DE102019118977A1 - Adsorber cooling - Google Patents

Abstract

Device for the safe implementation of a counterclockwise thermodynamic cycle (1) by means of an inflammable working fluid, which is guided in a closed, hermetically sealed working fluid circuit, having at least one compressor (2) for working fluid, at least one expansion device (4) for working fluid, at least two heat exchangers ( 3, 5) for working fluid each with at least two connections (7, 8, 9, 10) for heat transfer fluids, a housing (6) which includes all devices connected to the closed working fluid circuit and can include further devices, at least one sorption channel (11) with an adsorber (12) containing activated carbon, through which gas can flow and the sorption channel (11) with the adsorber (12) and its inlet (13) and optionally an outlet (14) is arranged within the housing (6), the Sorption channel (11) opposite the interior of the housing (6) through thermal insulation (15), the sorption channel (11) can be closed at the gas inlet (13) and at the gas outlet (14), a switchable induced draft fan (16) is optionally connected to the gas outlet (14) of the sorption channel (11), and in the sorption channel (11) ) at least one cooling line (17) is laid, which is connected to a cooling medium.

Description

The invention relates to irregular states in refrigeration circuits in which a working fluid acting as a refrigerant is conducted in a thermodynamic cycle, such as the Rankine cycle, as well as their adsorptive safety device. These are mainly heat pumps, air conditioning systems and cooling devices, as are common in residential buildings. Residential buildings are understood to mean private houses, apartment complexes, hospitals, hotel facilities, restaurants and combined residential and commercial buildings in which people live and work permanently, in contrast to mobile devices such as car air conditioning systems or transport boxes, or industrial systems or medical technology devices. What these cycle processes have in common is that they generate useful heat or useful cooling using energy and form heat displacement systems.

The thermodynamic cycle processes used have been known for a long time, as have the safety problems that can arise when using suitable working fluids. Apart from water, the most popular working fluids of the time are flammable and poisonous. In the past century, they led to the development of safety refrigerants, which consisted of fluorinated hydrocarbons. However, it turned out that these safety refrigerants lead to global warming and that their safety-related harmlessness led to constructive inattention. Up to 70% of the turnover was accounted for by the need to refill leaky systems and their leakage losses, which was accepted as long as this was perceived as economically justifiable in individual cases and encouraged the need for replacement.

Today's refrigeration circuits are equipped with these safety refrigerants of safety class A1, i.e. they are non-toxic and non-flammable. The most common refrigerants in the field of heat pump applications are the refrigerants R134a, R407C and R410A, all of them fluorocarbon compounds. The use of these refrigerants was not subject to any restrictions until January 2015, the introduction of the F-gas regulation (EU) 517/2014 on January 01, 2015 will in future restrict the use of fluorocarbon refrigerants via quantity restrictions in the European Union in such a way that the Prices of previous refrigerants will rise significantly. The aim of the F-gas regulation is the medium-term ban of greenhouse gas-promoting refrigerants and the replacement by natural refrigerants or chemical refrigerants with a significantly reduced global warming potential.

However, it is disadvantageous that almost all refrigerant alternatives belong to the group of flammable refrigerants, especially the technically most promising refrigerants such as R290 (propane) and R1270 (propylene).

It is therefore extremely problematic, on the one hand, to adopt the design principles for refrigerant-carrying thermodynamic processes, which have apparently proven themselves well with safety refrigerants, and, on the other hand, to use the system concepts from the time before the introduction of safety refrigerants. This is also due to the fact that individual devices have now become complex systems, which has multiplied the number of possibilities for malfunctions and their consequences.

