EP4617570A1

EP4617570A1 - Hydraulic separator

Info

Publication number: EP4617570A1
Application number: EP25162567.9A
Authority: EP
Inventors: Alessandro Bonolis; Emidio TIBERI
Original assignee: Cordivari SRL
Current assignee: Cordivari SRL
Priority date: 2024-03-11
Filing date: 2025-03-10
Publication date: 2025-09-17

Abstract

The present invention relates to a hydraulic separator (1) comprising a closed-vessel storage system (10) for the storage of a heat transfer fluid and for the hydraulic separation between at least two hydraulic circuits (20, 40; 30, 50) wherein said heat transfer fluid flows, said storage system (10) extending along a vertical axis (y) and comprising at least two first side connections (21) in correspondence with a first side thereof with respect to said vertical axis (y) and at least two second side connections (22) arranged opposite said at least two first side connections (21) with respect to said vertical axis (y), said first and second side connections (21, 22) being oriented parallel to a horizontal axis (x) perpendicular to said vertical axis (y). The two first side connections (21, 22) are adapted to be connected to a first hydraulic circuit (20, 40) and said two second side connections (22) are adapted to be connected to a second hydraulic circuit (30; 50) for the transfer or supply of said heat transfer fluid between at least said two hydraulic circuits (20, 30; 40, 50). Said storage system (10) has a capacity of at least 40 litres and comprises at least two closed-vessel tanks (2), each tank (2) having a body with axial symmetry along a longitudinal axis (t) parallel to said horizontal axis (x), at least two tanks (2), each of which providing a first (21) and a second (22) side connection at a respective end of the body along the respective longitudinal axis (t).

Said at least two tanks (2) are in fluid connection with each other in parallel through at least one vertical connection (23) parallel to said vertical axis (y), wherein said hydraulic separator (1) comprises an insulating layer (3) made of thermally insulating material, and a containment casing (11) within which said storage system (10) is arranged surrounded by said insulating layer (3).

