EP3945268B1 - Heat pump system - Google Patents

Description

The present invention relates to a heat pump system in which an evaporator, a compressor, at least one buffer storage tank with a condensing coil device for passing refrigerant and an expansion valve are arranged successively in a closed circuit, wherein a stainless steel coil for passing potable water, radially surrounded by the condensing coil device, is arranged in the buffer storage tank; and at least one cold domestic water inlet, one cold potable water inlet connected to the stainless steel coil, one outlet for underfloor heating fluid, one outlet for radiator heating fluid and one hot potable water outlet are arranged on the buffer storage tank.

A conventional heat pump system typically consists of an evaporator where a refrigerant evaporates, extracting heat from the surrounding medium. A compressor compresses the refrigerant into a hot gas, which is then liquefied in a condenser. During this process, heat is released back into the surrounding medium. An expansion valve injects the refrigerant back into the evaporator at reduced pressure. There, the refrigerant changes its state from liquid to gaseous and absorbs heat again. A buffer tank, capable of storing a high heat capacity, is connected to the condenser via heat pipes. A pump transports the heat from the condenser to the buffer tank. Due to the low achievable temperature level in the buffer tank, a heat pump system of this design can only supply low-temperature heating systems.

In another known design variant, the aforementioned system is supplemented by a hot gas lance, through which a small amount of hot gas is directed into the upper part of the buffer storage tank via an additional ring main. In this layer, the flow temperature of the buffer storage tank increases, allowing the stored water to be used advantageously, for example, for domestic hot water preparation.

Further efficiency gains can be achieved by integrating the condenser directly into the buffer storage tank. An example of such an arrangement is shown in the printed document. DE 10 2005 011 709 A1 This is a known design. Here, the condenser, in the form of a coil, is arranged within a domestic hot water storage tank, to which cold water can be supplied via one pipe. Hot water can be drawn from the storage tank via another pipe. Furthermore, an auxiliary electric heater is integrated within the condenser coil to heat the incoming cold water into the storage tank more quickly. This results not only in increased purchase costs but also in higher operating costs during the heat pump's service life and a relatively complex system configuration.

In addition, there are heat pump systems that do not have a buffer storage tank. In this case, the heat exchanger is designed as a separate unit that is integrated into the circuit of a heat pump system. A corresponding heat exchanger is known from publication 5 379 832 A. The heat exchanger disclosed therein has two liquid coils arranged in the interior of a double-walled hollow cylinder. The liquid coils are intertwined and almost completely fill the interior of the hollow cylinder. Water flows through the liquid coils. The refrigerant, on the other hand, flows through the interior of the hollow cylinder and flows past the outside of the liquid coils.

A similarly functioning separate heat exchanger is described in the printed document. US 2010/096115 A1 revealed. Here, the heat exchanger has a cylindrical housing in which several spirally wound pipe coils are arranged.

A heat pump system according to the preamble of claim 1 is from the utility model DE 20 2009 008 405 U1 This heat pump system is known. In this system, a separating agent is provided in the buffer tank above a central level between an upper and a lower coil unit of the condenser. The upper and lower coil units are connected by a tubular arrangement, allowing the refrigerant to flow through them from top to bottom. Since the upper coil unit carries hot gas and can therefore transfer the greatest amount of energy to the liquid in the buffer tank, the separating agent between the upper and lower coil units creates a barrier. Within the buffer tank, there is an area at the top with a very high temperature and an area at the bottom with a lower, but still high, temperature. The separating agents effectively minimize unwanted mixing of the storage fluid between the two areas.

However, pressure losses have occurred in this heat pump system, which have led to a reduction in the efficiency of the heat pump system.

It is therefore the object of the present invention to reduce pressure losses in the generic heat pump system and thereby achieve better heat transfer.

This problem is solved by a heat pump system according to claim 1.

In the present invention, the terms "above", "upper", "lower", "top" and "bottom" are to be understood as they would appear to an observer of an upright buffer storage tank during operation of the heat pump system according to the invention, as shown in Figure 1 The schematic representation shows the result. The same applies to all further details in this description.

The two strands of the condenser coil allow the pressurized, hot refrigerant to be divided between them, thus reducing pressure losses. Furthermore, the two condenser coils have a larger surface area in contact with the storage fluid of the buffer tank compared to a single coil. This results in improved heat transfer. Therefore, the heat pump system according to the invention exhibits increased efficiency.

