Gas-liquid cyclone separator

Abstract

Degassing device, suitable for the secondary circuit of a heat pump, which has a vertically arranged cylindrical housing (1) through which fluid can flow, and a tangential inlet (2) for a fluid flow is arranged in the upper part of the cylindrical housing, and a central opening (6) is provided at the upper end of the upper part of the cylindrical housing, wherein a sieve body (7) is sealingly fixed to this central opening (6), which sieve body projects into the cylindrical housing (1) and is equipped with a closing device to prevent fluid from escaping from the central opening, the central opening (6) is connected to a discharge line for gas, and a tangential outlet (4) for a fluid flow is provided at the lower end of the lower part of the cylindrical housing (1).

Description

[0001] The invention relates to the separation of flammable or harmful gaseous hydrocarbons, which may also be partially or per-halogenated, from a heat pump system into a heating circuit or cooling brine circuit installed in a building, hereinafter referred to as heat transfer circuit, by means of a device and a method for the highly efficient separation of the gas phase from a two-phase flow with a homogeneous liquid and a heterogeneous gaseous phase.

[0002] On the one hand, it is well known that heating circuits occasionally need to be vented because air can accumulate in the system. This usually occurs due to leaks at elevated points in the heating circuit, where a leak, combined with negative pressure, leads to air being sucked into the water circuit. In some cases, this also involves air dissolved in make-up water, which is released when it is heated. The same applies to brine-split systems, which contain brine in the heating circuit, and also to air conditioning systems. Depending on the purpose of such a heat transfer fluid circuit or the environmental conditions it has to cope with, additives can be added to the heat transfer fluid circuit in addition to the actual heat transfer medium, usually water. These are usually antifreeze or corrosion inhibitors.

[0003] On the other hand, flammable refrigerants are now used as working fluids in heat pumps and refrigeration and freezing systems. These refrigerants have the advantage that, if accidentally released, they do not harm the climate or the ozone layer, or at least their release is less harmful. However, such accidental releases should be avoided wherever possible due to their flammability and other harmful effects. How such an accidental release can be effectively prevented in a cold storage room or in a heat pump installation room is described, for example, in DE 10 2011 011 210 A1.

[0004] In refrigeration circuits where such working fluids are used, such unintentional releases can also occur via the heat exchangers used as condensers and evaporators, which are connected to the heat transfer medium, i.e., the heating circuit or cooling brine circuit, via their exchange surfaces. Unlike conventional gas-fired boilers, the working fluid in the refrigeration circuit is under higher pressure than the heat transfer fluid in the heating circuit or cooling brine circuit, so in the event of a leak, it could easily enter the lower-pressure heat transfer medium.

[0005] To prevent this as much as possible, conventional double-walled heat exchangers are used, as described, for example, in patents DE 11 2019 001 344 T5, DE 11 2019 001 350 T5, and DE 11 2019 001 351 T5 for heat pumps. These heat exchangers conduct the R290 working fluid against a water-propylene glycol brine as the heat transfer fluid. In addition to the high cost, this approach leads to efficiency losses, as the materials, such as stainless steel, are poor heat conductors and the thin air gap between the heat exchanger surfaces acts as an insulator. In practice, this means that higher temperature differences must be set in the heat exchangers, which reduces the efficiency of heat pumps.

[0006] The design of such double-walled heat exchangers, which represent a special case of interspace heat exchangers, is also complex because the air gap forming the space must be as small as possible. However, if different pressures arise on both sides of the heat-transferring fluids, which is common in heat pumps, the thin sheets tend to bend and bulge. There is also a tendency to warp during operation when temperature differences change and the sheets thermally expand or contract. This expansion and bending must be counteracted by webs and supports in the air gap, which creates additional stresses in the material and provokes material failure after frequent load changes. It would therefore be advantageous if such double-walled heat exchangers could be avoided.

[0007] Another known option is to use a refrigerant / air separator and a safety valve or a check valve in the heating circuit. WO 2021 / 160221 A1 describes a heat pump system with a primary circuit, in which a combustible working fluid is circulated, and with a secondary circuit designed as a heating circuit. A check valve closes in the flow direction of the heating circuit when a certain gas quantity is reached, and a degassing device prevents the flow of the heating circuit medium. A float serves as the degassing device.