Description

The present invention relates to a hydraulic separator.
More precisely, the present invention finds application in the field of thermohydraulics and specifically of pressurised tanks (or "closed-vessel tanks") adapted to contain a heat transfer fluid for heat exchange (heating or cooling).
Furthermore, the present invention finds a particularly advantageous application in systems providing a heat pump thermal generator, but it can also be used in systems with generators of traditional type (such as gas boilers, biomass boilers, cogeneration boilers, etc.).
In the state of the art, inertial storage systems, also referred to as thermal inertial storage or thermal flywheel, are known. These systems provide a closed-vessel storage that increases the volume of fluid in the hydraulic system, increasing its thermal inertia, i.e. the thermal energy stored in the fluid contained in the system.
In essence, a volume of fluid is added to the system and connected to the hydraulic circuits. This fluid reserve is "charged" with the thermal energy produced by the thermal generators and is used when necessary either by the secondary distribution circuit (heating or cooling terminals) or by the generators themselves (for example, for the defrosting operations of heat pumps).
Within the tank, the heated fluid stratifies. Thermal stratification in a tank means the creation of zones, in fluid connection, with differentiated temperatures. Typically, these "layers" are identified by an increasing temperature from the bottom to the top, according to the physical characteristics of the fluids that cause the warmer and lighter fluid to be positioned higher than the colder and heavier fluid, so that natural convection movements do not occur that could result in the mixing of fluid zones. It is particularly advantageous in heating/cooling systems because it increases the efficiency of the latest generation generators (condensing boilers, heat pumps), reducing the average temperature of the flywheel.
Further in the state of the art, storage systems acting as hydraulic separators are known. The hydraulic separator provides a closed-vessel storage used in hydraulic systems which, in addition to the function of increasing the volume of liquid in the hydraulic system, has the function of hydraulically separating at least two hydraulic circuits (typically that/those of the generator(s) from that/those of the user terminal(s)), thereby allowing the transfer of the same heat transfer fluid from one or more hydraulic circuits (primary circuits) to one or more hydraulic circuits (secondary circuits) to exchange heat, and enabling the independent management of the fluid flow rate of each hydraulic circuit, through a circulator (or other means/system of circulation), so that the circuits can be hydraulically sized independently. The separators have multiple fluid inlet and outlet connections to which two or more circuits are connected, each of which is linked to the separator with an inlet duct and an outlet duct.
Therefore, the hydraulic separator has the aim of transferring the flow of thermal energy through exchanges of fluid entering from the primary circuits (delivery from the generators) mainly to the secondary circuits (user terminals) and, vice versa (as a consequence of the laws of the closed-vessel circuits), the fluid flow entering from the secondary circuits (returning from the user terminals) must be mainly transferred to the primary circuits (generators).
In addition, in a hydraulic separator the circulation of each individual circuit must be allowed, in other words, the fluid flow between the inlet from and the outlet to each individual circuit must be allowed (as shown in the exemplifying diagrams in Figure 1).
The hydraulic separators are realised with features and technical solutions that achieve and promote the functions of thermal inertial storage and of hydraulic separation in hydraulic circuits.
To achieve the function of transferring the thermal energy of the fluid entering from the primary circuits mainly to the secondary circuits (and vice versa), the hydraulic separators are realised to direct the path of the fluid within them.
This can be achieved by creating different paths within them, each with different pressure drops (pressure difference) for the fluid between the inlet and outlet of the tank.
In particular, an optimal sizing of the hydraulic separator that makes the pressure drop between the inlet from and the outlet to the same circuit (delivery and return) negligible, compared to the overall pressure drops of each circuit, not only allows for the sizing and independent management of the circuits linked thereto, but also helps to avoid oversizing the system components (typically the circulators) and wasting operating energy.
One of the most common state-of-the-art technical solutions for achieving and promoting the functions of thermal inertial storage and hydraulic separation of the hydraulic separators, is to realise them with geometric shapes such that the pressure drops (pressure difference or d_p) in the "by-pass" circulation between the inlet from and the outlet to the same circuit (delivery and return) are greater than the pressure drops (pressure difference or d_p) between the inlet from a primary circuit and the outlet to a secondary circuit and vice versa (between the inlet from a secondary circuit and the outlet to a primary circuit), to prevent the "by-pass" circulation between the inlet and outlet of the same circuit from becoming dominant, as this would hinder an adequate energy transfer with the remaining circuits linked to the separator.
A typical example of this geometric shape to achieve this behaviour of the fluid is the so-called "3 diameters" empirical method, for which an example of an embodiment is shown in Figure 2. In this example, the tank has a cylindrical shape with the main axis arranged vertically with respect to the ground and having the cross-section with a 3d diameter equal to three times the value of the diameters d of the horizontal connections linked to the separator and spacing the connections by the same measure 3d from the upper and lower ends of the cylindrical tank and by twice that measure, therefore 6d, between the connections.
However, such known art hydraulic separators typically have relatively large dimensions, making them unsuitable for domestic applications. In fact, for a tank of about 50 litres, such separators generally have a height of about 1000÷1100 mm and a depth of about 350÷380 mm. For tanks of larger volumes, an even greater depth is required, for example for a cylindrical tank of 100 litres, the minimum depth is about 380÷400 mm. Therefore, these dimensions do not meet the compactness requirements of domestic users.
In order to solve the problems described, the patent document EP 1 760 406 B1 describes a compact manifold acting as a hydraulic separator, to which a primary circuit and a multiplicity of secondary circuits are connected. In order to reduce the dimensions, this manifold provides a plurality of ducts obtained with calibrated partitions and holes to allow the hydraulic disjunction (separation) between the circuits. However, this type of solution requires costly production processes due to its manufacturing complexity (internal processing, non-automated procedures, etc.).
Another state-of-the-art solution used to achieve and promote the hydraulic separation function of the hydraulic separators, and to avoid the "by-pass" circulation, is to insert into the flow path, between the inlet and outlet of the same circuit, obstructive elements, such as channels, partitions or other elements that introduce pressure drops into the flow passing through them, while keeping the fluid path as clear as possible between the inlet from a primary circuit and the outlet to a secondary circuit and vice versa; as shown for example in patent documents EP 1 612 489 B1 or WO 2020/240370 A1 .
The use of elements interposed in the fluid path is typical of the operation of hydraulic separators and distinguishes them from other applications, wherein such elements are inserted in the preferential path of the fluid, such as the exchange surfaces within heat exchangers, and introduce pressure drops that disadvantage the hydraulic separator function.
Other state-of-the-art solutions, aimed at reducing the dimensions, provide the realisation of shapes that differ from those with axial symmetry along a vertical axis, such as the parallelepiped shape.
