SAFETY FLUSHING DEVICE FOR A HEAT PUMP

Description

[0001] The invention relates to irregular conditions in refrigeration circuits in which a hazardous working fluid acting as a refrigerant is circulated in a thermodynamic cycle, such as the Clausius-Rankine cycle. These are primarily heat pumps, air conditioning systems, and refrigeration units commonly used in residential buildings. In particular, the invention relates to a heat pump that is installed within a residential building and also serves ventilation purposes.

[0002] Residential buildings include private homes, apartment 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 car air conditioning systems or transport crates, or even industrial facilities or medical devices. What these cyclic processes have in common is that they use energy to generate useful heat or cooling and form heat transfer systems.

[0003] A successful example of the state-of-the-art technology is the geoTHERM Plus system, as described in the company brochure "System geoTHERM," published by Vaillant GmbH in March 2009. Heat is extracted from a borehole, which is traversed by a brine circuit, absorbing or releasing heat. The heat pump itself, as well as its user installations, are installed within a building, which results in high safety requirements. Such a system represents the closest state of the art.

[0004] The thermodynamic cycles used have long been known, as have the safety problems that can arise with the use of suitable working fluids. Apart from water, the most common working fluids at the time were flammable and toxic. This led to the development of safety refrigerants consisting of fluorinated hydrocarbons in the last century. However, it became apparent that these safety refrigerants damaged the ozone layer and contributed to global warming, and that their lack of safety concerns led to negligent design. Up to 70% of sales were attributable to the need to refill leaking systems and their associated leakage losses, which was tolerated as long as it was considered economically justifiable in individual cases and encouraged the need for replacements.

[0005] For this reason, the use of these refrigerants has been subjected to restrictions, for example, in the European Union through the F-Gas Regulation (EU) 517 / 2014. This bans virtually all non-hazardous safety refrigerants, leaving only hazardous working fluids and water as options. Hazardous in this case means that they are either toxic, such as ammonia, or potentially flammable or explosive in contact with atmospheric oxygen, yet are hardly harmful to the environment.

[0006] The problems that arise in the safety design of such systems are clearly described in WO 2015 / 032905 A1. The lower flammability limit of R290 as a working fluid is approximately 1.7 percent by volume in air, which corresponds to 38 g / m3 in air. If the refrigeration process is carried out in a surrounding, hermetically sealed, but otherwise air-filled space with the working fluid R290, the problem arises of detecting a critical, explosive situation following a malfunction in which the working fluid escapes into this hermetically sealed space. Electrical sensors for detecting critical concentrations are difficult to implement in an explosion-proof manner, which is why the propane detection by the sensors themselves significantly increases the explosion risk, with the exception of infrared sensors. R290 is also toxic; inhalation above a concentration of approximately 2 g / m3 causes narcotic effects, headaches, and nausea.This concerns people who are supposed to solve an identified problem on site before there is a risk of explosion.

[0007] R290 is also heavier than air, so it sinks to the floor in still air and collects there. If some of the propane collects in a low-flow zone of the enclosed space containing the malfunctioning unit, the local explosion limits can be reached much faster than expected from the ratio of total space volume to the amount of R290 released. WO 2015 / 032905 A1 seeks to solve this problem by integrating an electrical generator into the opening or its locking mechanism in this space. When activated, this generator first generates and provides the electrical energy to activate the sensor. In the event of an alarm, the generator then does not release the locking mechanism but instead ventilates the enclosed space, and only then allows unlocking and opening.

[0008] DE 10 2009 029 392 A1 describes an explosion-proof refrigeration system in which, in the event of a leak, a fan evacuates the contaminated air within a gas-tight enclosure after all devices have been shut down. The leak is detected by a gas sensor. The extracted mixture is conveyed into the atmosphere, where it quickly mixes with ambient air and is diluted to the point where no explosive mixture is present. The device is intended for use wherever refrigeration systems are needed for cooling and there is a simultaneous heat demand, and is preferably used in a supermarket refrigeration system.

