Heat exchanger for a heating network

Abstract

A heat exchanger (20) for a heating network, in particular a cold district heating network or long-distance heating network, with at least one heat transfer surface for transferring heat from a network fluid of the heating network to a building heating fluid of a building heating system of a building (7), in particular a residential building, wherein at least one flow connection (5) for the building heating fluid and at least one return connection (5) for the building heating fluid are provided, is proposed, which is improved compared to the state of the art, in particular reducing the effort and / or increasing the energy efficiency and the economic efficiency and / or realizing new functionalities.This is achieved according to the invention by the heat exchanger (20) being designed as a ground heat exchanger (20), wherein the ground heat exchanger (20) has at least one ground contact surface for the ground and wherein the ground heat exchanger (20) has at least one heat network inlet (21) for receiving a heat network line (1), in particular a heat network pipe (1), of the heat network, wherein the heat network inlet (21) comprises at least the heat transfer surface.

Description

[0001] The invention relates to a heating network and a heat exchanger for a heating network, in particular a cold district heating network or a long-distance heating network, with at least one heat transfer surface for transferring heat from a network fluid of the heating network to a building heating fluid of a building heating system of a building, in particular a residential building, according to claims 1 or 11. State of the art

[0002] District heating networks are generally implemented as either local or regional heating networks. These networks supply heat to buildings for space heating and hot water. In district heating networks, the thermal energy is transported through a thermally insulated pipe system, the so-called heating network, which is usually buried underground; however, overhead lines are sometimes used. District heating primarily supplies residential buildings with space heating and hot water by transporting the heat from the generator or collection point to the consumers.

[0003] Local heating networks typically involve the local development of individual buildings, parts of buildings, or small residential areas with their own heat generation.

[0004] "Cold district heating" or "cold long-distance heating" are technical variations of a heating network that operate at low transmission temperatures close to ambient temperature and can therefore provide both heating and cooling. Transmission temperatures typically range from approximately 10-25 °C, meaning these systems operate at temperatures significantly lower than conventional district or long-distance heating systems. This allows different consumers to heat and cool simultaneously, independently of each other. Unlike conventional heating networks, hot water production and building heating are not achieved directly via heat exchangers, but rather via water-source heat pumps that extract their thermal energy from the heating network. Cooling can be provided either directly via the cold district heating network or, if necessary, indirectly via the heat pumps.

[0005] Cold district heating networks are also known as fifth-generation district heating networks. Due to their potential to be powered entirely by renewable energy and to contribute to balancing the fluctuating output of wind and solar power plants, cold district heating networks are considered a particularly promising option for a sustainable, potentially greenhouse gas- and emission-free heat supply, and thus a core technology for the energy transition in the heating sector.

[0006] Such district heating networks currently have one heat exchanger or so-called "transfer station" for each consumer, i.e., for each building (see, e.g., DE 10 2023 107 058 A1). These heat exchangers are located inside the building, thus transferring heat between the heat fluid of the district heating network and the building's heating system / circuit or the heat pump fluid. Purpose and advantages of the invention

[0007] In contrast, the object of the invention is to further improve corresponding heat exchangers and heating networks, in particular to reduce the effort and / or to increase energy efficiency and cost-effectiveness and / or to realize new functionalities.

[0008] This problem is solved, starting from a heat exchanger or heat network of the type mentioned in the introduction, by the features of claim 1 or 11. Advantageous embodiments and further developments of the invention are possible by the measures mentioned in the dependent claims.

[0009] Accordingly, a heat exchanger according to the invention for a heating network, in particular a cold district heating network or long-distance heating network, comprises at least one heat transfer surface for transferring heat from a network fluid of the heating network to a building heating fluid of a building heating system, in particular of a residential building, wherein at least one flow connection for the building heating fluid and at least one return connection for the building heating fluid are provided, wherein the heat exchanger is designed as a ground heat exchanger, wherein the ground heat exchanger has at least one ground contact surface for the ground and wherein the ground heat exchanger has at least one heating network inlet for receiving a heating network line, in particular a heating network pipe, of the heating network, wherein the heating network inlet comprises at least the heat transfer surface.

[0010] This measure enables entirely new functionalities and advantages for district heating networks, especially low-temperature district heating networks. For example, by designing the heat exchanger as a ground-source heat exchanger, i.e., located underground or below the ground surface, it becomes possible to flexibly connect or couple the building heating system and / or building cooling / air conditioning system to the district heating network or the corresponding district heating pipeline without significant structural and / or economic effort.

