DISTRICT HEATING TRANSFER STATION AND METHOD FOR OPERATING THE SAME

Abstract

District heating transfer station (1) comprising: a tank (3), at least two heat exchangers (5), a district heating inlet connection (7) and a district heating outlet connection (9), assigned to each heat exchanger (5) is a heat exchanger inlet connection (11) and a heat exchanger outlet connection (13), a flow distributor arrangement (29), and a loading control (47), wherein the district heating inlet connection (7) and the district heating outlet connection (9) each open into an internal volume (15) of the tank and form a fluid connection with a district heating inlet nozzle (17) and / or district heating outlet nozzle (19) accessible on the outside of the tank such that a heat-storing district heating fluid originating from a district heating source (21) can be fed into the internal volume (15) of the tank (3) via the district heating inlet connection (7) and, after flowing through the internal volume (15) of the tank (3), can be discharged from the internal volume (15) of the tank (3) via the district heating outlet connection (9), wherein the heat exchanger inlet connection (11) and the heat exchanger outlet connection (13) are each connected to an internal volume (23) of the associated heat exchanger (5) and form a fluid connection with a domestic heat inlet connection (25) and / or domestic heat outlet connection (27) accessible on the outside of the tank (3), via which a heat-storing domestic heat fluid can be fed into the internal volume (23) of the heat exchanger (5) and / or discharged from the internal volume (23) of the heat exchanger (5), wherein a first of the heat exchangers (39) is configured to supply domestic heat fluid heated therein to a heating circuit (41) of a building and wherein a second of the heat exchangers (43) is configured to supply domestic heat fluid heated therein to a hot water supply (45) of a building, wherein both heat exchangers (5) are accommodated in the internal volume (15) of the tank (3), wherein both heat exchangers (5) have an internal volume (23) which is smaller than the internal volume (15) of the tank (3) through which the district heating fluid is to flow, wherein the flow distributor arrangement (29) is arranged in the internal volume (15) of the tank (3) between an opening (31) of the district heating inflow connection (7) and an opening (33) of the district heating outflow connection (9) and is configured to distribute a flow of district heating fluid emerging from the opening (31) of the district heating inflow connection (7) over a larger cross-section and to slow it down in the process, wherein the loading control (47) is configured to control a cyclically repeated loading of the tank (3) with heat-storing district heating fluid, wherein the loading control (47) is configured to - to control an exchange of district heating fluid in the tank (3) during a first sub-cycle by allowing an inflow of heat-storing district heating fluid originating from a district heating source (21) through the district heating inflow connection (7) and allowing an outflow of district heating fluid stored in the tank (3) through the district heating outflow connection (9), and - to block an exchange of district heating fluid in the tank (3) during a second sub-cycle.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a district heating transfer station and a method for operating the same. TECHNICAL BACKGROUND

[0002] There are various approaches to meeting heat demand in a building, for example. A frequently practiced approach is to burn fuels locally in a heating system within the building to generate heat.

[0003] In an alternative approach, heat is generated at an external location away from the building and then delivered to the building as district heating using a heat-storing district heating fluid in a heat cycle. The district heating fluid can be heated at the external location, for example by generating heat through the combustion of fuels or by providing it as waste heat from industrial processes or from a combined heat and power plant and transferring it to the district heating fluid. The district heating fluid can, for example, be a liquid and can have the highest possible heat capacity in order to be able to store a lot of heat. The district heating fluid can then be pumped from the external location, for example through insulated pipes of a district heating circuit, to the building to be heated.

[0004] Within the building, a local building heat supply is generally provided that is separate from the district heating circuit. The building heat supply can have a building heat circuit, which can, for example, comprise pipes and / or radiators in the building. A heating fluid can be conveyed through this, which can be used to heat surfaces within the building, such as floors, walls, or radiator surfaces. In addition, the building heat supply can also include a hot water supply in the building, with domestic water being heated as the heating fluid in this case. The district heating circuit and the building heat supply, including its building heat circuit, are typically completely separate from one another with regard to the heating fluids flowing within them.

[0005] To establish heat exchange between the district heating circuit and the building's heat supply, a district heating transfer station is provided. In this station, heat from the district heating circuit can be transferred to the building's heat supply via one or more suitable heat exchangers.

[0006] A heat storage unit can often be provided as a buffer storage for the building's heat supply, in which heat fed in from the district heating circuit can be temporarily stored until it is needed in the building. In conventional heating systems, the district heating transfer station usually comprises a tank in which a large volume of the domestic heat fluid of the building's heat supply is held. Heat from the district heating circuit can be transferred to the domestic heat fluid by district heating fluid flowing through a heat exchanger housed in the tank. With the help of such a heat storage unit, the building's heat supply can provide high heat outputs in the building when needed, without the district heating circuit itself having to be able to provide such high heat outputs at all times.Instead, the district heating circuit generally only needs to provide the average heat output required in the building.

[0007] However, it has been observed that district heating transfer stations designed according to the conventional concept described above may have disadvantages with regard to the efficiency of heat supply or heat transfer.

[0008] GB 1 425 508 A discloses a heating system for single-family houses.

[0009] FR 2 342 469 A1 discloses a heating substation for metering heat energy and for automatically controlling indoor temperatures in rooms.

[0010] DE 32 44 005 A1 discloses an energy transfer system.

[0011] DE 30 41 982 A1 discloses a domestic hot water storage tank for district heating systems.

[0012] EP 2 163 745 A1 discloses a heat accumulator and a manufacturing method therefor.

[0013] DE 10 2012 101 276 A1 discloses a heat exchanger for a heating system or a heat supply system. SUMMARY OF THE INVENTION AND EMBODIMENTS

[0014] There may therefore be a need for a district heating transfer station that enables highly efficient heat supply and heat transfer. In particular, there may be a need for a district heating transfer station that, on the one hand, is simple and robust in design and can therefore be provided cost-effectively, and, on the other hand, enables efficient use of the provided district heat for heat supply within a building. Furthermore, there may be a need for a method for operating such a district heating transfer station, by means of which the provided district heat can be efficiently used for heat supply in a building.

[0015] The aforementioned needs can be at least partially met by the subject matter of one of the independent claims of the present application. Advantageous embodiments are specified in the dependent claims and the following description.

[0016] According to a first aspect of the present invention, a district heating transfer station is provided as defined in claim 1.

[0017] According to a second aspect of the present invention, a method for operating a district heating transfer station according to an embodiment of the first aspect of the invention is described, as defined in claim 9.

