Security concept which is effective in two steps adsorptive

Abstract

Device for separating leakage-related contamination from the air in the casing of a heat pump, which is to be installed in a building and in which a closed refrigeration circuit with a hazardous refrigerant is operated within the sealed casing of the heat pump, by means of sorptive measures, wherein at least one outer adsorber is provided which is pneumatically connected to the environment of the heat pump casing and to the interior of the heat pump casing, and has an inlet side to the interior of the heat pump casing and an outlet side to the interior of the building, wherein furthermore at least one inner adsorber is provided which is pneumatically connected to the interior of the heat pump casing, but has no pneumatic connection to the environment of the heat pump casing and only at least one inlet side from the interior of the heat pump casing.

Description

[0001] The invention relates to an adsorptive protective device for use in heat pumps with hazardous refrigerants for domestic energy supply. If these refrigerants are unintentionally released, they can be harmful to the environment and climate, toxic to humans, or flammable. Such a release must therefore be prevented. The adsorbive protective device is implemented in a two-stage design, with both stages operating independently of each other. The stages comprise an actively flowed-through and a passively flowed-through sorption bed. The sorption can be physical adsorption, chemical chemisorption, or a combination of both. Hereinafter, the term adsorption will be used.

[0002] German patent application DE 10 2019 114 738 A1 discloses a device for the safe operation of a left-hand thermodynamic cycle, in particular a heat pump, using flammable and / or toxic refrigerants. The refrigerant is circulated in a closed, hermetically sealed working fluid circuit, comprising at least one compressor for the working fluid, at least one expansion device for the working fluid, at least two heat exchangers for the working fluid, each with at least two sink and source connections for heat transfer fluids, an inner housing that encompasses all components connected to the closed working fluid circuit and may include further components, and at least one external adsorber that provides at least one pneumatic connection via the sorbent between the inner housing and the installation location.This path, which refrigerant-containing gas can take from the interior through the sorbent into the installation environment, always remains open.

[0003] From the publication DE 10 2019 114 744 A1, a further device for the safe execution of a left-handed thermodynamic cycle, in particular a heat pump, with flammable and / or toxic refrigerants is known, in which the refrigerant is also guided in a closed, hermetically sealed working fluid circulation, also comprising at least one compressor for working fluid, at least one expansion device for working fluid, at least two heat exchangers for working fluid each with at least two sinks or...The device comprises source-side connections for heat transfer fluids, an inner housing encompassing all components connected to the closed working fluid circuit and potentially including further components, and at least one external adsorber, which provides at least one pneumatic connection via the sorbent between the inner housing and the installation room. Furthermore, the device is designed such that, in the event of overpressure within the inner housing, it is lifted, thereby opening the path through the external adsorber where the refrigerant is separated. In a depressurized state, this path is always closed by the sorbent.

[0004] The function of the external adsorber is to remove any escaping gaseous refrigerant from the refrigeration circuit in the event of a leak. For this purpose, the external adsorber is filled with an adsorbent. This type of technology is described, for example, in DE 10 2011 116 863 A1, a method for securing a device for a thermodynamic cycle that is operated with a process fluid containing or consisting of at least one environmentally hazardous, toxic, and / or flammable substance. In the event of a leak in the device for a thermodynamic cycle, an adsorbent is brought into contact with the process fluid, in particular ammonia, propane, or propene, and the substance is selectively bound by the adsorbent. The adsorbent is regenerated after use.DE 195 25 064 C1 describes a refrigeration machine with a gas-tight housing which accommodates all refrigerant-carrying components of the machine, a space connecting the interior of the gas-tight housing to an outlet is provided, and the space is filled with a substance that absorbs the refrigerant.

[0005] For a linearly elongated, open-ended external adsorber, the sorption bed presents a flow resistance which, in the event of a leak, leads to a pressure increase within the refrigeration circuit casing. During the leak, the free volume of the inner casing becomes saturated with refrigerant in the gas phase. The internal pressure increase in the slightly pressurized refrigeration circuit casing generates an equalizing flow through the external adsorber towards the installation room, and the refrigerant is absorbed by the sorbent within the external adsorber. After the pressure potential towards the installation room has equalized, the flow from the refrigeration circuit casing into the external adsorber decreases until it comes to a standstill.

[0006] A refrigerant partial pressure develops in the inner housing, depending on the loading state of the adsorbent at the inlet of the outer adsorber. Due to the high loading of the adsorbent at the inlet of the outer adsorber, a high, potentially flammable concentration results, creating a critical atmosphere in the free volume within the refrigeration circuit housing. The hazard potential is derived from the size of the free volume within the refrigeration circuit housing. This also applies analogously to toxic and other hazardous refrigerants that may leak. Therefore, opening the housing for repair purposes is not readily possible.