These embodiments, in addition to issues related to the complexity of the production processes (such as internal structural reinforcements, non-automated procedures, etc.), involve limitations in the product's features and performance, such as difficulties in achieving stratification, which can only be achieved through calibrated partitions and holes, or difficulties in achieving the operating pressures typical of hydraulic circuits, which results in a greater use of materials (high thicknesses) and low maximum operating pressure limits (as an indication, not higher than 3 bar).
The aim of the present invention is to obtain a hydraulic separator having compact dimensions while maintaining an optimal containment capacity, therefore, at least 40÷50 litres.
Furthermore, the aim of the present invention is to obtain a solution that does not require complex and costly realisation processes.
Another aim of the present invention is that the tank achieves optimal stratification of the temperatures of the contained fluid, in fluid connection with multiple distinct hydraulic circuits.
In addition, the aim of the present invention is to be able to work at optimal operating pressures of the contained fluid (as an indication, from 3 bar to 10 bar).
The object of the present invention is a hydraulic separator comprising a closed-vessel storage system for the storage of a heat transfer fluid, said storage system having a capacity of at least 40 litres and extending along a vertical axis and comprising at least two first side connections in correspondence with a first side thereof with respect to said vertical axis and at least two second side connections arranged opposite said at least two first side connections with respect to said vertical axis, said first and second side connections being oriented parallel to a horizontal axis perpendicular to said vertical axis, said side connections being adapted to be connected to hydraulic circuits for the transfer or supply of said heat transfer fluid, wherein said storage system comprises at least two closed-vessel tanks, each tank having a body with axial symmetry along a longitudinal axis parallel to said horizontal axis, at least two tanks providing said first and/or second side connection in correspondence with a respective end of the body along the respective longitudinal axis, said at least two tanks being in fluid connection with each other in parallel through at least one vertical connection parallel to said axis vertical, wherein said hydraulic separator comprises an insulating layer made of thermally insulating material, and a containment casing within which said storage system is arranged surrounded by said insulating layer.
In addition, an object of the present invention is a hydraulic separator comprising a closed-vessel storage system for the storage of a heat transfer fluid and for the hydraulic separation between at least two hydraulic circuits wherein said heat transfer fluid flows, said storage system extending along a vertical axis and comprising at least two first side connections in correspondence with a first side thereof with respect to said vertical axis and at least two second side connections arranged opposite said at least two first side connections with respect to said vertical axis, said first and second side connections being oriented parallel to a horizontal axis perpendicular to said vertical axis, said two first side connections being adapted to be connected to a first hydraulic circuit and said two second side connections being adapted to be connected to a second hydraulic circuit for the transfer or supply of said heat transfer fluid between at least said two hydraulic circuits, wherein said hydraulic separator is characterised in that said storage system has a capacity of at least 40 litres and comprises at least two closed-vessel tanks, each tank having a body with axial symmetry along a longitudinal axis parallel to said horizontal axis, at least two tanks each of which providing a first and a second side connection at a respective end of the body along the respective longitudinal axis, said at least two tanks being in fluid connection with each other in parallel through at least one vertical connection parallel to said vertical axis, wherein said hydraulic separator comprises an insulating layer made of thermally insulating material, and a containment casing within which said storage system is arranged surrounded by said insulating layer.
In particular, according to the invention, the casing can have an overall size wherein the height along the vertical axis is less than/equal to 1100 mm, the width along the horizontal axis is less than/equal to 600 mm, and the depth along a transverse axis perpendicular to the horizontal and vertical axes is less than 300 mm.
Moreover, according to the invention, the shape of the body of one or each tank can be partially cylindrical, optionally the end portions of each tank may have a semi-elliptical or torospherical section.
Further according to the invention, each tank can have the same capacity, the same shape, and the same dimensional footprint, such that the respective side connections are aligned on the same axis parallel to the vertical axis and the respective longitudinal axes are coplanar on a vertical plane comprising the vertical axis and the horizontal axis.
Alternatively, according to the invention, said storage system can provide at least three tanks, wherein the at least one vertical connection between two first tanks can be arranged on the side opposite the at least one vertical connection between two other tanks with respect to said vertical axis.
Or, according to the invention, each tank can have a smaller capacity compared to the tank arranged below it along said vertical axis.
In addition, according to the invention, each tank can have a body of equal width along the longitudinal axis, wherein the body of each tank can have a diameter smaller than the tank arranged below it.
Furthermore according to the invention, the body of each tank can be made of a material compatible with containing pressurised fluids at high temperatures (up to 95°C), for example metal, preferably carbon steel or stainless steel or technopolymer, and wherein the vertical connections can be pipes made of the same material as the body of the tanks and can be joined to the body of the tanks to which they are connected by welding.
Further according to the invention, each tank can be able to operate at an operating pressure even higher than 3 bar.
Furthermore, according to the invention, the area of the passage section of the at least one vertical connection between two tanks can be at least twice the area of the passage section of the largest side connection of said two tanks.
Moreover, according to the invention, the insulating layer can be based on polyurethane foam.
In addition, each tank can be free of obstructive elements within it, for example internal partitions and/or channels.
Preferably according to the invention, the diameter of the passage section of the side connections of each tank and of the at least one vertical connection between at least two tanks can be dimensioned such that, during use, when at least said two first side connections are connected to a first hydraulic circuit and the second side connections are connected to a second hydraulic circuit, the flow of the heat transfer fluid flowing between said hydraulic circuits through said connections has a pressure drop that is smaller in the passage between the side connections of the same tank compared to the pressure drop in the passage between the first side connections of two tanks through the at least one vertical connection.
In addition, the object of the present invention is a system comprising a hydraulic separator as described and at least two hydraulic circuits in fluid connection with said side connections of said hydraulic separator, wherein at least one hydraulic circuit is in fluid connection with a heat generator, in particular a boiler or a heat pump, and wherein at least one hydraulic circuit is in fluid connection with a heating terminal system, in particular radiators or fan coil units or a floor heating system.
In addition, the object of the present invention is a system comprising a hydraulic separator as described and at least two hydraulic circuits in fluid connection with said side connections of said hydraulic separator for the flow of said heat-transfer fluid, wherein at least one first hydraulic circuit is in fluid connection with a heat generator, in particular a boiler or a heat pump, and at least two first side connections of said hydraulic separator and wherein at least one second hydraulic circuit is in fluid connection with a heating terminal system, in particular radiators or fan coil units or floor heating system, and at least two second side connections of said hydraulic separator.
Finally, the object of the present invention is a process for the realisation of the hydraulic separator as described, which includes the following steps:

a) inserting the storage system inside the casing;
b) filling the gap between the storage system and the casing by injecting a polyurethane foam.

The invention will now be described for illustrative but not limitative purposes, with particular reference to the drawings of the attached figures, wherein:

Figure 1 shows a cutaway perspective view of a known art hydraulic separator in four usage configurations;
Figure 2 shows a front sectional view of a known art hydraulic separator, realised according to the so-called "three diameters" empirical method;
Figure 3 shows an exploded perspective view of a hydraulic separator according to the invention in a first embodiment;
Figure 4 shows a perspective view of the hydraulic separator of Figure 3;
Figure 5a shows a front sectional view of the hydraulic separator of Figure 3 along the section plane V of Figure 4;
Figure 5b shows a side view of the tank of Figure 5a;
Figure 6 shows a front sectional view of the separator of Figure 3, showing possible internal flow paths of the contained fluid;
Figure 7 shows a front perspective view of a plurality of horizontal tanks connected in parallel to the hydraulic separator of Figure 3;
Figure 8 shows a heating system comprising the hydraulic separator of Figure 3;
Figure 9 shows a side view of a hydraulic separator according to the invention in a second embodiment;
Figure 10 shows a front sectional perspective view in section of the hydraulic separator, highlighting two possible fluid paths between the side connections; and
Figure 11 shows a graph of the pressure drops (pressure difference or d_p) of the heat transfer fluid flow while passing through the hydraulic separator of Figure 10 according to the fluid paths shown, as the flow rate of the heat transfer fluid varies.

Referring to Figures 3 - 8, a hydraulic separator according to the invention is shown in a first embodiment, indicated by the numerical reference 1.
The hydraulic separator 1 according to the invention is adapted to perform the dual function of hydraulic separator for the connection to a plurality of hydraulic circuits, in particular at least two, and of inertial storage or thermal flywheel.
Said hydraulic separator 1, to also be used as an inertial storage tank, must have a fluid volume proportionate to the thermal power and to the characteristics of the generator(s) to which it is connected. For example, for heat pump generators, this volume varies (depending on the type) between 2.5 ÷ 6 litres/thermal kW.
For the most common applications, such as flats, the required dimensions of the inertial storage tank and hydraulic separator are typically not less than 40÷50 litres of storage.
In addition, to ensure compactness, the hydraulic separator 1 has the following overall dimensions:

a depth not exceeding 300 mm (including insulation), to meet, for example, the requirements for wall-recessed installation, installation in narrow corridors or balconies, installation within closets or pre-assembled technical boxes;
a height not exceeding 1000÷1100 mm to meet, for example, the requirements for installation under a window, under a boiler, above furniture, within wall cupboards and pre-assembled technical boxes; and
a width not exceeding that of a window or door of a technical room (600÷800 mm), both to allow easy handling of the product and to meet, for example, the requirements for installation on small domestic walls (behind a door or behind a window) and compatibility with built-in elements (for example, as a replacement for a boiler, a pre-assembled technical box, etc.).