The DE 10 2011 116 863 A1 describes a method for securing a device for a thermodynamic cycle which is operated with a process fluid that contains or consists of at least one environmentally hazardous, toxic and / or inflammable 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. Zeolite, also in combination with imidazole or phosphates, and also CuBTC are proposed as adsorbents; the adsorbent can be in the form of a bed, a shaped body, a paint, a spray film or a coating. The support structure of the molded body can consist of a microstructure, lamellar structure, tube bundle, tube register and sheet metal and must be mechanically stable and greatly increase the surface area. The potentially contaminated air is usually circulated continuously, but it can also be initiated by a sensor that switches on the ventilation when a threshold value is reached or when an accident is detected. The adsorption can be carried out inside or outside a closed space.

The 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 with an outlet is provided, and the space is filled with a substance that sorbs the refrigerant. The amount of sorbent material is dimensioned in such a way that the entire amount of any refrigerant that may escape can be absorbed and kept away from the environment. The space filled with the sorbent material is open to the surroundings. With refrigerants that are heavier than air, the space is open at the bottom, with those that are lighter, it is open at the top, so that a conveying fan is not required. The sorbent is placed in the housing and completely encloses the refrigeration machine or the refrigerant-carrying devices. On its way to the outside, baffles are provided which prevent short-circuit currents and force escaping gas through the sorbent. A double-walled embodiment in which the sorbent is arranged in the double jacket is also possible. A measuring device for refrigerant can be provided at the exit of the space filled with the sorbent substance to the environment.

The EP 3 106 780 A1 describes a heat pump system which is housed in an airtight housing lined with a binder. An adsorption unit with forced ventilation can be arranged inside this housing, which cleans the air in the housing in recirculation mode. This recirculation mode can be carried out continuously or only in the event of a fault or at regular intervals. Downstream of this sorption stage, a pilot burner, a pilot flame, a catalytic burner or a heating wire can also be arranged, which burns any remaining combustible impurities. A fresh air supply in connection with the discharge of purified exhaust air is also conceivable.

The JP 2000 105003 A describes a refrigeration unit which is operated with a flammable working fluid, wherein the unit can consist of two parts, one of which is set up inside a building and the other outside in the open air. In order to prevent working fluid from escaping in the event of a leak, the inner walls of the inner housing are lined with adsorbent material and the lines of the part placed on the outside are coated with a coating of adsorbent material. Activated carbon, among other things, is proposed as an adsorbent.

The problem with the use of activated carbon as an adsorbent is that activated carbon ages in the air over time because slow oxidation processes take place. Due to the requirements of a safety concept for the availability over the service life of devices in which counter-clockwise circular processes are operated, such as heat pumps, degradation of the adsorbent must be avoided, especially if it could happen unnoticed.

Depending on the design, installation location and mode of operation of a heat pump, for example, there are different requirements for possible contamination of the adsorbent by co-adsorbents, i.e. VOC, water vapor from air humidity, atmospheric oxygen, temperature changes, and others. A distinction must be made between linings and sorption beds with flow. In the case of sorption beds with a flow, a distinction must be made between those that are in recirculation mode within a housing and those that ventilate to the outside. The invention relates to the former, although combinations with the previously mentioned circulating air-operated sorption beds and linings can also be used.

It is assumed in the following that the sorption bed is located in a channel with an inflow side and an outflow side within the housing, in which the counterclockwise cycle is also carried out. Instead of an elongated, linear sorption channel, however, other types of sorption channels can also be used and the units of the cyclic process carried out can also be arranged in a separate capsule housing, which is located within the common housing with the sorption channel, and are also covered by the invention, also those in which the sorption process takes place outside the housing ..

The loading of such sorption beds, which are open inwardly and outwardly in relation to the housing, by contamination is caused by diffusion and convection of contaminants, in the case of adsorption by the contaminating adsorptive. The contaminates can cause reversible or irreversible degradations of the sorption capacity of the sorption bed with respect to the exiting working fluid. The diffusion flow is driven solely by the concentration gradient, while convective inputs are caused by weather-induced air pressure or temperature gradients between the housing and the environment. The resulting pressure differences lead to equalizing flows into the housing and thus also through the sorption bed and the transport of contaminants into the sorption bed.