In an advantageous embodiment of the heat pump system according to the invention, the total length of the outer condenser coil is equal to the total length of the inner condenser coil. This ensures that each of the circuits has the same pressure losses, allowing the circuits to be optimally rejoined after passing through the buffer storage tank.

Preferably, the outer condenser helix has an upper outer condenser helix and an associated lower outer condenser helix, between which a horizontal separating agent is arranged; and the inner condenser helix has an upper inner condenser helix and an associated lower inner condenser helix, between which the horizontal separating agent is arranged, wherein the stainless steel helix extends continuously from a region below the horizontal separating agent to a region above the horizontal separating agent.

According to the invention, the heat pump system has an insulating ring that surrounds a number of coils of the condenser coil assembly in the buffer storage tank and forms a heat buffer zone around these coils, with a fluid inlet and a fluid outlet located at the bottom of the heat buffer zone and a fluid outlet at the top of the heat buffer zone. Thus, a warm fluid can be generated and buffered in a section of the buffer storage tank and discharged directly from this zone to the outside for further use, for example, as a fluid for operating underfloor heating.

This method eliminates the need to encase the coils of the condenser coil assembly in this area, which would be impossible to install, especially with closely spaced coils, due to space constraints. Instead, the insulating ring forms a kind of basket or vessel around the number of coils of the condenser coil assembly, in which the fluid remains for a specific period of time to be heated in a controlled manner.

According to the invention, this can be technically achieved by dividing an outer shell of the insulation ring by a section of an inner circumference of the domestic hot water storage tank. is formed and an inner sheath of the insulation ring surrounds the stainless steel helix, with the heat buffer area being formed between the outer sheath and the inner sheath and the fluid inlet and fluid outlet passing through the outer sheath.

According to the invention, the outer shell of the insulation ring is formed by a section of the inner circumference of the domestic hot water storage tank, and the inner shell of the insulation ring is guided around the stainless steel coil, wherein a number of coils of the outer condenser coil and the inner condenser coil are arranged in the heat buffer area located between the outer shell and the inner shell, and wherein a fluid inlet leading through the outer shell is arranged at the bottom of the heat buffer area and a fluid outlet leading through the outer shell is arranged at the top of the heat buffer area.

It is particularly advantageous if, according to one embodiment of the present invention, the insulation ring is arranged below the horizontal separating element. This makes it possible to effectively utilize the heat from the condenser coil assembly, which has already cooled down somewhat in the lower part of the buffer storage tank.

Particularly efficient hot water production is achieved when, in one embodiment of the heat pump system according to the invention, the stainless steel coil extends vertically through the entire buffer storage tank. In this embodiment, the stainless steel coil is inserted into the bottom of the buffer storage tank, while hot drinking water is drawn from the coil at the top. This allows the drinking water circulating in the coil to be preheated at the bottom of the buffer storage tank, resulting in faster heating. For example, the temperature of the drinking water at the bottom of the buffer storage tank is approximately 8 to 10 °C, in the middle of the tank approximately 30 °C, and can be increased to approximately 50 °C at the top, depending on requirements.

A preferred embodiment of the present invention, its structure, function and advantages, will be described below with reference to Figure 1 described, in which a heat pump system 1 according to the present invention is shown schematically in a cutaway side view.

The heat pump system 1 has a single, closed refrigerant circuit, which, during the operation of the heat pump system 1, is traversed by a refrigerant 6, such as a partially halogenated fluorocarbon or mixture, propane, propene, a propane-butane mixture, ammonia or carbon dioxide, in a flow direction indicated by the arrows.

The heat pump system 1 has an evaporator 2, which is designed as a heat exchanger and in which the refrigerant 6 is evaporated. The refrigerant 6 thereby extracts heat from the surrounding medium. The evaporator 2 is connected via a line to a compressor 3. The compressor 3 compresses the evaporated refrigerant 6 into a so-called hot gas. The compressor 3 is in turn connected via a line to a condenser, which, according to the invention, is designed as a condensing coil assembly 5. In the arrangement according to the invention, the condensing coil assembly 5 is provided within a buffer storage tank 4 and forms a structural unit with it.

