FI3748257T3 - Device for the safe performance of a left-rotating thermodynamic circular process by means of a flammable working fluid with the use of fluidadsoption - Google Patents

Description

1 20171754.3

DEVICE FOR THE SAFE PERFORMANCE OF A LEFT-ROTATING THERMODYNAMIC

CIRCULAR PROCESS BY MEANS OF A FLAMMABLE WORKING FLUID WITH THE USE OF

FLUIDADS OPTION

The invention relates to irregular conditions in refrigeration circuits in which a working fluid acting as a refrigerant is carried in a thermodynamic circular process, such as the Clausius-Rankine circular process. Predominantly, these are heat pumps, air conditioners and refrigeration units, as they are commonly used in residential buildings.

In this context, residential buildings are understood to be private homes, apartment building complexes, hospitals, hotel complexes, restaurants and combined residential and commercial buildings in which people live and work permanently, as opposed to mobile devices such as automotive air-conditioning systems or transport boxes, or even industrial plants or medical equipment. What these circular processes have in common is that they use energy to generate useful heat or useful cold and form heat displacement systems.

The thermodynamic circular processes that are used have been known for a long time, as well as the safety problems that can arise when using suitable working fluids.

Apart from water, the best known working fluids at the time are flammable and toxic.

They led to the development of safety refrigerants in the last century, which consisted of fluorinated hydrocarbons. However, these safety refrigerants were found to damage the ozone layer, lead to global warming, and their safety-related harmlessness led to design oversights. Up to 70% of the turnover was accounted for by the need to refill leaking systems and their leakage losses, which was accepted as long as this was perceived as economically justifiable in the individual case and promoted the need for replacement.

The use of these refrigerants was subjected to restrictions for this reason, in the European Union for example by the F-Gas Regulation (EU) 517/2014.

It is therefore extremely problematic, on the one hand, to adopt the design principles for refrigerant-carrying thermodynamic processes that seem to have worked well for safety refrigerants, and on the other hand, to build on the plant concepts from the time before the introduction of safety refrigerants. This is also due to the fact that in the meantime single devices have become complex plants, which has multiplied the number of possibilities for malfunctions and their consequences. This results in the following regulations for the safety concept as an example: - During normal operation, the plant must be absolutely leak-proof.

2 20171754.3 - Neither in the event of a leakage in the condenser or liguefier nor in the event of a leakage in the evaporator working fluid may enter the coupled useful heat or useful cold circuit. - No working fluid must be able to escape from the refrigeration circuit unnoticed. - In the compactor, the working fluid must not escape through the bearing. - In the relaxing system, the working fluid must not diffuse through the valve seat or cause leakage due to cavitation. - Encapsulated parts must remain accessible for maintenance and inspection purposes. - There shall be no hazards in case of emergencies. - The plant shall be capable of being integrated into existing premises. - The refrigerant shall be able to be drained and charged.

The term emergency must be viewed broadly. Power failures, earthguakes, landslides, floods, fires, technical faults and extreme climatic conditions are conceivable.

If the plants are operated in a network, a network failure or network disturbance is also to be considered an emergency. Against such hazards or disturbances, the device shall be inherently safe. However, a failure of available primary power may also constitute an emergency and shall not result in the development of a hazard. All of these emergencies may also occur in combination.

In this context, the various designs and applications for such thermodynamic circular processes must be considered separately, for example, in the case of fixed plants for residential buildings, the following: - Household refrigerators, - Household freezers, - Household dryers, - Household refrigerator-freezer combinations, - Refrigeration chambers for hotel and catering, - Freezer chambers for hotel and catering, - Air conditioner for house, hotel and catering, - Hot water production for house, hotel and catering, - Heating for house, hotel and catering

3 20171754.3 - Sauna-swimming pool facilities for house, hotel and catering, - Combined plants for the applications mentioned above, whereby this list is not exhaustive.