Said hydraulic separator 1 provides an externally insulated storage system 10. Said storage system 10 comprises a plurality of tanks 2, in particular at least two. Each tank 2 has a shape with axial symmetry along a respective longitudinal axis of symmetry t, preferably the shape of each tank 2 is partially cylindrical.
The main body of each tank 2 is cylindrical, while the two opposite ends or bottoms may have a semi-elliptical or torospherical section or in any case a section that optimises the mechanical resistance to internal/external pressure.
For the sake of brevity, hereinafter reference will be made to the "cylindrical shape" to indicate one of such shapes with axial symmetry, without limitation to the strict geometric definition of the cylindrical shape.
Advantageously, the tanks 2 are able to work at operating pressures required by a hydraulic circuit, even exceeding 3 bar, or even more, thanks to the axial symmetry geometry of the body of the tanks 2 which intrinsically has greater resistance to pressure and also allows the use of materials and of production procedures suitable for pressure vessels and standardised by the regulations in force for pressure equipment (such as Directive 2014/68/EU PED).
The respective longitudinal axis of symmetry t of each tank 2 is parallel to a horizontal x-axis. Said tanks 2 are in fluid connection with each other in parallel. Specifically, fluid connection in parallel means that each tank 2 can be connected to at least one hydraulic circuit with at least one inlet and one outlet. In addition, hydraulic connection in parallel means that the heat transfer fluid entering a first side connection 21 of any tank 2 can exit from any side connection 21, 22 of any other tank 2. For example, see Figure 6, which shows an example of the dynamics of flows within the hydraulic separator 1 according to the invention. In this example, the fluid, in particular a single heat transfer fluid adapted to be contained within the hydraulic separator 1, enters from a first side connection 21 of the upper tank 2 and exits from any one or more side connections 21, 22 of the other tanks 2.
As shown in the figures, the cylindrical-shaped tanks 2 are arranged with their axes of symmetry t parallel to one another and parallel to a horizontal x-axis. In addition, said tanks 2 are arranged one above the other along a vertical y-axis, which is perpendicular to the horizontal x-axis.
Each tank 2 provides at least one side inlet/outlet connection 21, 22 for the fluid circulating in the linked circuits (shown, for example, in Figure 8) and at least one vertical connection 23 that allows the fluid connection with one or more of the remaining tanks 2.
For example, in Figure 8 the hydraulic separator 1 according to the invention has four tanks 2 connected in parallel, which are arranged one above the other along the vertical y-axis. Each tank 2 is vertically connected to the adjacent tank through two vertical connections 23. In addition, each tank 2 has two side connections 21, 22, arranged on opposite sides of the cylindrical body with respect to said vertical y-axis and along its own axis of symmetry t.
In addition, the terminal or end tanks 2 along said vertical y-axis each have two additional vertical connections 24 for connecting to equipment typically used in thermohydraulic systems, such as temperature probes, safety valves, air vent valves, drain valves, heating elements etc., or for additional hydraulic connections.
In other embodiments, not shown, other vertical connections or connections on other sides, such as the front side, may be provided, either in addition to or as replacement for the vertical connections 24.
Figure 8 shows such a hydraulic separator 1 included in a system 100 comprising four hydraulic circuits 20, 30, 40, 50, each hydraulically connected to respective side connections 21, 22, and to either a heat generator 9, 90 or a heating terminal 7, 70.
More specifically, a first hydraulic circuit 20 is connected to the first side connections 21 of the two upper tanks 2 which are on the same side of the hydraulic separator 1 (considered with respect to the vertical y-axis, in this case the left side) and to a first heat generation system 90, in particular a boiler 90. This first hydraulic circuit 20 is also commonly referred to as a primary circuit.
A second hydraulic circuit 30 is connected to the second side connections 22 of the same two upper tanks 2, opposite the first side connections 21 with respect to said vertical y-axis (therefore on the right side of the image), and to a first heating terminal system 7, in particular radiators 7. This second hydraulic circuit 20 is also commonly referred to as a secondary circuit.
The same heat transfer fluid flows between the two hydraulic circuits 20 and 30 through the respective side connections 21, 22 and vertical connections 23 of the tanks 2 of the hydraulic separator 1.
A third hydraulic circuit 40 can be connected to the first side connections 21 of the two tanks 2 positioned lower relative to the two upper tanks, which are on the same side as the side connections 21 of the first two upper tanks 2 connected to the first hydraulic circuit 20 and to a second heat generation system 9, in particular a heat pump 9. In this case as well, the third hydraulic circuit 40 can be referred to as an additional primary circuit.
Finally, a fourth hydraulic circuit 50 is connected to the second side connections 22 of the same two lower tanks 2, opposite the first side connections 21 with respect to said vertical y-axis (therefore on the right side of the image) and to a second heating terminal system 70, in particular a floor heating system. In this case as well, the third hydraulic circuit 40 can be referred to as an additional secondary circuit.
The same heat transfer fluid flows between the four hydraulic circuits 20, 30, 40, 50 through the respective side connections 21, 22 and vertical connections 23 of the tanks 2 of the hydraulic separator 1.
As can be observed, the fluid contained in the hydraulic separator 1 stratifies in each tank 2, realising a multi-level thermal stratification throughout the entire storage of the hydraulic separator 1, with thermal zones at different temperatures (one for each tank 2), vertically separated by the walls of the tanks 2, without the need for internal partitions and channels.
In an example of an embodiment, the tanks 2 are all identical, in other words they have the same capacity and the same shape, in particular cylindrical, so that during assembly the side connections 21, 22 are aligned and the main horizontal axes t are coplanar on a vertical plane parallel to the vertical y-axis. In this embodiment, the front footprint, in height along the y-axis and in width along the horizontal x-axis, is minimised compared to other embodiments of storage systems 10 of equal overall capacity wherein tanks with different capacities are used.
An example is shown in Figure 9 where a hydraulic separator 1 can be observed, comprising a storage system 10 that includes a plurality of tanks 2, each having a decreasing capacity compared to the previous one. Specifically, each tank 2 has a cylindrical shape with equal width, but differing diameters, in particular decreasing diameters.
Optionally, such tanks 2 could also have different shapes, different capacities or different geometries.
The side connections 21, 22 of the tanks 2 of the storage system 10 of the hydraulic separator 1 according to the invention allow the fluid connection with one or more external circuits of the same system and with the corresponding equipment.
