EP4455559A1

EP4455559A1 - Gas-liquid separator for a heat medium circulation system

Info

Publication number: EP4455559A1
Application number: EP23169621.2A
Authority: EP
Inventors: Kohei Nishida; Takuya Nakao
Original assignee: Daikin Europe NV
Current assignee: Daikin Europe NV
Priority date: 2023-04-24
Filing date: 2023-04-24
Publication date: 2024-10-30

Abstract

The current invention relates to a gas-liquid separator for a heat medium circulation system, which device permits safe operation of the heat medium circulation system even in the event of a refrigerant leak.

Description

FIELD OF THE INVENTION

The present invention relates to a gas-liquid separator. More in particular, the invention relates to a gas-liquid separator for a heat medium circulation system.

BACKGROUND

EP2080975A1 in the name of ATLANTIC CLIMATISATION ET VENT , discloses a device for heat exchange between fluids belonging to two circuits. The device has a reservoir to receive coolant e.g., water, and a coolant inlet equipped at a lower part of the reservoir. A coolant outlet is equipped at an upper part of the reservoir. A coaxial heat pipe is arranged at inside of the reservoir, and is immersed in the coolant. An inner tube of the pipe is connected to the inlet at an end of the reservoir, and opens at another end of the reservoir. The inner tube is provided as a passage for the coolant. An outer tube of the pipe is provided as a passage for refrigerant.
EP1965164A1 in name of ATLANTIC CLIMATISATION ET VENT , discloses a device for heat exchange between fluids belonging to two circuits. The device has a reservoir to receive coolant fluid. The reservoir is equipped with a coolant fluid inlet arranged in a lower part of the reservoir and an outlet of a coolant fluid arranged in an upper part. An exchanger with coaxial tubes is arranged inside the reservoir, and is immersed in the fluid. An inner tube is connected to the inlet at an end, and is opened in the reservoir at another end. The tube has a section between the inlet and the exchanger, where the section is uncovered by an outer tube in which leakage opening is arranged.
These known devices, like any other devices having refrigerant using heat exchanger are susceptible to develop refrigerant leakages. None of the devices disclosed in EP '975 nor in EP '164 include any leak remediation of prevention features. Furthermore, none of the disclosed devices include elements or features to prevent the passage of any leaked refrigerant to any user-side element.

SUMMARY OF THE INVENTION

The present invention aims to resolve at least some of the problems and disadvantages mentioned above.
The invention thereto aims to provide gas-liquid separator for a heat medium circulation system, said gas-liquid separator having improved gas-liquid separation which prevent the spreading of any leaked refrigerant to any user-side elements e.g., heat exchangers.
The present invention thereof serve to provide a solution to one or more of above-mentioned disadvantages. To this end, the present invention relates to a gas-liquid separator for a heat medium circulation system according to claim 1.
In a first aspect, the invention relates to a gas-liquid separator for a heat medium circulation system, comprising;

a tank for receiving a heat medium;
a heat medium inlet that allows the heat medium returning from at least one usage-side heat exchanger to flow into the tank;
a heat medium outlet that allows the heat medium to flow out of the tank to the at least one usage-side heat exchanger;
an internal heat exchanger having a heat medium passage and an adjoining refrigerant passage, said internal heat exchanger being immersed in the heat medium inside the tank and permitting exchange of heat between a refrigerant flowing in the refrigerant passage and the heat medium flowing in the heat medium passage;
a first inlet of the internal heat exchanger, said first inlet being an inlet of the heat medium passage and is connected to the heating medium inlet; and a first outlet of the internal heat exchanger, which first outlet is the outlet of
the heat medium passage and is open inside the tank.

The heat medium outlet opens into the tank at a lower position than where the first outlet of the internal heat exchanger opens into the tank. Refrigerants used in heat pumps, air-conditioning or other similar refrigerant using installations have lower densities than water or other heat mediums with which said refrigerants are expected to exchange heat (e.g. mineral oil). The device of the present invention is particularly suited, though not exclusively, to the use of water as a heat medium. Water has a higher density than refrigerants, even when said refrigerants are compressed above normal operating pressures expected in heat pumps or air conditioning installations. The present invention takes advantage of the difference of density between refrigerant and heat medium, in particular the buoyancy effects produced by said difference. In this way, any refrigerant making its way to the inside of the tank along with the heat medium via the first outlet will naturally have the tendency to separate from said heat medium and float upwards and pool over the heat medium. By having the first outlet of the heat exchanger located above the heat medium outlet, the path of any leaked refrigerant being introduced into the tank will never intersect said heat medium outlet. In this way, the risk of any refrigerant flowing out of the tank and into any usage-side heat exchanger is very nearly removed. By preference, the refrigerant passage of the internal heat exchanger is part of a refrigerant circuit including at least one compressor for compressing said refrigerant.
In a preferred embodiment, the device further comprises:

a heat medium outlet port provided on the tank,
an outlet tube having a proximal end provided inside the tank, the distal end
of the outlet tube being connected to the heat medium outlet port.

