensate. Therefore, under certain circumstances, condensate in the heat generator can be pushed back into the upstream condensate collection vessel by the evaporation taking place there, so that heat generation is interrupted due to a lack of liquid heating medium in the heat generator and, in the worst case, the heat generator can even overheat. Such an unstable operating condition can occur in particular when the pipes forming the circuit have a small cross-section, in particular

in particular the pipes leading back from the radiators to the condensate collecting vessel, and if a low installation height for the entire system is also required, so that the height difference between the lowest radiator and the condensate collecting vessel can only be small, in this case the overpressure in the condensate collecting vessel caused by gravity is no longer high enough to force heating medium into the heat generator and thus ensure that there is always sufficient condensate available in the heat generator.

The present invention is therefore based on the problem of avoiding the disadvantages of the prior art and in particular of providing a heat distribution system filled with a heat transfer medium, with which either interior spaces in buildings can be heated or the energy required for a heat pump circuit can be transferred via a

5 condenser. Above all, this heat distribution system should be suitable as a heating system for operating an underfloor heating system, where the flow temperature can be low. Furthermore, there should be low requirements for the height of the system and it should be possible to provide pipes for the underfloor heating and the pipes leading away from it with a small cross-section, without the unstable conditions described above occurring when the system is in operation.

This problem is solved by a heat distribution system according to claim 1. Preferred embodiments of the invention are specified in the subclaims.

The heat distribution system according to the invention is used to heat interior spaces in buildings or to transfer thermal energy from a heat reservoir to a heat pump circuit.

The heating system differs from known heating systems in that the elements for heating the interior spaces are connected to the collecting tank on the flow side and return side.

The heat transfer system filled with a heat transfer medium has a heat exchanger for transferring heat from or to a heat or cold generator, a collecting tank for the heat transfer medium and a pipe system. In the case of a heating system, the pipe system can preferably be used as a floor pipe system. The heat exchanger is connected to a heat pump circuit for heat generation or heat removal.

The solution according to the invention results in a secondary circuit, which in turn comprises two sub-circuits in which the heat transfer medium is located:

The first circuit comprises the heat exchanger for transferring heat from a heat generator to the secondary circuit or from the secondary circuit to a cooling circuit as well as the collecting tank for the heat transfer medium.

The second circuit again includes the collecting tank and a pipe system, which is used, for example, to heat interior spaces or to transfer heat from a heat reservoir, for example the ground or groundwater, into the circuit.

The following description initially concerns the application according to the invention of a heating system in which heat is transferred via the heat exchanger into the secondary circuit. 30

In the case of a heat distribution system that is operated as a heating system, by introducing the vaporous heat transfer medium

from the heat exchanger first into the collecting vessel before it can enter heating elements that form a pipe system for heating in an application, safely preventing the steam generated in the heat exchanger from escaping not only into the pipe system to the heating elements as desired, but also to the collecting vessel.

The system according to the invention also ensures that the heat exchanger is always sufficiently filled with condensate flowing back from heating elements and thus the heating output of the system can be continuously ensured. Even if the cross-sections of the heating elements in the case of underfloor heating and the pipe system for returning the heat transfer medium from the heating elements to the collecting tank and also the height difference between the lowest heating elements and the collecting tank are relatively small, there is no risk of an unstable operating state with this configuration. By transferring the evaporated heat transfer medium first to the collecting tank and only then to the heating elements, it is ensured that the steam generated in the heat exchanger is only directed to the heating elements.

A further advantage is that the heating output in individual interior rooms in buildings is automatically regulated according to the respective heating requirements, since a lower temperature in an interior room inevitably leads to the condensation of the steam introduced into the pipe system and thus more energy is released there than in a room with a higher temperature.

The advantages stated above also apply accordingly to the other application according to the invention, in which heat is transferred from the heat reservoir via the secondary circuit into a heat pump circuit.

The heat exchanger is connected to a heat pump circuit to generate heat. Due to the chosen arrangement instead of a circuit in which the primary heat pump circuit is directly integrated into the heating circuit and there is no additional separation via a heat exchanger, no special measures need to be taken to prevent oil-containing coolants from escaping from the pipe system. Such measures would include, for example, the double-walled design of the pipes in the pipe system, which is extremely expensive. In addition, these double-walled pipes have the further disadvantage that they are difficult to install.

The heat exchanger is connected to the collecting tank, in the case of a heating system in such a way that vaporous heat transfer medium emerging from the heat exchanger can enter a vapor space in the collecting tank. The vapor formed does not first have to pass through the condensate also contained in the collecting tank, which would create a flow resistance for the vapor. The risk of the condensate flowing back into the collecting tank is thus further reduced.

