Water heater with double refrigerant loops

Abstract

The object of the present invention is to provide a heating system with a heat pump, or more generally a water storage conditioning system with a heat pump, in which the heat transfer fluid is divided into at least two distinct, separate refrigerant circuits between which no fluid passes. The two circuits define the same heat exchanger body having a water tank. It is advantageous to employ microchannel technology to fabricate the exchanger that provides higher efficiency and flexibility in designing heat exchange surfaces for multiple loops on the same tank. A heat pump having two different circuits and equal total power for each circuit has less fluid charge and less power required for the compressor compared to a single circuit heat pump. In addition, the method is more robust in terms of failure: holes at any point in the loop cause only partial heat transfer fluid loss.

Description

Technical Field

[0001] It is an object of the present disclosure to provide a storage water heating system having a heat pump and optionally using propane.

[0002] More generally, the present disclosure applies to any heat pump system comprising a heat exchanger in heat exchange relationship with a body to be heated and / or cooled, the body usually consisting of a fluid containing tank. Such systems may be heat pumps for sanitary water heating a sanitary water tank or heat pump air conditioning systems conditioning a technical fluid for supplying radiators, floor air conditioning systems or fan coils. Heating and air conditioning may be incorporated into a single system. Background Art

[0003] The heat pump system comprises a refrigerant circuit in which a heat transfer fluid flows. In this circuit, the heat transfer fluid is pushed by the compressor to the condensing part, after which the condensed heat transfer fluid is guided by a first connection through a throttle to the evaporating part; the heat transfer fluid changes into gaseous form in the evaporating part and returns from the evaporating part to the compressor via a second connection. The condenser and the evaporator form two heat exchangers. In heat pump systems for air conditioning, the circulation direction of the heat transfer fluid can be reversed, and the part of the refrigerant circuit that exchanges heat with the technical fluid tank can be used as both a condenser and an evaporator.

[0004] Since 2014, the EU Fluorinated Greenhouse Gas Regulation UE No.517 / 2014 has set a cap on the amount of fluorinated greenhouse gases placed on the market, thus promoting a phased reduction of fluorinated greenhouse gases; as a result, the market has begun to develop products that can use gases with less environmental impact and refrigerants with a lower global warming potential (e.g. propane R290). On the other hand, propane has no odor and is very flammable.

[0005] Technological advances such as propane heat pumps are designed to reduce risk. In particular, these machines deliver very small amounts of refrigerant in the system.

[0006] In the event of a gas leak, the risk of fire is proportional to the concentration of gas in the air that can ignite (e.g. a spark). Therefore, the amount of gas contained in the circuit is a risk factor. However, there is a limit to how much gas can be reduced in the refrigerant circuit, since reducing gas means reducing the power of the heat pump, with other characteristics being equal.

[0007] Other improvements introduced include a sealed refrigerant circuit with no contact points with the hydraulic circuit and compressor, designed to prevent propane leaks.

[0008] Heat pump water heaters with two heat transfer circuits configured to work in parallel are known, where the dual circuit provides the flexibility to reduce consumption when full nominal power is not required. In the known circuits, two condensers are connected toFigure 1.a Different parts of the storage tank are heat exchanged.

[0009] So-called microchannel heat exchangers are known, which are heat exchange devices used, for example, in air conditioning systems of domestic or commercial vehicles. A microchannel heat exchanger comprises a body in which channels, generally referred to as microchannels, are present. As the name implies, microchannels are characterized in that the cross section of the channels is smaller than that of conventional windings. The purpose of using microchannel technology is to increase the contact area and thus the efficiency of the exchanger. Such exchangers are usually flat and the microchannels are arranged along a straight line when viewed in cross section. Microchannel exchangers are known in which all the microchannels are connected at one end to a single delivery manifold from which the fluid flows out and at the other end to a single return manifold to which the fluid continues to flow. See Figure 1.b .