[0011] The fluidic or hydraulic separation of the district heating circuit or network fluid from the building heating fluid, e.g., heat pump fluid and / or building heating water, or the like, is advantageously achieved within the heat exchanger / ground source heat exchanger not inside the building, as is the case with the prior art, but outside the building and / or below ground level or in the ground. This eliminates the need for complex, expensive, and failure-prone branch connections in the district heating network. This increases operational reliability and simplifies the installation and operation of the district heating network, and also results in significant cost savings.

[0012] Furthermore, different operating parameters can be implemented in the respective, i.e., fluidically separated, fluid systems. For example, different pressures can be achieved in the heating network and in the building system; in particular, a comparatively low pressure for the building heating fluid can be implemented. This increases the safety and the flexibility or adaptability of the entire system.

[0013] Furthermore, a so-called "transfer station" within the building is unnecessary, meaning that corresponding construction / living space is not required or built upon. This improves the building's economic efficiency.

[0014] The heat transfer surface is advantageously arranged between the connection lines of the heat exchanger / ground source heat exchanger or between the heat exchanger supply and return lines. This means, among other things, that the heat transfer surface connects the two connection lines of the heat exchanger / ground source heat exchanger or between the heat exchanger supply and return lines.

[0015] For example, it is sufficient that only two supply or connection lines of the heat exchanger / ground source heat exchanger, e.g., the heat exchanger flow and return lines, need to be routed through the building envelope or building wall. This results in minimal effort and low thermal losses through the building envelope.

[0016] The ground surrounding the heat exchanger / ground source heat exchanger acts as thermal insulation for heat transfer and / or as an energy storage medium for the district heating network. This allows for a particularly energy-efficient operating mode with relatively low energy losses and / or an energy storage function. This also improves the economic viability and functionality of the system.

[0017] For example, the heat network inlet is designed as a cylindrical recess in the ground source heat exchanger, such that the heat transfer surface is formed as a cylindrical shell and / or such that the heat transfer surface is arranged around the cylindrical recess. This allows a tubular heat network pipe to be easily routed through the heat exchanger / ground source heat exchanger. For example, the ground source heat exchanger is designed as a pipe-to-ground source heat exchanger. In a further embodiment of the invention, the heat network inlet is designed as an inner cavity of the ground source heat exchanger and / or the pipe-to-ground source heat exchanger. This allows the heat network or heat network pipe to be arranged within the inner cavity. Furthermore, heat transfer can be fully realized around the heat network pipe. These measures each enable a structurally advantageous heat network or heat network pipe.

[0018] It is optionally proposed to arrange the district heating network inlet concentrically with respect to the ground source heat exchanger and / or the pipe-to-ground source heat exchanger and / or the heat transfer surface and / or the cylindrical shell. This enables particularly advantageous, comprehensive heat transfer between the district heating network or district heating network pipe and the heat exchanger / ground source heat exchanger or building heating system / building heating fluid.

[0019] In a particular embodiment of the invention, a longitudinal axis of the heat network inlet is simultaneously a longitudinal axis of the ground source heat exchanger and / or the pipe-to-ground source heat exchanger and / or the heat transfer surface and / or the cylindrical shell. This has proven to enable particularly efficient operation. For example, the size / area of ​​the heat transfer or heat transfer surface can also be easily adapted to the specific conditions or parameters by adjusting the length of the heat exchanger or ground source heat exchanger.

[0020] In an optional embodiment of the invention, at least one building heating fluid pipe of the building's heating system comprises at least one helical section, wherein the helical section is arranged between the flow connection and the return connection. For example, the helical section is arranged concentrically with respect to the ground source heat exchanger and / or the pipe-to-ground source heat exchanger and / or the heat transfer surface and / or the cylindrical shell, and / or the longitudinal axis of the heating network connection is simultaneously a longitudinal axis of the helical section. This enables a particularly space-saving design. Heat transfer can thus be fully realized around the heating network pipe. This ensures high system efficiency.

[0021] For example, at least one heat-conducting layer is provided for heat conduction between the network fluid / heating network pipe and the building heating fluid / coil section / building heating system. This facilitates heat transfer. For example, the heat-conducting layer is designed as a liquid floor and / or arranged between the heating network inlet or pipe and the heat transfer surface.

[0022] In a particular embodiment of the invention, the heat-conducting layer is designed as a heat storage medium for storing heat for the building heating fluid and / or for the coil section and / or for the building heating system. This allows for advantageous heat transfer while simultaneously realizing an additional functionality, namely a heat storage function. For example, a buffer function can be implemented by the heat storage medium, thus advantageously enabling peak load damping or similar applications. The heat storage medium can also exhibit a phase change, e.g., from liquid to solid. In this case, a large portion of the thermal energy supplied to it can be stored in the form of conversion enthalpy or so-called "latent heat."This latent heat storage system can therefore store very large amounts of heat, especially within a small temperature range around the phase change, exceeding the capacity of heat storage systems that utilize only the thermal energy of a single substance. Consequently, the system's space utilization and energy density are advantageously improved.