[0009] 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. Zeolite, also in combination with imidazole or phosphates, and CuBTC are proposed as adsorbents. 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 a microstructure, a lamellar structure, a tube bundle, a pipe register, or sheet metal and must be mechanically stable and have a high surface area. Circulation of the potentially contaminated air is usually continuous, but can also be initiated by a sensor that activates the ventilation when a threshold is reached or when an emergency is detected. Adsorption can be performed inside or outside an enclosed space.

[0010] DE 20 2016 103 305 U1 describes an explosion-proof device for controlling heat transfer fluids at different temperature levels, comprising an enclosure, a base element, a closed refrigerant circuit with the usual equipment, an extraction device with a fan, and a gas sensor for detecting flammable gases. The heat exchangers are positioned outside the enclosure. If the sensor is triggered, a leak is suspected, and the fan draws the mixture from the enclosure into a duct leading to a location outside the enclosure. The device's preferred location is a shopping center.

[0011] It's also known that flammable and explosive working fluids can simply be released into the atmosphere in the event of leaks. In May 2012, the Federal College of Refrigeration and Air Conditioning Technology stated that the impact of R290 on global warming is very low, so releasing it into the atmosphere has been the standard practice to date for disposing of this refrigerant. However, certain safety precautions must be taken to minimize the occurrence of an explosive atmosphere as much as possible.

[0012] EP 3 598 039 B1 (or WO2018167861A1) is considered to be the closest prior art and describes an air conditioning system which can also be used as a heat pump and whose refrigeration circuit contains a flammable refrigerant, for example propane, wherein the compressor, the switching device for the refrigerant and the heat source or heat sink side heat exchanger are arranged in an outdoor unit, the refrigerant is led to an indoor unit, from where the heat or cold is transferred to a heat transfer circuit by means of a double-walled heat exchanger.

[0013] In the event of a leak within the indoor unit, air contaminated with refrigerant is channeled out of the indoor unit through a line outside the building. The double-walled heat exchanger connected to the useful heat consumers or the useful cooling consumers can be encapsulated within the indoor unit, and this capsule can also be connected to a line leading to the environment outside the building. To ensure volume balance, openings can be provided for the indoor unit and the capsule, allowing air from inside the installation room into the capsule. The presence of a fan inside the indoor unit is also described, although it appears to only draw air from outside into the indoor unit's capsule.

[0014] The object of the invention is therefore to provide a device and a method for a safe and efficient flushing of a housing for a heat pump which is installed in a residential building and in the interior of which a left-handed thermodynamic cycle is carried out in a closed, hermetically sealed working fluid circulation by means of a hazardous, propane-containing working fluid, and the device also has a hot water function.

[0015] The invention solves this problem by means of a method and a device for flushing a capsule housing of a brine-water heat pump, in which a left-rotating thermodynamic cycle is carried out by means of a dangerous, propane-containing working fluid in a closed, hermetically sealed working fluid circuit, and which is suitable for installation in a building and further comprising a heat pump housing, 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 capsule housing is provided in the heat pump housing, which encloses all apparatus and fittings through which working fluid flows, a device for forced ventilation to the capsule housing, at least one gas sensor in the capsule housing, upon whose alarm the forced ventilation of the capsule housing (107) is activated, an external connection with an air duct for purge air, which is connected to the interior of the capsule housing and leads to the environment outside the building, wherein depending on the detected gas concentration of working fluid either the forced ventilation to the outside of the building through the air duct (103) or the forced ventilation through the activated carbon adsorber (111) is activated.

[0016] In one embodiment, it is provided that in the case of higher concentrations of working fluid or rapid concentration increases, forced ventilation is carried out to the outside and in the case of low concentrations of working fluid, forced ventilation is carried out through the activated carbon adsorber.

[0017] In one embodiment, in the case of higher concentrations of working fluid or rapid concentration increases, forced ventilation is carried out to the outside and previously through the activated carbon adsorber.