[0010] Microchannel heat exchangers can be used as condensers in storage heating systems for producing sanitary or technical hot water or as evaporators and condensers in air conditioning systems.

[0011] Thus, there are no solutions for improving the safety of propane heat pumps other than those that provide better loop sealing; and there are no applications of microchannel technology other than those aimed at improving heat exchange. Summary of the invention

[0012] The present disclosure aims to improve the safety of heat pumps with respect to gas leaks. According to the present disclosure, this is achieved by dividing the heat transfer fluid into two independent refrigerant circuits between which it is not possible to mix the heat transfer fluid; the proposed solution enables these independent circuits to define a same heat exchanger made of channels or preferably at least partially microchannels.

[0013] In this document, unlike the prior art, channels (optionally microchannels) are used to form a double cross-circuit heat exchanger, which includes two independent refrigerant circuits and is configured so that there is no fluid connectivity between one refrigerant circuit and the other refrigerant circuit, and the two independent refrigerant circuits share the same heat exchanger body, which is configured so that a heat transfer fluid flows through two paths (hereinafter referred to as "flow paths"). Each flow path belongs to a different refrigerant circuit, and each flow path includes a plurality of channels, which are configured to be arranged in a heat exchange relationship with at least one identical body to be heated or cooled. The channels belonging to the same circuit are interconnected to form a seamless passage between an inlet connection portion located upstream of each flow path and an outlet connection portion located downstream.

[0014] Since at least part of the channels of each flow path are arranged alternately with the channels of another flow path on the heat exchange surface between the exchanger body and the body to be heated or cooled, both circuits exchange heat with the same body.

[0015] Channels of the same flow path can be directly interconnected via a common connecting manifold or via a bypass connection.

[0016] Preferably, the channels are at least partially made by microchannel technology.

[0017] Since two compressors can be utilized whose combined power provides the maximum necessary power, this further allows the power to be regulated at at least two levels and to be reduced when the heating demand is lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The features of the present disclosure will be better highlighted by the following description of a preferred embodiment, according to the patent claims, and are illustrated by way of a non-limiting example only in the attached drawings, in which:

[0019] Figure 1.a A heat pump water heater with two refrigerant circuits according to the prior art is shown;

[0020] Figure 1.b A heat pump water heater with two refrigerant circuits according to the prior art is shown, the two refrigerant circuits having different condenser configurations;

[0021] Figure 1.c A heat pump water heater with two refrigerant circuits and two series-connected water tanks according to the prior art is shown;

[0022] Figure 2 A heat pump water heater with two refrigerant circuits according to a possible embodiment of the present disclosure is shown;

[0023] Figure 3.a shows a front view of a microchannel heat exchanger according to a possible embodiment of the present disclosure;

[0024] Figure 3.b shows a cross-sectional view of a microchannel heat exchanger;

[0025] Figure 3.c It shows that Figure 3.a The heat exchanger shown further incorporates the features shown;

[0026] Figure 4.a A heat pump water heater with two refrigerant circuits is shown in another possible embodiment of the present disclosure;

[0027] Figure 4.bA portion of a heat pump system having two reservoirs and two refrigerant circuits is shown in another possible embodiment of the present disclosure;

[0028] Figure 4.c shows a possible heating diagram of a dual-tank water heater according to a possible embodiment of the present disclosure, the dual-tank water heater including two heat pumps and two refrigerant circuits; and

[0029] Figure 5 A top view of a portion of a heat pump system having two reservoirs and two refrigerant circuits in another possible embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0030] The features of the preferred variants of the present disclosure are now described using the reference numerals contained in the drawings. It should be noted that although the above drawings are schematic, they reproduce the elements in the present disclosure according to the proportions between the spatial dimensions and directions of the elements compatible with possible embodiments.

[0031] It should also be noted that any dimensional and spatial terms (such as "lower", "upper", "inner", "outer", "front", "back", etc.) refer to the positions of elements as shown in the accompanying drawings, and there is no intention of any limitation regarding possible operating positions.