[0023] In an exemplary embodiment of the invention, each building or building heating system has an associated heat exchanger according to one of the preceding claims. This allows for individual adjustments to be implemented without significant effort.

[0024] Currently, state-of-the-art heating networks are implemented with two pipes, one for the supply and the other for the return. In this way, network fluid is diverted from the supply line to the building's heat exchanger to extract heat. The cooled network fluid is then returned to the return line. According to a particular embodiment of the invention, the heating network is designed as a closed ring main with a single annular pipe for the network fluid. This significantly reduces the design and cost costs. Furthermore, operational reliability is considerably improved by minimizing or eliminating branches, thus substantially reducing the risk of leakage.

[0025] For example, at least one heat source is hydraulically arranged / connected in parallel to the heating network; in particular, several heat sources are provided that are hydraulically arranged / connected in parallel to the heating network. This allows for the flexible integration of a wide variety of heat sources and / or multiple heat sources into the heating network. Accordingly, adjustments can be made as needed to suit the required and / or locally available energy sources.

[0026] In general, the invention can be used primarily for cold local heating networks as well as adapted for district heating networks.

[0027] For example, cold district heating networks according to exemplary variants of the invention can have the following features or advantages individually or in combination with one another: - Open trench in which a suitable main pipe, possibly with a significantly larger dimension, e.g. approx. 300 mm diameter instead of the previously usual 160 mm, is laid for the transport of the network / source fluid. Before the main pipe of the heating network is installed, a spiral heat exchanger (HX), or so-called collector, with the heat transfer surface according to the invention, is guided / arranged around the main pipe of the heating network. Advantageously, the heat exchanger can be in direct contact with the main pipe. However, it can also be arranged at a certain distance around the main pipe. Especially in the case of a variant with a distance, a thermally conductive material must be provided for the thermal connection between the main pipe and the heat exchanger or the heat exchanger surface. The connections of the heat exchanger lead as directly as possible to the consumer, e.g., the user's heat pump, and are thus hydraulically connected to it. The trench should ideally be backfilled with a highly thermally conductive material, such as flowable fill or similar. Additional requirements for the backfill may include high stability to prevent settlement and resistance to temperatures down to approximately -5 °C around the heat exchanger tube. - The backfill material can serve as a "compensating battery" or heat storage unit, or be designed to act as a buffer, for example, when heat is drawn off. This allows, for example, the main pipe and the heat source to be operated without antifreeze. - The aforementioned effects are enhanced, for example, by the fact that the heat exchanger around the main pipe extracts more heat from the surrounding soil than conventional cold district heating networks.

[0028] Furthermore, the following features or advantages can be implemented individually or in combination for district heating pipes or district heating networks according to exemplary variants of the invention: - The hydraulic concept is analogous to the previously mentioned cold district heating networks. - The main pipe or a main pipe / heating network section already has the heat exchanger integrated and is, if necessary, completely prefabricated industrially and, if necessary, connected on site to other sections of the heating network. As with conventional district heating pipes, the main pipe has a protective outer sheath and / or thermal insulation. For example, according to a particular embodiment of the invention, the heat exchanger is arranged between the main pipe and the insulation, and is embedded, for example, in a form-fitting manner in a medium to ensure optimal heat transfer.

[0029] Further advantages over conventional systems: - The main network can be operated without frost protection, e.g. with geothermal probes or other geothermal or waste heat sources. - The consumer unit can be operated with antifreeze and should therefore be operated according to the heat pump manufacturer's instructions. If there is a leak in this circuit, it only affects the individual circuit and not the main line or the district heating network. - The network can be installed as a single-circuit system rather than a dual-circuit system. A direct network connection, i.e., a branch line, to each consumer is not required during installation. The risk of a complex system failure due to a leak in a consumer line is eliminated. Any number of sources, e.g., geothermal and / or waste heat sources, etc., can be advantageously connected to the main network or network line via tangential inlets / outlets. The associated pumps ensure a continuous and controllable flow. - The network operates with significantly lower pressure loss due to the larger diameter of the main pipe, which is inherent to its design. The total pumping power required is reduced to a fraction, resulting in a substantial and lasting reduction in operating costs. - Due to the storage effects described above and increased heat gains from the surrounding soil, the main network and the central heat source(s) can be dimensioned smaller and more economically.