In an example of an embodiment shown in Figure 7, the cross connections 23 between the tanks 2 are made by welding pipe sections onto the cylindrical body of the tanks 2. This advantageously allows a complete sealing without using third-party connecting elements that would require gaskets, seals, etc. Such third-party material could, in fact, be susceptible to wear and fluid leakage.
In addition, the hydraulic separator 1 according to the invention, in all the embodiments described, provides that the interconnected tanks 2 of the storage system 10 are insulated by an insulating layer 3, preferably based on polyurethane foam, which adheres to the tanks 2 and completely envelops them.
Such an insulating layer 3 advantageously ensures compliance with the minimum dispersion values according to the ErP Directive 2009/125/CE and the related implementing regulation EU 814/2013.
It is particularly advantageous that the external surfaces, in particular those made of metallic material, of each tank 2 are completely covered with insulating material adhered to the surfaces themselves to ensure low energy dispersion, in fact this allows the hydraulic separator 1 according to the invention to also function as a thermal storage and to have a dispersion lower than 16.66 + 8.33 V^0.4 Watt, where V refers to the volume of fluid contained in the hydraulic separator.
In addition, such an insulating layer 3 when based on polyurethane foam, advantageously allows complete adhesion to all surfaces of the tanks 2 which, thanks to the closed-cell structure of the polyurethane foam, prevents contact with the atmosphere and, consequently, the formation of condensation from ambient humidity, in case the storage is used in cooling applications (or in any case with fluid temperatures below the dew point of the air outside the storage in the installation environment).
In an example of an embodiment, the foaming process is carried out with an external cover or casing 11 mounted before the foaming, which allows a quick and economical process while ensuring a complete adhesion of the foam both to the tanks and to the cover, giving the product excellent structural and aesthetic properties, since there is no possibility of sliding and/or detachment of the cover from the foam.
In addition, the hydraulic separator 1 according to the invention can provide an external casing 11 for outdoor installation, adapted to withstand atmospheric agents. In an example of an embodiment, the material of the external cover 11 can be galvanised and/or painted sheet metal or made of a zinc-magnesium alloy with excellent corrosion resistance properties, widely used for outdoor applications.
Figure 3 shows an example of an embodiment of the hydraulic separator 1 according to the invention with the components assembled together before the foaming process. In particular, it shows the interconnected tanks 2, the sheets of the external cover 11 and a bracket 12 for the wall-mounted hanging connection.
The external cover 11, together with the bracket 12, is mounted before the foaming, so that the bracket 12 holds the tanks 2 in position within the cover 11 during the foaming.
The foam acts as an adhesive between the tanks 2 and the casing 11, securing them in their final configuration.
Subsequently, the bracket 12 can be unscrewed and used to fix the product to the wall.
In other embodiments, the hydraulic separator 1 can be installed on a base.
Advantageously, the hydraulic separator according to the invention can also be used as an inertial storage and, advantageously, has a compact size, in relation to its storage capacities.
In particular, the hydraulic separator according to the invention offers an advantageous simplicity of realisation, resulting in lower realisation costs.
In addition, the hydraulic separator 1 according to the invention is advantageously able to direct the flow path without using internal partitions or channels, but through geometric proportions between the elements realised to achieve different pressure drops (or pressure difference d_p) in the different paths within it. This is obtained by proportioning the diameter of the vertical connections 23 between the tanks 2 according to the diameter of the inlet and outlet side connectors 21, 22 of the hydraulic circuits, which is, in turn, dimensioned according to the type of hydraulic circuit system, so as to obtain an optimal ratio of the pressure drops between the paths of the fluid within the hydraulic separator according to the invention and to achieve the optimal hydraulic separation of the circuits connected to it.
Preferably, the passage area or section of the vertical connections 23 between the tanks 2 can be at least twice the passage area of the largest side connection 21, 22.
In support of what has just been stated, a demonstration of the optimal ratio of the pressure drops (or pressure difference d_p) between the paths of the fluid within the hydraulic separator 1 according to the invention is provided below.
Looking at Figure 10, two first side connections 21, respectively a1 and b1, connected to a first circuit 20, 40, in particular a primary circuit, and two second side connections 22, respectively a2 and b2, connected to a second circuit 30, 50, in particular a secondary circuit, are considered. Based on what has been stated, under all operating conditions, the flow entering from the first side connection a1 must be prevented from finding a preferential path towards the first side connection b1, i.e. a path with lower pressure drops (or pressure difference d_p) compared to the path from the first side connection a1 to the second side connection a2, such as to generate the phenomenon of recirculation (by-pass) without fluid exchange between the first side connection a1 and the second side connection a2.
In the following example, an embodiment according to the invention is considered wherein all the side connections 21, 22 and the vertical connections 23 have the same diameter of the passage section.
The flow resistance between the various connections is evaluated by measuring the pressure drops (or pressure difference d_p) between them. In a first test, a flow is circulated between the first side connection a1 of a first tank A and the first side connection b1 of a second tank B, and in a second test, a flow is circulated between the first side connection a1 of a first tank A and the second side connection a2 of the same tank A.
The graph of Figure 11 of the pressure drops d_p, as the flow rate m_vol varies, shows that the flow resistance (or pressure drop) d_p between a1 and b1 in the first test is always greater than the flow resistance d_p between a1 and a2 in the second test, therefore the by-pass phenomenon will always be avoided. This is ensured under all operating conditions, since there are no obstacles between a1 and a2, while between a1 and b1 there is a narrowing of the section, caused by the vertical connection 23, which constitutes an obstacle, i.e. a hydraulic resistance to the flow.
In addition, the absolute values of the pressure drops d_p, between any two connections of the hydraulic separator 1, are fully in line with the reference values currently acceptable according to the state of the art (400-500 mm w.c.). Because of what has been discussed above, the hydraulic separator 1 according to the invention fully meets the requirement of low pressure drops (or pressure difference d_p) for the flows passing through any combination of connections of the hydraulic separator 1.
To further detail what has been discussed, the example just described could also be formalised using the following mathematical formulas: ${dp}_{a 1 a 2} = {dp}_{a 1} + {dp}_{a 2}$ ${dp}_{a 1 b 1} = {dp}_{a 1} + {dp}_{23} + {dp}_{b 1}$ where

