EP3657104A1 - Moulded parts for heat pumps - Google Patents

Abstract

The invention relates to molded parts for introduction into the cavities in the housing of a heat pump in which an inflammable working fluid is operated in a refrigeration cycle, the molded parts being designed and matched to one another in such a way that no gap or cavity remains after the introduction into the housing that is larger than the extinguishing distance, based on a stoichiometric working fluid-air mixture.

Description

The invention relates to irregular conditions in working fluid circulations in which a working fluid acting as a refrigerant is conducted in a thermodynamic cycle, such as the Clausius-Rankine cycle. Mainly these are 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 complexes, restaurants, combined residential and commercial buildings as well as commercial establishments in which people live and / or work permanently, in contrast to mobile devices such as automotive air conditioning systems or transport boxes, or also free-standing industrial plants or medical devices. What these cycle processes have in common is that they generate useful heat or cold using energy and form heat transfer systems.

The thermodynamic cycle processes used have long been known, as are the safety problems that can arise when using suitable working fluids. Apart from water, the best known working fluids at that time were flammable and toxic. In the past century, they led to the development of safety refrigerants, which consisted of fluorinated hydrocarbons. However, it was shown that these safety refrigerants damage the ozone layer, lead to global warming and that their safety-related safety led to constructive inattentiveness. Up to 70% of sales was attributable to 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 promoted the need for replacement.

For this reason, the use of these refrigerants has been subject to restrictions, for example in the European Union through the F-Gas Regulation (EU) 517/2014.

• Im Normalbetrieb muss die Anlage absolut dicht sein.
• Weder bei einer Leckage im Kondensator noch bei einer Leckage im Verdampfer darf Arbeitsfluid in den gekoppelten Nutzwärme- oder Nutzkältekreislauf gelangen.
• Es darf kein Arbeitsfluid aus dem Kältekreislauf unbemerkt entweichen können.
• Im Verdichter darf das Arbeitsfluid nicht durch die Lagerung entweichen.
• Im Entspannungssystem darf das Arbeitsfluid nicht durch den Ventilsitz diffundieren oder durch Kavitation zu Leckagen führen.
• Gekapselte Teile müssen für Wartungs- und Kontrollzwecke zugänglich bleiben.
• In Notfällen dürfen sich keine Gefahren einstellen.
• Die Anlage soll in vorhandene Räumlichkeiten integrierbar sein
• Das Kältemittel soll abgelassen und eingefüllt werden können.

On the one hand, it is extremely problematic to adopt the design principles for refrigerant-carrying thermodynamic processes, which seem to have proven their worth with safety refrigerants, and on the other hand to base them on the system concepts from before the safety refrigerants were introduced. 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. This results, for example, in the following requirements for the security concept:

• In normal operation, the system must be absolutely tight.
• Working fluid must not enter the coupled useful heating or cooling circuit either in the case of a leak in the condenser or in the evaporator.
• No working fluid must be able to escape from the refrigeration cycle without being noticed.
• The working fluid in the compressor must not escape through storage.
• In the expansion system, the working fluid must not diffuse through the valve seat or lead to leaks due to cavitation.
• Encapsulated parts must remain accessible for maintenance and inspection purposes.
• No dangers may arise in emergencies.
• The plant should be able to be integrated into existing premises
• The refrigerant should be able to be drained and filled.

The concept of an emergency must be seen widely. Power outages, earthquakes, landslides, floods, fires, technical errors and extreme climatic conditions are conceivable. If the systems are operated in a network, a power failure or a network fault is also to be regarded as an emergency. Against such dangers or disturbances the device is said to be inherently safe. However, a failure of the available primary energy can also justify an emergency and must not result in the development of danger. All of these emergencies can also occur in combination.

• Haushaltskühlschränke,
• Haushaltsgefrierschränke,
• Haushaltstrockner,
• Haushaltskühl-Gefrierkombinationen,
• Kühlkammern für Hotel- und Gastronomie,
• Gefrierkammern für Hotel- und Gastronomie,
• Klimaanlage für Haus, Hotel- und Gastronomie,
• Warmwassererzeugung für Haus, Hotel- und Gastronomie,
• Beheizung für Haus, Hotel- und Gastronomie,
• Sauna-Schwimmbadanlagen für Haus, Hotel- und Gastronomie,
• Kombinierte Anlagen für die oben genannten Anwendungen,

wobei diese Aufzählung nicht vollständig ist.The various designs and applications for such thermodynamic cycle processes have to be considered separately, for example the following for fixed systems for residential buildings:

• Household refrigerators,
• Freezers,
• Household dryer,
• Household fridge-freezers,
• Cooling chambers for hotel and catering,
• Freezers for hotels and restaurants,
• Air conditioning for home, hotel and catering,
• Hot water generation for home, hotel and catering,
• Heating for home, hotel and catering,
• Sauna swimming pool facilities for home, hotel and catering,
• Combined systems for the above-mentioned applications,

this list is not exhaustive.