[0018] Embodiments of the invention may be considered, among others and without limiting the invention, to be based on ideas or findings described below: By way of introduction, a basic idea for embodiments of the invention described herein as well as possible advantages will be briefly explained, whereby this explanation is to be interpreted as merely a rough summary and not as limiting the invention: In conventional district heating transfer stations with heat storage, district heating fluid flows through a relatively small heat exchanger to transfer heat to a service heat fluid, which is temporarily stored in a tank that is larger than the heat exchanger.

[0019] This basic concept, which has been pursued for many years, is reversed in the district heating transfer station described here. Instead of the domestic heat fluid, the district heating fluid in the district heating transfer station serves as a heat storage unit and is temporarily stored in a large-volume tank. The tank contains a heat exchanger that is small in comparison to the tank volume, through which the domestic heat fluid is passed to absorb heat from the heat storage unit and make it available to the building's heat supply.

[0020] By reversing the conventional basic concept, various advantages can be achieved. Among other things, the tank can be cyclically loaded with district heating fluid, whereby the district heating fluid can remain in the tank for extended periods between two loading processes in order to successively transfer heat to the domestic heat fluid. During these periods, the district heating fluid does not flow through the tank and is preferably not actively mixed. Instead, the district heating fluid remains stationary in the tank, allowing heat stratification to occur. Due in part to this heat stratification, heat can be transferred to the domestic heat fluid particularly efficiently. Heat transfer can be carried out until the return temperature, at which the district heating fluid can leave the tank again, has dropped significantly.Because the return temperature in the district heating circuit can be low, the overall heat transfer achieved with the district heating transfer station can be very efficient. The flow temperature in the district heating circuit can also be lower than is the case with conventional district heating transfer stations. In addition, a difference in temperature between the fluid transporting the district heat and the fluid serving as a heat storage device can generally be eliminated, since both functions are carried out by the district heating fluid. This can also improve the efficiency of the district heating transfer station. In the event that several heat consumers, ieFor example, if both a building heating circuit and a hot water supply are to be supplied, the district heating transfer station described here can operate all heat consumers simultaneously at full capacity. Furthermore, if necessary, the district heating transfer station's tank, which serves as a heat storage unit, can be quickly filled with fresh, hot district heating fluid, so that high heating output can be provided quickly.

[0021] In the following, possible features of embodiments of the invention and the advantages to be achieved thereby are described in detail.

[0022] Embodiments of the district heating transfer station described herein can be used to supply heat to various building types, such as single-family homes, multi-family homes, industrial buildings, or similar. The district heating transfer station can be connected to a district heating network and draw heat from it, and can also be connected to a heat supply network within the building, to which a portion of the drawn heat is to be transferred. Depending on the intended use, the district heating transfer station can be configured for suitably adapted heat transfer capacities. Heat transfer capacities can range from 1 kW to 500 kW.

[0023] The tank of the district heating transfer station can be a container in which a significant storage volume of heat-storing district heating fluid can be accommodated. The internal volume of the tank can, for example, range from 100 liters to 5,000 liters. After deducting a volume occupied by one or more heat exchangers accommodated in this internal volume, this internal volume essentially corresponds to the volume through which district heating fluid can flow within the tank. The tank can be designed, inter alia, by the materials used in it and its construction, to withstand the relatively high pressures in the range up to 25 bar and / or the relatively high temperatures in the range up to 130 °C, as typically prevail in district heating fluid in a district heating network. For example, the tank can be constructed with a metal wall, in particular a steel wall.The wall may have a thickness of more than 4 mm, preferably a thickness in the range of 4 to 20 mm. In order to be able to manufacture the tank simply and cost-effectively, the tank may, for example, have a substantially cylindrical geometry in which a cylindrical shell wall is closed at an upper and a lower end by a substantially circular base part and a substantially circular lid, respectively. However, the tank may also be designed with other geometries. The tank may be configured to be arranged upright, e.g., with a vertically extending central axis of the cylindrical shell wall.

[0024] The interior volume of the tank can be hermetically sealed in such a way that fluids can only be introduced via special inlet connections and discharged via corresponding outlet connections. In particular, a district heating inlet connection is provided in order to be able to charge hot district heating fluid, which is supplied from a district heating source, into the interior volume of the tank. For this purpose, the district heating inlet connection can, for example, have piping which, on the one hand, opens into a district heating inlet nozzle provided on the outside of the tank and, on the other hand, opens into the interior volume of the tank. The piping can, for example, be designed as a metal pipe so that the district heating inlet connection can withstand the temperatures and pressures from the district heating network. The district heating inlet connection can be embedded in a wall of the tank and traverse this wall with its piping.Similarly, the district heating outflow connection can, on the one hand, open into a district heating outflow nozzle arranged on the outside of the tank and, on the other hand, extend into the internal volume of the tank. The district heating inflow connection can be arranged at a higher position on the tank than the district heating outflow connection. Preferably, the district heating inflow connection is arranged as high up on the tank as possible, for example in the top 10% or top 20% of the tank, whereas the district heating outflow connection is arranged as far down on the tank as possible, for example in the bottom 10% or bottom 20% of the tank. Accordingly, a large proportion, preferably a predominant proportion, of the internal volume of the tank can be located vertically between the district heating inflow connection and the district heating outflow connection.

[0025] The heat exchanger can be designed, inter alia with regard to the materials used in it and its construction, to withstand pressures in the range up to 25 bar and / or temperatures in the range up to 130 °C, as typically prevailing in a district heating system intended to supply heat to a building. Furthermore, the materials and construction can be suitably adapted to enable heat transfer between the district heating fluid surrounding the heat exchanger, on the one hand, and the domestic heat fluid flowing through the heat exchanger, on the other hand, with a desired heat transfer performance. For this purpose, a wall of the heat exchanger, which on the one hand comes into contact with the district heating fluid and on the other hand comes into contact with the domestic heat fluid, can be designed with a sufficiently large surface area. The wall can have a thickness of more than 2 mm, preferably a thickness in the range of 2 to 6 mm.For example, such a wall can be formed as the wall of a heat exchanger tube. The heat exchanger tube can be straight or curved. In particular, the heat exchanger tube can preferably be spiral-shaped. The wall can be made of a material that enables high heat transfer. For example, the wall can be made of metal, possibly steel, stainless steel, copper, aluminum, or similar.