The energy for the operation of the plants, including the thermal energy to be shifted, can come from various sources: - Terrestrial heat from terrestrial heat reservoirs, - Geothermal heat, - District heat, - Electrical energy from general power supply, - Electrical solar energy, - Solar heat, - Waste heat, - Hot water reservoir, - Ice reservoir, - Latent heat storage, - Fossil fuels such as natural gas, crude oil, coal, - Renewable resources such as wood, pellets, biogas , - Outside air, - Combinations of the energy sources mentioned above, whereby this list is also not exhaustive.

The problems that arise in the safety design of such plants are vividly described in WO 2015/032905 A1. For example, the lower ignition limit of propane as a working fluid is approximately 1.7% by volume in air, which is equal to 38 g/m? in air. As far as the refrigeration process is carried out in a hermetically sealed space surrounding it, but otherwise filled with air, with the working fluid propane, the problem of detecting a critical, explosive situation arises after a malfunction in which the working fluid leaks into this hermetically sealed space. Electrical sensors used to detect critical concentrations are difficult to make explosion-proof, so it is propane detection by the sensors themselves that greatly exacerbates the explosion risk, with the exception of infrared sensors. Propane is also toxic, with inhalation above a concentration of approx.

4 20171754.3 2 g/m? causing narcotic effects, headaches and nausea. This affects people who are expected to solve an identified problem on site, even before explosive hazard develops.

Propane is also heavier than air, hence it sinks to the floor in still air and accumulates there, whereby it mixes with the room air after a certain time, which also depends on the leakage rate and room height. Thus, a part of the propane should accumulate under very unfavorable conditions in a low-flow zone of the sealed space in which the disturbed aggregate is located, the local explosion limits may be reached much more guickly than would be expected from the ratio of total space volume to amount of propane leaked. WO 2015/032905 A1 seeks to solve this problem in that a generator of electric current is integrated into the opening or its interlock of this space and, when actuated, in a first step generates and provides the electric energy with which the sensor is activated and which, in the event of an alarm, does not release the interlock but causes the sealed space to be ventilated, and only in a second step allows it to be unlocked and opened.

Already at the beginning of the technology of compression refrigeration machines, attempts were made to form a closed room in which all the equipment could be safely accommodated and which completely encloses it. DE-PS 553 295 describes an encapsulated compression refrigeration machine in which the refrigerant compactor 1, its drive motor 2, evaporator 3, condenser 4 and control valve 5 are enclosed in a double-walled capsule 6 and 7, respectively. An underpressure is applied in the interspace between the double-walled capsule and leakages that could occur at the openings for cooling water and brine are extracted. The extracted working fluid can then be recovered if applicable. It should be noted that there is no ambient air within the encapsulated space and, due to the underpressure in the double jacket, cannot penetrate into the encapsulated interior.

DE 10 2011 116 863 A1 describes a method for securing a device for a thermodynamic circular process, which is operated with a process fluid that contains or consists of at least one environmentally hazardous, toxic and/or flammable substance. In the case of a leakage in the device for a thermodynamic circular process, 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. Zeolites, also in combination with imidazole or phosphates, also CuBTC are proposed as adsorbents, the adsorbent may be eguipped in the form of a bulk, a

20171754.3 shaped body, a paint, a spray film or a coating. The support structure of the shaped body may consist of microstructure, lamellar structure, tube bundle, tube register and sheet metal and must be mechanically stable as well as highly surface enlarging. Recirculation of the potentially contaminated air is usually continuous, but can also be initiated by a 5 sensor that turns on ventilation after a threshold is reached or when an accident is detected. The adsorption can be performed inside or outside a sealed space.

DE 195 25 064 C1 discloses a device according to the preamble of claim 1.