[0008] Quick vents and membrane degassers are also known as degassing devices. The problem with these is that the ignition limits for gas-air mixtures containing flammable refrigerants cannot be reliably maintained during degassing, so safe and non-hazardous discharge must be ensured.

[0009] Further quick vents are described in the documents DE 20 2018 003 488 U1, DE 10 2010 032 394 A1, DE 20 2018 000 709 U1, EP 2 988 043 B1, EP 1 035 365 B1 and WO 2006 / 000453 A1.

[0010] Gas separators that are suitable for heating circuits and that can be used for secondary circuits of heat pumps are also described in EP 3 513 855 A1. Here, a horizontally aligned cylindrical gas separator is equipped with a stationary screen chamber, whereby the screen of the screen chamber is cylindrical, prismatic, truncated cone-shaped, or pleated sleeve-shaped, and the gas separator and the screen chamber are axially parallel. The screen chamber is formed by a perforated plate, but can also be designed as a wire mesh. The liquid-gas mixture initially enters a first sub-chamber, which contains the screen chamber, without any swirl. The screen chamber is flooded, but the flow is considerably calmer, and the gas bubbles can rise. There they reach the upper second sub-chamber, which has a gas outlet, while the liquid flows into the lower second sub-chamber and is withdrawn from there.Since small bubbles rise slowly in a steady flow, a long fluid residence time is required, resulting in a large construction volume. This is especially true since added antifreeze agents such as glycol slow the rise of the bubbles even further.

[0011] In cases where flammable refrigerants may be present in the gas-air mixture to be separated, deaerators have also been described in which separation is performed within the deaerator itself. This is preferably achieved using membranes; one such membrane separator is described in EP 3 747 532 A1.

[0012] Further methods and devices for addressing the gas separation problem are known from EP 3 764 001 A1 and EP 3 882 526 A1. In EP 3 764 001 A1, a bypass flow of a heat transfer fluid is used for a jet nozzle to cause a pressure drop through the resulting flow acceleration, which leads to dissolved refrigerant being released from the liquid in gaseous form and becoming separable.

[0013] In EP 3 882 526 A1, gaseous refrigerant and air are separated together from a heat transfer fluid and then separated from each other using a membrane. While both techniques can be successfully combined, it cannot be prevented that additional dissolved refrigerant could be present in the heat transfer fluid of the secondary circuit and then, under unfavorable conditions, outgas at an unfavorable location in the heat transfer circuit.

[0014] EP 4 166 854 A1 describes a device and a method by which refrigerant released due to leakage is safely dissolved in the heat transfer fluid. This is done by means of a mixing station and, if necessary, with the addition of a solution-improving substance.

[0015] However, these methods and devices are complex and expensive and often do not solve the problem satisfactorily under all operating conditions. The current separation efficiency of series components using previous technologies has so far reached 40 to 70% for typical installation sizes. These components are often associated with very high pressure drops. High separation efficiencies can currently only be achieved with large installation volumes. However, an average separation efficiency of at least 95% is required with a leakage mass flow of up to approximately 0.25 g / s and a volume flow in the heating circuit of more than 3500 l / h. The installation space should not exceed a cylindrical dimension with an outer diameter of 150 mm and a height of 400 mm, preferably a cylindrical dimension with an outer diameter of 130 mm and a height of 300 mm.At the same time, a pressure drop of less than 80 mbar should be achieved when 3500 l / h flow through the separator, so that the higher pump output does not reduce the overall efficiency of a heat pump system. For larger flow rates, the cross-sectional areas should be selected accordingly, and scalability should be possible.

[0016] The object of the invention is therefore to provide a degassing device which is compact and has a very high separation efficiency, suitable for a secondary circuit for heat pumps.

[0017] The task is solved by a degassing device for the secondary circuit of a heat pump, - which has a vertically arranged cylindrical housing and is permeable to flow, and - a tangential inlet for a liquid flow is arranged in the upper part of the cylindrical housing, - a central opening is provided at the upper end of the upper part of the cylindrical housing, - a sieve body is sealingly fixed to this central opening, which protrudes into the cylindrical housing and is equipped with a closing device to prevent liquid from escaping from the central opening, - the central opening is connected to a gas outlet, - a tangential outlet for a liquid flow is provided at the lower end of the lower part of the cylindrical housing.