[0026] The heat exchanger is entirely housed within the internal volume of the tank. In order to feed domestic heat fluid into the heat exchanger and subsequently discharge it again, at least one heat exchanger inlet connection and at least one heat exchanger outlet connection are provided on the tank. These can be designed similarly to the district heating inlet and outlet connections described above and each have an external end leading into domestic heat inlet nozzles and domestic heat outlet nozzles arranged on the outside of the tank. However, the internal ends of the one or more heat exchanger inlet connections and heat exchanger outlet connections should not openly lead into the internal volume of the tank, but should be connected to the internal volume of the heat exchanger.Accordingly, domestic heat fluid can be introduced into the heat exchanger via the heat exchanger inlet connection and discharged again via the heat exchanger outlet connection, creating a closed domestic heat fluid circuit in which the domestic heat fluid does not come into direct contact with the district heating fluid. Of course, the domestic heat fluid can absorb heat from the district heating fluid through thermal contact through the heat exchanger wall.

[0027] The internal volume of the heat exchanger through which the domestic heat fluid flows should be significantly smaller than the internal volume of the tank through which the district heating fluid flows. This allows the district heating fluid contained in the internal volume of the tank to serve as a large heat storage unit or large heat reservoir, capable of storing a significantly larger amount of heat than could be extracted by the heat exchanger in a relatively short period of time.

[0028] As explained in more detail below, the district heating transfer station can thus be used in cyclical operation, in which the tank is loaded with heat-storing district heating fluid in cyclical repetitions at longer intervals during a first sub-cycle. Due to the large heat-storing internal volume of the tank, heat can then be successively extracted from the district heating fluid via the heat exchanger during a second sub-cycle. Since there is preferably no significant mixing within the district heating fluid in the tank during this second sub-cycle, a temperature stratification can build up in the district heating fluid, with a higher temperature higher up in the tank than further down in the tank. A resulting temperature profile that gradually decreases from top to bottom can be advantageously used to transfer heat as efficiently as possible from the district heating fluid to the domestic heat fluid.

[0029] According to one embodiment, the internal volume of the heat exchanger can be less than 50% of the internal volume of the tank through which the district heating fluid flows. Preferably, the internal volume of the heat exchanger can even be less than 30%, less than 20%, less than 15%, or less than 10% of the internal volume of the tank through which the district heating fluid flows. For example, in a district heating transfer station whose tank holds at least 1500 l, the internal volume of the heat exchanger or the sum of all internal volumes of several heat exchangers accommodated in the tank can be less than 200 l, preferably less than 150 l.

[0030] The larger the internal volume of the tank compared to the internal volume of the heat exchanger, the more heat can be stored in the district heating fluid stored in the tank in relation to the heat that can be extracted quickly by the heat exchanger. The heat exchanger and its internal volume are usually designed in such a way that the heat demand in a building can be met. Accordingly, the tank of the district heating transfer station should be suitably dimensioned in order to be able to store, for example, the heat required in the building for several hours. The more heat that can be stored in the tank, the longer the second sub-cycles can be. During these cycles, the district heating fluid remains stationary in the tank between two tank loadings, thus advantageously allowing stable heat stratification to develop.

[0031] According to the first aspect of the invention, the district heating transfer station comprises a flow distributor arrangement which is arranged in the internal volume of the tank between an opening of the district heating inflow connection and an opening of the district heating outflow connection and which is configured to distribute a flow of district heating fluid emerging from the opening of the district heating inflow connection over a larger cross-section and to slow it down in the process.

[0032] With the help of the flow distributor arrangement, a flow of district heating fluid emerging from the district heating inlet connection can thus be distributed within the internal volume of the tank. The flow distributor arrangement should be designed such that the district heating fluid, which originally flows out of the relatively small cross-section of the district heating inlet connection, is distributed over the largest possible cross-section within the internal volume of the tank. At the same time, the flow velocity of the escaping district heating fluid is also reduced. The flow distributor arrangement should preferably be arranged as close as possible to the district heating inlet connection, in particular closer to it than to the district heating outlet connection, so that any district heating fluid flowing in there is first distributed by the flow distributor arrangement before it can flow through a predominant portion of the internal volume of the tank.

[0033] Overall, this can ensure, among other things, that the district heating fluid flowing into the tank circulates the district heating fluid already in the tank as little as possible, thereby disrupting any heat stratification that may have already formed. Instead, the incoming district heating fluid, which is typically hotter than the district heating fluid already in the tank, can accumulate over a wide cross-section within the heat tank above the cooler, older district heating fluid. Heat stratification essentially remains, with cooler layers being displaced downwards into the tank by the incoming, hotter district heating fluid with as little turbulence as possible, or ultimately being discharged from the tank via the district heating drain connection.

[0034] According to a specific embodiment, the flow distributor arrangement can be designed as a perforated plate which, with respect to a flow of the district heating fluid through the internal volume of the tank, is designed and arranged such that at least a predominant portion of supplied district heating fluid flows through holes in the perforated plate after exiting the district heating inlet connection and before entering the district heating outlet connection.

[0035] The perforated plate can be designed as a flat structure in which a plurality of holes or openings are formed. The total area of all holes can comprise between 1% and 90%, preferably between 5% and 50%, of the total area of the perforated plate. The cross-sectional area of an individual hole can be significantly smaller than the cross-sectional area from which district heating fluid flows from the district heating inlet connection. For example, the cross-sectional area of a hole can be in the range of 80 mm 2 up to 200 mm 2 whereas the cross-sectional area of the district heating inflow connection is typically in the range of 200 mm 2 up to 2000 mm 2Accordingly, in order to flow through the perforated plate, the incoming district heating fluid must flow through several of the openings. This fans out and slows down the flow. The holes can be evenly distributed in the perforated plate. All holes can have the same cross-sectional area. Alternatively, the holes can be irregularly distributed across the perforated plate and / or have different cross-sectional areas. For example, fewer and / or smaller holes can be provided near the opening of the district heating inlet connection than far from this opening. The perforated plate can be made of a heat-resistant and / or mechanically resilient material in order to withstand the flow of hot district heating fluid. For example, the perforated plate can be made of metal, in particular steel.

[0036] According to a further specific embodiment, at least a predominant part of the heat exchanger can be arranged in a part of the internal volume of the tank which is arranged downstream of the flow distributor arrangement with respect to a flow of the district heating fluid through the internal volume of the tank.

[0037] In other words, the flow distributor arrangement and the heat exchanger should preferably be arranged in the internal volume of the tank such that incoming, hot district heating fluid must first flow through the flow distributor arrangement before reaching the heat exchanger or at least a predominant portion thereof. In other words, the heat exchanger should preferably be arranged downstream of the flow distributor arrangement and thus be located in a partial volume of the internal volume of the tank in which a stable thermal stratification can develop, as far as possible, since a flowing district heating fluid is distributed and slowed down by the flow distributor arrangement before reaching this partial volume. A heat exchanger arranged in this way can transfer heat particularly efficiently from the district heating fluid to the domestic heat fluid flowing through the heat exchanger.