The condenser coil 5 is a heat exchanger in which the refrigerant 6 is condensed or liquefied, whereby heat is transferred from the refrigerant 6 to the storage fluid 24, which is typically water and located in the buffer storage tank 4 and surrounding the condenser coil 5. According to the invention, the condenser coil 5 is not a separate heat exchanger but is formed in a helical shape within the buffer storage tank 4.

As it is in Figure 1 As can be seen, the refrigerant 6 flows through the condenser coil 5 in the buffer storage tank 4, utilizing the preferred flow direction of the refrigerant 14 from top to bottom due to gravity. Because of the coil shape of the condenser coil 5, the refrigerant 6 travels a long path within the condenser coil 5 and thus also within the buffer storage tank 4, thereby transferring a particularly large amount of energy to the surrounding medium, i.e., in this example, Figure 1 to the storage fluid 24. The surrounding medium flows very slowly or is completely still.

The condenser coil 5 is connected via a line to an expansion valve 7. The expansion valve 7 injects the refrigerant 6 at reduced pressure into the evaporator 2, to which the expansion valve 7 is connected via a line. whereupon the refrigerant 14 cycle described above is restarted.

In other embodiments of the invention, not shown here, the heat pump system 1 can include an intermediate heat exchanger, such as that described, for example, in the publication DE 20 2009 008 405 U1 As shown, the intermediate heat exchanger is located between the outlet of the condenser coil 5 and the inlet of the expansion valve 7, and between the outlet of the evaporator 2 and the inlet of the compressor 3. With such an intermediate heat exchanger, residual heat contained in the refrigerant 6 coming from the condenser coil 5 located in the buffer storage tank 4 can be used to increase the temperature of the refrigerant 14 or hot gas flowing into the compressor 3, thereby increasing the overall efficiency of the heat pump system 1.

The buffer tank 4 is in the example of Figure 1 a cylindrical or cuboid container or a container with an approximately oval cross-section that stands upright during operation, but can also be a container with another suitable geometry that allows the storage fluid 24 to be taken into and taken out of the buffer storage 4.

Above a central level of the buffer storage tank 4, a horizontal separating agent 13 is provided therein, which separates an upper helix section of the condenser helix device 5 from a lower helix section of the condenser helix device 5, wherein the upper helix section is connected to the lower helix section by tubular connecting agents 513, 523 in the example shown.

In the illustrated embodiment, the tubular connecting elements 513, 523 are arranged at a side edge of the buffer storage tank 4, but in other embodiments of the invention not shown, they can also be arranged centrally, passing through the separating element 13. The arrangement and height of the tubular connecting elements 513, 523, which are not coiled in the illustrated example, depend on the arrangement and thickness of the separating element 13.

In the Figure 1 In the illustrated embodiment, the separating agent 13 is designed as a horizontal, flat separating plate without any interruptions. In other, In embodiments of the present invention not shown, other suitable horizontal separating elements 13, such as those made of other materials like plastic or a suitable thermal insulation material, and/or in a corrugated or profiled form, can also be used within the buffer storage tank 4. The separating element 13 can also be curved or angled. Furthermore, it can also be positioned at a slight angle within the buffer storage tank 4. Likewise, the separating element 13 can be discontinuous rather than continuous and can, for example, have holes or slots that can serve, for instance, for the passage of the connecting elements 513, 523.

The separating agent 13 preferably extends over at least 50% of the internal cross-section of the buffer storage tank 4 that receives the storage fluid 24, but allows unimpeded passage of the non-coiled, tubular connecting elements 513, 523 and a certain amount of transfer of the storage fluid 24 between the areas formed above and below the separating agent 13, while preventing spontaneous mixing between these areas. Accordingly, a particularly suitable thermal stratification forms in the buffer storage tank 4, wherein the upper coiled area has particularly high temperatures and wherein the areas below the separating agent 13 also have elevated temperatures compared to cold tap water, but these temperatures are lower than in the area above the separating agent 13.

This is achieved in particular by the fact that the refrigerant 6 is still present as a hot gas in the upper helix region of the condenser coil assembly 5 and is therefore able to release a particularly large amount of heat energy to the surrounding medium, i.e., to the storage fluid 24 surrounding the upper helix region, while only in a change of state region in the lower helix region does a change of state of the refrigerant 14 from gaseous to liquid take place, which means that the refrigerant 6 can release less energy there and accordingly the storage fluid 24 has lower temperatures.

