Gas leakage management

Abstract

Device and method for the secondary circuit of a heat pump, the primary circuit of which comprises a refrigeration circuit with a flammable or hazardous refrigerant and whose operating pressure is higher than the pressure of the secondary circuit, further comprising an auxiliary heater in the secondary circuit downstream of the heat exchanger in this line, wherein the auxiliary heater has a vertical, cylindrical housing, the cylindrical housing having an upper part and a lower part, 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 gas separator is sealedly fixed to this central opening, the gas separator is connected to at least one gas outlet, and flow-through heating elements are provided in the lower part of the cylindrical housing of the auxiliary heater.A vent for a liquid flow is arranged at the lower end of the lower part of the cylindrical housing.

Description

[0001] The invention relates to the prevention of the transfer 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.

[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 their accidental release neither harms the climate nor the ozone layer, or at least their release is less harmful. However, such accidental release should be avoided whenever 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 flammable working fluid is circulated, and with a secondary circuit designed as a heating circuit. In the flow direction of the heating circuit, a check valve is closed 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. Quick air vents and membrane degassers are also known as degassing devices. The problem here is that the ignition limits for gas-air mixtures containing flammable refrigerants cannot be reliably maintained during degassing, and therefore safe and harmless discharge must be ensured.

[0008] Further quick vents are described in 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. In cases where flammable refrigerants are expected to be present in the gas-air mixture to be separated, vents have also been described in which separation is already performed within the vent itself. This is preferably achieved using membranes; suitable membrane separators are described, for example, in EP 3 747 532 A1 and EP 3 932 513 A1 by the applicant. Another separation and venting process and a corresponding device are described in DE 10 2019 111 017 A1, in which the gas-air mixture is discharged together. A safety valve, a quick vent, and a bubble separator can be integrated. An early precursor to this is described in JP S48-50 338 A.

[0009] However, these methods and devices are complex and expensive and often do not solve the problem satisfactorily under all operating conditions. The object of the invention is therefore to provide a device and method suitable for heat pumps in which such a leak-related transfer of refrigerant could occur due to the pressure conditions, and which should then be managed without great effort and damage. This takes advantage of the fact that modern heat pumps usually also have auxiliary heaters, which are usually electrically operated and are used during peak loads or for the occasional heating of drinking water to prevent Legionella growth.

[0010] The task is solved by a device for the secondary circuit of a heat pump, whose primary circuit has a refrigeration circuit with a flammable or dangerous refrigerant and whose working pressure is above the pressure of the secondary circuit, the heat pump comprising at least one compressor, at least one expansion device, and at least two heat exchangers, one of which is connected by lines to a secondary circuit with a heat transfer medium, further comprising an additional heater in the secondary circuit downstream of the heat exchanger in this line, wherein the additional heater has a vertical, cylindrical housing, the cylindrical housing has an upper part and a lower part, 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 gas separator is sealingly fixed to this central opening,the gas separator is connected to at least one gas outlet, heating devices are provided in the lower part of the cylindrical housing of the auxiliary heater around which flow can take place, and an outlet for a liquid flow is arranged at the lower end of the lower part of the cylindrical housing.

[0011] The tangential inlet at the top creates a rotating flow, pushing the liquid outward and any gaseous components inward due to their lower density, similar to a hydrocyclone. If gas is present in the liquid, a funnel-shaped liquid surface is created, from which the gas can be extracted in the center of the top. This gas is separated by the gas separator and, since it may contain flammable components, is discharged to the outside via a pipe.

[0012] Designs relate to the upper part of the cylindrical housing and the tangential liquid inlet. The liquid inlet can be designed as a nozzle. The fact that the flow is accelerated by the nozzle effect creates a pressure drop that improves bubble formation for dissolved gas. To enhance the centrifugal effect, baffles can be provided in a further design; these can narrow or widen the flow cross-section and thus the flow. Furthermore, the upper part of the cylindrical housing can have a larger diameter than the lower part. All of this can also be achieved in combination. For example, the baffle can initially narrow the flow to create a nozzle effect and then widen and deflect it, slowing the flow so that it can enter the lower part of the cylindrical housing without significant turbulence.

[0013] Further designs concern the lower part of the cylindrical housing and the fluid drain. The heating devices are located in the lower part. These can be either electric heating coils or pipes through which hot fluid flows, where the fluid has been heated with a conventional burner. Operation with waste heat from other heat sources is also possible in this way. Regardless of the heating medium, the heating coils can consist either of U-profiles inserted from below into the lower part of the cylindrical housing or of heating coils connected at the sides.

[0014] Further embodiments relate to the gas separator. This is preferably designed as a membrane separator, which separates the gas phase from the liquid phase via a first membrane and air from refrigerant vapors via a second membrane.

[0015] The invention also achieves the object by a corresponding method for preventing the transfer 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, by means of a cylindrical gas separator with integrated additional heater provided downstream of the heat exchanger, wherein a heat carrier flow is introduced into a tangential inlet into a vertical, cylindrical housing, wherein the heat transfer medium flow with gas bubbles contained therein is pressed against the outer wall of the upper part of the cylindrical housing by centrifugal forces, whereby the gas bubbles reach the center of the flow, where they are separated by centrifugal force and drawn upwards via a gas separator, while the heat transfer medium flow is guided downwards past heating devices of the additional heater and leaves the cylindrical housing via an outlet arranged in the lower part of the housing.