[0038] According to the first aspect of the invention, the district heating transfer station comprises at least two heat exchangers and, associated with each heat exchanger, a heat exchanger inlet connection and a heat exchanger outlet connection. Both heat exchangers are accommodated in the internal volume of the tank. Both heat exchangers have an internal volume that is smaller than the internal volume of the tank through which the district heating fluid is to flow.

[0039] In other words, the district heating transfer station can have multiple heat exchangers within its tank's internal volume. Each heat exchanger can be separately flowed through by domestic heat fluid, absorbing heat from the district heating fluid. The heat exchangers can be part of separate heat circuits or separate heat supplies. If necessary, heat exchangers can also be interconnected or connected to one another. For example, two or more heat exchangers can be connected in series or parallel. Each heat exchanger or group of heat exchangers can be used for a specific function.

[0040] According to the first aspect of the invention, a first of the heat exchangers is configured to supply domestic heat fluid heated therein to a heating circuit of a building, and a second of the heat exchangers is configured to supply domestic heat fluid heated therein to a hot water supply of a building.

[0041] Since in this example the two heat exchangers are used for different functionalities and therefore generally have to deliver different heat outputs or temperatures, it may be advantageous to design the two heat exchangers differently and / or to arrange them differently in the internal volume of the tank.

[0042] For example, domestic heat fluid intended to supply a heating circuit usually needs to be provided at a lower flow temperature than domestic heat fluid intended to be supplied by a hot water supply. Accordingly, it may be advantageous to position the heat exchanger for the heating circuit further down in the internal volume of the tank, i.e., where a relatively low temperature prevails due to the thermal stratification within the tank. The heat exchanger for the hot water supply, on the other hand, can be positioned further up in the warmer part of the tank.

[0043] Alternatively or additionally, according to one embodiment, at least two of the heat exchangers may be configured to supply domestic heat fluid heated therein to a heating circuit of a building.

[0044] In this example, two or more heat exchangers of the district heating transfer station are used for the same functionality, namely heating the building. While this functionality could also be implemented using a single heat exchanger, distributing it across two heat exchangers can be advantageous in that the district heating transfer station can be designed in a somewhat modular manner. Depending on the intended use of the district heating transfer station, a single or multiple heat exchangers can be used to implement the heating functionality. For example, if the district heating transfer station is used in a single-family home, only a single heat exchanger may be required for heating, whereas in an apartment building, multiple heat exchangers may be required. A modular design of the district heating transfer station in this regard can thus expand its range of possible applications.The multiple heat exchangers can be interconnected. In particular, the multiple heat exchangers can be interconnected in parallel. In this case, it is advantageous to ensure that the multiple heat exchangers are designed for essentially the same or similar heat transfer capacities. The surface area through which each heat exchanger is in thermal contact with the surrounding district heating fluid should advantageously be the same or similar in size for heat exchangers interconnected in parallel. To accommodate the multiple heat exchangers effectively within the internal volume of the tank, they can be designed with different geometries.

[0045] For example, according to one embodiment, the at least two heat exchangers can be arranged coaxially to one another.

[0046] For this purpose, for example, the piping of a heat exchanger can be geometrically designed such that it extends along a virtual cylinder surface. The piping can, for example, be spiral-shaped. The diameter of the cylinder surface can be selected to be different for each of the heat exchangers. Accordingly, the heat exchangers can be nested within one another and arranged coaxially to one another in the internal volume of the tank. While the spiral-shaped heat exchangers, for example, have different diameters in the radial direction, they can be arranged overlapping in the axial direction. This enables a space-saving and at the same time efficient arrangement of the multiple heat exchangers in the tank.

[0047] Additionally or alternatively, the at least two heat exchangers can be arranged at different heights within the internal volume of the tank.

[0048] Since a targeted heat stratification can be built up in the tank of the district heating transfer station, the temperatures at which the service heat fluid can be extracted from the respective heat exchangers can be influenced by arranging heat exchangers at different heights within the tank.

[0049] For example, a heat exchanger used to heat domestic heat fluid for a hot water supply can be located in an upper section of the tank. Due to thermal stratification, high district heating fluid temperatures prevail in this upper section, allowing the water for the hot water supply to be heated to, for example, over 60°C via this heat exchanger. A heat exchanger used to heat domestic heat fluid for a heating circuit can be located in a lower section of the tank. Due to thermal stratification, temperatures there are typically lower, but these may be sufficient to heat the domestic heat fluid to a flow temperature sufficient for the heating circuit.

[0050] If different heating circuits are intended for different heating types, they may also need to be heated to different flow temperatures. Accordingly, different heat exchangers for this purpose can be arranged at different heights within the tank. For example, a heat exchanger for a heating circuit with radiators, which typically need to be heated to 40-60 °C, can be positioned higher in the tank than a heat exchanger for a heating circuit with underfloor, wall, or ceiling heating, which typically only need to be heated to 20-40 °C.

[0051] Accordingly, the district heating transfer station presented here may be able to supply different heating circuits with different temperature requirements without necessarily requiring further technical measures such as the provision of a mixer for temperature adjustment by adding fluid with a lower temperature.

[0052] According to the first aspect of the invention, the district heating transfer station has a loading control configured to carry out a method in which a cyclically repeated loading of the tank with heat-storing district heating fluid takes place. The loading control is configured to - to control, during a first sub-cycle, an exchange of district heating fluid in the tank by allowing an inflow of heat-storing district heating fluid originating from a district heating source through the district heating inflow connection and allowing an outflow of district heating fluid stored in the tank through the district heating outflow connection, and - to block an exchange of district heating fluid in the tank during a second sub-cycle.

[0053] In other words, the district heating transfer station can be configured, using its loading control system, such that district heating fluid does not flow continuously through the district heating transfer station, i.e., hotter district heating fluid does not flow continuously into the tank through the district heating inlet connection, while cooler district heating fluid flows out of the tank through the district heating outlet connection. Instead, the tank should be loaded discontinuously, i.e., in cycles.

[0054] In a first sub-cycle, at least a portion of the district heating fluid previously in the tank is replaced by fresh, hotter district heating fluid by allowing this to flow in through the district heating inlet connection, wherein the district heating fluid to be replaced is allowed to flow out of the tank through the district heating outlet connection.

[0055] During such a loading of the tank in the first cycle, for example, a significant volume fraction, e.g., more than 20%, 30%, or 40%, of the internal volume of the tank can be filled with fresh district heating fluid. Preferably, even a predominant volume fraction, e.g., more than 50%, 60%, or even 70% of the internal volume of the tank is filled with fresh district heating fluid. However, during loading, not the entire tank contents necessarily need to be replaced with fresh district heating fluid; rather, for example, more than 10%, 20%, or even more than 30% of the previous tank contents can remain.