[0018] Should a leak occur, the resulting overpressure causes the air mixture to escape from the capsule housing directly into the environment. It is also planned that an air stream is led out of the capsule housing and into the adsorber by means of a conveying fan. The adsorber can vent either into the room where the heat pump is installed or back into the capsule housing. In one variant, the adsorber is also used as an upstream filter for venting to the outside of the building. This avoids concentration peaks of gaseous working fluid in the gas mixture to be discharged. However, the venting then has to take longer, during which the adsorber is slowly desorbed or discharged. This creates a homogenization effect.

[0019] Depending on the detected gas concentration, either forced ventilation to the outside can be activated, which is to be done in the case of higher concentrations or rapid concentration increases, or only forced ventilation through the adsorber in the case of low concentrations of working fluid, or homogenization by the adsorber as an upstream filter.

[0020] The invention also achieves the object by means of a device with a brine-water heat pump for the safe implementation of a left-rotating thermodynamic cycle process by means of a dangerous, propane-containing working fluid, which is guided in a closed, hermetically sealed working fluid circuit, suitable for installation in a building, comprising a heat pump housing, 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 device for forced ventilation, wherein a capsule housing is provided in the heat pump housing, which encloses all apparatus and fittings through which working fluid flows, at least one gas sensor is arranged in the capsule housing, the alarm of which activates the forced ventilation of the capsule housing, an external connection with an air duct for purge air is provided, which is connected to the interior of the capsule housing and leads to the environment outside the building.wherein an activated carbon adsorber (111) with a conveying fan (110) is connected to the capsule housing (107), wherein the outlet of the activated carbon adsorber (111) is either fed back into the capsule housing (103) or into the installation location of the air-brine-water heat pump or to a connection leading out of the building.

[0021] The quenching diameter refers to the hydraulic diameter. The quenching diameter corresponds to the boundary layer of the flow as it would occur in an air duct without flow grilles. The grilles themselves can be made of thin sheets, honeycombs, or spirals of corrugated or segmented sheet metal. The design depends on the shape of the air duct for the purge air, which can be designed as a flat duct, for example.

[0022] In a further embodiment, a conveying fan designed to be explosion-proof is provided in the air duct for purge air. For this purpose, the capsule housing must have an air inlet, either integrated into the air duct or designed as openings in the capsule housing through which air can flow in but not out, for example, through louvre flaps that can only be opened in one direction.

[0023] In a further embodiment, an ejector and a compressed gas container are connected to the air duct (103) for purge air as a forced ventilation device, the ejector being operated with the compressed gas from the compressed gas container as the propellant. In an advantageous embodiment, the compressed gas container is filled with air, inert gas, or oxygen-depleted air. This ensures that the ignitable gas mixture is diluted or rendered inert in the event of a malfunction. This option is useful in rare cases of major leaks.

[0024] The invention is explained in more detail below using examples. These examples show: Fig. 1 schematically shows a state-of-the-art heat pump installed in a residential building, Fig. 2 the same heat pump with safety features, Fig. 3 the heat pump with an ejector, Fig. 4 the heat pump with the adsorber as a pre-filter, Fig. 5a und 5b two flow grids in the cross-section of the flushing channel.

[0025] Fig. 1 shows a residential building 100 equipped with a brine-water heat pump 101, which is also used as a hot water device. The brine-water heat pump 101 has the hot water elements in the upper part, such as the drinking water storage tank 2, the electric auxiliary heater 7, the safety temperature limiter 6, and a cable duct 1. An electrical switch box 3 with a control board 4 and a connection for the power supply 5 are provided on the front.

[0026] The thermodynamic devices that carry the working fluid in the refrigeration circuit are arranged in the lower part. These are the compressor 12, the expansion valve 14, the evaporator 18, the condenser 19 and the 3-way valve 8. In addition, there are the pumps for the heat transfer fluids, these are the heating circuit pump 9 and the brine pump 17, as well as the filling and emptying valves for the heating circuit 10 and the brine circuit 16.