[0018] The tangential inlet at the top creates a rotating flow, pushing the liquid outward and any gas particles present inward due to their lower density. If gas is present in the liquid, a funnel-shaped liquid surface is created, from the top of which the gas can be extracted in the center. This gas is then discharged to the outside via a pipe.

[0019] Design options include the upper part of the cylindrical housing and the tangential liquid inlet. The liquid inlet can be configured as a nozzle. The flow is accelerated by the nozzle effect, creating a pressure drop that improves bubble formation for dissolved gas. The nozzle can be configured as a thrust jet nozzle or a thrust vector controller, allowing a uniform flow velocity to be achieved for varying flow rates, and the flow direction to be adjusted to create a helical flow. The flow direction can be adjusted both vertically and laterally.

[0020] This is technically easily achievable using adjustable and curved plates that can be slid into and over one another in a known manner, like a baffle. In a further embodiment, the flow entering the cylindrical housing tangentially is imparted an initial swirl upon entry by baffles, which twists the incoming liquid jet. The nozzle and the twisting can be integrated into a common inlet device. This locally accelerates the flow, which contributes to better and faster outgassing of dissolved gas.

[0021] Further designs concern the sieve body. While in the simplest case, its sole function is to prevent liquid from entering the gas outlet, the ingress of liquid can calm the flow, making it easier for gas bubbles to collect near the central axis and rise upwards. For this purpose, the sieve body is preferably designed as a cylindrical, truncated cone-shaped, or prism-shaped perforated plate that extends from the gas outlet at the top of the cylindrical housing to the lower region of the cylindrical housing.

[0022] In further embodiments, the holes in the perforated plate of the sieve body are embossed in such a way that a serrated surface forms on the edges of the openings facing the central axis, similar to a kitchen grater. This facilitates the passage of bubbles passing through the openings, preventing them from sticking to the holes. They are therefore not held in place by surface tension and can easily detach.

[0023] In a further embodiment, the sieve body can rotate with the flow. It does not require its own drive, but it must be freely mounted. Since fewer shear forces occur in the liquid near the sieve body surface, the resulting gas bubbles can penetrate more easily, reducing pressure loss and allowing higher peripheral speeds to be set, thus reducing the overall volume.

[0024] In a further embodiment, a mesh is provided within the sieve body to prevent foam formation. The mesh can be made of wire wool or a durable plastic, such as Teflon-coated plastic.

[0025] Depending on the number of bubbles and the total gas volume, droplet overflow is to be expected. For this reason, a droplet separator is provided at the gas outlet within the sieve body in one design. The mesh and droplet separator can also be constructed together.

[0026] The invention is described below by way of example with reference to Fig. 1 to Fig. 8. Here, Fig. 1 the housing of the degassing device from the outside, Fig. 2 an overview sketch with the main flow directions, Fig. 3 an overview sketch with flow velocity and pressure curve, Fig. 4 a longitudinal section of the container with sieve body, Fig. 5 a cross section through the inflow plane of a first embodiment, Fig. 6 a perspective sketch of the first embodiment, Fig. 7 a cross section through the inflow plane of a second embodiment, Fig. 8 a perspective sketch of the second embodiment.

[0027] Fig. 1 shows the housing 1 of the degassing device from the outside. At the top of the housing 1 is the inflow device 2, which may also contain internal components not shown here and into which the gas-containing liquid 3 flows. Furthermore, at the bottom of the housing 1 is the outflow device 4, from which the degassed liquid 5 flows. The inflow device 2 and the outflow device 4 are both arranged tangentially, whereby it is irrelevant whether they are radially offset from one another, i.e. rotated relative to one another, or vertically aligned. In the upper area is the gas outlet 6, which may also be connected to another separator or a separation device for air and flammable gas.

[0028] Fig. Figure 2 shows an overview sketch of the housing 1, cut open from the side, with the inflow device 2, the outflow device 4, the gas outlet 6 and the main flow directions of the liquid 3 during inflow, the liquid flow 8 pushed outwards by centrifugal force and guided downwards in a spiral manner, the degassed liquid 5 and the upward-flowing gas 9, which reaches the sieve body 7, which is connected to the gas outlet 6. Because the centrifugal forces push the liquid outwards against the container wall, a negative pressure is created inside around the central axis, in which the gas bubbles can collect and rise upwards. At the height of the sieve body 7, the resulting parabolic liquid level causes the gas to collect as a homogeneous phase and is discharged via the gas outlet 6.