[0056] After the tank has been freshly charged, further exchange of district heating fluid in the tank can be prevented in a subsequent second sub-cycle. Accordingly, the previously introduced district heating fluid remains in the tank together with district heating fluid that was not exchanged during charging. Since essentially no flows or turbulence are induced within the tank contents during the second sub-cycle, particularly because no fresh district heating fluid flows in, the desired thermal stratification can be established within the tank contents.

[0057] To enable the tank to be loaded with fresh district heating fluid during the first sub-cycle, while preventing further exchange of district heating fluid in the tank during the second sub-cycle, the loading control system can have one or more controllable valves. A valve can allow the flow of district heating fluid when open and block it when closed.

[0058] The respective state of the valve can be specified by the control logic of the loading control system. For this purpose, the control logic can be equipped, for example, with a processor and / or evaluation electronics, which can be used to decide whether a first sub-cycle for loading the tank should currently be initiated or whether no such loading is permitted in a second sub-cycle.

[0059] For this purpose, the control logic can, for example, receive signals from a sensor system in the loading control system. This sensor system can, for example, have one or more heat sensors that can be used to measure temperatures at one or more locations within the internal volume of the tank. Depending on the measured temperatures, the control logic can then decide whether to transition from a current second sub-cycle to a first sub-cycle to initiate a fresh loading of the tank, or whether to transition from a current first sub-cycle to a second sub-cycle to temporarily interrupt loading of the tank.

[0060] Alternatively, the control logic can control a transition from a first to a second subcycle, or vice versa, according to fixed or variable patterns. For example, a first subcycle can always be executed for a fixed period of time.

[0061] According to a specific embodiment, a duration of the first sub-cycle may be shorter than a duration of the second sub-cycle.

[0062] In other words, the time required to charge the tank with fresh district heating fluid can be significantly shorter than the time during which no district heating fluid flows in, thus keeping the tank contents essentially stationary to create the desired thermal stratification. For example, the second sub-cycle can be more than twice as long, preferably more than ten times as long, as the first sub-cycle. The duration of the first sub-cycle can typically be between 5 minutes and 180 minutes, depending on the partial volume of district heating fluid to be exchanged. The duration of the second sub-cycle can typically be between 15 minutes and 3000 minutes, depending on the amount of heat stored in the tank and the heat output extracted by the heat exchanger.The longer the second sub-cycle is compared to the first sub-cycle, the longer the district heating transfer station can generally be operated in a state in which the desired heat stratification is achieved in its tank and the higher the sufficient efficiency of heat transfer in the district heating transfer station can be.

[0063] According to a further embodiment, the loading control may be configured to initiate the first sub-cycle starting from the second sub-cycle as soon as a temperature of domestic heat fluid flowing through the heat exchanger and / or as soon as a temperature of district heating fluid in the internal volume of the tank falls below a predefined limit temperature.

[0064] In other words, the loading control can, for example, have a temperature sensor by means of which the temperature of the domestic heat fluid and / or the district heating fluid flowing through the district heating transfer station or located therein can be measured. This temperature can, for example, correspond to the return temperature of the domestic heat fluid after it has given off its heat, for example, to the building or the water in a hot water supply and is to be heated again by flowing through the heat exchanger. Alternatively, the temperature can also be the flow temperature of the domestic heat fluid, i.e. the temperature that the domestic heat fluid has after flowing through the heat exchanger. As a further alternative, a temperature of the district heating fluid in the tank can also be measured. For example, the temperature of the district heating fluid can be measured at a position in the tank which is close to orlocated at the level of the district heating outlet connection. Alternatively, the temperature of the district heating fluid can be measured at a position in the tank that is close to or at the level of the district heating inlet connection.

[0065] In all of these cases, the temperature value determined during such a measurement can be used as an indicator of whether the district heating fluid in the district heating transfer station has cooled so much since the last tank loading that sufficient heat transfer performance can no longer be guaranteed, and thus a new tank loading should be initiated by transitioning from the second sub-cycle to the first sub-cycle. In this way, it can be ensured that, on the one hand, heat transfer efficiency is optimized by selecting the second sub-cycle as long as possible, while, on the other hand, the desired heat transfer performance is always guaranteed by loading the tank of the district heating transfer station with fresh district heating fluid in a timely manner.

[0066] The termination of the first sub-cycle, i.e., stopping a loading with hot district heating fluid, can also be controlled based on temperature. For example, loading can be stopped as soon as the temperature of the district heating fluid in the tank exceeds a predetermined minimum temperature value. Depending on the application, this temperature can be measured at a suitable location within the tank, for example, near or at the level of the district heating outflow connection or the district heating inflow connection. This can be used, for example, to ensure that a sufficient, but not excessive, volume of hot district heating fluid is introduced into the tank during a loading process.

[0067] In principle, time-dependent control of the loading processes is also conceivable. For example, the first sub-cycle can always be initiated at a specific time or always after a certain period of time has elapsed since the completion of a previous loading process. Furthermore, the first sub-cycle can be ended after a specified time period, and the second sub-cycle can be started.

[0068] It should be noted that possible advantages and configurations of embodiments of the invention are described herein partly with reference to a district heating transfer station according to the invention and partly with reference to a method according to the invention for operating such a district heating transfer station. A person skilled in the art will recognize that the described features can be appropriately transferred, adapted, exchanged, or modified to achieve further embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Embodiments of the invention will now be described with reference to the accompanying drawings, wherein neither the drawings nor the description are to be construed as limiting the invention. Fig. 1 shows a sectional view through a conventional district heating transfer station. Fig. 2 shows a sectional view through a district heating transfer station according to an embodiment of the invention.

[0070] The figures are merely schematic and not to scale. The same reference numerals designate identical or equivalent features in the various figures. DESCRIPTION OF PREFERRED EMBODIMENTS

[0071] Fig. 1 shows a conventional district heating transfer station 101. The district heating transfer station 101 draws heat-storing district heating fluid from a district heating source 121. For this purpose, the district heating fluid is passed through a district heating heat exchanger 105, which is accommodated in a tank 103. Compared to the volume of the tank 103, the district heating heat exchanger 105 is relatively small. Domestic heat fluid in the form of heating water is accommodated in an internal volume 115 of the tank 103. With the help of the district heating heat exchanger 105, a portion of the heat stored in the district heating fluid is transferred to the heating water. Due to the large internal volume 115 of the tank 103, the heating water acts as a heat accumulator. A portion of the heating water can be withdrawn from the internal volume 115 and fed to a heating circuit 141 or a radiator 149 accommodated therein. A hot water heat exchanger 143 is also accommodated in the internal volume 115.By means of this hot water heat exchanger 143, heat stored in the domestic heat fluid in the internal volume 115 of the tank 103 can be transferred to fresh water, which is to be provided as hot water at a tap 153 from a water inlet 151.