The condenser coil assembly 5 has an outer condenser coil 51, preferably arranged on an inner circumference 40 of the buffer storage tank 4, and an inner condenser coil 52 running between the outer condenser coil 51 and the stainless steel coil 8. The outer condenser coil 51 thus has, in a cross-section Top view of the buffer storage tank 4 shows a larger diameter than the inner condenser coil 52.

In the illustrated embodiment, however, the total length of the outer condenser coil 51 is equal to that of the inner condenser coil 52. This is achieved by the inner condenser coil 52 extending further downwards than the outer condenser coil 51.

The outer condenser helix 51 has an upper outer condenser helix 511 formed above the separating agent 13 and a lower outer condenser helix 512 connected to it by means of the connecting agent 513 and arranged below the separating agent 13. The inner condenser helix 52 has an upper inner condenser helix 521 and a lower inner condenser helix 522 connected to it by means of the connecting agent 523 and arranged below the separating agent 13.

In a sectional top view of the buffer storage tank 4, the upper, outer condenser coil 511 and the lower, outer condenser coil 512 are arranged one above the other in an annular outer coil area of the buffer storage tank 4, the upper, inner condenser coil 521 and the lower, inner condenser coil 522 are arranged one above the other in an annular inner coil area of the buffer storage tank 4, wherein the inner radius of the outer coil area is larger than the outer radius of the inner coil area.

The upper and lower coil sections, i.e., the upper outer condenser coil 511 and the upper inner condenser coil 521 enclosed by it, as well as the lower outer condenser coil 512 and the lower inner condenser coil 522 enclosed by it, wind around a stainless steel coil 8 running vertically from bottom to top through the interior of the buffer tank 4. This means that the stainless steel coil 8 runs almost continuously through the entire buffer tank 4, through the horizontal separating agent 13. The stainless steel coil 8 is thus surrounded by the warm coils of the condenser coil assembly 5 and the storage fluid 24 in the buffer tank 4, which is heated by the condenser coil assembly.

The stainless steel helix 8 preferably has a smaller diameter than the helixes of the condenser helix assembly 5. Drinking water is circulated in the stainless steel helix 8. 9, which is introduced cold into the stainless steel coil 8 through an inlet 42 and is extracted from it as hot water 9b at a dispensing device 44.

The lower coil section of the heat pump system 1 can, as described in the printed document DE 20 2009 008 405 U1 As described, a section of the coil is encased in a sheath, such as a pipe, through which a fluid can flow. The sheath can be located at any point along the lower coil section and can be of any length. The fluid circulating in the sheath can be drawn off at a discharge device, preferably located in the middle third of the buffer tank 4, for transfer and use in a connected circuit.

Preferably, this fluid is pumped through the casing in the lower coil section of the condenser coil 5, against the flow direction of the refrigerant 14, using a pumping device. This allows the fluid to absorb heat from the refrigerant 6 particularly effectively. For example, this makes the fluid especially suitable as a radiator fluid.

In the embodiment of Figure 1 However, due to space constraints, no casing is provided on the condenser coil assembly 5. Instead, an insulation ring 14 is arranged in a section of the lower coil area of the condenser coil assembly 5, i.e., around the lower, outer condenser coil 512 and simultaneously around the lower, inner condenser coil 522 surrounded by it. In the illustrated embodiment, the outer casing of the insulation ring 14 is formed by a section of the inner circumference 40 of the domestic hot water storage tank 4. The inner casing 142 of the insulation ring 14 surrounds the stainless steel coil 8. A number of coils of the lower, outer condenser coil 512 and the lower, inner condenser coil 522 are arranged in a heat buffer area 140 of the insulation ring 14 located between the outer casing 141 and the inner casing 142. At the bottom of the heat buffer area 140, a fluid inlet 46 leading through the outer jacket 141 for a fluid 11a is arranged, and at the top of the heat buffer area 140, a fluid outlet 47 leading through the outer jacket 141 for the heated fluid 11b is arranged.

However, in another variant of the invention, not shown here, a sheathing is also provided in this area. This area also serves for heating. The storage fluid 24 in the buffer tank 4 can be extracted from the buffer tank 4 via a withdrawal device. The last section after the lowest coil of the lower condenser coil in the buffer tank 4 is designed as a straight pipe and directs the refrigerant 6 from the buffer tank 4 back into the cycle of the heat pump system 1 described above.