[0032] See also Figure 2 and / or Figure 4.a The heat pump system 1 includes two independent refrigerant circuits 5A, 5B, and is configured such that there is no fluid connectivity between one refrigerant circuit 5A, 5B and the other refrigerant circuit 5B, 5A. In the order of fluid flow, each refrigerant circuit includes a compressor 50A, 50B, a first connecting portion 51A, 51B, at least one condensing portion 52A, 52B, 521A, 521B, at least one second connecting portion 53A, 53B, and an evaporating portion 54A, 54B.

[0033] According to the present disclosure, two refrigerant circuits 5A, 5B share the same heat exchanger body 4, suitable for cooperation and heat exchange with the body to be heated or cooled 3, 31, 32. The heat exchanger body 4 is constructed so that a heat transfer fluid flows through at least two flow paths 52A, 52B, 521A, 521B, each belonging to a corresponding refrigerant circuit 5A, 5B. Generally, the heat exchanger 4 can act as both a condenser and an evaporator, depending on the circulation direction of the fluid; as is known, the circulation direction of the fluid can be reversed. A heat exchanger body 4 with microchannel technology and a double cross circuit distribution is described below.

[0034] As a non-limiting example, to simplify the description, hereinafter, see Figure 2 and Figure 4.a , the heat pump system 1 is described as being configured to heat a water tank 3, 31, 32, for example a domestic water or technical water reservoir 3, 31, 32 for air conditioning. In this case, the heat exchanger 4 is a condenser.

[0035] like Figure 2 and / or Figure 4.a and Figure 4.b As shown, at least two parts 52A, 52B, 521A, 521B can be arranged inside the heat exchanger 4, suitable for heat exchange with the body 3, 31, 32 to be heated or cooled; therefore, the condensation part includes and defines at least one flow path 52A, 52B, 521A, 521B, which is constructed to exchange heat with the body 3, 31, 32.

[0036] See also Figure 3.c , the heat exchanger 4 includes two flow paths, the first flow path 52A, 521A includes a plurality of channels 4A11, 4A12, 4A21, ..., 4Aij, and the second flow path 52B, 521B includes a plurality of channels 4B11, 4B12, 4B21, ..., 4Bij. The channels belonging to the same circuit are interconnected to form a seamless passage between the inlet connection part 51A, 51B located upstream of each flow path 52A, 52B, 521A, 521B and the outlet connection part 53A, 53B located downstream. On the heat exchange surface between the heat exchanger body 4 and the body 3, 31, 32 to be heated or cooled, at least a part of the channels of each flow path 52A, 52B, 521A, 521B are alternately arranged with the channels of another flow path 52B, 52A, 521B, 521A.

[0037] Preferably, the channels 4A11, 4A12, 4A21, ..., 4Aij, 4B11, 4B12, 4B21, ..., 4Bij of the same circuit 5A, 5B are associated in one or more groups 4A1, 4A2, ..., 4Aj, 4B1, 4B2, ..., 4Bj, see Figure 3.a According to a possible embodiment, the channels 4A11, 4A12, 4A21, 4Aij, 4B11, 4B12, 4B21, ..., 4Bij in the groups 4A1, 4A2, ..., 4Aj, 4B1, 4B2, ..., 4Bj are arranged side by side with each other and are in thermal contact with the body 3, 31, 32 to be heated or cooled.

[0038] Preferably, each flow path 52A, 521A, 52B, 521B comprises at least one inlet manifold 7A1, 7A2, ..., 7Aj and 7B1, 7B2, 7Bj and at least one outlet manifold 8A1, 8A2, 8Aj and 8B1, 8B2, ..., 8Bj, respectively. More precisely, each group 4A1, 4A2, ..., 4Aj, 4B1, 4B2, ..., 4Bj is associated with a common input manifold 7A1, 7A2, ..., 7Aj, 7B1, 7B2, ..., 7Bj and a common output manifold 8A1, 8A2, ..., 8Aj, 8B1, 8B2, ..., 8Bj.