[0072] In the conventional district heating transfer station 101 described above, the heating water serves as a heat storage tank. As a result, the maximum district heating output provided by the district heating source 121 can be lower than in a configuration in which no heat storage tank exists.

[0073] The conventional district heating transfer station 101 has the district heating heat exchanger 105 and the hot water heat exchanger 143. In general, the district heating heat exchanger 105 is designed to be sufficiently powerful to provide the maximum heat output typically required by the heating circuit 141. However, if hot water is required over a longer period of time, e.g., hot water with a heat output of 40 kW is drawn, and the district heating heat exchanger 105 is only designed for a heat output of, for example, 50 kW, then the temperature in the heating water serving as a heat storage device will drop over time unless the heat output is limited to a maximum of 10 kW for the duration of the hot water draw.

[0074] In the conventional district heating transfer station 101, a flow temperature must typically be at least 70-75 °C due to the difference between the temperature of the incoming district heating fluid and the temperature of the heat-storing heating water. This is particularly true because two heat exchangers, i.e., the district heating heat exchanger 105 and the hot water heat exchanger 143, are thermally connected in series to implement the hot water supply, whereby a hot water temperature of at least 60 °C is always desired to kill Legionella.

[0075] Furthermore, in the conventional district heating transfer station 101, a return temperature of the district heating fluid is typically 3-10 K higher than a temperature of the heat-storing heating water in the tank 103 due to the district heating heat exchanger 105 and the associated temperature gradient.

[0076] In the conventional district heating transfer station 101, the temperature gradient during heat storage loading is also relatively high with low heat transfer capacity of the district heating heat exchanger 105 and rapid loading.

[0077] The conventional district heating transfer station 101 is typically controlled by a control valve 155, which is partially opened based on the return temperature to the heating network. Multiple circulation of the heating water until a low temperature is reached in the heat storage tank, and control via the return temperature of the heating circuit, are generally not used.

[0078] Fig. Figure 2 illustrates a district heating transfer station 1 according to an embodiment of the present invention. The district heating transfer station 1 comprises a tank 3, in whose interior volume 15 one or more heat exchangers 5 are arranged.

[0079] The tank 3 essentially consists of a cylindrical wall 59, a base 61, and a lid 63. Together, these components of the tank 3 surround the interior volume 15. The components, and thus the entire tank 3, are designed such that a hot liquid serving as a district heating fluid, which may, for example, have a temperature of over 40 °C and a pressure of over 25 bar, can be received and stored in the interior volume 15.

[0080] In an upper region of the tank 3, a district heating inlet nozzle 17 accessible from the outside and a district heating inlet connection 7 connected to it are provided. The district heating fluid, which is provided by a district heating source 21, can be conducted into the tank 3 via the district heating inlet connection 7. This allows the tank 3 to be loaded with district heating fluid and thus with the heat stored in the district heating fluid. The district heating inlet nozzle 17 is arranged in the region of the cylindrical wall 59 of the tank 3. A region of the district heating inlet connection 7 located within the tank 3 is guided further upwards within the internal volume 15, i.e. in the direction of the cover 63, in order to be able to feed the district heating fluid as high as possible into the tank 3 through an opening 31 of the district heating inlet connection 7.

[0081] In a lower region of the tank 3, a district heating discharge nozzle 19 accessible from the outside and a district heating discharge connection 9 connected to it are provided. District heating fluid can be discharged from the tank via the district heating discharge connection 9 and can then flow back to the district heating source 21 in a circuit. The district heating discharge nozzle 19 is arranged in the region of the cylindrical wall 59 of the tank 3. A region of the district heating discharge connection 9 located within the tank 3 extends further downwards within the internal volume 15, i.e., towards the bottom 61, in order to be able to discharge the district heating fluid from the tank 3 through an opening 33 of the district heating discharge connection 9 as close as possible to the bottom 61.

[0082] Near the lid 63, within the interior volume 15 of the tank 3, there is a flow distributor arrangement 29 in the form of a perforated plate 35. The perforated plate 35 comprises a plurality of small holes 37. The perforated plate 35 can, for example, extend substantially along the entire cross-section of the tank 3. The perforated plate 35 is arranged below the opening 31 of the district heating inlet connection 7. Accordingly, district heating fluid flowing out of this opening 31 must flow through holes 37 of the perforated plate 35 before it can reach the underlying part of the interior volume 15 of the tank 3. In the process, the flow of the district heating fluid is widened and slowed. Accordingly, the introduced district heating fluid can slowly displace lower layers of the district heating fluid already present in the tank 3 downwards over a wide cross-section, i.e. towards the district heating discharge connection 9, without significantly circulating it.

[0083] As a result, a stable thermal stratification can build up over time within the internal volume 15 of the tank 3, which can be maintained at least partially even when fresh district heating fluid flows in, i.e., when the district heating transfer station is recharged. With such thermal stratification, warmer district heating fluid is located in the higher-lying areas of the internal volume 15, whereas the temperature of the district heating fluid within the internal volume 15 gradually decreases toward the bottom.

[0084] In the example shown, a total of four heat exchangers 5 are arranged in the internal volume 15 of the tank 3. Each of these heat exchangers 5 is formed with a spiral heat exchanger tube. All heat exchangers 5, or the spiral courses of their heat exchanger tubes, are arranged coaxially with one another. A central axis common to all heat exchangers 5 extends vertically through the tank 3 and essentially coincides with a central axis of the cylindrical wall 59. Three first heat exchangers 39 are arranged radially further outward than a second heat exchanger 43 located further in the center of the tank 3. Each of these heat exchangers 5 encloses an internal volume 23 that is considerably smaller than the internal volume 15 of the tank 3. The sum of all internal volumes 23 of all heat exchangers 5 is also considerably smaller than the internal volume 15 of the tank 3 not occupied by the heat exchangers 5.