The proximal end of the outlet tube is the heat medium outlet. In this way, the heat medium outlet is distanced further from the first outlet of the heat exchanger. This advantageously permits further reducing the risk of any refrigerant flowing out of the tank and into any usage-side heat exchanger.
In a preferred embodiment, the proximal end of the outlet tube has a larger internal diameter than the heat medium outlet port. In this way, pressure loss along the outlet tube is advantageously minimized, thereby greatly reducing the risk of cavitation in a pump placed downstream from the heat medium outlet port. By preference, the tank is further equipped with a heat medium level indicator which indicator is in communication with a controller configured to stop the pump if the heat medium level is too low. In this way, cavitation in the pump is advantageously avoided.
In a preferred embodiment, the outlet tube is inside the tank, and one end of the outlet tube is connected to the heat medium outlet port and the outlet tube extends in the direction of the height of the tank. This configuration of the outlet tube advantageously permits extracting heat medium from the upper, warmer layer of heat medium inside the tank. By preference, the height of the proximal end of the outlet tube is lower than the height of the first outlet. In this way, ingress of any leaked refrigerant into the user side and any user heat exchangers is advantageously avoided. In an embodiment, the outlet tube may be telescopic and comprise at least two sections, the height of the heat medium outlet being automatically adjustable by means of a buoy in connection to the upper section of the outlet tube. Said connection being, for example a length of cable, a rod or chain, said length being longer than the distance of the first outlet to the top inner surface of the tank. In this way, the device is able to operate even if the tank is not completely full, while still keeping the heat medium outlet below the first outlet of the heat exchanger.
In a preferred embodiment, the internal heat exchanger is a double tube heat exchanger having a heat medium passage in which the heat medium flows and a refrigerant passage in which the refrigerant flows defining the tubes of the double tube heat exchanger. By preference, both tubes of the heat exchanger are substantially coaxial. In this way, the heat exchange between the refrigerant and the heat medium is advantageously made more uniform along the length of the heat exchanger. By preference, the inner tube of the heat exchanger is configured as a heat medium passage and the space between the inner and outer tube is configured as a refrigerant passage. In this way, both the heat medium inside the tank and the heat medium inside the heat exchanger are, advantageously, able to simultaneously exchange heat with the refrigerant flowing through the refrigerant passage of the heat exchanger.
In a preferred embodiment, the double tube heat exchanger is formed in a helical shape, wherein the central axis of the helix extends in the height direction of the tank. In this way the heat exchanger advantageously has a larger heat exchange area, said heat exchange area being defined by both the inner and outer sides of the refrigerant passage. The larger heat exchange area permits more heat to be exchanged between the refrigerant and the heat medium before the refrigerant returns to the compressor side of the refrigerant circuit. Furthermore, the helical shape of the internal heat exchanger permits a more efficient use of the internal space of the tank, advantageously allowing, for example, for smaller tanks to be used.
In a preferred embodiment, the first inlet is located near the bottom of the tank and connected to the heat medium inlet, and the first outlet is located above the first inlet, the first outlet opening inside the tank. In this way, the heated heat medium enters the tank via the first outlet at a height where the heat medium inside the tank is warmer. Furthermore, by locating the first outlet higher than the first inlet, advantageously permits delivering any leaked refrigerant higher inside the tank and above the heat medium outlet.
In a preferred embodiment, the shape of the tank is substantially cylindrical shaped, the tank being installed so that a center axis of the tank extends in the height direction of the tank. The shape of the tank is particularly easy and economical to manufacture while offering superior strength against internal pressure. Furthermore, this shape and orientation of the tank permit a more efficient use of its internal volume and, in particular, advantageously permit the most convenient internal shape for the installation of an internal helical heat exchanger.
In an eleventh aspect, the first outlet is located adjacent and substantially tangential to a wall of the tank. By preference, the helical shape of the heat exchanger includes at least two turns, the last of which turns includes the first outlet, the distal end of said last coil being located at least 10mm farther from the axis of the helix than each preceding turn. In this way, heat medium leaving the first outlet is advantageously ejected near the inner lateral walls of the tank and in a direction that is substantially tangential to said walls. By locating the first outlet farther from the axis of the helical heat exchanger, a gap between all but part of the last coil of heat exchanger and the inner walls of the tank is left. By virtue of the contact of the heat medium in the tank and the outer tube of the helical heat exchanger, convection currents are created around the heat exchanger. These convection currents, advantageously push the heat medium introduced via the first inlet upwards and along the inner walls of the tank, in this way further accelerating the rise of any leaked refrigerant to the top inner volume of the tank and away from the heat medium outlet.
In a preferred embodiment, spiral grooves are provided on an inner wall of the tank, said inner wall being rounded. By preference, these grooves have the same rotation as the coils of the heat exchanger. more preferably, the pitch of the spiral groves is at least the same as the pitch of the helix of the heat exchanger. Most preferably, the pitch of the spiral groves increases progressively as the grooves reach the top inner volume of the tank. In this way, the flow of the heat medium entering the tank along the inner walls of the tank is used to further accelerate its rise towards the top of the tank and away from the heat medium outlet.