[0039] If the fluid flowing out of the first of two groups 4B1 and 4B2, 4A1, 4A2 and 4A3 belonging to the same flow path 52A, 52B is introduced into the second of the two groups via a direct connection or substantial coincidence between the outlet manifold 8B1, 8A2 of the first group and the inlet manifold 7B2, 7A3 of the second group, the two groups are continuous.

[0040] According to one possible embodiment, the channels 4A11, 4A12, 4A21, ..., 4Aij, 4B11, 4B12, 4B21, ..., 4Bij in the groups 4A1, 4A2, ..., 4Aj, 4B1, 4B2, ..., 4Bj are arranged side by side and are in thermal contact with the body 3, 31, 32 to be heated or cooled.

[0041] According to one possible embodiment, the exchanger body 4 includes a first head-end manifold 10 and a second head-end manifold 11, the first head-end manifold including a plurality of manifolds 7A1, 7B1, 8B2, 8A2, ..., 7Aj, ..., 7Bj, 7Bj and partitions 10.1, 10.k suitable for achieving separation between the manifolds, and the second head-end manifold includes a plurality of manifolds 8A1, 8B1, 7B2, 7A2, ..., 8Aj, ..., 8Bj and partitions 11.1, 11.h.

[0042] Preferably, all the channels 4A11 , 4A12 , 4A21 , . . . , 4Aij , 4B11 , 4B12 , 4B21 , . . . , 4Bij are arranged with both ends thereof aligned along the extending direction of the head-end manifolds 10 , 11 .

[0043] Two groups associated with the same flow path 52A, 52B may be continuous and adjacent, such as in the case of groups 4A2, 4A3 or 4B1, 4B2; in this case, the two groups are preferably connected by an outlet manifold 8A2 or 8B1, which makes the first group 4A2 or 4B1 fluidly connected to the second group 4A3 or 4B2 respectively. In other words, each of the above-mentioned output manifolds 8A2 or 8B1 directly serves as an output sleeve of the first group and directly serves as an input sleeve 7A3 or 7B2 of the second group. Since there is no corresponding partition, the output sleeve 8A2 or 8B1 and the input sleeve 7A3 or 7B2 are directly connected to each other.

[0044] If two consecutive groups along the same loop (such as groups 4A1, 4A2 or 4B2, 4B3) are not adjacent, the two groups are connected by suitable connectors or bypasses 9A or 9B, respectively, which are constructed to connect the output sleeve of the first group 8A1 or 8B2 to the inlet sleeve of the second group 7A2 or 7B3, respectively.

[0045] like Figure 3.a In the embodiment example shown in FIG. 5 , each circuit 5A, 5B has three groups 4A1, 4A2, 4A3, 4B1, 4B2, 4B3, a fitting with external connections 9A, 9B and a direct connection between the outlet manifold 8B1, 8A2 and the subsequent inlet manifold 7B2, 7A3. For each circuit 5A, 5B, the number of groups may be other than three and the number does not have to be the same.

[0046] According to a preferred embodiment, the channels 4A11, 4A12, 4A21, ..., 4Aij, 4B11, 4B12, 4B21, ..., 4Bij are made by microchannel technology.

[0047] The channels 4A11, 4A12, 4A21, ..., 4Aij, and 4B11, 4B12, 4B21, ..., 4Bij may be constructed so that the distribution of the heat exchange areas of the different circuits 5A, 5B is not uniform for the entire area of ​​the exchanger 4, but the circuits 5A, 5B are mainly used for heat exchange with one area. In this case, the first refrigerant circuit 5A, 5B includes a greater number of microchannels in a portion of a single exchanger body than the second refrigerant circuit 5B, 5A.