• Erdwärme aus Erdwärmespeichern,
• Geothermische Wärme,
• Fernwärme,
• Elektrische Energie aus allgemeiner Stromversorgung,
• Elektrische Solarenergie,
• Solarwärme,
• Umgebungswärme der Luft,
• Abwärme,
• Warmwasserspeicher,
• Eisspeicher,
• Latentwärmespeicher,
• Fossile Energieträger wie Erdgas, Erdöl, Kohle,
• Nachwachsende Rohstoffe wie Holz, Pellets, Biogas,
• Kombinationen aus den oben genannten Energiequellen,

wobei auch diese Aufzählung nicht vollständig ist.The energy for operating the systems, including the thermal energy to be moved, can come from various sources:

• Geothermal energy from geothermal energy storage,
• Geothermal heat,
• District heating,
• Electrical energy from general power supply,
• Electrical solar energy,
• Solar heat,
• Ambient heat of the air,
• Waste heat,
• Hot water tank,
• Ice storage,
• Latent heat storage,
• Fossil energy sources such as natural gas, oil, coal,
• Renewable raw materials such as wood, pellets, biogas,
• Combinations of the above energy sources,

although this list is also not complete.

The problems that arise with the safety design of such systems are discussed in the WO 2015/032905 A1 described vividly. The lower ignition limit of propane as working fluid is approximately 1.7 percent by volume in air, which corresponds to 38 g / m ³ in air. If the cooling process is carried out in a surrounding, hermetically sealed, but otherwise air-filled room with the working fluid propane, there is the problem of recognizing a critical, explosive situation after a fault in which the working fluid escapes into this hermetically sealed room. Electrical sensors for the detection of critical concentrations are difficult to carry out explosion-proof, which is why the propane detection by the sensors themselves considerably increases the risk of explosion, with the exception of infrared sensors. Propane is also toxic; when inhaled above a concentration of approx. 2 g / m ³ , there are narcotic effects, headaches and nausea. This affects people who are supposed to solve a recognized problem on site before there is a risk of explosion.

Propane is also heavier than air, so it sinks to the ground in calm air and accumulates there. If a part of the propane is collected in a low-flow zone of the closed room, in which the disturbed aggregate is located, the local explosion limits can be reached much faster than the quotient of total room volume to the amount of propane escaping. The WO 2015/032905 A1 seeks to solve this problem by integrating an electric current generator into the opening or locking of this space and, when actuated, in a first step generates and provides the electrical energy with which the sensor is activated, and which in the event of an alarm Locking then does not release, but causes ventilation of the closed room and only allows unlocking and opening in a second step.

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 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. As an adsorbent, zeolite, also in combination with imidazole or phosphates, CuBTC are also proposed. The adsorbent can be in the form of a bed, a molded part, a paint, a spray film or a coating. The support structure of the molded part can consist of microstructure, lamella structure, tube bundle, tube register and sheet metal and must be mechanically stable and greatly increase the surface area. Circulation of the potentially contaminated air usually takes place continuously, but can also be initiated by a sensor that switches on the ventilation after a threshold value has been reached or in the event of a recognized accident. The adsorption can be carried out inside or outside a closed room.

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, which cleans the air in the housing in recirculation mode, can be arranged within this housing. This air recirculation mode can be carried out continuously or only in the event of a fault or at regular intervals. A pilot 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 fresh air supply in connection with the discharge of cleaned exhaust air is also conceivable.

Attempts have also been made to prevent the spread of flames by using flame arrestors. The DE 698 24 142 T2 describes an explosion prevention device for a refrigerator that uses a combustible coolant. A mesh element is used as an explosion prevention device, the mesh size of which is equal to or smaller than an extinguishing distance for the combustible coolant used. This mesh element is placed over elements that could generate sparks. If propane or isobutane is used, the mesh size should be chosen to be equal to or smaller than 2 mm.

The US 2013/0284464 A1 proposes a similar network or grid, whereby in addition to the mesh size, the distance from the possible ignition source should also be in the same range as the mesh size. In both cases, metal grids, perforated grids, chain mail or metal nets are used. However, these can lead to unpleasant noises in vibrating systems and are difficult to fix permanently. In the event of a maintenance intervention, their removal is correspondingly complex and dangerous in the event of a malfunction.