DE 195 25 064 C1 describes a refrigeration machine with a gas-tight formed housing that 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 refrigerant-sorbing substance. Thereby, the amount of the sorbent substance is dimensioned in such a way that the entire amount of any leaking refrigerant can be absorbed and kept away from the environment. The space filled with the sorbent substance is open to the environment. For heavier than air refrigerants, the space is open at the bottom; for lighter-than-air refrigerants, the space is open at the top, eliminating the need for a delivery blower. The sorbent is introduced into the enclosure and completely surrounds the refrigeration machine or the refrigerant-carrying apparatus. On its way out, chicanes are provided to prevent short-circuit flows 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 outlet of the space filled with the sorbent substance to the environment.

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

The systems presented have so far had little success on the market. This can be attributed to the following reasons: - Ease of installation: In the case of modernization of old heating systems, the new devices to be installed must be dismountable and transportable. For example, they

6 20171754.3 must be able to be brought down cellar stairs and into crooked and low cellar rooms.

Assembly, commissioning and maintenance must be possible on site without great effort.

This largely excludes large and heavy pressure vessels, as well as systems that can no longer be dismantled after an accident. - Ease of diagnosis: The operating conditions should be easily recognizable from the outside. This affects the visibility and verifiability with regard to possible leakages and includes the filling level of the working fluid and the filling level of any sorbents that may have been introduced. - Ease of maintenance: System diagnostics should be possible without much additional effort. Safety-relevant systems should be able to be tested regularly or to be checked for their reliability. If system diagnostics cannot be carried out easily, possibly stressed parts should be easily replaceable with new parts. - Fail-safety: The systems should be secured against disruptions on the one hand, but at the same time be able to run reliably, at least in emergency operation. In the event of a temporary external disruption, the systems should either restart automatically or be able to be restarted without great effort. - Energy efficiency: The systems should be able to be operated in an energy-efficient manner; high self-consumption of energy for security measures counteracts this. - Robustness: In the event of major disruptions, whether external or internal to the system, controllability must be guaranteed. This applies, for example, to ventilation systems that can become blocked or pressure vessels that are pressurized or get hot, for example in the event of a fire. - Costs: The security measures should not be significant in terms of acquisition costs or running costs and should not exceed the savings in energy costs compared to conventional systems. They should be cost effective.

There is also a conflict of objectives. If working fluid emerges from a small leakage, a binding agent, with it an adsorbent or a chemical binding agent, should be able to absorb all of the working fluid even at low partial pressures. This is best done in a slow throughflow through a finely distributed medium. In the event of a conceivable, albeit very rare, rupture of a line carrying working fluid, a large quantity of working fluid is released under high pressure in a very short time, which suddenly puts the mostly pressure-tight housing under pressure. Tests resulted in peak pressure values of up to 25

7 20171754.3 hPa, which would lead to deformation of typical designs and the subseguent emergence of working fluid.

In such cases, not only must all working fluid be contained, as has long been known in the state of the art, but depressurization must occur quickly. Closed devices with a finely divided medium, which would oppose a high flow resistance to a working fluid during inflow or throughflow, would not be suitable for bringing about the required rapid pressure relief.

But also conventional devices, which provide an adsorber through which flow occurs or a container filled with another binding agent, in which an escaping working fluid-air mixture is cleaned before it can escape into the installation space, are problematic. The sum of the individual pressure losses, which results from the inlet pressure loss, that of the sorption bed and the outlet pressure loss, would still be so high that a considerable overpressure would be reguired in the housing in order to guickly drive enough working fluid -air mixture through such a device in order to reduce guickly developing overpressure without an additional fan in this way. However, this overpressure is not desirable and should not arise in the first place if possible, so it must not be necessary to guickly reduce it itself. This creates an inner conflict of objectives.

The object of the invention is therefore to provide an improved device which better solves the problems presented, including the conflict of objectives, and no longer has the disadvantages.