[0048] This measure allows controlling the stratification of the temperature in a heat pump system that exchanges heat with a vertical low-input storage 3, 31, 32. For example, the first refrigerant circuit may include a greater number of microchannels in the highest part of the storage 3, 31, 32 than the second refrigerant circuit. In this case, it is preferred that the refrigerant circuit having a greater number of channels in the highest part of the storage 3, 31, 32 is dimensioned to have a higher power than the other refrigerant circuit.

[0049] Preferably, the fluid is passed in a top-to-bottom direction (ie upstream relative to the movement of the water in the tank during pumping).

[0050] Furthermore, if it is desired to heat only a limited amount of water and not the entire tank, it is possible to activate only the compressor of the refrigerant circuit which exchanges heat mainly with the highest part of the tank.

[0051] In general, there may be more than two different independent circuits 5A, 5B defining the same heat exchanger body 4 configured with microchannels 4A11, 4A12, 4A21, ..., 4Aij, 4B11, 4B12, 4B21, ..., 4Bij and the structure shown. The heat exchanger body 4 may be a condenser in the case of a heat pump for heating, or an evaporator in the case of a heat pump for cooling. According to a possible embodiment, both the evaporator and the condenser may be a single exchanger body made of microchannels configured to define two or more independent circuits, without a connection point between one circuit and another, so that mixing of the heat transfer fluid is not possible.

[0052] like Figure 2 In the case of sanitary water or technical water heaters, the heat pump can be configured to heat or cool the water tanks 3 , 31 , 32 .

[0053] Water heaters for sanitary or technical water are known which have reservoirs distributed over two water tanks. This feature is used to obtain dimensions more suitable for specific manufacturing needs. According to a possible embodiment, the same heat exchanger body 4 (for example, condenser body 4) with microchannel technology and double cross-circuit distribution can be made to maximize the contact surface with two side-by-side water tanks 31, 32, such as Figure 4.a and Figure 4.b In this case, the heat exchanger body in contact with the water tank can advantageously be provided with thermal bridges 44 which improve the heat exchange along the slots formed in the contact line between the two water tanks and the exchanger 4. These thermal bridges 44 can be made of any thermally conductive material.

[0054] According to a possible embodiment, in a dual-tank water heater, the channels in the heat exchanger body 4 belonging to the first refrigerant circuit 5A, 5B mainly exchange heat with the first water tank 31, 32, that is, at least one of the two refrigerant circuits exchanges more heat with one water tank than with the other water tank. The heat pump system and the specific dual cross heat exchanger can be configured so that each water tank 31, 32 can exchange heat in the same amount or in different amounts. In either case, each water tank 31, 32 can exchange heat in different proportions relative to each of the two refrigerant circuits 5A, 5B. The heat exchange rate of the refrigerant circuit 5A, 5B between the two water tanks 31, 32 can be changed, for example, by different heat exchange areas of the refrigerant circuit 5A, 5B with the first water tank 31, 32 (rather than the second water tank 32, 31) or by bringing the initial part of the circuit into contact with the first water tank 31, 32 (rather than the second water tank 32, 31). The initial part of the circuit is the part where the fluid flows which has the highest absolute temperature difference with the internal temperature of the tank.

[0055] As an example, two water tanks can be connected in series; the first water tank 31 can be an input water tank connected to a cold water pipe, and the second water tank 32 can be an output water tank connected to a hot water output pipe or a faucet; the input water tank 31 is connected in series with the output water tank 32 so that water from the cold water pipe can flow from the input water tank 31 to the output water tank 32. The first refrigerant circuit 5A can be configured to exchange less than 50% of its heat on average with the first water tank 31 and the remaining heat with the second water tank 32. For example, the first circuit can be configured to exchange 30% or 20% of the heat to the first water tank and the remaining heat to the second (output) water tank. It should be understood by experts in the field that the heat exchange depends on the relative temperature difference between the refrigerant circuit 5A, 5B and the water tanks 3, 31, 32; therefore, the expression "configured to exchange less than 50% of its heat on average with the first water tank 31 and the remaining heat with the second water tank 32" means that the relative percentages of heat exchange refer to the situation where the water tanks 31, 32 have substantially the same temperature.