[0030] Exemplary features and advantages of the aforementioned main components: - Main pipe: Advantageously, this is a ring main extending to as many consumers as possible, which is either systemically separated as a heat exchanger or systemically connected as an outlet. This ring main can be single-circuit, i.e., there is no supply / return system or two pipes as in the prior art. The heat exchanger (HX) is the heat exchanger in the main circuit or heating network, comprising the heat exchange surface. It is hydraulically connected directly to the consumer, typically a heat pump on-site or to the district heating system. No additional heat exchanger or circulation pump is required. It is advantageously helical or spiral (wound) and can be lengthened or adjusted during installation to suit local requirements and positioned / fixed around the main pipe. The heat exchanger typically has an integrated connection line. - Backfilling: The quality of the backfilling is specifically designed for the function of the system. - Trench: The dimensioning of the trench for embedding the systems becomes significantly more compact compared to conventional supply and return systems, precisely because of the possible reduction to only one circuit and the integrated heat extraction by the heat exchanger. Character description

[0031] An embodiment of the invention is shown in the drawing and is explained in more detail below with reference to the figures.

[0032] In detail: Fig. 1 a schematic view of a section of a district heating network with a first heat exchanger according to the invention, Fig. 2 a schematic cross-section through the first heat exchanger according to Fig. 1, Fig. 3 a schematic view of a section of a cold district heating network with a second heat exchanger according to the invention, Fig. 4 a schematic cross-section through the second heat exchanger according to Fig. 3 and Fig. 5 a schematic view of a section of a cold district heating network with a heat source.

[0033] In Fig. Figure 1 schematically depicts a section of a district heating network with a single main pipe 1 and a collector 2 or heat exchanger 20 according to the invention. The collector 2 or heat exchanger (HX) 20 is arranged in a trench 4 in the ground and has two connecting lines 5 for the HX supply and return, as well as an interior space 21 or receptacle 21 for the main pipe 1. The lines 5 are routed into a building 7 via building entry points 6, and these lines are encased in a heat transfer medium 13. The heating system in this building 7 is then supplied by means of the heat energy transferred from the HX 2.

[0034] Fig. Figure 2 illustrates the cross-sectional structure of the main pipe 1 and its cladding or integration within the trench 4. In this exemplary embodiment, the entire structure is advantageously concentric. The heat transfer medium 13 is completely surrounded by the main pipe 1 and contains the collector 2. Thermal insulation 14 is arranged around the heat transfer medium 13, and finally, the trench 4 is located on the outside.

[0035] Collector 2 or heat exchanger (HX) 20 exhibits, as in Fig. Figure 1 indicates a helical section that runs around the main pipe 1. This achieves advantageous heat transfer between the collector 2 or heat exchanger (HX) 20 and the main pipe 1 of the heating network.

[0036] The collector 2 or heat exchanger (HX) 20 according to the embodiment of the Fig. Figure 3 has a corresponding helical section. However, here the heating network is designed as a cold district heating network, so that the collector 2 or heat exchanger (HX) 20 or the heating network is somewhat different from the example according to the Fig. 1 and Fig. 2 is trained. This shows Fig. 4 schematically, that in this advantageous variant a liquid soil 3 or heat-conducting material 3 is present, which includes the collector 2 or heat exchanger (HR) 20 or completely / on both sides encases it.

[0037] In Fig.Figure 5 schematically illustrates an example of connecting a heat source 12 to the main pipe 1. Advantageously, a tangential outlet 8 and a tangential inlet 9 are provided, connecting the main pipe 1 to the source 12. By way of example, a parallel hydraulic connection of the source 12 to / with the main pipe 1 is provided. This connection also advantageously includes a pump 10 and an optional distributor 11.

[0038] In principle, collector 2 or heat exchanger (HX) 20 can transfer thermal energy from the main pipe 1 to building 7 or its heating system, as well as thermal energy from building 7 or a heating / cooling system, a building air conditioning system, or the like, to the main pipe 1. The latter is particularly advantageous in cold district heating networks.