The invention solves this problem with a device according to claim 1. The device is therefore suitable for the safe performance of a left-rotating thermodynamic circular process by means of a flammable working fluid which is conducted in a closed, hermetically sealed working fluid circuit. The device having the following: - a closed working fluid circuit with the flammable working fluid, having at least one compactor for working fluid, at least one relaxing apparatus for working fluid, and at least two heat exchangers for working fluid having in each case two connections for heat exchanger fluids; and - a closed housing consisting of an outer housing part and an inner housing part which encloses all apparatus attached to the closed working fluid circuit, and can comprise further apparatus, wherein

8 20171754.3 - the housing is formed from an arrangement of two housing parts nested in one another, wherein the inner housing part is at least partially enclosed by the outer housing part, - wherein both housing parts have five sides closed for gas and one side open for gas, - the sides respectively open for gas are arranged on sides of the nested housing parts which are opposite one another, - on the open side of the inner and the open side of the outer housing part is provided respectively one passage for gas, - between the two housing parts an interspace is formed on several sides, and - this interspace is filled with a binding agent for working fluid in a capacity with which emerging working fluid can be completely absorbed, - the interspace can be flowed through only in the case of an overpressure occurring in the interior of the inner housing part, in that the overpressure has the effect of the outer housing part being pushed apart in a parallel manner with respect to the inner housing part, as a result of which a passage opening is opened for gas from the inner housing part into the interspace, - the interspace and the passage opening are formed in terms of flow technology such that the flow resistance occurring when throughflow takes place is equal everywhere.

In most cases, a Clausius-Rankine process, which is operated with R290, serves as a left-rotating circular process. The adsorbent active carbon is preferably used as the binding agent. All gaseous or liguid media with which heat is transferred are to be understood here as heat exchanger fluids, such as air, water, brine, heat transfer oils or the like.

The nesting of the two housing parts can be done in different ways. The outer housing part can be placed on the lower, inner housing part from above, whereby the underside of the outer housing part is completely open. The aggregates of the circular process are then all arranged in the inner housing part and the connections are made below and do not pierce the outer housing part. The outer housing part can also be arranged below and can form a kind of trough for the inner housing part, wherein the inner housing part is placed on the outer housing part from above. The aggregates of the

9 20171754.3 circular process are then all arranged in the outer housing part, the connections are made below and do not pierce the inner housing part. The outer housing part can also be pushed laterally over the inner housing part.

In these arrangements, one housing part is always fixed and the other is movable along an axis, whereby this movement is guided by suitable mounting in order to prevent tilting. If an overpressure event occurs, the overpressure causes the movable housing part to move due to this pressure and to open the way to the gap between the two housing parts. An adsorbent, which is preferably a fill having a low flow resistance, is arranged in this interspace.

Although the movement of the movable housing part clears the way for the escaping gas, this does not mean that the housing has to be gas-tight beforehand. Thus, screens can be used to support the movable housing part, which bring about pressure equilibrium with the surroundings, diffusion can also take place. However, ventilation occurs mainly through the sorption bed.

At the points where the gas path into the interspace is cleared, rounded channels and flow straighteners are preferably provided so that a homogeneous gas flow is created. In order to limit the movement of the movable housing part, a limit stop is preferably provided.

In a further embodiment, the movable housing part is mounted on a shaped body or a fill made of an adsorbent which, in the event of small leakages, causes the emerging working fluid to be bound without the gas path into the interspace being opened up. In this way, there is a different treatment of occasional small and very rare large leakage events.

In a further embodiment it is provided that the interspace between the two housing parts is provided on 4 sides. In this way, a high flow cross section with a large smoothing effect can be achieved. This results in a circumferential interspace, wherein the opposite surfaces of the two housing parts neither have to be parallel to one another, nor have to be flat, but can also have structuring.

If the two housing parts are arranged vertically one inside the other, the pressure at which the gas path should open into the interspace can be defined by the weight of the moving housing part. However, if this does not fit, springs can compensate for the reguired difference.

10 20171754.3

It goes without saying that elements such as retaining screens, bases and assembly aids or the like can also be used in the usual way and the two housing parts themselves can also have covers, removable side parts, service openings, safety valves and the like for assembly purposes.

Further refinements relate to the measures that are used to ensure that the permissible overpressure in the housing is maintained if a significant disruption occurs.