[0027] It is freely selectable whether these arrangements are made as described above, or whether the hot water section and the cooling circuit are arranged side by side, or exactly the other way around, one above the other. The nameplate 11, the recessed handles 13, and the condensate tray 15 are located in the base area.

[0028] Fig. 2 shows the changes brought about by the safety concept. First, the part containing the thermodynamic devices is encapsulated by a capsule housing 107. This encapsulation is sealed to the outside, but air can still flow in from the outside. From the capsule housing 107, an air duct 103 leads directly to the outside through a wall opening as an external connection 104. At the external outlet 105 of the air duct 103, only protective grilles or similar protective devices against the ingress of animals or dirt are provided. It is expedient if the air duct 103 is short and the heat pump 101 is installed directly against an external wall 102.

[0029] A check valve can be installed at the internal inlet of the air duct located in the capsule housing 107 to prevent the inflow of outside air during normal operation. Otherwise, in the event of a serious leak, a large amount of air can quickly escape, safely preventing pressure buildup in the capsule housing 107 as well as in the entire housing of the heat pump 101. This venting can be assisted by the explosion-proof conveying fan 106 if necessary. In such cases, the heat pump is immediately stopped.

[0030] A further safety measure is provided by the adsorber 111, which is directly connected to the capsule housing 107 via the suction port 109. Furthermore, a gas sensor 108 is provided, which switches on the conveying fan 110 when working fluid is detected in the capsule housing 107. In this case, purified air is released into the interior through the interior outlet 112. This type of venting is selected for small leaks; in such cases, the heat pump can continue to run in emergency mode for a while.

[0031] However, in many applications, the heat pump cannot be installed directly against an exterior wall. If the air duct is longer, the formation of an ignitable mixture in the air duct must also be considered and prevented. The following options are available for this purpose.

[0032] Fig. 3 shows the air duct (103) for purge air and, as a forced ventilation device, an ejector (114) and a compressed gas container (115) connected to it. The ejector is operated with the compressed gas from the compressed gas container as the propellant. This allows for dilution of the gas mixture. The measures with the conveying fan 106 and the ejector 114 can also be used in combination.

[0033] Fig. 4 shows the activated carbon adsorber 111 as an upstream filter. In the event of a small leak, the gas at the outlet of the activated carbon adsorber can be directly recirculated as purified air via the internal outlet 112 into the installation room. In this case, the activated carbon adsorber acts as an activated carbon box; such an activated carbon box can be installed in a very space-saving, flat design behind the heat pump. By equalizing the concentration of working fluid at the adsorber outlet, the gas concentration in the exhaust gas can be significantly reduced, even in the event of larger leaks.

[0034] However, with larger air duct cross-sections, it is difficult to prevent large quantities of working fluid from accumulating in the air duct if the installation requires the air duct to be routed over a long distance. To reliably prevent ignition in the air duct, the air duct is equipped with flow grids made of very thin sheets with thicknesses in the tenths of a millimeter range.

[0035] Fig. 5a shows such an arrangement for a rectangular channel, which can be connected to a flat-panel activated carbon adsorber in a space-saving manner. The purge pipe grids 113 are inserted rectangularly into the rectangular channel; the grid widths depend on the expected concentrations and the respective design gas flow velocity.

[0036] Fig. 5b shows a corresponding arrangement for a circular duct, the flow grids can be formed by a spiral sheet or by several round sheets inserted into one another, which are held by sector boundaries or are formed by corrugated sheets, as they are also known for flame protection devices.