Contaminants from the housing in which the cycle process is carried out are oxygen, monohydric and polyhydric alcohols, moisture, drawing grease, cutting oils, foaming agents and RCM oils. In the case of activated carbon as the adsorbent material, the aging or degradation is determined by the temperature and the total amount of gas through which it flows.

• - mindestens einen Verdichter für Arbeitsfluid,
• - mindestens eine Entspannungseinrichtung für Arbeitsfluid,
• - mindestens zwei Wärmeübertrager für Arbeitsfluid mit jeweils mindestens zwei Anschlüssen für Wärmeüberträgerfluide,
• - ein Gehäuse, welches wenigstens den Verdichter und die Entspannungseinrichtung für Arbeitsfluid umfasst und weitere Einrichtungen umfassen kann,
• - mindestens einen Sorptionskanal mit einem Aktivkohle enthaltenden Adsorber, der von Gas durchströmt werden kann
• - und der Sorptionskanal mit dem Adsorber sowie seinem Gaseinlass verbunden ist, wobei
• - der Sorptionskanal gegenüber dem Inneren des Gehäuses durch eine thermische Dämmung begrenzt wird,
• - der Sorptionskanal am Gaseinlass verschließbar ist, und
• - im Sorptionskanal mindestens eine Kühlleitung verlegt ist, die an ein Kühlmedium angeschlossen ist.

The object of the invention is therefore to provide a safe device which no longer has the disadvantages described and whose degradation of the activated carbon adsorber is minimal. The invention solves the problem by a device for the safe implementation of a counterclockwise thermodynamic cycle by means of an inflammable working fluid, which in a closed, hermetically sealed working fluid circulation is performed, having

• - 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 connections for heat transfer fluids,
• - A housing which comprises at least the compressor and the expansion device for working fluid and can comprise further devices,
• - At least one sorption channel with an adsorber containing activated carbon through which gas can flow
• - And the sorption channel is connected to the adsorber and its gas inlet, wherein
• - the sorption channel is limited to the interior of the housing by thermal insulation,
• - The sorption channel at the gas inlet can be closed, and
• - At least one cooling line that is connected to a cooling medium is laid in the sorption channel.

In one embodiment it is provided that the sorption channel is equipped with a gas outlet and is connected to it. It can also be provided that a switchable induced draft fan is connected to the gas outlet of the sorption duct.

In one embodiment, the adsorber, the sorption channel and the gas inlet and gas outlet are arranged within the housing. However, it is also possible to arrange these outside the housing or, like the heat exchangers, evaporators and condensers, to integrate them into the housing wall.

Normally, the gas inlet and gas outlet of the sorption channel are closed with the activated carbon adsorber. The activated carbon is kept at a very low temperature by the cooling medium, which is well below the interior temperature of the housing. This drop in temperature has two effects: on the one hand, aging and degradation slow down, and on the other hand, the absorption capacity of the activated carbon increases. To do this, the adsorber must be kept permanently cool, which is why good thermal insulation is required.

In one embodiment of the invention, the device has a leakage detection system which automatically opens the closures at the gas inlet and, if present, at the gas outlet and automatically switches on the induced draft fan, if present, when a leak is detected. The leak detection system is usually a gas detector, a propane gas detector can be used, but other detection systems are also suitable. In the event of a power failure, the induced draft fan should always have a charged battery.

Further requirements concern the cooling medium. Although it is possible without any problems to use an externally available cooling medium if it is available cheaply, two possibilities can also be used to use cooling media that are used as working fluids in the cycle. It can alternatively be provided that either the cooling medium is relaxed working fluid, which flows in the flow direction after the expansion device and before the heat exchanger acting as an evaporator, or that the cooling medium is relaxed working fluid, which flows in the flow direction after the heat exchanger acting as an evaporator to the compressor.

In normal operation, only the heat loss that occurs despite the thermal insulation needs to be compensated, which means only a small loss. If the cycle is a heat pump that draws the energy from the evaporator, its use as a cooling medium even means an improvement in the heat yield. Otherwise, in the case of very low heat inputs to be compensated for by the thermal insulation, it can also be useful to pass only a small partial flow of the working fluid through the cooling lines.