[0029] Fig. 3 shows an overview sketch with the radial course of the tangential velocity 10 and the radial course of the system pressure 11, each qualitatively, over the diameter of the housing 1. The other elements correspond to those in Fig. 1 and Fig. 2.

[0030] Fig. Figure 4 shows a longitudinal section of the container 1 with the sieve body 7, which is fixed at the upper end 12 and at the lower end 13. Instead of the fixations 14, guided bearings can also be provided if the sieve body 7 is to rotate.

[0031] Fig. Figure 5 shows a cross-section through the inflow plane of a first embodiment of the housing 1, in which the inflow device 2 and the outflow device 4 are both located in a vertical plane. The remaining elements correspond to those in the previous figures.

[0032] Fig. Figure 6 shows a perspective sketch of the first embodiment, the elements corresponding to those in the previous figures.

[0033] Fig. Figure 7 shows a cross-section through the inflow plane of a second embodiment of the housing 1, in which the inflow device 2 and the outflow device 4 are both located on the same side plane. The remaining elements correspond to those in the previous figures.

[0034] Fig. Figure 8 shows a perspective sketch of the second embodiment, the elements corresponding to those in the previous figures. List of reference symbols 1 housing 2 Inflow device 3 gaseous liquid 4 Outlet device 5 degassed liquid 6 Gas outlet 7 sieve bodies 8 Fluid flow 9 upward flowing gas 10 radial course of the tangential velocity 11 radial course of the system pressure 12 upper end of sieve body 13 lower end of sieve body 14 Fixation / Storage QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2011 011 210 A1

[0003] DE 11 2019 001 344 T5

[0005] DE 11 2019 001 350 T5

[0005] DE 11 2019 001 351 T5

[0005] WO 2021 / 160221 A1

[0007] DE 20 2018 003 488 U1

[0009] DE 10 2010 032 394 A1

[0009] DE 20 2018 000 709 U1

[0009] EP 2 988 043 B1

[0009] EP 1 035 365 B1

[0009] WO 2006 / 000453 A1

[0009] EP 3 513 855 A1

[0010] EP 3 747 532 A1

[0011] EP 3 764 001 A1

[0012] EP 3 882 526 A1 [0012, 0013] EP 4 166 854 A1

[0014]

Claims

[1] Degassing device suitable for the secondary circuit of a heat pump, - which has a vertically arranged cylindrical housing (1) and is permeable to flow, and - a tangential inlet (2) for a liquid flow is arranged in the upper part of the cylindrical housing, and - a central opening (6) is provided at the upper end of the upper part of the cylindrical housing, characterized by , that - a sieve body (7) is sealingly fixed to this central opening (6), which protrudes into the cylindrical housing (1) and is equipped with a closing device to prevent liquid from escaping from the central opening, - the central opening (6) is connected to a gas outlet, - a tangential outlet (4) for a liquid flow is provided at the lower end of the lower part of the cylindrical housing (1). [2] Device according to claim 1, characterized bythat the tangential inlet (2) in the upper housing part of the cylindrical housing (1) is designed as a nozzle. [3] Device according to claim 2, characterized by that the nozzle is designed as a thrust jet nozzle with which the inflow velocity of the incoming flow (3) can be adjusted. [4] Device according to one of claims 2 or 3, characterized by that the inflow direction of the incoming flow (3) is adjustable. [5] Device according to one of claims 2 to 4, characterized by that a device for twisting the liquid flow is provided in front of or in the nozzle. [6] Device according to one of claims 1 to 5, characterized by that the sieve body (7) is designed as a cylindrical, frustoconical or prism-shaped perforated plate which extends from the gas outlet (6) on the upper side of the cylindrical housing (1) to the lower region of the cylindrical housing (1). [7] Device according to claim 6, characterized by that the holes in the perforated plate of the sieve body (7) are shaped in such a way that a serrated surface is formed on the edges of the openings directed towards the central axis. [8] Device according to one of claims 6 or 7, characterized by that the sieve body (7) is freely mounted and can rotate with the flow around the central axis. [9] Device according to one of claims 6 to 8, characterized by that a mesh is provided within the sieve body (7). [10] Device according to one of claims 6 to 8, characterized by that a droplet separator is provided at the gas outlet (6) within the sieve body (7).

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