[0007] The object of the invention is therefore to provide a sorption device in which the described problems no longer occur.

[0008] The problem is solved by means of at least one device for separating leakage-related contamination from the air in the casing of a heat pump, which is to be installed in a building and in which a closed refrigeration circuit with a hazardous refrigerant is operated, by sorptive measures, wherein at least one outer adsorber is provided which is pneumatically connected to the environment of the heat pump casing and to the interior of the heat pump casing, and has an inlet side to the interior of the heat pump casing and an outlet side to the interior of the building, wherein furthermore at least one inner adsorber is provided which is pneumatically connected to the interior of the heat pump casing, but has no pneumatic connection to the environment of the heat pump casing and only at least one inlet side from the interior of the heat pump casing.

[0009] Such an additional adsorber connected to the inner casing, hereinafter referred to as an internal adsorber, which is not pneumatically connected to the installation space and therefore not subject to airflow, represents at least one separate sorptive collection capacity for the refrigerant in the gas phase. Such an internal adsorber does not necessarily have to be located inside the heat pump casing; it can also be, for example, attached externally, connected to the inner casing only via an opening. This has the advantage that it can be retrofitted and easily replaced if necessary. It is also advantageous to provide a multitude of such internal adsorbers in the free spaces within the heat pump casing instead of a single internal adsorber.

[0010] Due to the prevention of active flow, the sorption kinetics of this internal adsorber are significantly reduced compared to that of the external adsorber; typically, the factor is between 0.01 and 0.8. This gives the internal adsorber the property of adsorbing the refrigerant in the gas phase within the interior space with a time delay, thus reducing the gas concentration to a non-critical range.

[0011] When positioning the internal adsorber within the heat pump casing, a position at the lowest point of the casing should be avoided. This prevents the opening of the internal adsorber from coming into direct contact with fluids that could impair its sorption function, especially if moisture such as condensate accumulates (i.e., source or sink fluid). Therefore, each internal adsorber must be protected against liquid ingress from inside the heat pump casing. The position and shape of the internal adsorbers can be adapted to the available installation space. Consequently, the casing housing the adsorber must be designed to prevent the absorption of any leaked fluid, except for refrigerant, in its liquid phase. Therefore, inlet openings must be provided in the upper area of ​​the internal adsorber and in the upper area inside the heat pump casing.When designing the internal adsorber, the openings must be protected in such a way as to prevent a direct flow of refrigerant onto the adsorption bed.

[0012] Further design considerations relate to the external adsorber and its structural coordination with the internal adsorbers. The geometry of the external adsorber should be dimensioned such that, in the event of a leak, the impedance of the sorption bed for the escaping refrigerant and the displaced air from the remaining volume of the heat pump's inner casing is so low that the pressure rise should not exceed 50 kPa. Preferably, the pressure drop across the adsorber bed is significantly lower, so that no high pressure can build up in the inner casing.

[0013] In general, the opening cross-section of the external adsorber towards the internal volume of the heat pump housing Ain should be significantly larger than the opening cross-section of the external adsorber towards the installation room Aout. This results in a significantly higher impedance for the non-absorbing air flowing into the installation room.

[0014] In the case of refrigerant R290, the inlet area relative to the amount of refrigerant in the refrigeration circuit is between 50 cm² / kg R290 and 105 cm² / kg R290, and the outlet area is between 1 cm² / kg R290 and 105 cm² / kg R290.

[0015] The free volume should be as small as possible to minimize the amount of air to be displaced, thus allowing the flow resistance encountered by the displaced air to be neglected. The flow length L, together with the cross-sectional profile and external geometry, ensures a defined impedance of the sorption bed. Again, the design should not generate a pressure rise above 50 kPa in the refrigeration circuit casing at maximum leakage rate. The flow length through the external adsorber should range from 1 cm / kg R290 to 100 cm / kg R290.

[0016] The following section considers the design of the internal adsorber. The geometry of the internal absorber should be dimensioned such that, in the event of a leak, the impedance of the sorption bed for the escaping refrigerant and the displaced air from the remaining volume of the heat pump casing is sufficiently high, and the kinetics of the sorption process of the external adsorber are such that loading of the internal adsorber only occurs within a small penetration depth. This results in a mean penetration rate range, i.e., the velocity of a breakthrough front, for the internal adsorber of: 1 mm / h R290 to 1000 mm / h R290 at 50 kPa overpressure and a saturated R290 atmosphere, using R290 as the refrigerant as an example.

[0017] The geometry of the internal adsorber should be adapted according to the penetration rate. The penetration rate is largely determined by the sorptive properties of the adsorbent and the geometry of the sorbent particle. Generally, the sorbent is described by its geometric specifications and chemical-physical data. In addition to the maximum loading capacity (isotherms), information describing the sorbent material is also provided.