The cooling lines are to be laid in the cooling channel in such a way that the adsorbent material remains accessible so that it can be removed and replaced if necessary. At the same time, however, sufficient heat transfer surface should be installed. This can be done by laying a cooling line in the middle of the sorption channel and equipping it with cooling fins in the longitudinal direction. The distances between the cooling fins should be greater than the particles of the activated carbon if an activated carbon bed is used as an adsorbent.

Left-turning circular processes are often not operated continuously throughout the year. After longer periods of standstill, it is therefore possible that no cooling medium has flowed through the cooling lines for a long time and the activated carbon adsorber has become warm. Since such restart processes are at the same time the operating states in which there is the highest risk of leakage, it makes sense to keep the adsorber always cooled. This Cooling can be done by Peltier elements, the task of which is to compensate for the temperature compensation through thermal insulation during downtimes.

Furthermore, latent heat accumulators can be used to slow down such a standstill-related temperature compensation. This can be done either as an additional layer on the thermal insulation or in the form of pellets that are mixed into the activated charcoal bed. Salts that carry out phase changes in the relevant temperature range can serve as materials, whereby they have to be provided with protective covers. Such materials are described in the prior art.

Since the activated carbon adsorber is closed during normal operation, it can be preloaded beforehand with a medium which has a lower adsorptive bond than the inflammable working fluid which is to be separated in the event of a leak. During the adsorption of the working fluid, the heat of adsorption causes the activated carbon adsorber to be heated, which is undesirable. On the other hand, the desorption of the displaced medium causes cooling. The medium to be displaced can already be adsorbed beforehand under high partial pressure, with the typical hysteresis curves causing initially no complete desorption at a reduced partial pressure. This overload with a medium to be displaced can lead to the fact that the heat effect is completely compensated for by the adsorption, although the lower adsorptive binding of the medium tends to use less binding energy. The higher amount of desorbed medium compensates for this. Nitrogen and carbon dioxide are used as preferred media; their desorption into the housing also reduces the risk of ignition in the event of a leak.

• - das Adsorbens mit einem Adsorbat vorbeladen ist, welches vom Adsorptiv verdrängt wird und dabei das Adsorbens kühlt,
• - das Adsorbat, mit dem das Adsorbens vorbeladen ist, Stickstoff oder Kohlendioxid ist,
• - das Adsorbens, welches mit dem Adsorbat vorbeladen ist, Aktivkohle ist,
• - das Adsorptiv, welches das Adsorbat verdrängt, das Kältemittel R290 ist.

In preferred embodiments it is therefore provided that

• - the adsorbent is preloaded with an adsorbate which is displaced by the adsorptive and thereby cools the adsorbent,
• - the adsorbate with which the adsorbent is preloaded is nitrogen or carbon dioxide,
• - the adsorbent which is preloaded with the adsorbate is activated carbon,
• - The adsorptive that displaces the adsorbate is the refrigerant R290.

The housing can either be closed or designed with openings. If the gas is to remain inside the housing, either a forced circulation must be provided, which is operated by a conveying fan, or the adsorption of the working fluid that has escaped takes place solely through diffusion. If the discharge of the gas depleted of working fluid or completely freed from it can be allowed, either a conveyor fan can suck the gas out of the sorption duct and convey it to the outside via an outlet opening, whereby an equally large air flow must be fed in from the outside through an opening, or the Any overpressure in the housing that may arise in the event of a leak drives the gas through the sorption channel out of the outlet opening.

However, as soon as the remaining working fluid diffuses into the sorption channel after pressure equalization has taken place, a negative pressure would arise that has to be equalized. If one were to allow a return flow through the outlet opening and the associated sorption channel, partial desorption would also have to be expected, which is undesirable. For this reason, a separate inlet opening is provided in the housing, which is designed as a vacuum protection.