DESCRIPTION OF FIGURES

The following description of the figures of specific embodiments of the invention is merely exemplary in nature and is not intended to limit the present teachings, their application or uses. Throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

Figure 1 shows a schematic representation of the gas-liquid separator equipped with a lateral heat medium outlet port.
Figure 2 shows a schematic representation of the gas-liquid separator equipped with a bottom heat medium outlet port.
Figure 3 shows a section view of the gas-liquid separator with a coaxial heat exchanger.
Figure 4 shows a coaxial heat exchanger having an extended first outlet.
Figure 5 shows a top section view of the gas-liquid separator equipped with the coaxial heat exchanger having an extended first outlet.

DETAILED DESCRIPTION OF THE INVENTION

The invention is further described by the following non-limiting examples which further illustrate the invention, and are not intended to, nor should they be interpreted to, limit the scope of the invention.
The present invention concerns gas-liquid separator for a heat medium circulation system. The heat medium circulation system comprises of the gas-liquid separator, a pump, a controller that controls at least the pump and a usage-side heat exchanger like a radiator. The gas-liquid separator includes a heat medium tank with an internal heat exchanger for exchanging heat between a heat medium and a refrigerant, the passages for each of these fluids being both inside the tank and immersed in heat medium. The heat medium passage of the internal heat exchanger, the pump, the usage-side heat exchanger are connected by heat medium pipes, and the heat medium circulates inside the heat medium pipes. The refrigerant passage of the internal heat exchanger, an expansion valve, a heat source-side heat exchanger and a compressor are connected by refrigerant pipes, and the refrigerant circulates inside the refrigerant pipes. In this embodiment, propane can be used as a refrigerant. Also, R32 refrigerant can be also used. The heat medium passage includes a first outlet in fluid communication with the internal volume of the tank, which first outlet is located above a heat medium outlet in fluid communication with user-side elements. The location of said first outlet relative to the heat medium outlet allows for superior liquid gas separation, as any refrigerant leaking into the tank quickly returns to a gaseous state and floats to the top of the internal volume of the tank. The first outlet being located higher than the heat medium outlet means that any rising refrigerant never crosses the heat medium outlet. This prevents the passage of any refrigerant towards any user-side element.
Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.
As used herein, the following terms have the following meanings:

"A", "an", and "the" as used herein refers to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more than one compartment.
"Comprise", "comprising", and "comprises" and "comprised of" as used herein are synonymous with "include", "including", "includes" or "contain", "containing", "contains" and are inclusive or open-ended terms that specifies the presence of what follows e.g., component and do not exclude or preclude the presence of additional, non-recited components, features, element, members, steps, known in the art or disclosed therein.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.
The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range, as well as the recited endpoints.
Whereas the terms "one or more" or "at least one", such as one or more or at least one member(s) of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any ≥3, ≥4, ≥5, ≥6 or ≥7 etc. of said members, and up to all said members.
Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention. The terms or definitions used herein are provided solely to aid in the understanding of the invention.
Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may do so. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.
With as a goal illustrating better the properties of the invention the following presents, as an example and limiting in no way other potential applications, a description of a number of embodiments of the gas-liquid separator based on the invention, wherein:

FIG.1 shows a schematic representation of the gas-liquid separator (1) equipped with a lateral heat medium outlet port (10). The gas-liquid separator (1) includes a tank (2), which tank encloses a coaxial heat exchanger (3). The heat exchanger (3) includes a refrigerant passage (6, not shown) in fluid connection with one end of a refrigerant inlet tube (14) and one end of a refrigerant outlet tube (15), said tubes (14, 15) providing for fluid connection with a refrigerant circuit outside of the tank (2). A first inlet (7) of the heat exchanger (3) is shown extending out of the tank (2), in this way enabling the ingress of heat medium to the heat medium passage (5, not shown) of the heat exchanger (3) and into the tank (2) via the first outlet (9) of the heat exchanger. An outlet tube (11) is shown disposed to the lateral wall of the tank (2). The outlet tube (11) provides fluid connection between a heat medium outlet (4) on the inside of the tank (2) and a heat medium outlet port (10). The figure shows the heat medium outlet (4) placed at a height lower than that of the first outlet of the heat exchanger (3). The figure shows the trajectory of any leaked refrigerant in a gaseous state (17) leaked through the first outlet (9). An over-pressure valve (16) is shown on top of the tank (2), said over-pressure valve (16) being in fluid communication with the inside of the tank (2). The valve (16) is configured to open automatically if the pressure inside the tank (2) exceeds a predetermined safety threshold (e.g., 60% of the failure pressure of the tank). The valve (16) may be a mechanical or an electro-mechanical valve, preferably a solenoid valve assembly equipped with a pressure indicator and a controller. The pressure indicator being configured to send a signal with information related to the pressure inside the tank (2) to the controller, and the controller being configured to compare the signal received from the pressure indicator with a pre-set safety pressure. The controller is configured to send a signal to the solenoid valve if the pressure inside the tank (2) exceeds said pre-set safety pressure, the signal containing instructions to cause the solenoid valve to open and to control the aperture of said valve.
FIG. 2 shows a schematic representation of the gas-liquid separator (1) equipped with a bottom heat medium outlet port (10). The gas-liquid separator (1) includes a tank (2), which tank encloses a coaxial heat exchanger (3). The heat exchanger (3) includes a refrigerant passage (6, not shown) in fluid connection with one end of a refrigerant inlet tube (14) and one end of a refrigerant outlet tube (15), said tubes (14, 15) providing for fluid connection with a refrigerant circuit outside of the tank (2). A first inlet (7) of the heat exchanger (3) is shown extending out of the tank (2), in this way enabling the ingress of heat medium to the heat medium passage (5, not shown) of the heat exchanger (3) and into the tank (2) via the first outlet (9) of the heat exchanger. An outlet tube (11) is shown disposed to the bottom wall of the tank (2) and oriented in substantial alignment with the axis of the tank (2). The outlet tube (11) provides fluid connection between a heat medium outlet (4) on the inside of the tank (2) and a heat medium outlet port (10), said heat medium outlet (4) having a larger diameter than the heat medium outlet port (10). The figure shows the heat medium outlet (4) placed at a height lower than that of the first outlet of the heat exchanger (3). The figure shows the trajectory of any leaked refrigerant in a gaseous state (17) leaked through the first outlet (9). An over-pressure valve (16) is shown on top of the tank (2), said over-pressure valve (16) being in fluid communication with the inside of the tank (2). The valve (16) is configured to open automatically if the pressure inside the tank (2) exceeds a predetermined safety threshold (e.g., 60% of the failure pressure of the tank). The valve (16) may be a mechanical or an electro-mechanical valve, preferably a solenoid valve assembly equipped with a pressure indicator and a controller. The pressure indicator being configured to send a signal with information related to the pressure inside the tank (2) to the controller, and the controller being configured to compare the signal received from the pressure indicator with a pre-set safety pressure. The controller is configured to send a signal to the solenoid valve if the pressure inside the tank (2) exceeds said pre-set safety pressure, the signal containing instructions to cause the solenoid valve to open and to control the aperture of said valve.
FIG. 3 shows a section view of the gas-liquid separator (1) with a coaxial heat exchanger (3). The figure shows the heat exchanger (3) having an inner tube (12) placed inside an outer tube (13). The inner tube (12) defines a heat medium passage (5), while the space between the inner tube (12) and the outer tube (13) defines a refrigerant passage (6). A refrigerant inlet tube (14) near the proximal end of the heat exchanger (3), and refrigerant outlet tube (15) located near the distal end of the heat exchanger (3) provide fluid connection with a refrigerant circuit (not shown).
FIG. 4 shows a coaxial heat exchanger (3) having an extended first outlet (9). The shown heat exchanger (3) shares an almost identical construction to those of the embodiments shown in FIG. 1-3, differing only in the longer first outlet (9). The features of this embodiment of the heat exchanger (3) is better appreciated in FIG. 5.
FIG. 5 shows a top section view of the gas-liquid separator (1) equipped with the coaxial heat exchanger (3) having an extended first outlet (9). The figure shows the distal end of the first outlet (9) converging towards the wall of the tank (2) and away from the axis of the heat exchanger (3) until the axis of the extended first outlet (9) is tangential with the walls of the tank (2).
FIG. 6 shows a section view of the gas-liquid separator (1) with a coaxial heat exchanger (3) and a plurality of spiral groves (18) having the same pitch and rotation as the coils of the heat exchanger (3). In another embodiment (not shown) the pitch of the grooves (18) increases progressively as the grooves reach the top inner volume of the tank (2). Said grooves (18) having also the same rotation direction as the coils of the heat exchanger (3).