dp_a1a2 is the hydraulic resistance d_p of the flow of the heat transfer fluid in the passage between the first side connection a1 and the second side connection a2 of the first tank A,
dp_a1b1 is the hydraulic resistance d_p of the flow of the heat transfer fluid in the passage between the first side connection a1 of the first tank A and the first side connection b1 of the second tank B,
dp_a1 is the hydraulic resistance d_p of the flow of the heat transfer fluid in the passage through the first side connection a1 of the first tank A,
dp_b1 is the hydraulic resistance d_p of the flow of the heat transfer fluid in the passage through the first side connection b1 of the second tank 2,
dp_a2 is the hydraulic resistance d_p of the flow of the heat transfer fluid in the passage through the second side connection a2 of the first tank A,
dp₂₃ is the hydraulic resistance d_p of the flow of the heat transfer fluid in the passage through the vertical connection 23 between the two tanks A and B,
since all the resistances d_p are greater than zero, it follows that dp_a1a2 < dp_a1b1 under all operating conditions.

Thanks to the absence of obstructive elements within each tank 2, such as channels, partitions or other elements, the heat transfer fluid preferentially flows between the first side connection 21 and the second side connection 22 of the same tank 2, advantageously preventing the occurrence of the by-pass phenomenon, i.e. a condition where dp_a1a2 > dp_a1b1, as in similar examples of hydraulic separators illustrated in the state of the art.
In other embodiments, the vertical connections 23 may not be symmetrical with respect to the sagittal plane yz of Figure 5a (in particular alternately coupled on the right and left sides of the cylindrical bodies of the tanks 2).
Moreover, the hydraulic separator according to the invention advantageously exhibits resistance to high pressures. This is achieved thanks to the axially symmetrical geometry of the tank bodies, enabling high operating pressures (dependent on the thicknesses and materials used) and higher maximum achievable pressures compared to those in the known art for the realisation of other compact geometries.
Furthermore, the hydraulic separator according to the invention enables simplicity and versatility in thermal insulation to preserve the stratification and to comply with regulations on energy dispersion in thermal accumulators (EU Reg. 814/2013 of the ErP directive).
In particular, thanks to the resistance to both internal and external high pressures of the axially symmetrical embodiment, it is possible to carry out the "foaming" of the product by forming polyurethane foam within a mould in which the storage is introduced, without the risk of the foam pressure causing the storage to implode or deform. This technical solution of foaming directly onto the tank is particularly advantageous because it offers low costs for the same insulation performance and good insulating performance even with limited thicknesses (a fundamental characteristic for compact products) and also does not present condensation issues in the case of low temperatures (refrigeration applications).
To the aforementioned advantages are added the benefits of the storage system of the hydraulic separator according to the invention, which comprises a plurality of axially symmetrical tanks arranged horizontally.
In particular, this storage system enables an advantageous natural internal temperature stratification. Thanks to the horizontal arrangement of the tanks, a multi-level thermal stratification is achieved with thermal zones at different temperatures (one for each tank), vertically separated (as shown in Figure 8) by their walls, without the need for internal partitions and channels.
In addition, this allows a thermal separation and stratification of the inlet/outlet flows of the fluid at different temperatures between circuits linked to the same tank of the separator, reducing the mixing of the fluid between circuits at different temperatures linked to different tanks of the separator, without the need to add internal partitions and channels.
In the foregoing, the preferred embodiments have been described, and variations of the present invention have been suggested, but it is to be understood that those skilled in the art may make modifications and changes without thereby departing from the relative scope of protection, as defined by the attached claims.