• 1: eine Wärmepumpe mit einem Sorptionskanal und Zwangsumluft,
• 2: eine Wärmepumpe mit einem Sorptionskanal und Lufteinleitung,
• 3: eine Wärmepumpe mit einem Sorptionskanal und Zwangsspülung,
• 4: eine Wärmepumpe mit einem Sorptionskanal und passiver Spülung.

The invention is explained in more detail below with the aid of four basic sketches. Here show:

• 1 : a heat pump with a sorption duct and forced air circulation,
• 2 : a heat pump with a sorption duct and air inlet,
• 3 : a heat pump with a sorption channel and forced flushing,
• 4th : a heat pump with a sorption channel and passive flushing.

1 shows a heat pump with a cooled adsorber and forced circulation using a schematic diagram of a refrigeration circuit 1 with a compressor 2 , a capacitor 3 , a pressure reduction 4th and an evaporator 5 in one housing 6th . The heat pump has a heat source connection 7th , a heat source flow 8th , a heat sink feed 9 and a heat sink connector 10 .

Furthermore, the sorption channel is in the housing 11 with the activated carbon adsorber 12 arranged. The sorption channel 11 is with the cooling pipe 17th equipped, also optionally with the Peltier elements 19th and latent heat storage pellets. The cooling pipe 17th is integrated into the cycle, the cooling medium is also the working fluid. It will be behind the relaxation device 4th , which is usually a regulated expansion valve, tapped and passed through the cooling line 17th back into the refrigeration cycle 1 led where it went in the evaporator 5 got. Furthermore, the sorption channel is after all Thermally insulated sides, taking into account the thermal insulation 15th great importance is attached.

The refrigeration cycle 1 is used in this example with the flammable working fluid propane, which is also known as R290 is known to operate. Propane is heavier than air, so in the event of a leak in the refrigeration circuit it will sink 1 tends to be in the housing 6th downwards, although it mixes well with small leaks. Such a leak is caused by the gas detector 18th recognized. In the lower part of the case 6th is therefore an opening with a lockable gas inlet 13th provided, through which an air-propane mixture from the interior into the sorption channel 11 with the activated carbon adsorber 12 gets when gas inlet 13th and gas outlet 14th at the request of the gas detector 18th be opened.

In such a case, the gas detector also pulls this 18th automatically activated induced draft fan 16 a defined amount of gas through the activated carbon adsorber, with purified air, optionally enriched with the inert gases nitrogen and carbon dioxide, being returned to the housing. If possible, the cooling circuit will be used 1 Operated a little further to increase the cooling capacity for the activated carbon adsorber 12 ensure. As soon as the activated carbon adsorber is loaded, gas will be admitted 13th and gas outlet 14th closed again and the induced draft fan 16 is switched off like the rest of the heat pump and the service is called.

Fig _{. 2} shows an embodiment in which the forced circulation is dispensed with. In the event of a leak, the inflammable gas components diffuse through the gas inlets 13th which in this example are located both on the top and on the bottom of the sorption channel 11 are located in the activated carbon adsorber 12 .

3 shows an embodiment in which an induced draft fan 16 the loaded gas, as in 1 shown, the gas through the sorption channel 11 pulls as soon as a leak is detected. In contrast to this, however, the gas does not circulate within the housing 6th but to the outside via the outlet opening 21st directed. A corresponding amount of air is introduced through the inlet opening 20th tracked from the outside.

4th shows an embodiment in which an induced draft fan is dispensed with. In the event of a leak, the resulting overpressure causes gas to escape through the outlet opening 21st can escape. Since the leaked working fluid in the housing 6th subsequently completely in the activated carbon adsorber 12 is deposited, the then resulting negative pressure must be in the housing 6th by opening the inlet port 20th be balanced.