[0018] Regardless of the manufacturing process, i.e., whether from powder, granules, or extrudate, the particle size is specified, which also influences the fixed-bed porosity and thus the flow characteristics of the sorption bed, and consequently the impedance. The hydraulic diameter, i.e., the mesh size, ranges from 0.01 mm to 15 mm. Due to the low penetration rate, the adsorbent can also form as a solid with a corresponding macroscopically porous structure or as a structured molded body.

[0019] Further design features relate to the geometric shapes of both the internal and external adsorbers. The following design characteristics are applied to the adsorption beds. Geometric ratios of entry area to bed depth (single-sided, double-sided, multi-sided opening), layering with different sorbents (material, grain sizes / bulk density, ratio of active to inert material (filler)), cross-sectional changes over the bed depth, the bed can be bent and / or folded.

[0020] Further details concern the installation and placement of the internal adsorbers. Each internal adsorber can be spatially The components can be integrated both within the dense heat pump housing shell and within the housing shell, as well as tightly and form-fittingly connected to / into the heat pump housing shell, or arranged around the refrigeration circuit housing in the form of a rectangular or annular gap design with corresponding openings to the interior or a combination thereof.

[0021] For externally connected internal adsorbers, the enclosure of the heat pump housing can be vertically or horizontally divided, with the shape of the heat pump housing being replicated accordingly. The service opening can be left open. It is also possible to combine external internal adsorbers with sound insulation, for example by incorporating adsorbent particles into insulating materials, such as by filling them with open-cell foam.

[0022] A major advantage of such internal adsorbers is that during a leakage phase, only a small amount of refrigerant is initially adsorbed, and then, in the phase after the leakage ceases, sufficient adsorption capacity remains available to ensure that the concentration reduction within the heat pump casing is kept to a non-critical minimum. This has also been demonstrated in numerous test series with R290.

[0023] If multiple internal adsorbers are used, for example to fill the gaps between installations, the geometric relationships, as well as their mounting and placement, can vary depending on the available space and requirements.

[0024] The invention is explained by means of examples in the Fig. 1 bis Fig. 7 explained in more detail, it shows Fig. 1: a heat pump housing with an external adsorber and an internal adsorber, Fig. 2: a heat pump housing with an external adsorber and three internal adsorbers, Fig. 3: three designs of different internal adsorbers, Fig. 4: a heat pump housing with an external adsorber and another internal adsorber with several openings, Fig. 5: a heat pump housing with an external adsorber and an internal adsorber integrated into the housing wall, Fig. 6: a heat pump housing with an external adsorber and an internal adsorber flanged to the outside of the heat pump housing, Fig. 7: three variants of internal adsorbers that partially enclose the heat pump housing.

[0025] Fig. 1 Figure 1 shows a heat pump housing 1 with an external adsorber 10 and an internal adsorber 13. A conventional left-hand rotating refrigeration circuit 4 is used, comprising a compressor 3, an expansion valve 5, an evaporator 6, and a condenser 7. These components can be expanded in various ways, for example, by adding a switching option for cooling purposes and a separate circuit for domestic hot water preparation. The refrigeration circuit also includes heat sink connections 8 and heat source connections 9.

[0026] The external adsorber 10 conforms to conventional state-of-the-art technology and can be stretched, bent, folded, divided, and equipped with different layers of adsorbents. Furthermore, its cross-section can be varied across the bed depth, i.e., it can be stepped, linear, or discontinuous, either increasing or decreasing in width. Its specific design, however, is always determined in conjunction with the design of the internal adsorber 13 and based on the properties of the refrigerant and adsorbent.

[0027] The external adsorber 10 has at least one inlet area 11, which is directed into the interior of the heat pump housing, and an outlet area 12, which is connected to the environment, i.e., usually to the installation room, via a pneumatic connection. Alternatively, there can also be a connection to the environment outside the building or a switchable connection between the building interior and the outside environment.

[0028] During the separation process in the event of a leak, the inflowing quantity of the refrigerant-air mixture is greater than the outflowing quantity, which is depleted of the refrigerant gas components. Accordingly, not only the flow cross-sections of the external adsorber 10, but also the opening cross-sections 11 and 12 can be adapted to the expected gas volumes in their anticipated size; the dimensioning depends on the empty space volume and the refrigerant inventory of the heat pump.

[0029] The internal adsorber 13 is located inside the heat pump housing 1, with its opening situated in the upper area. This reliably prevents soot buildup due to liquid accumulation, such as condensation.

[0030] Fig. 2 Figure 1 shows a heat pump housing 1 with an external adsorber 10 and three internal adsorbers 131, 132, and 133. These three internal adsorbers 131, 132, and 133 fill the voids in the heat pump housing 1 between the individual components. They can also be formed from encased foams impregnated with an adsorbent. The remaining components correspond to those of the Fig. 1 .