List of numbered items:

1: gas-liquid separator
2: tank
3: coaxial heat-exchanger
4: heat medium outlet
5: heat medium passage
6: refrigerant passage
7: first inlet
8: heat medium inlet
9: first outlet
10: heat medium outlet port
11: outlet tube
12: inner tube
13: outer tube
14: refrigerant inlet tube
15: refrigerant outlet tube
16: over-pressure valve
17: leaked refrigerant gas trajectory
18: grooves

The present invention is in no way limited to the embodiments shown in the figures. On the contrary, methods according to the present invention may be realized in many different ways without departing from the scope of the invention.

Claims

A gas-liquid separator for a heat medium circulation system, comprising;
a tank for receiving a heat medium;

a heat medium inlet that allows the heat medium returning from at least one usage-side heat exchanger to flow into the tank;

a heat medium outlet that allows the heat medium to flow out of the tank to the at least one usage-side heat exchanger;

an internal heat exchanger having a heat medium passage and an adjoining refrigerant passage, said internal heat exchanger being immersed in the heat medium inside the tank and permitting exchange of heat between a refrigerant flowing in the refrigerant passage and the heat medium flowing in the heat medium passage; a first inlet of the internal heat exchanger, said first inlet being an inlet of the heat medium passage and is connected to the heating medium inlet; and

a first outlet of the internal heat exchanger, which first outlet is the outlet of the heat medium passage and is open inside the tank; characterized in that, the heat medium outlet opens into the tank at a lower position than where the first outlet of the internal heat exchanger opens into the tank.
The device according to claim 1, further comprising;
a heat medium outlet port provided on the tank,

an outlet tube having a proximal end provided inside the tank, the distal end of the outlet tube being connected to the heat medium outlet port;

characterized in that, the proximal end of the outlet tube is the heat medium outlet.
The device according to claim 2, characterized in that, the proximal end of the outlet tube has a larger internal diameter than the heat medium outlet port.
The device according to any one of the claims 2 to 3, characterized in that, the heat medium outlet port is provided on or near the bottom of the tank.
The device according to claim 4, characterized in that, the outlet tube is inside the tank, and one end of the outlet tube is connected to the heat medium outlet port and the outlet tube extends in the direction of the height of the tank.
The device according to any of the claims 1 to 5, characterized in that, the internal heat exchanger is a double tube heat exchanger having a heat medium passage in which the heat medium flows and a refrigerant passage in which the refrigerant flows defining the tubes of the double tube heat exchanger.
The device according to claim 6, characterized in that, the double tube heat exchanger is formed in a helical shape, wherein the central axis of the helix extends in the height direction of the tank.
The device according to any of the claims 1-7, characterized in that, the heat medium outlet opens into the tank in the upper half of the tank.
The device according to any of the claims 1-8, characterized in that, the first inlet is located at or near the bottom of the tank and connected to the heat medium inlet, and the first outlet is located above the first inlet, the first outlet opening inside the tank.
The device according to any of the claims 1-9, characterized in that, the shape of the tank is cylindrical shaped, the tank being installed so that a center axis of the tank extends in the height direction of the tank.
The device according to claim 10, characterized in that, the first outlet is located adjacent and tangential to a wall of the tank.
The device according to any of the claims 10-11, characterized in that, the helical shape of the heat exchanger includes at least two turns, the last of which turns includes the first outlet, the distal end of said last coil being located at least 10 mm farther from the axis of the helix than each preceding turn.
The device according to any of the claims 1-12, characterized in that, spiral grooves are provided on an inner wall of the tank, said inner wall being rounded.