In a preferred embodiment, the collecting tank is arranged above the heat exchanger. The static pressure of the liquid heat transfer medium, which corresponds to the height difference between the liquid level in the collecting tank and half the height of the heat exchanger, is intended to compensate for the pressure loss in the heat exchanger caused by the liquid flow there. If the flow rate through the heat exchanger is high and/or a heat transfer medium with a high viscosity in the liquid state is selected, the height difference during installation must be large.

In the opposite case, the same applies.

In the same way, the collecting tank should be arranged below the heating elements. The static pressure of the liquid heat transfer medium, corresponding to the height difference between the liquid level of the heat transfer medium in the heating elements and the liquid level in the collecting tank, should in this case just compensate for the pressure loss in the heating elements.

The steam formed in the heat exchanger and fed into the collecting tank is conveyed to the heating elements via another line that extends into the steam space in the collecting tank. The only thing that is used for conveying the steam is the static pressure of the condensate flowing out of the heating elements. The heat transfer medium condenses in the heating elements and flows from there back into the collecting tank. The flow and return temperatures of the medium are, in the best case, the same, but differ by only a few degrees at most. This means that almost exclusively the condensation heat of the heat transfer medium is used for heating. This has the advantage that no superheated steam is used, but only wet steam, so that the heat transfer to the heating elements is optimal. After passing through the collecting tank, the condensate is returned to the heat exchanger.

In a preferred embodiment of the invention, downpipes are provided between the pipe system and the collecting tank and are arranged in such a way that condensate can flow by gravity from the pipe system into the collecting tank in the case of heat being transferred from the heat generator to the pipe system (heating system) or from the collecting tank (2) into the pipe system (3) in the case of heat being transferred from the pipe system to the cold generator (geothermal heat exchanger). Shut-off solenoid valves can be provided in the downpipes for setting the room temperature. At least one

A suitable temperature measuring and control device is provided, the output signals of which are used to control the solenoid valves.

For a heating system, the heating elements serve as a pipe system for underfloor heating. They can be laid in the form of heating coils in a floor filling, in walls for wall heating and/or in ceilings of interior rooms for ceiling heating. Several (two or more) pipes of the pipe system are connected, for example, on the return side to a collecting line, with the collecting line being connected to the collecting tank via a downpipe.

Preferably, pipes with an external diameter of 4 to 10 mm are used for the heating elements. This minimizes the installation effort and optimizes the heat transfer. The easier installation effort results from the fact that the pipes can be easily attached to a wooden floor, for example, without additional screed, and the resulting unevenness can be leveled out with leveling compound. A carpet or parquet floor can be laid on top of this. Better heat transfer results from the fact that the inner surface of the pipe and thus the heat transfer are greater the smaller the diameter of the pipe, so that a large number of pipes with a small cross-section are cheaper than a few pipes with a larger cross-section. Copper pipes are preferably used for optimal heat transfer.

The heat transfer medium used is preferably a coolant that is commonly used in refrigeration machines. Such coolants have, for example, a boiling point of 15 to 35 ⁰ C at a pressure of 2 to 15 bar. This allows the operating range of a heating system to be selected within the desired interior temperature, so that heating above the boiling point is not necessary. This results in optimal heat transfer from the coolant to the heating elements and thus to the interior. The less effective heat transfer from superheated

The application of heated steam to the heating element walls to exploit the heating by reducing the temperature of the steam is avoided.

The system described can be installed outside a building, for example in a shaft.

The above statements on a heating system apply to a geothermal heat exchanger in the same way. In this case, heat is transported from the pipe system to the heat exchanger and then transferred to a heat pump circuit. The heat transfer medium evaporates in the pipe system and is passed on as steam via the collecting vessel to the heat exchanger. There, the heat transfer medium condenses again. The condensate is then transported back to the pipe system via the collecting vessel.

The invention will be described in more detail using the figures shown below. They show:

Fig. 1: Schematic representation of the heating system with

closed heat pump for heat generation;

Fig. 2: Schematic representation of the installation of heating elements in a wall filling indoors; Fig. 3: Schematic representation of a geothermal heat exchanger.

Fig. 1 shows a heating system with a heat exchanger 1, which is integrated on the one hand into the secondary circuit S required for heating and on the other hand into the circuit of a heat pump W.

The heat exchanger is connected on the secondary side to the collecting tank 2 via line 4. Line 4 preferably leads from above into the steam chamber in the collecting tank 2. Another line 6 branches off from the steam chamber of the collecting tank 2, which leads to the heating elements 3

leads, here the pipes of an underfloor heating system. The coolant condenses in these pipes. The heating elements 3 are connected on the return side via the line 5 to the sump of the collecting tank 2. During operation, the condensate is in this sump. This can be returned to the heat exchanger 1 via another line 7 extending into the sump of the collecting tank 2 and evaporated there again.