The heat pump system 1 has a casing 26, which is approximately oval in shape and whose interior is lined with foam for thermal and noise insulation. In the illustrated embodiment, the thickness of the foam is approximately 10 cm, but in other embodiments of the present invention not shown, it can also have a different thickness.

The jacket 26 surrounds a steel housing of the buffer storage tank 4. Inside the buffer storage tank 4 is the storage fluid 24, the upper and lower condensing coils of the condensing coil assembly 5 described in detail above, and the stainless steel coil 8 arranged inside the upper condensing coil for generating hot water.

The jacket 26 further surrounds the compressor 3 and the evaporator 2, which are connected to each other and to the condenser coils via lines. In the Figure 1 In the illustrated embodiment of the heat pump system 1, the evaporator 2 and the compressor 3 are integrated into one and the same housing formed by the jacket 26 within the buffer storage tank 4. Air surrounds the evaporator 2 and the compressor 3.

Furthermore, a control and/or regulation unit 29 for the heat pump system 1 is provided on one side of the casing 26. In the Figure 1 In the illustrated embodiment, the control unit 29 is integrated into a sheet metal part. The control unit 29 can be used to regulate the temperatures and temperature distribution in the buffer storage tank 4. Furthermore, the water supply and withdrawal to and from the buffer storage tank 4 can be regulated. For this purpose, the control unit 29 is coupled to various sensors, such as temperature sensors, provided in or on the heat pump system 1. The control unit 29 can also include a display unit through which a user of the heat pump system according to the invention can see the current status. 1. It can control various parameters, such as the different temperatures at the inputs and outputs of the buffer storage 2.

Claims (5)

1. Heat pump system (1), wherein an evaporator (2), a compressor (3), at least one buffer tank (4) with a condenser coil device (5) for conducting refrigerant (6), and an expansion valve (7) are arranged successively in a closed circuit, wherein a stainless steel coil (8) for conducting drinking water (9) and radially surrounded by the condenser coil device (5) is arranged in the buffer tank (4); and wherein at least one cold service water inlet (41), a cold drinking water inlet (42) connected to the stainless steel coil (8), an outlet (43) for underfloor heating heating fluid (11b), an outlet (44) for radiator heating heating fluid (12), and a hot drinking water outlet (45) are arranged at the buffer tank (4);
   characterized in that

   the condenser coil device (5) comprises an outer condenser coil (51) and an inner condenser coil (52) running between the outer condenser coil (51) and the stainless steel coil (8), and the heat pump system (1) comprises an insulation ring (14) that runs around a number of coils of the condenser coil device (5) in the buffer tank (4), forming a thermal buffer zone (140) around these coils, wherein a fluid inlet (46) is arranged at the bottom of the thermal buffer zone (140) and a fluid outlet (47) is arranged at the top of the thermal buffer zone (140), and

   an outer jacket (141) of the insulation ring (14) is formed by a section of an internal circumference (40) of the buffer tank (4), and an inner jacket (142) of the insulation ring (14) runs around the stainless steel coil (8), wherein the thermal buffer zone (140) is formed between the outer jacket (141) and the inner jacket (142), and the fluid inlet (46) and the fluid outlet (47) pass through the outer jacket (141).
2. Heat pump system according to claim 1, characterized in that the total length of the outer condenser coil (51) is equal to the total length of the inner condenser coil (52).
3. Heat pump system according to claim 1 or 2, characterized in that the outer condenser coil (51) comprises an upper outer condenser coil (511) and a lower outer condenser coil (512) connected thereto, with a horizontal separation means (13) arranged between them; and the inner condenser coil (52) comprises an upper inner condenser coil (521) and a lower inner condenser coil (522) connected thereto, with the horizontal separation means (13) arranged between them, wherein the stainless steel coil (8) extends continuously from an area below the horizontal separation means (13) into an area above the horizontal separation means (13).
4. Heat pump system according to claim 3, characterized in that the insulation ring (14) is arranged below the horizontal separation means (13).
5. Heat pump system according to any one of the preceding claims, characterized in that the stainless steel coil (8) extends vertically through the entire buffer tank (4).