• Montagefreundlichkeit: Im Falle von Modernisierungen von alten Heizungsanlagen müssen die neu zu installierenden Vorrichtungen zerlegbar und transportabel sein. Beispielsweise müssen sie über Kellertreppen und in verwinkelte und niedrige Kellerräume verbracht werden können. Zusammenbau, Inbetriebnahme und Wartung müssen ohne großen Aufwand vor Ort möglich sein. Dies schließt große und schwere Druckbehälter weitgehend aus, ferner Systeme, die nach einer Havarie nicht mehr demontierbar sind.
• Diagnosefreundlichkeit: Die Betriebszustände sollten von außen gut erkennbar sein, dies betrifft die Sichtbarkeit und Prüfbarkeit bezüglich möglicher Leckagen und schließt den Füllstand des Arbeitsfluids sowie den Befüllungsgrad ggf. eingebrachter Sorbenzien ein.
• Wartungsfreundlichkeit: Systemdiagnosen sollten ohne großen zusätzlichen Aufwand erfolgen können. Sicherheitsrelevante Systeme sollten regelmäßig getestet bzw. auf ihre Zuverlässigkeit geprüft werden können. Sofern Systemdiagnosen nicht einfach durchführbar sind, sollten möglicherweise belastete Teile leicht durch Neuteile austauschbar sein.
• Ausfallsicherheit: Die Systeme sollen einerseits gegen Störungen gesichert sein, gleichzeitig aber zuverlässig laufen können, wenigstens im Notbetrieb. Im Falle einer vorübergehenden externen Störung sollten die Systeme entweder selbstständig wieder anfahren oder ohne großen Aufwand wiederangefahren werden können.
• Energieeffizienz: Die Anlagen sollen energetisch günstig betrieben werden können, ein hoher Eigenverbrauch an Energie für Sicherheitsmaßnahmen wirkt dem entgegen.
• Robustheit: Im Falle größerer Störungen, seien sie extern oder systemintern aufgeprägt, muss die Beherrschbarkeit gewährleistet sein, dies betrifft z.B. Lüftungssysteme, die verstopfen können oder Druckbehälter, die unter Druck stehen oder heiß werden, etwa bei einem Brand.
• Kosten: Die Sicherheitsmaßnahmen sollen weder bei den Anschaffungskosten noch bei den laufenden Kosten bedeutend sein und die Einsparungen bei den Energiekosten gegenüber herkömmlichen Systemen übersteigen. Sie sollen günstig sein.

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 dismantled and transportable. For example, they must be able to be moved up and down cellar stairs and into angled and low basement rooms. Assembly, commissioning and maintenance must be possible on site without much effort. This largely excludes large and heavy pressure vessels, as well as systems that cannot be dismantled after an accident.
• Ease of diagnosis: The operating states should be clearly recognizable from the outside, this concerns the visibility and testability with regard to possible leaks and includes the level of the working fluid and the degree of filling of any sorbents that may have been introduced.
• Ease of maintenance: System diagnostics should be able to be carried out without much additional effort. Security-relevant systems should be tested regularly or their reliability should be checked. If system diagnoses are not easy to carry out, it should be easy to replace parts that are under load with new parts.
• Reliability: On the one hand, the systems should be secured against malfunctions, but at the same time they should run reliably, at least in emergency operation. In the event of a temporary external fault, the systems should either restart independently or be restarted with little effort.
• Energy efficiency: The plants should be able to be operated at low energy costs, a high self-consumption of energy for security measures counteracts this.
• Robustness: In the event of major faults, whether external or internal, controllability must be guaranteed, for example, ventilation systems that can clog or pressure vessels that are under pressure or become 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 cheap.

The object of the invention is therefore to provide a device which ensures that the working fluid escaping in the event of a fault is either stored safely or is safely adsorbed or safely absorbed without an explosion-critical state being able to arise in the area in which the working fluid-carrying device is installed or used.

The invention solves this problem by means of molded parts which are introduced into the cavities in the housing of a heat pump and fill them so comprehensively that there is no such large empty volume at any point which at least requires an ignitable refrigerant-air mixture which occurs due to leakage for ignition.