[0056] Advantageously, one tank of water at a set temperature is provided in a given heating time, rather than two tanks of water at the same set temperature in a much longer heating time. This means that one user only has to wait a shorter time for a shower, while the second user has to wait the entire dual tank heating time for a second shower volume.

[0057] According to one aspect of the present disclosure, the first refrigerant circuit 5A is configured to exchange more than 50% of its heat with the output water tank 32 and the remaining heat with the input water tank 31. This allows more than half of the power of the first heat pump A to be concentrated on the output water tank, thereby shortening the time to reach the set temperature in the output water tank. In this case, the second refrigerant circuit 5B can be configured to perform different percentages of heat exchange with the two water tanks, for example, more than 50% of heat exchange with the input water tank.

[0058] According to one aspect of the present disclosure, a method for heating water using a heat pump system 2 (including a dual cross-circuit 5A, 5B and two water tanks 31, 32) includes the following steps: turning on a first heat pump A corresponding to a refrigerant circuit 5A, wherein the refrigerant circuit 5A is configured to exchange more than 50% of its heat with an output water tank 32 until the output water tank reaches a set temperature; then, turning off the first heat pump A and turning on a second heat pump B corresponding to a refrigerant circuit 5B, wherein the refrigerant circuit 5B is configured to exchange more than 50% of its heat with an input water tank 31 until the input water tank 31 reaches a set temperature.

[0059] The system has the following advantages: if both heat pumps are on, each tank can fully exchange heat with both heating circuits 5A, 5B; if only one heat pump is on, a preferred tank can be heated preferentially. By appropriate design of the dual crossover refrigerant circuits, the heating rate of the output tank can be increased relative to the heating rate of the input tank. It should be noted that once the output tank 32 approaches the set temperature and the input tank 31 eventually falls below the set temperature, the amount of heat exchange with the input tank 31 will naturally increase until the input tank 31 reaches the set temperature. Therefore, the two refrigerant circuits 5A, 5B can be constructed to exchange more than 50% of their heat with the output tank 32 when the temperatures of the two tanks are the same.

[0060] Alternatively, a possible embodiment of the present disclosure is a water tank water heating heat pump system, comprising two heat pumps and two water tanks connected in series, wherein the first water tank is configured as an input water tank for cold water, the second water tank is configured as an output water tank for hot water, each heat pump comprises a refrigerant circuit, the refrigerant circuits are configured to perform heat exchange with the water tanks, and at least one refrigerant circuit is configured to perform heat exchange with the two water tanks, the pair of refrigerant circuits are configured to heat the output water tank at a higher rate than heating the input water tank, at least until the output water tank reaches a set temperature. In the case of a water heater, the two heat exchange circuits are two condenser circuits.

[0061] For the double water tank form in series, the two refrigerant circuits can (but not necessarily) have at least a portion of the channels of each flow path alternately arranged with the channels of the other flow path, that is, the two refrigerant circuits do not have to be double cross-type. In the case where the refrigerant circuit is not double cross-type, the advantages of this embodiment are simple structure and the ability to transfer more heat to the output water tank, thereby obtaining hot water for a shower in a shorter time than the time required to heat the entire amount of water (two water tanks).

[0062] Figure 4.c A possible schematic diagram of the heating time for each tank is shown. This effect can be achieved when at least one of the condenser heat exchangers is configured to exchange more heat with the output tank. When the output tank is close to the maximum temperature that the heat pump can heat it to, more heat will be exchanged with the input tank due to the higher temperature difference between the input tank and either of the two condenser heat exchangers.