[0085] The first three heat exchangers 39 serve to supply heat from the district heating transfer station 1 to a heating circuit 41, i.e., to radiators 49 provided therein or similar heat consumers. For this purpose, domestic heat fluid can be introduced into one of the respective first heat exchangers 39 via a domestic heat inlet connection 25 and a heat exchanger inlet connection 11. After the domestic heat fluid has flowed through the heat exchanger 39, it can be discharged at the opposite end through a heat exchanger outlet connection 13 and a domestic heat outlet connection 27 arranged on the outside of the tank 3. The heat exchanger inlet connection 11 is located further down on the tank 3 than the heat exchanger outlet connection 13, so that service heat fluid passed through the heat exchanger 39 is first passed through the cooler, lower part of the district heating fluid held in the tank and then through the hotter, upper part of the district heating fluid.In this way, heat can be transferred particularly efficiently from the district heating fluid to the domestic heat fluid.

[0086] The three first heat exchangers 39 and their helical piping are arranged coaxially to one another. The heat exchangers 39 differ in terms of their diameter. One of the heat exchangers 39, which has a larger diameter, can have a shorter height than another of the heat exchangers, which has a smaller diameter, so that the overall length of the heat exchanger tube for each of the first heat exchangers 39 can be approximately the same. Accordingly, all three first heat exchangers 39 can have the same or similar heat exchanger output. Therefore, these heat exchangers 39 can be operated in parallel, i.e., connected in parallel to the heating circuit 41. Depending on the heat demand to be covered by the district heating transfer station 1, a number of first heat exchangers can be selected to be larger or smaller in a modular manner.

[0087] For example, a simple steel tube with a substantially smooth surface can be used as the heat exchanger tube for the first heat exchanger 39. Such a heat exchanger can be manufactured relatively easily and inexpensively.

[0088] The second heat exchanger 43 serves to supply a hot water supply 45. Cold fresh water can be supplied from a water inlet 51 to a heat exchanger inlet connection 11 of the second heat exchanger 43. After the water has flowed through the second heat exchanger 43, it can be drained at a heat exchanger outlet connection 13 in order to then supply a faucet 53 with hot water, for example.

[0089] For hygiene reasons, a stainless steel pipe, for example, can be used as the heat exchanger pipe. The heat exchanger pipe can have a rough or textured surface. This enables a relatively high heat transfer. Furthermore, the second heat exchanger 43 can usually be operated more efficiently because it is supplied with cold fresh water at flow temperatures of typically below 20 °C, whereas flow temperatures in the first heat exchanger 39 are generally significantly higher. Accordingly, the second heat exchanger 43 can generally be smaller than the first heat exchangers 39, both in terms of its dimensions and its heat transfer capacity. Since hot water should be heated to high temperatures of over 60 °C, at least temporarily, the second heat exchanger 43 can be arranged high up in the tank 3 orextend into the upper areas of tank 3, since particularly hot district heating fluid is stored there due to the heat stratification.

[0090] Operation of the district heating transfer station 1 can be controlled using a loading control 47. The loading control 47 can control a state of a control valve 55. In an open state, the control valve 55 can allow district heating fluid to be drained from the district heating outlet connection 9 of the tank 3. At the same time, fresh, hot district heating fluid flows in through the district heating inlet connection 7. In a closed state, the control valve 55 blocks the draining of district heating fluid from the tank 3. At the same time, a check valve 57 prevents district heating fluid from escaping from the tank 3 through the district heating inlet connection 7.

[0091] To load tank 3, the loading control 47 controls the control valve 55 to its open state during a first partial cycle. Accordingly, hot district heating fluid can flow into the interior volume 15 of the tank from above, displacing cooler district heating fluid, which can then flow out through the district heating outlet connection 9 at the bottom of tank 3.

[0092] After at least an upper portion of the internal volume 15 has been filled with fresh, hot district heating fluid by such charging, the charging controller 47 can then set the control valve 55 to its closed state during a second sub-cycle. The second sub-cycle can last significantly longer than the first sub-cycle required for charging. During this second sub-cycle, heat can be successively transferred from the district heating fluid via the heat exchangers 5 to the domestic heat fluid for both the heating circuit 41 and the hot water supply 45. As a result, the district heating fluid in the tank 3 gradually cools. Since this process occurs relatively slowly, a stable heat stratification can develop in the internal volume 15 of the tank 3.In the quasi-stationary district heating fluid, warmer areas accumulate higher up in the internal volume 15, whereas cooler portions of the district heating fluid sink downwards and collect near the bottom 61.

[0093] In particular, the ability to maintain a stable heat stratification in the tank 3 of the district heating transfer station 1 over longer periods of time enables a number of advantages compared to conventional district heating transfer stations.

[0094] For example, this allows for both relatively low return temperatures and relatively low flow temperatures in the district heating network. For example, return temperatures of approximately 35 °C and flow temperatures of approximately 65 °C appear possible. This can increase the overall efficiency of the district heating system and maximize power transfer.

[0095] Since the first heat exchanger 39 for the heating circuit 41 and the second heat exchanger 43 for the hot water supply 45 can be operated in parallel to one another within the tank 3, maximum heating outputs can be provided simultaneously for both the heating circuit 41 and the hot water supply 45.

[0096] Because the district heating fluid itself is used as a heat storage device in the district heating transfer station 1, there is no need for a temperature gradient between the district heating system and the heat storage device in the district heating transfer station, unlike in conventional district heating transfer stations 1. Fresh charging with hot district heating fluid can be achieved quickly and in a technically simple manner. In particular, a simple outlet flap can be used as the control valve 55, which can be fully opened, thus eliminating the need to set a throttled flow. This can be achieved in a technically simple, error-free, and durable manner.

[0097] The loading controller 47 can be configured to be programmable. In particular, the loading controller 47 can be coupled to a data network, for example, a LAN (Local Area Network), via which the loading controller 47 can receive data or transmit data to other devices. Based on received data, operation of the loading controller 47 can be controlled. For example, the loading controller 47 can be parameterized and / or software updates can be transmitted. Data transmitted to other devices can be used, for example, for analysis purposes. In particular, energy consumption and / or diagnostic data can be transmitted.

[0098] The possibility of data transmission can achieve various advantages. For example, billing for heat extraction can be automated. A temperature difference between flow and return temperatures can be monitored. Switching thresholds and / or switching times for charging the district heating transfer station can be changed and optionally influenced by other parameters such as measured data, which can indicate an ambient temperature, for example, or data made available in other ways, such as weather data. In particular, charging processes can be controlled or initiated, and parameters relating to the first sub-cycle and / or the second sub-cycle can be suitably specified. This can be used to adjust temperature differences or to optimize the efficiency of the district heating transfer station.Parameterization can be performed, for example, by a manufacturer of the district heating transfer station or by an operator of the district heating network. Furthermore, information about energy consumption can be provided to the operator of the district heating transfer station.