List of reference symbols

1

Refrigeration cycle

2

compressor

3

capacitor

4th

Pressure reduction

5

Evaporator

6th

casing

7th

Heat source connection

8th

Heat source flow

9

Heat sink supply

10

Heat sink connection

11

Sorption channel

12

Activated carbon adsorber

13

Gas inlet

14th

Gas outlet

15th

Thermal insulation

16

Induced draft fan

17th

Cooling pipe

18th

Gas detector

19th

Peltier element

20th

Inlet opening

21st

Outlet opening

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102011116863 A1 [0006]
• DE 19525064 C1 [0007]
• EP 3106780 A1 [0008]
• JP 2000105003 A [0009]

Claims (20)

Device for the safe implementation of a counterclockwise thermodynamic cycle (1) by means of an inflammable working fluid which is guided in a closed, hermetically sealed working fluid circuit, comprising - at least one compressor (2) for working fluid, - at least one expansion device (4) for working fluid, - at least two heat exchangers (3, 5) for working fluid, each with at least two connections (7, 8, 9, 10) for heat transfer fluids, - a housing (6) which comprises at least the compressor (2) and the expansion device (4) and other devices - at least one sorption channel (11) with an adsorber (12) containing activated carbon through which gas can flow - and the sorption channel (11) is connected to the adsorber (12) and its gas inlet (13), characterized in that, that - the sorption channel (11) is limited with respect to its exterior by thermal insulation (15), - the sorption channel al (11) can be closed at the gas inlet (13), and - at least one cooling line (17) connected to a cooling medium is laid in the sorption channel (11). Device according to Claim 1 , characterized in that the sorption channel (11) is equipped with a gas outlet (14) and is connected to it. Device according to Claim 2 , characterized in that a switchable induced draft fan (16) is connected to the gas outlet (14) of the sorption channel (11). Device according to one of the Claims 2 or 3 , characterized in that the adsorber (12), the sorption channel (11) and the gas inlet (13) and gas outlet (14) are arranged within the housing (6). Device according to Claim 1 , characterized in that a leakage detection system (18) is provided in the housing, which opens the closure at the gas inlet (13). Device according to one of the Claims 3 to 5 , characterized in that when the closure at the gas inlet (13) is opened, the closure at the gas outlet (14) also opens and the induced draft fan (16) is switched on when a leak is detected. Device according to Claim 5 , characterized in that the leakage detection system (18) is a gas detector for flammable gas, in particular propane. Device according to one of the Claims 1 to 7th , characterized in that the cooling medium is relaxed working fluid which flows in the flow direction after the expansion device (4) and before the heat exchanger (5) acting as an evaporator. Device according to one of the Claims 1 to 7th , characterized in that the cooling medium is relaxed working fluid which flows in the flow direction after the heat exchanger (5) acting as an evaporator to the compressor (2). Device according to one of the Claims 8 or 9 , characterized in that a partial flow of the working fluid is used as a cooling medium. Device according to one of the Claims 8 or 9 , characterized in that the entire working fluid is used as a cooling medium. Device according to one of the Claims 1 to 11 , characterized in that the at least one cooling line (17) has cooling ribs in the longitudinal direction. Device according to one of the Claims 1 to 12 , characterized in that additional Peltier elements (19) are used for cooling or cooling. Device according to one of the Claims 1 to 13th , characterized in that additional latent heat stores are provided for keeping the temperature in the sorption channel. Device according to one of the Claims 1 to 14th , characterized in that the adsorbent is preloaded with an adsorbate which is displaced by the adsorptive and thereby cools the adsorbent. Device according to Claim 15 , characterized in that the adsorbate with which the adsorbent is preloaded is nitrogen or carbon dioxide. Device according to Claim 15 , characterized in that the adsorbent which is preloaded with the adsorbate is activated carbon. Device according to Claim 15 , characterized in that the adsorptive which displaces the adsorbate is the refrigerant R290. Device according to one of the Claims 1 to 18th , characterized in that the housing is connected to an inlet opening (20) and an outlet opening (21). Device according to Claim 19 , characterized in that the outlet opening (21) is connected to a conveying fan (16).

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