[0039] Furthermore, the following features, functions and advantages can generally be realized individually or in combination with each other through a special further development of the invention: - Frost-free operation of the geothermal heat source 12, - Collector 2 or heat exchanger (HX) 20: Inlet from heat pump e.g. less than or equal to approx. -3°C, outlet from heat pump e.g. less than or equal to approx. 0°C, - Cold heating network or development line: Source / Geothermal: > 0°C, i.e., frost-free operation of heat source 12 is feasible, - this allows for higher peak performance (peak heat extraction) than above 0°C, - A sufficiently large distance between the heat pump source circuit and the heating network / development line, together with the surrounding subsurface or soil, acts as a buffer storage, so that peak load damping is achievable. - optional or additional use of latent heat, whereby an additional function and advantage is that moisture in the ground serves as a latent heat storage medium (ice formation / thawing), which leads to a greater storage effect and peak load damping. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2023 107 058 A1

[0006]

Claims

[1] Heat exchanger (20) for a heating network, in particular a cold district heating network or a long-distance heating network, with at least one heat transfer surface for transferring heat from a network fluid of the heating network to a building heating fluid of a building heating system of a building (7), in particular a residential building, wherein at least one supply connection (5) for the building heating fluid and at least one return connection (5) for the building heating fluid are provided, characterized by , that the heat exchanger (20) is designed as a ground heat exchanger (20), wherein the ground heat exchanger (20) has at least one ground contact surface for the ground and wherein the ground heat exchanger (20) has at least one heat network inlet (21) for receiving a heat network line (1), in particular a heat network pipe (1), of the heat network, wherein the heat network inlet (21) includes at least the heat transfer surface. [2] Heat exchanger according to claim 1, characterized by, that the heat network intake (21) is designed as a cylindrical recess (21) of the ground heat exchanger (20), such that the heat transfer surface is designed as a cylindrical shell and / or such that the heat transfer surface is arranged around the cylindrical recess (21). [3] Heat exchanger according to any of the preceding claims, characterized by , that the ground heat exchanger (20) is designed as a pipe ground heat exchanger (20). [4] Heat exchanger according to any of the preceding claims, characterized by , that the heat network intake (21) is designed as an inner cavity (21) of the ground heat exchanger (20) and / or the pipe ground heat exchanger (20). [5] Heat exchanger according to any of the preceding claims, characterized by , that the heat network intake (21) is arranged concentrically with respect to the ground heat exchanger (20) and / or the pipe ground heat exchanger (20) and / or the heat transfer surface and / or the cylinder jacket. [6] Heat exchanger according to any of the preceding claims, characterized by , that a longitudinal axis of the heat network recording (21) is simultaneously a heat exchanger longitudinal axis of the ground heat exchanger ()20 and / or the pipe ground heat exchanger (20) and / or the heat transfer surface and / or the cylinder jacket. [7] Heat exchanger according to any of the preceding claims, characterized by , that at least one building heating fluid pipeline of the building heating system of the building (7) comprises at least one helix section, wherein the helix section is arranged between the flow connection (5) and the return connection (5). [8] Heat exchanger according to any of the aforementioned claims, characterized by , that the helical section is arranged concentrically with respect to the ground heat exchanger (20) and / or the pipe ground heat exchanger (20) and / or the heat transfer surface and / or the cylinder jacket and / or that the longitudinal axis of the heat network intake (21) is also a helical longitudinal axis. [9] Heat exchanger according to any of the preceding claims, characterized by , that at least one heat-conducting layer (3) is provided for heat conduction between the network fluid / heating network pipe and the building heating fluid / coil section / building heating system. [10] Heat exchanger according to any of the preceding claims, characterized by that the heat-conducting layer is designed as a heat storage medium for storing heat for the building heating fluid and / or for the coil section and / or for the building heating system. [11] A heat network, in particular a cold district heating network or a long-distance heating network, with a heat exchanger, wherein the heat exchanger (20) comprises at least one heat transfer surface for transferring heat from a network fluid of the heat network to a building heating fluid of a building heating system of a building (7), in particular a residential building, wherein at least one supply connection (5) for the building heating fluid and at least one return connection (5) for the building heating fluid are provided, characterized by , that the heat exchanger (20) is designed as a ground heat exchanger ()20, wherein the ground heat exchanger (20) has at least one ground contact surface for the ground and wherein the ground heat exchanger (20) has at least one heat network inlet (21) for receiving a heat network line (1), in particular a heat network pipe (1), of the heat network, wherein the heat network inlet (21) includes at least the heat transfer surface. [12] Heat network according to the aforementioned claim, characterized by, that the heat exchanger (20) is designed according to one of the aforementioned claims 1 to 10. [13] Heat network according to one of the aforementioned claims, characterized by , that each building (7) or each building heating system has an associated heat exchanger (20) according to one of the aforementioned claims 1 to 10. [14] Heat network according to one of the aforementioned claims, characterized by , that the heating network is designed as a closed ring main (1) with a single ring pipe (1) for the network fluid. [15] Heat network according to one of the aforementioned claims, characterized by , that at least one heat source (12) is arranged / connected hydraulically parallel to the heat network. [16] Heat network according to one of the aforementioned claims, characterized by , that several heat sources (12) arranged / connected hydraulically in parallel to the heat network are provided.

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