[0016] The advantage of this is that the centrifugal flow promotes heat transfer at the heating devices by creating a forced flow. Furthermore, gas bubbles from outgassing refrigerant cannot cling to the heat transfer surfaces, as is often observed with boiling liquids. This applies to all types of heating devices, such as heating loops or, depending on the design of the heating devices, ceramic radiators.

[0017] In further embodiments of the method, it is provided that the heating devices of the additional heater are heated with electrical current, with waste heat or with solar thermal energy or combinations thereof.

[0018] The invention is described below by way of example with reference to Fig. 1 bis Fig. 3 explained in more detail. Fig. 1a, 1b, 1c show a first embodiment, Fig. 2a, 2b, 2c show a second embodiment, Fig. 3a, 3b, 3c show a third embodiment.

[0019] Fig. 1 shows the device in a first embodiment, wherein Fig. 1a a longitudinal section and Fig. 1 b and Fig. 1c show two sections across the height. Fig. 1a shows the additional heater 1 with the inlet 2, the upper housing part 3, the gas separator 4, the lower housing part 5, the heating devices 6 and the outlet 7. Fig. 1b shows a section S1-S2 seen from below through the upper housing part 3 with the guide plate 8. Fig. 1c shows a section S3-S4 seen from above with the heating devices 6 and the drain 7.

[0020] Fig. 2 shows the device in a second embodiment, wherein Fig. 2a a longitudinal section and Fig. 2b und Fig. 2c show two sections across the height. In contrast to Fig. 1 The upper and lower housing sections 3 and 5, respectively, have the same diameter and are made from a single piece. The guide vane 8 initially tapers the flow cross-section and then widens it, creating a jet effect.

[0021] Fig.3 shows the device in a second embodiment, wherein Fig. 3a a longitudinal section and Fig. 3b und Fig. 3c show two sections across the height. In contrast to Fig. 2 No guide plate is used in the upper housing part 3, but the inlet 2 is designed as a nozzle. List of reference symbols

[0022] 1Auxiliary heater 2Inlet 3Upper housing section 4Gas separator 5Lower housing section 6Heating devices 7Drain 8Baffle

Claims

1. Device for the secondary circuit of a heat pump, - the primary circuit of which has a refrigeration circuit with a flammable or dangerous refrigerant whose working pressure is higher than the pressure of the secondary circuit, - the heat pump comprising at least one compressor, at least one expansion device, at least two heat exchangers, - one of which is connected by lines to a secondary circuit with a heat transfer medium, - further comprising an additional heater (1) in the secondary circuit downstream of the heat exchanger in this line characterized in that- the additional heater (1) has a vertical, cylindrical housing, - the cylindrical housing has an upper housing part (3) and a lower housing part (5), - a tangential inlet (2) for a liquid flow is arranged in the upper housing part (3) of the cylindrical housing, - a central opening is provided at the upper end of the upper housing part (3) of the cylindrical housing, - a gas separator (4) is sealingly fixed to this central opening, - the gas separator (4) is connected to at least one outlet for gas, - heating devices (6) around which flow can occur are provided in the lower housing part (5) of the cylindrical housing of the additional heater (1), - an outlet (7) for a liquid flow is arranged at the lower end of the lower housing part (5) of the cylindrical housing.

2. Device according to claim 1, characterized in that the tangential inlet (2) in the upper housing part (3) of the cylindrical housing is designed as a nozzle.

3. Device according to one of claims 1 or 2, characterized in that at least one guide plate (8) is provided on the tangential inlet (2) in the upper housing part (3) of the cylindrical housing.

4. Device according to claim 3, characterized in that at least one guide plate (8) narrows the flow cross-section.

5. Device according to claim 3, characterized in that at least one guide plate (8) widens the flow cross-section.

6. Device according to claim 1, characterized in that in the lower housing part (5) of the cylindrical housing of the additional heater (1) heating coils are provided as heating devices (6).

7. Device according to claim 6, characterized in that U-profiles or heating spirals or ceramic bodies or combinations thereof are provided as heating coils in the lower housing part (5) of the cylindrical housing of the additional heater (1).

8. Device according to claim 1, characterized in that the gas separator (4) is designed as a membrane separator.

9. Device according to claim 8, characterized in that the gas separator (4) is equipped with a first membrane for separating the gas phase from the liquid phase and with a second membrane for separating air and refrigerant vapors.

10. A method for preventing the transfer 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, by means of a cylindrical gas separator (4) with integrated additional heater (1) provided downstream of the heat exchanger, wherein a heat transfer medium flow is introduced into a tangential inlet (2) in a vertical, cylindrical housing (3), characterized in that- the heat transfer medium flow with gas bubbles contained therein is pressed against the outer wall of the upper part (3) of the cylindrical housing by centrifugal forces, - whereby the gas bubbles reach the centre of the flow, where they are separated by centrifugal force and drawn off upwards via a gas separator (4), - whilst the heat transfer medium flow is guided downwards past the heating devices (6) of the additional heater (1) - and leaves the cylindrical housing via an outlet (7) arranged in the lower housing part (6).

11. Method according to claim 10, characterized in that the heating devices (6) of the additional heater (1) are heated with electric current, with waste heat or with solar thermal energy or combinations thereof.

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