[0037] It is understood that the Fig. 2 bis 5 The measures shown can also be used in combination. List of reference symbols

[0038] 1Cable duct 2Drinking water tank 3Electrical control box 4Control board 5Power supply connection 6Safety temperature limiter STB of the auxiliary heater 7Electric auxiliary heater 83-way valve 9Heating circuit pump 10Heating circuit fill and drain valve 11Nameplate 12Compressor 13Recessed handles 14Expansion valve 15Condensate tray 16Brine circuit fill and drain valve 17Brine pump 18Evaporator 19Condenser 100Residential building 101Heat pump 102Exterior wall 103Air duct 104Exterior connection 105Exterior outlet 106Conveyor fan 107Capsule housing 108Gas sensor 109Suction connection 110Conveyor fan 111Activated carbon adsorber 112Inner outlet 113Flush pipe grille 114Ejector 115Pressure gas container

Claims

1. Method for flushing a capsule housing of a brine-water heat pump, in which a counterclockwise thermodynamic cycle is conducted by means of a hazardous, propane-containing working fluid in a closed, hermetically sealed working fluid circuit, and which is suitable for installation in a building and further comprises - a heat pump housing, - at least one compressor (12) for working fluid, - at least one expansion device (14) for working fluid, - at least two heat exchangers (18, 19) for working fluid, each with at least two connections for heat transfer fluids, - a capsule housing (107) in the heat pump housing, which encloses all devices and fittings through which the working fluid flows, - a device for forced ventilation (106, 114) to the capsule housing (107), - at least one gas sensor (108) in the capsule housing (107), the alarm of which activates the forced ventilation of the capsule housing (107), - an external connection (104) with an air duct (103) for purge air which is connected to the inside of the capsule housing (107) and leads to the environment outside the building, - an activated carbon adsorber (111) with a conveying fan (110), the outlet of the activated carbon adsorber (111) being fed through connecting lines into the capsule housing and into the installation site of the air / brine / water heat pump and to a connection leading out of the building characterised in that depending on the detected gas concentration in the working fluid, either the forced ventilation to the outside of the building through the air duct (103) or the forced ventilation through the activated carbon adsorber (111) is activated.

2. Process according to claim 1, characterised in that in the case of higher concentrations of working fluid or rapid increases in concentration, forced aeration is carried out to the outside and in the case of low concentrations of working fluid, forced aeration is carried out through the activated carbon adsorber.

3. Process according to claim 2, characterised in that in the case of larger concentrations of working fluid or rapid increases in concentration, the forced ventilation is carried out externally and beforehand through the activated carbon adsorber.

4. Brine-water heat pump for the safe performance of a counterclockwise thermodynamic cycle by means of a hazardous, propane-containing working fluid which is conducted in a closed, hermetically sealed working fluid circuit, suitable for installation in a building, comprising - a heat pump housing, - at least one compressor (12) for working fluid, - at least one expansion device (14) for working fluid, - at least two heat exchangers (18, 19) for working fluid, each with at least two connections for heat transfer fluids, - a device for forced ventilation (106, 114), wherein - a capsule housing (107) is provided in the heat pump housing, which encloses all apparatus and fittings through which the working fluid flows, - at least one gas sensor (108) is arranged in the capsule housing (107), the alarm of which activates the forced ventilation of the capsule housing (107), - an external connection (104) with an air duct (103) for purge air is provided, which is connected to the inside of the capsule housing (107) and leads to the environment outside the building. characterised in that an activated carbon adsorber (111) with a conveying fan (110) is connected to the capsule housing (107), wherein the outlet of the activated carbon adsorber (111) is either led back into the capsule housing (103) or into the installation site of the air / brine / water heat pump or to a connection which leads out of the building.

5. Brine-water heat pump according to claim 4, characterised in that a flow grille (113) is used in the air duct (103) for purge air, the flow ducts of which have duct widths which prevent ignitability by being selected smaller than the quenching diameter of an ignitable mixture.

6. Brine-to-water heat pump according to one of claims 4 or 5, characterised in that a conveying fan (106) is provided in the air duct (103) for purge air as a device for forced ventilation, which is designed to be explosion-proof7. Brine-water heat pump according to one of claims 4 or 5, characterised in that an ejector (114) and a compressed gas container (115) are connected to the air duct (103) for purge air as a device for forced ventilation, the ejector being operated with the compressed gas from the compressed gas container as motive gas.

8. Brine-water heat pump according to claim 7, characterised in that the pressurised gas container (115) is filled with air or with inert gas or with oxygen-depleted air.