This overpressure should be limited to 2.5 mbar or 0.25 hectopascals. It is optional to provide individually or in combination that - the free inflow-cross-section in the interspace is between 0.008 and 0.068 m? per kg of working fluid, - the ratio between the free inflow-cross-section into the interspace to the free outflow-cross-section from the interspace is between 0.35 and 2.41, - the interspace is not open to gas flows in the non- pressurized state, - the active carbon is used as an adsorbent fill in pellet, granulate and/or ball form in a diameter range from 0.5 to 10 millimeters and a length-to-diameter ratio of 1 to 20, - the active carbon is doped such that at normal temperatures the rate of adsorption is between 0.025 and 0.4 kg working fluid per kg adsorbent, - the run length of the adsorbent arranged by the in the interspace is between 0.01 and 1.08 meters per kg working fluid.

The invention is explained in more detail below using two schematic diagrams. Hereby show:

Fig. 1a a first embodiment in the closed state,

Fig. 1b a first embodiment in the open state,

Fig. 2a a second embodiment in the closed state,

Fig. 2b a second embodiment in the open state,

Fig. 3 a plan view of the interspace.

1a shows a first embodiment in the closed state using a schematic diagram of a refrigeration circuit 1 with a compactor 2, a condenser 3, a pressure reducer 4 and an evaporator 5 in a closed housing, which is formed from an inner housing part 6 and an outer housing part 11. Here, the inner housing part 6 is open at the bottom and

11 20171754.3 closed at the top, while the outer housing part 11 is open at the top and closed at the bottom. The inner housing part 6 rests in and on the outer housing part 11 like a trough.

The housing includes a heat source connection 7, a heat source flow 8, a heat sink flow 9 and a heat sink connection 10. In this example, the refrigeration circuit 1 is operated with the flammable working fluid propane, which is also known under the designation R290.

Propane is heavier than air, so if there is a leakage in the refrigeration circuit 1, it will tend to sink downwards in the inner housing 6, although it mixes well in the case of small leakages. There it can be caught and bound by the adsorbent layer 13 in the case of small leakages. In the closed state, the inner housing part 6 rests loosely on the adsorbent layer 13.

Figure 1b shows the first embodiment in the open state after a sudden, significant leakage event. Here, the pressure inside the inner housing part 6 increases so quickly that the adsorbent layer cannot absorb the emerging working fluid quickly enough. Due to the increase in pressure, the inner housing part 6 is lifted until the inner pressure and the weight of the inner housing part 6 are in equilibrium. The gas, which consists of a mixture of working fluid and air, enters the interspace 12 through the passage opening 14 positioned at the bottom, where it is passed upwards through a further adsorption layer, which offers only a very low flow resistance. Most of the working fluid is adsorbed therein. A small residual flow exits through the passage opening 15 into the environment. After the end of the overpressure event, the inner housing part 6 moves back to its starting position. The loaded adsorbent is then professionally removed.

Fig. 2a shows an alternative embodiment in the closed state, whose main difference to the first variant is that the inner housing part 6 is not positioned in the outer housing part 11 like in a trough, but that the outer housing part 11 is arranged over the inner housing part 6 like a hat. Otherwise the structure is analogous.

Figure 2b shows the alternative embodiment in the open state. In this case, the outer housing part is lifted by the resulting overpressure and releases a passage opening 14 which, in contrast to the first embodiment variant, is arranged at the top. Due to the increase in pressure, the outer housing part 11 is lifted until the internal pressure and the weight of the housing part 11 are in equilibrium. The gas, which consists of a mixture of working fluid and air, enters the interspace 12 through the passage opening 14 positioned at the top, where it is passed downwards through a further adsorption layer, which offers only a very low flow resistance. Most of the working fluid is adsorbed therein. A small

12 20171754.3 residual flow exits through the passage opening 15 into the environment. After the end of the overpressure event, the outer housing part 11 moves back to its starting position.

The loaded adsorbent is then professionally removed.