Claims

A hydraulic separator (1) comprising a closed-vessel storage system (10) for the storage of a heat transfer fluid and for the hydraulic separation between at least two hydraulic circuits (20, 40; 30, 50) wherein said heat transfer fluid flows, said storage system (10) extending along a vertical axis (y) and comprising at least two first side connections (21) in correspondence with a first side thereof with respect to said vertical axis (y) and at least two second side connections (22) arranged opposite said at least two first side connections (21) with respect to said vertical axis (y), said first and second side connections (21, 22) being oriented parallel to a horizontal axis (x) perpendicular to said vertical axis (y),
said two first side connections (21) being adapted to be connected to a first hydraulic circuit (20; 40) and said two second side connections (22) being adapted to be connected to a second hydraulic circuit (30; 50) for the transfer or supply of said heat transfer fluid between at least said two hydraulic circuits (20, 30; 40, 50),

wherein said hydraulic separator (1) is characterised in that said storage system (10) has a capacity of at least 40 litres and comprises at least two closed-vessel tanks (2), each tank (2) having a body with axial symmetry along a longitudinal axis (t) parallel to said horizontal axis (x), at least two tanks (2), each of which providing a first (21) and a second (22) side connection at a respective end of the body along the respective longitudinal axis (t),

said at least two tanks (2) being in fluid connection with each other in parallel through at least one vertical connection (23) parallel to said vertical axis (y),

wherein said hydraulic separator (1) comprises an insulating layer (3) made of thermally insulating material, and a containment casing (11) within which said storage system (10) is arranged surrounded by said insulating layer (3).
The hydraulic separator (1) according to claim 1, wherein the casing (11) has an overall size where the height along the vertical axis (y) is less than/equal to 1100 mm, the width along the horizontal axis is less than/equal to 600 mm, and the depth along a transverse axis (z) perpendicular to the horizontal (x) and vertical (y) axes is less than 300 mm.
The hydraulic separator (1) according to claim 1 or 2, wherein the shape of the body of one or each tank (2) is partially cylindrical, optionally the end portions of each tank (2) have a semi-elliptical or torospherical section.
The hydraulic separator (1) according to any one of the preceding claims, wherein each tank (2) has the same capacity, the same shape, and the same dimensional footprint, such that the respective side connections (21, 22) are aligned on the same axis parallel to the vertical axis (y) and the respective longitudinal axes (t) are coplanar on a vertical plane comprising the vertical axis (y) and the horizontal axis (x).
The hydraulic separator (1) according to any one of claims 1 - 3, wherein said storage system (10) provides at least three tanks (2), wherein the at least one vertical connection (23) between two first tanks (2) is arranged on the side opposite the at least one vertical connection (23) between two other tanks (2) with respect to said vertical axis (y).
The hydraulic separator (1) according to any one of claims 1 - 3 or 5, wherein each tank (2) has a smaller capacity compared to the tank (2) arranged below it along said vertical axis (y).
The hydraulic separator (1) according to the preceding claim, wherein each tank (2) has a body of equal width along the longitudinal axis (t), wherein the body of each tank (2) has a diameter smaller than the tank (2) arranged below it.
The hydraulic separator (1) according to any one of the preceding claims, wherein the body of each tank (2) is made of a material compatible with containing pressurised fluids at high temperatures (up to 95°C), for example metal, preferably carbon steel or stainless steel or technopolymer, and wherein the vertical connections (23) are pipes made of the same material as the body of the tanks (2) and are joined to the body of the tanks (2) to which they are connected by welding.
The hydraulic separator (1) according to any one of the preceding claims, wherein each tank (2) is able to operate at an operating pressure even higher than 3 bar.
The hydraulic separator (1) according to any one of the preceding claims, wherein the area of the passage section of the at least one vertical connection (23) between two tanks (2) is at least twice the area of the passage section of the largest side connection (21, 22) of said two tanks (2).
The hydraulic separator (1) according to any one of the preceding claims, wherein the insulating layer (3) is based on polyurethane foam.
The hydraulic separator (1) according to any one of the preceding claims, wherein each tank (2) is free of obstructive elements within it, for example internal partitions and/or channels.
The hydraulic separator (1) according to any one of the preceding claims, wherein the diameter of the passage section of the side connections (21, 22) of each tank (2) and of the at least one vertical connection (23) between at least two tanks (2) are dimensioned such that, during use, when at least said two first side connections (21) are connected to a first hydraulic circuit (20, 40) and the second side connections (22) are connected to a second hydraulic circuit (30, 50), the flow of the heat transfer fluid flowing between said hydraulic circuits (20, 30, 40, 50) through said connections (21, 22, 23) has a pressure drop (d_p) that is smaller in the passage between the side connections (21, 22) of the same tank (2) compared to the pressure drop (d_p) in the passage between the first side connections (21) of two tanks (2) through the at least one vertical connection (23).
A system (100) comprising a hydraulic separator (1) according to any one of the preceding claims and at least two hydraulic circuits (20, 30, 40, 50) in fluid connection with said side connections (21, 22) of said hydraulic separator (1) for the flow of said heat transfer fluid,
wherein at least one first hydraulic circuit (20, 40) is in fluid connection with a heat generator (9, 90), in particular a boiler (90) or a heat pump (9), and at least two first side connections (21) of said hydraulic separator (1), and

wherein at least one second hydraulic circuit (30, 50) is in fluid connection with a heating terminal system (7, 70), in particular radiators (7) or a floor heating system (70), and at least two second side connections (22) of said hydraulic separator (1).
A process for the realisation of the hydraulic separator (1) according to claim 11, which includes the following steps:
a) inserting the storage system (10) inside the casing (11);

b) filling the gap between the storage system (10) and the casing (11) by injecting a polyurethane foam.