The collecting tank 2 and the heat exchanger 1 are arranged in a shaft 11 sunk into the ground.

On the primary side, the heat exchanger is connected to a heat pump circuit W. The coolant emerging from the heat exchanger 1 and condensed in the primary circuit first enters an expansion valve 10, where it is cooled to a low temperature. The coolant is then fed into the evaporator 9, for example into a heat exchanger operated by the ambient air, in which the coolant is evaporated. The coolant is then fed via the compressor 8. There it is compressed and then returns to the heat exchanger 1.

The commercially available refrigerant R134A is used as the heat transfer medium in the secondary circuit S. Preferably, flammable propane is not used. Therefore, leaks in an indoor pipe system cannot cause any safety risks.

Fig. 2 shows the installation plan for underfloor heating in four interior rooms R. The vapor of the coolant flows from the collecting tank via line 6 into the individual interior rooms R in a building. Line 6 has an external diameter of 28 mm. Line 6 continues into further lines 13, which have an external diameter of 15 mm. Lines 13 continue into the heating coils 3, which are laid in a meandering shape in the floor filling (not shown here). The heating

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coils 3 have an external diameter of 6 mm. The coolant condenses in the heating coils 3 and thus releases heat into the interior R. The heating coils 3 are connected to collecting lines 12. These also have an external diameter of 6 mm. The collecting lines 12 lead into the downpipes 5 (external diameter 6 mm). From there, the condensate is returned to the collecting tank. All lines are made of copper pipes.

A downpipe 5 is provided for each interior space R. Solenoid valves can also be integrated into the downpipes 5, with which the flow of the condensate can be regulated. The solenoid valves are controlled by suitable temperature measuring and control devices, which can be provided in each interior space R.

Fig. 3 shows a heat distribution system for transferring heat from the ground to a heat pump circuit. The heat stored in the ground 11 is transferred via a pipe system 3 to the coolant contained in the pipe system 3, for example propane. The coolant evaporates in the process. The steam is led via line 5 into the steam space of a collecting tank 2. From there the steam reaches the heat exchanger 1 via line 7. In the heat exchanger 1 the steam gives off the condensation energy to the coolant in the heat pump circuit and condenses in the process. The resulting condensate is returned to the collecting tank 2 via a line 4. From there the condensate returns via line 6 into the pipe system 3 laid in the ground.

The heat pump circuit is usually formed from a heat exchanger 9, the compressor pump 8 and an expansion valve 10.

Claims (9)

aa ·· · · a·· a a · Protection claims: 1. Heat distribution system filled with a heat transfer medium with a heat exchanger for transferring heat from or to a heat or cold generator, a collecting tank for the heat transfer medium and a pipe system for releasing or absorbing heat, the heat exchanger being connected to a heat pump circuit, characterized in that the pipe system (3) is connected to the collecting tank (2) on the flow side and return side. 10 2. Heat distribution system according to claim 1, characterized in that the heat exchanger (1) is connected to the collecting tank (2) in such a way that vaporous heat transfer medium emerging from the heat exchanger (1) can enter a vapor space located in the collecting tank (2). 3. Heat distribution system according to one of the preceding claims, characterized in that downpipes (5) are provided between the pipe system (3) and the collecting tank (2) and are arranged in such a way that condensed heat transfer medium flows by means of gravity in the case of heat transfer from the heat generator to the pipe system (3) from the pipe system (3) into the collecting tank (2) or in the case of heat transfer from the pipe system to the refrigeration generator from the collecting tank (2) into the pipe system (3). 4. Heat distribution system according to one of the preceding claims, characterized in that shut-off solenoid valves are provided on the downpipes (5) for temperature adjustment. 5. Heat distribution system according to claim 4, characterized in that at least one suitable temperature measuring and control device is provided, the output signals of which serve to control the solenoid valves for temperature adjustment. 6. Heat distribution system according to one of the preceding claims, characterized in that the pipe system (3) serves as underfloor heating 5 and is laid in the form of heating coils in a floor filling, in walls and/or in ceilings of interior rooms R. 7. Heat distribution system according to claim 6, characterized in that several pipes of the pipe system (3) are connected on the return side to a collecting line (12) and the collecting line (12) is connected to the collecting container (3) via a downpipe (5). 8. Heat distribution system according to one of the preceding claims, characterized in that pipes with an external diameter of 4 to 10 mm are provided for the pipe system (3). 9. Heat distribution system according to one of the preceding claims, characterized by a refrigerant as heat transfer medium with a boiling point of 15 to 35 ^° C at a pressure of 2 to 15 bar.