[0031] Fig. 3 shows three versions of different internal adsorbers 131, 132 and 133, as used in Fig. 2 They are used, and are additionally equipped with refrigerant jet protection devices. In this case, these are the splash guard plates 134, which are fixed over the openings.

[0032] Fig. 4 shows a heat pump housing 1 with an external adsorber 10 and another internal adsorber 135 with several openings, which can also be divided.

[0033] Fig. 5 Figure 1 shows a heat pump housing 1 with an external adsorber 10 and an internal adsorber 136 integrated into the housing wall. The opening of the internal adsorber 136 faces the interior; the choice of material for the internal adsorber 136 contributes to the housing stability.

[0034] Fig. 6 Figure 1 shows a heat pump housing 1 with an external adsorber 10 and an external internal adsorber 137, which is flanged to the outside of the heat pump housing 1. Instead of openings, a channel 15 is provided through which the refrigerant-air mixture can, if necessary, enter the external internal adsorber 137. The channel 15 can be equipped with a shut-off device, thus allowing for easy replacement during routine maintenance.

[0035] Fig. 7Figure 1 shows three variants of internal adsorbers 138, 16, and 139 that partially enclose the heat pump housing 1. Although they are located on the outside of the heat pump housing 1, they are internal adsorbers because their openings 17 point directly into the interior of the heat pump housing 1 and there is no pneumatic connection to the outside. This arrangement is particularly advantageous when the heat pump housing 1 is formed on its exterior by modular struts, which could also be used to seal and accommodate the enclosing internal adsorbers. It is advantageous if the internal adsorbers only enclose a portion of the heat pump housing 1 and the remaining, unenclosed portion is covered by the service opening and the external adsorber. Reference symbol list

[0036] 1 Heat pump casing / Heat pump housing shell 2 Refrigeration circuit 3 Compressor 4 Refrigeration circuit piping 5 Expansion valve 6 Evaporator 7 Condenser 8 Heat sink connections 9 Heat source connections 10 External adsorber 11 External adsorber inlet area 12 External adsorber outlet area 13 Internal adsorber 131 Vertical internal adsorber 132 Molded internal adsorber 133 Corner internal adsorber 134 Splash guards 135 Internal adsorber with multiple openings 136 Internal adsorber integrated into the heat pump wall 137 External internal adsorber 138 Rectangular external internal adsorber 139 Round external internal adsorber 14 Internal adsorber inlet area 15 Duct 16 Circular external internal adsorber

Claims

1. Device for separating leakage-related contamination from the air in the housing of a heat pump, which can be installed in a building and in which a closed refrigeration circuit (2) with a hazardous refrigerant is operated within the sealed shell of the heat pump housing (1), by means of sorptive measures, wherein the device comprises the heat pump housing (1), and wherein at least one external adsorber (10) is provided, which is pneumatically connected to the environment of the heat pump housing (1) and to the interior of the heat pump housing (1), and has an inlet side to the interior of the heat pump housing (1) and an outlet side to the interior of the building, wherein at least one internal adsorber (13) is also provided, which is pneumatically connected to the interior of the heat pump housing (1), but has no pneumatic connection to the environment of the heat pump housing (1) and only has at least one inlet side from the interior of the heat pump housing, characterised in that each internal adsorber (13) is protected against liquid ingress from the interior of the heat pump housing (1), and inlet openings of each internal adsorber (13) are arranged in the upper region inside the heat pump housing (1).

2. Device according to Claim 1 , characterised in that at least one internal adsorber (13) is arranged inside the sealed heat pump housing (1).

3. Device according to one of claims 1 or 2, characterised in that at least one internal adsorber is integrated into the wall of the sealed heat pump housing (1).

4. Device according to one of claims 1 to 3, characterised in that at least one internal adsorber (13) is connected to / in the shell of the heat pump housing (1) in a sealed and form-fitting manner.

5. Device according to claim 1, characterised in that at least one internal adsorber (13) in the form of a rectangular or ring-shaped gap design with corresponding openings towards the interior or a combination thereof is arranged around the heat pump housing (1).

6. Device according to one of claims 1 to 5, characterised in that the sorption bed in the external adsorber (10) is dimensioned such that it does not allow an internal pressure in the heat pump housing (1) of more than 50 kPa when air flows out.

7. Device according to claim 1, characterised in that the ratio of the air outlet area to the gas inlet area of the external adsorber (10) is less than 1.

8. Device according to claim 7, characterised in that the ratio of the air outlet area to the gas inlet area of the external adsorber (10) is less than 0.1.

9. Device according to claim 8, characterised in that the ratio of the air outlet area to the gas inlet area of the external adsorber (10) is less than 0.01.

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