Figure 3 shows a greatly simplified representation of a plan view of the first and second embodiment. The outer housing part 11 encloses the inner housing part 6 and forms a circumferential interspace 12 in which the adsorbent is arranged. Preferably, the adsorbent is attached in a detachable manner to the non-moving housing part.

Alternatively, the circumferential interspace can also be formed from several compartments, for example, one on each of the respective outsides, which makes it easier to detach them after loading.

List of reference numerals 1 Refrigeration circuit 2 Compactor 3 Condenser 4 Pressure reducer 5 Evaporator 6 Inner housing part 7 Heat source connection 8 Heat source flow 9 Heat sink flow 10 — Heat sink connection 11 Outer housing part 12 Interspace 13 Adsorption layer 14 Passage opening 15 Passage opening

Claims (11)

Patent Claims 1. Device for the safe execution of a left-circulating thermodynamic circulation process (1) by means of a flammable working fluid, which is transported in a closed, hermetically sealed working fluid circuit, comprising: - a closed working fluid circuit with a flammable working fluid, at least one compressor (2) for the working fluid, at least one expansion device (4) for the working fluid and at least two heat exchangers (3, 5) for the working fluid each time with at least two connections (7, 8, 9, 10) for the heat exchanger fluids; and - a closed housing, which consists of an outer housing part (11) and an inner housing part (6), which comprises all equipment connected to the closed working fluid circuit, and may comprise other equipment, where the housing is formed from an arrangement consisting of two nested housing parts, whereby the outer the housing part (11) surrounds the inner housing part (6) at least partially, an intermediate space (12) is formed between both housing parts on several sides, and this intermediate space (12) is filled with a binder intended for the working fluid with a capacity that can receive the working fluid coming out completely , characterized by the fact that - both housing parts each have five closed sides and one side open to gas, - each side open to gas is placed on opposite sides of the nested housing parts (6, 11), - the open sides of the inner and outer housing parts each have gas passage for, - the flow can pass through the intermediate space (12) only in the inner housing part (6) — in the event of an overpressure occurring inside, such that the overpressure causes the outer housing part (11) to push apart parallel to the inner housing part (6), thanks to which the passage opening (14) is opened for gas from the inner housing part (6) to the intermediate space (12), and - the intermediate space (12) and the through-hole (14) are formed flow-technically — so that the flow resistance set at the through-flow is the same everywhere. 2. The device according to claim 1, characterized in that the binder is an adsorbent, preferably from activated carbon, and the working fluid is R290. 3. A device according to one of claims 1 or 2, characterized by the fact that the moving housing part is supported on top of the shape-cap mobile mass formed from an adsorbent. 4. A device according to one of claims 1-3, characterized in that the intermediate space (12) between both housing parts (6, 11) is arranged on 4 sides. 5. A device according to one of claims 1-4, characterized in that the pressure drop in the intermediate space (12) in the flow is limited to a maximum of 2.5 hPa. 6. Device according to claim 5, characterized in that the free inflow cross-section in the intermediate space (12) is 0.008-0.068 m? per kg of working fluid. 7. Device according to claim 5, characterized in that the ratio between the free inflow cross-section into the intermediate space (12) and the free outflow cross-section from the intermediate space is 0.35-2.41. 8. A device according to claim 5, characterized in that the intermediate space (12) is not open to gas flows in a non-pressurized state. 9. Device according to claim 2, characterized in that activated carbon is used as adsorbent bulk in the form of pellets, granules and/or balls with a diameter range of 0.5-10 millimeters and a length-to-diameter ratio of 1- 20. 10. A device according to one of claims 2-9, characterized in that the activated carbon is doped in such a way that the adsorption rate at normal temperature is 0.025-0.4 kg of working fluid per kg of adsorbent. 11. A device according to one of claims 2, 3, 9 and 10, characterized by the fact that the travel length through the adsorbent placed in the intermediate space (12) is 0.01-1.08 meters per kg of working fluid.