The determining variable is the so-called "quenching distance", which is the largest distance between two walls at which no explosive mixtures can still be ignited. For the working fluid propane, also known as R290, this extinguishing distance according to " Artur Gutkowski, Laminar Burning Velocity under Quenching Conditions for Propane-Air and Ethylene-Air Flames, January 2006, https://www.researchgate.net/publication/242567175 "2 millimeters for a stoichiometric propane-air mixture, while the distance for non-stoichiometric mixtures can be significantly larger.

At the ignition limits themselves, the permissible maximum distance is larger because the gas compositions are not stoichiometric. Nevertheless, for safety reasons, it is provided in the present case that there is no gap or cavity at any point in the housing which is greater than the extinguishing distance, based on a stoichiometric working fluid / air mixture.

This is achieved by means of molded parts that reproduce the contours of the individual installations and units of the heat pump in the housing in a stamp-matrix manner. In the places where the vibrations or small movements occur in the housing these moldings have soft, conformable surfaces, otherwise they are divided in such a way that they can be inserted one after the other into the interior of the housing and preferably inserted one into the other. In one embodiment, molded dome connectors are used for this. In another embodiment, the molded parts have tongue and groove connections. In a further embodiment, the molded parts are shaped as textile pillows. In a further embodiment, the molded parts have sections of Velcro strips with which they can be detachably connected to one another.

Further configurations result from the materials used. The molded parts are preferably made from adsorbents. Here, a non-combustible porous framework material, e.g. made of zeolite can be used, which in a known manner with an adsorbent, e.g. Activated carbon, is impregnated. A flexible material can also be used as the framework material, for example silicone foam, which is also impregnated. In the case of textile pillows, fine-grained fillings can also be used, the gap volume of which is small. These fillings can also consist of adsorbents. Instead of granular fillings, fabric mats can also be introduced into the pillow-shaped molded parts. The textile outer material of the pillow-shaped molded parts preferably consists of diffusion-open textile fabric in the mesh size range from 0.1 to 6 millimeters, depending on the granule size of the filled material. The material of the textile fabric preferably consists of flame-retardant fibers that are temperature-stable up to 70 degrees Celsius from renewable raw materials.

If adsorbents are used, they can be preloaded with an inert gas, which is displaced or desorbed by the working fluid. The total loading capacity of the adsorbent introduced should be dimensioned in such a way that, if necessary, the entire emerging working fluid can be adsorbed.

The molded parts can also be designed so that the noise generated in the heat pump is insulated. For this purpose, molded parts should be used, the natural vibration frequency of which corresponds to the main frequencies of the installed machines, especially the compressor. Pillow-shaped moldings with sand-like fillings also provide considerable noise insulation.

• mindestens einen Verdichter für Arbeitsfluid,
• mindestens eine Entspannungseinrichtung für Arbeitsfluid,
• mindestens zwei Wärmeübertrager für Arbeitsfluid mit jeweils mindestens zwei Anschlüssen für Wärmeüberträgerfluide,
• ein geschlossenes und druckdichtes Gehäuse, welches alle am geschlossenen Arbeitsfluidumlauf angeschlossenen Einrichtungen umfasst, weitere Einrichtungen umfassen kann,
• und mit den erfindungsgemäßen Formteilen ausgestattet ist.

The invention also encompasses the use of the molded parts in a heat pump for safely performing a left-turning thermodynamic Clausius-Rankine cycle using an inflammable working fluid, which in the gaseous state is heavier than air under atmospheric conditions and is conducted in a closed, hermetically sealed working fluid circuit

• at least one compressor for working fluid,
• at least one relaxation device for working fluid,
• at least two heat exchangers for working fluid, each with at least two connections for heat transfer fluids,
• a closed and pressure-tight housing, which comprises all devices connected to the closed working fluid circuit, can comprise further devices,
• and is equipped with the molded parts according to the invention.

Heat transfer fluids are to be understood here as all gaseous or liquid media with which heat is transferred, for example air, water, brine, heat transfer oils or the like.

In a particular embodiment of the invention, propane is used as the working fluid and activated carbon is used as the adsorbent. The activated carbon can be doped in a known manner in such a way that optimal loading by propane takes place.

The invention is explained in more detail below with the aid of a sketch. Here shows Fig. 1 typical molded parts and their arrangement.

Fig. 1 shows a scroll compressor 1 in a section of a housing. The scroll compressor 1 is mounted on a vibration-damping foundation 2 with rubber feet 3, around the foundation is a flat molded part 4 with recesses for the rubber feet. The distance up to the scroll compressor 1 is one millimeter. The molded part 4 is shaped as a foamed body impregnated with activated carbon in accordance with the dimensions of the scroll compressor.