[0099] Finally, it should be noted that terms such as "having," "comprising," etc., do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality. Furthermore, it should be noted that features or steps described with reference to one of the above embodiments may also be used in combination with other features or steps of other embodiments described above. Reference signs in the claims are not to be considered as limitations. LIST OF REFERENCE SYMBOLS 1 district heating transfer station 3 tanks 5 heat exchangers 7 District heating inflow connection 9 District heating drain connection 11 Heat exchanger inlet connection 13 Heat exchanger drain connection 15 Internal volume of the tank 17 district heating inlet nozzles 19 district heating drain nozzles 21 District heating source 23 Internal volume of the heat exchanger 25 domestic heat inlet nozzles 27 Domestic heat drain nozzles 29 Flow distributor arrangement 31 Mouth of the district heating inlet connection 33 Outlet of the district heating drain connection 35 perforated sheet 37 holes 39 first heat exchanger 41 Heating circuit 43 second heat exchanger 45 Hot water supply 47 Loading control 49 radiators 51 Water inflow 53 faucet 55 Control valve 57 Check valve 59 cylindrical wall 61 Floor 63 lids 101 conventional district heating transfer stations 103 Tank 105 district heating heat exchangers 115 Internal volume of the tank 121 district heating source 141 Heating circuit 143 hot water heat exchangers 149 radiators 151 Water inflow 153 faucet 155 Control valve

Claims

[1] District heating transfer station (1) comprising: a tank (3), at least two heat exchangers (5), a district heating inlet connection (7) and a district heating outlet connection (9), assigned to each heat exchanger (5) is a heat exchanger inlet connection (11) and a heat exchanger outlet connection (13), a flow distributor arrangement (29), and a loading control (47), wherein the district heating inlet connection (7) and the district heating outlet connection (9) each open into an internal volume (15) of the tank and form a fluid connection with a district heating inlet nozzle (17) and / or district heating outlet nozzle (19) accessible on the outside of the tank such that a heat-storing district heating fluid originating from a district heating source (21) can be fed into the internal volume (15) of the tank (3) via the district heating inlet connection (7) and, after flowing through the internal volume (15) of the tank (3), can be discharged from the internal volume (15) of the tank (3) via the district heating outlet connection (9), wherein the heat exchanger inlet connection (11) and the heat exchanger outlet connection (13) are each connected to an internal volume (23) of the associated heat exchanger (5) and form a fluid connection with a domestic heat inlet connection (25) and / or domestic heat outlet connection (27) accessible on the outside of the tank (3), via which a heat-storing domestic heat fluid can be fed into the internal volume (23) of the heat exchanger (5) and / or discharged from the internal volume (23) of the heat exchanger (5), wherein a first of the heat exchangers (39) is configured to supply domestic heat fluid heated therein to a heating circuit (41) of a building and wherein a second of the heat exchangers (43) is configured to supply domestic heat fluid heated therein to a hot water supply (45) of a building, wherein both heat exchangers (5) are accommodated in the internal volume (15) of the tank (3), wherein both heat exchangers (5) have an internal volume (23) which is smaller than the internal volume (15) of the tank (3) through which the district heating fluid is to flow, wherein the flow distributor arrangement (29) is arranged in the internal volume (15) of the tank (3) between an opening (31) of the district heating inflow connection (7) and an opening (33) of the district heating outflow connection (9) and is configured to distribute a flow of district heating fluid emerging from the opening (31) of the district heating inflow connection (7) over a larger cross-section and to slow it down in the process, wherein the loading control (47) is configured to control a cyclically repeated loading of the tank (3) with heat-storing district heating fluid, wherein the loading control (47) is configured to - to control an exchange of district heating fluid in the tank (3) during a first sub-cycle by allowing an inflow of heat-storing district heating fluid originating from a district heating source (21) through the district heating inflow connection (7) and allowing an outflow of district heating fluid stored in the tank (3) through the district heating outflow connection (9), and - to block an exchange of district heating fluid in the tank (3) during a second sub-cycle. [2] District heating transfer station according to claim 1, wherein the internal volume (23) of the heat exchangers (5) is less than 50% of the internal volume (15) of the tank (3) through which the district heating fluid is to flow. [3] District heating transfer station according to one of the preceding claims, wherein the flow distributor arrangement (29) is designed as a perforated plate (35) which, with respect to a flow of the district heating fluid through the internal volume (15) of the tank (3), is designed and arranged such that at least a predominant portion of supplied district heating fluid flows through holes (37) in the perforated plate (35) after exiting the district heating inlet connection (7) and before entering the district heating outlet connection (9). [4] District heating transfer station according to one of the preceding claims, wherein at least a predominant part of the heat exchangers (5) is arranged in a part of the internal volume (15) of the tank (3) which is arranged downstream of the flow distributor arrangement (29) with respect to a flow of the district heating fluid through the internal volume (15) of the tank (3). [5] District heating transfer station according to one of the preceding claims, wherein at least two of the heat exchangers (5) are configured to supply domestic heat fluid heated therein to a heating circuit (41) of a building. [6] District heating transfer station according to one of the preceding claims, wherein the at least two heat exchangers (5) are arranged coaxially to one another and / or wherein the at least two heat exchangers (5) are arranged at different heights within the internal volume (15) of the tank (3). [7] District heating transfer station according to one of the preceding claims, wherein a duration of the first sub-cycle is shorter than a duration of the second sub-cycle. [8] District heating transfer station according to one of the preceding claims, wherein the loading control (47) is configured to initiate the first sub-cycle starting from the second sub-cycle as soon as a temperature of domestic heat fluid flowing through the at least one heat exchanger (5) and / or as soon as a temperature of district heating fluid in the internal volume (15) of the tank (3) falls below a predefined limit temperature. [9] Method for operating a district heating transfer station (1) according to one of the preceding claims, the method comprising: Controlling a cyclically repeated loading of the tank (3) with heat-storing district heating fluid such that - during a first sub-cycle, an exchange of district heating fluid in the tank (3) is enabled by allowing an inflow of heat-storing district heating fluid originating from a district heating source (21) through the district heating inflow connection (7) and allowing an outflow of district heating fluid stored in the tank (3) through the district heating outflow connection (9), and - during a second sub-cycle, an exchange of district heating fluid in the tank (3) is blocked. [10] The method of claim 9, wherein a duration of the first sub-cycle is shorter than a duration of the second sub-cycle. [11] Method according to one of claims 9 and 10, wherein, starting from the second sub-cycle, the first sub-cycle is initiated as soon as a temperature of service heat fluid flowing through the at least one heat exchanger (5) and / or as soon as a temperature of district heating fluid in the internal volume (15) of the tank (3) falls below a predefined limit temperature.

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