[0063] Once the output tank is heated, less heat will be exchanged with the output tank and more heat will be exchanged with the input tank. One possible implementation of the dual tank format in series is that each refrigerant circuit is configured so that the percentage of heat exchanged with each tank (both tanks are at the same initial temperature) is different between the two circuits, i.e. one circuit exchanges more heat with the input tank than the other circuit.

[0064] Therefore, one aspect of the present disclosure is a method of heating a dual-tank water heater, the dual-tank water heater comprising: two water tanks connected in series, wherein the first water tank is configured as an input water tank for cold water, and the second water tank is configured as an output water tank for hot water; and two heat pumps, wherein each heat pump comprises a condenser-type heat exchanger configured to perform heat exchange with the water tanks, at least one condenser-type heat exchanger is configured to perform heat exchange with the two water tanks, and at least one condenser-type heat exchanger is configured to exchange more heat with the output water tank than with the input water tank. The method comprises the following steps:

[0065] - starting a first heat pump and keeping it running, the first heat pump comprising a condenser heat exchanger configured to exchange more heat with the output water tank than with the input water tank, until the water in the output water tank reaches a set temperature;

[0066] - optionally shutting down the first heat pump and keeping at least one heat pump running, the heat pump comprising a condenser heat exchanger configured to exchange heat with an input water tank until the water in the input water tank reaches a set temperature.

[0067] Typically, the microchannel heat exchanger body 4 with a double cross-circuit distribution can cooperate with a cylindrical (but not limited to cylindrical) body 3, 31, 32 for heat exchange.

[0068] One aspect of the present disclosure relates to a method for realizing a heat exchanger body 4, wherein the channels are characterized by a double cross-circuit distribution. The method comprises:

[0069] - a channel extrusion step, preferably forming a cylindrical profile;

[0070] - a step of manufacturing the head-end manifolds 10, 11 by extrusion and / or stretch forming;

[0071] - a step of assembling the channels and the head end manifolds 10, 11; and

[0072] - A step of placing a solder suitable for soldering or welding and performing the soldering or welding in a furnace by a heating step. Preferably, any stretch forming process of the head end manifold uses aluminum.

[0073] This process guarantees versatility in the variety of designs that can be made in terms of the number, size and shape of the channel sections and the dimensions of the exchanger.

Claims

1. A heat pump system (1, 2) with a double cross-circuit, comprising two independent refrigerant circuits (5A, 5B), one refrigerant circuit (5A, 5B) having no fluid connectivity with the other refrigerant circuit (5B, 5A), wherein: - two refrigerant circuits (5A, 5B) share the same heat exchanger body (4) associated with the body to be heated or cooled (3, 31, 32), the heat exchanger body (4) being configured to allow a heat transfer fluid to flow through two flow paths (52A, 52B, 521A, 521B), each flow path belonging to one of the two refrigerant circuits (5A, 5B), each flow path (52A, 52B, 521A, 521B) comprising a plurality of channels (4A11, 4A12, 4A21, ..., 4Aij, 4B11, 4B12, 4B21, ..., 4Bij), the channels being interconnected to form a seamless passage between an inlet connection portion (51A, 51B) located upstream of each flow path (52A, 52B, 521A, 521B) and an outlet connection portion (53A, 53B) located downstream, - and wherein, on the heat exchange surface between the heat exchanger body (4) and the body to be heated or cooled (3, 31, 32), at least a portion of the channels of each flow path (52A, 52B, 521A, 521B) alternates with the channels of another flow path (52B, 52A, 521B, 521A), It is characterized in that the channels (4A11, 4A12, 4A21, ..., 4Aij, 4B11, 4B12, 4B21, ..., 4Bij) of the same circuit (5A, 5B) are associated in one or more parallel channel groups (4A1, 4A2, ..., 4Aj, 4B1, 4B2, ..., 4B) and are in a heat exchange relationship with the body to be heated or cooled (3, 31, 32).