An annular molded part 5, which is divided in the middle, so that there are two semicircular rings, is placed over the molded part 4, which is flush with the suspensions of the scroll compressor 1. The ring-shaped molded part 5 is designed as a pillow and contains a dimensionally stable but flexible fabric. The two parts of the molded part 5 are connected to one another with Velcro.

Above it is another ring-shaped molded part 6, the inner surface of which nestles softly against the scroll compressor 1 and the body of which is made of a rigid rigid foam, on the top of which a cushion with a filling of activated carbon particles and a diffusion-open fabric is attached. This molded part 6 extends to the working fluid inlet 7 of the scroll compressor 1, which it touches from the underside with the soft surface of the filled cushion.

Above the working fluid inlet is a further dimensionally stable molded part 8, which is equipped like the molded part 6 and which extends to the working fluid outlet 9, which it touches from the underside with the soft surface of the filled cushion. Above the working fluid outlet 9, on the top of the scroll compressor, is the molded part 10, which is formed from a cushion with a bed of activated carbon preloaded with inert gas.

The molded parts 6 and 8 are inserted into one another, the molded part 10 is fastened to the molded part 8 with Velcro. None of the molded parts is directly connected to the floor or the scroll compressor.

As with the example of the scroll compressor, all other heat pump devices within the housing are equipped with molded parts. Due to the plug-in design, quick assembly and disassembly is ensured, in addition, the molded parts have a noise-reducing effect and adsorb the escaping working fluid in the event of leakages.

Reference symbol list

1

Scroll compressors

2nd

foundation

3rd

Rubber feet

4th

Molding

5

Molding

6

Molding

7

Working fluid inlet

8th

Molding

9

Working fluid outlet

10th

Molding

Claims (19)

Molded parts for insertion into the cavities in the housing of a heat pump in which an inflammable working fluid is operated in a refrigeration cycle
characterized in that
the molded parts (4, 5, 6, 8, 10) are designed and matched to one another so that after insertion into the housing there is no gap or cavity that is larger than the extinguishing distance, based on a stoichiometric working fluid-air mixture . Shaped parts according to claim 1, characterized in that the shaped parts are simulated in a stamp-matrix manner to the contours of the individual installations and units of the heat pump in the housing. Molded parts according to claim 1, characterized in that the molded parts, which are modeled on the vibrating parts of the heat pump, have soft, conformable surfaces with respect to these vibrating surfaces. Molded parts according to claim 1, characterized in that the molded parts are divided and can be used one after the other in the interior of the housing. Molded parts according to claim 4, characterized in that the molded parts can be inserted into one another. Molded parts according to claim 4, characterized in that the molded parts can be connected with dome connectors. Molded parts according to claim 4, characterized in that the molded parts have tongue and groove connections. Shaped parts according to claim 4, characterized in that the shaped parts have sections of Velcro strips with which they can be releasably connected to one another. Shaped parts according to claim 4, characterized in that the shaped parts are shaped as textile pillows. Shaped parts according to one of claims 1 to 9, characterized in that the shaped parts contain adsorbents. Shaped parts according to one of claims 1 to 9, characterized in that the shaped parts contain absorbents. Shaped parts according to one of claims 1 to 9, characterized in that the shaped parts have a non-combustible framework material. Shaped parts according to claim 12, characterized in that the shaped parts are impregnated with an adsorbent. Shaped parts according to one of claims 9 to 13, characterized in that the shaped parts have fine-grained fillings with a small gap volume. Molded parts according to claim 12, characterized in that the upper material of the molded parts is made of diffusion-open textile fabric that is stable up to 70 degrees Celsius in the mesh size range of 0.1 to 6 millimeters. Shaped parts according to one of claims 10 to 15, characterized in that the adsorbents of the shaped parts are preloaded with an inert gas. Shaped parts according to one of claims 1 to 16, characterized in that the natural vibration frequency of the shaped parts corresponds to the main frequencies of the installed machines. Use of molded parts according to one of claims 1 to 17 for a heat pump, the working fluid of which is propane and the extinguishing distance is 2 millimeters. Use of molded parts according to one of claims 1 to 18 for a heat pump, in which a left-turning thermodynamic Clausius-Rankine cycle with an inflammable working fluid, which is conducted in a closed, hermetically sealed working fluid circuit - at least one compressor for working fluid, - at least one relaxation device for working fluid, at least two heat exchangers for working fluid, each with at least two connections for heat transfer fluids, at least one of the heat exchangers is designed as a condenser, - a closed housing, - which includes all facilities connected to the closed working fluid circuit, - And may include other facilities.

Images