2. The heat pump system (1, 2) according to the above claims, wherein each flow path (52A, 521A, 52B, 521B) comprises a common inlet manifold (7A1, 7A2, 7Aj, 7B1, 7B2, ..., 7Bj) and a common outlet manifold (8A1, 8A2, ..., 8Aj, 8B1, 8B2, ..., 8Bj) associated with each group (4A1, 4A2, ..., 4Aj, 4B1, 4B2, ..., 4Bj), and the same flow path (52A , 52B, 521A, 521B) are connected to each other by an outlet manifold (8A2 or 8B2), and the outlet manifold directly serves as the inlet manifold (7A3 or 7B2) of the consecutive group, and two consecutive but non-adjacent groups are connected by a suitable connector or bypass (9A, 9B), and the connector or bypass is constructed to connect the outlet manifold of the first group (8A1, 8B2) with the inlet manifold of the second group (7A2, 7B3), respectively.

3. A heat pump system (1, 2) according to any one of the above claims, wherein the channels (4A11, 4A12, 4A21, ..., 4Aij, 4B11, 4B12, 4B21, ..., 4Bij) are at least partially microchannels (4A11, 4A12, 4A21, ..., 4Aij, 4B11, 4B12, 4B21, ..., 4Bij).

4. The heat pump system (1, 2) according to any one of the preceding claims, comprising propane gas in at least one of the two refrigerant circuits (5A, 5B).

5. A water storage water heater (1, 2), comprising a heat pump system according to any of the above claims, wherein the heat exchanger body (4) comprises the condensing parts (52A, 52B, 521A, 521B) of the two refrigerant circuits (5A, 5B), and the body to be heated or cooled (3, 31, 32) comprises a heat transfer fluid or household fluid storage tank (3, 31, 32).

6. The storage water heater (1, 2) according to claim 5, wherein the storage tank (3, 31, 32) is configured to be vertically arranged, has a lower inlet and an upper outlet, and relative to the second refrigerant circuit (5B, 5A), the first refrigerant circuit (5A, 5B) includes a greater number of channels in the heat exchanger body (4) above the storage tank (3, 31, 32).

7. The water storage water heater (2) according to claim 5 or 6, wherein the body (3, 31, 32) to be heated or cooled comprises two water tanks (31, 32).

8. The storage water heater (2) according to claim 7, comprising at least one thermal bridge (44) located in the space defined between the common heat exchanger body (4) and the joining line between the two water tanks (31, 32).

9. The storage water heater (2) according to any one of claims 7 or 8, wherein the channel of the heat exchanger body (4) belonging to the first refrigerant circuit (5A, 5B) is constructed so that more heat is exchanged with the first water tank (31, 32) than with the second water tank (32, 31).

10. The storage water heater (2) according to any one of claims 7 or 8, wherein the channels of the heat exchanger body (4) belonging to at least one of the refrigerant circuits (5A, 5B) are constructed so that more heat is exchanged with the output water tank (32) than with the input water tank (31) when the two water tanks have substantially the same temperature.

11. A method for heating a double-tank water heater, the double-tank water heater comprising: Two water tanks connected in series, wherein the first water tank is configured as an input water tank for cold water and the second water tank is configured as an output water tank for hot water; and two heat pumps, each heat pump comprising a condenser heat exchanger, the condenser heat exchanger being configured to perform heat exchange with the water tank, at least one condenser heat exchanger being configured to perform heat exchange with two water tanks, and at least one condenser heat exchanger being configured to exchange more heat with the output water tank than with the input water tank; the method comprising the following steps: - starting a first heat pump and keeping it running, the first heat pump comprising a condenser heat exchanger configured to exchange more heat with the output water tank than with the input water tank, until the water in the output water tank reaches a set temperature; - optionally shutting down said first heat pump, and - keeping at least one of the heat pumps in operation, the heat pump comprising a condenser heat exchanger configured to exchange heat with the input water tank until the water in the input water tank reaches a set temperature.

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