EP3792572A1 - Safety coil device for a heat pump - Google Patents

Abstract

Brine-water heat pump for the safe implementation of a counterclockwise thermodynamic cycle by means of a dangerous working fluid, which is guided in a closed, hermetically sealed working fluid circuit, suitable for installation in a building, having 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) being provided in the heat pump housing which encloses all apparatus and fittings through which the working fluid flows, and a wall opening (104) with an air duct (103) for scavenging air is provided, which is connected to the interior of the capsule housing (107) and leads to the environment outside the building.

Description

The invention relates to irregular states in refrigeration circuits in which a dangerous working fluid acting as a refrigerant is conducted in a thermodynamic cycle, such as the Clausius-Rankine cycle. These are mainly heat pumps, air conditioning systems and cooling devices, as are common in residential buildings. In particular, the invention relates to a heat pump which is installed inside a residential building and which also fulfills ventilation purposes.

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 devices. What these cycle processes have in common is that they generate useful heat or useful cooling using energy and form heat displacement systems.

A successful example from the known state of the art is the geoTHERM-Plus-System; as described in the company publication "System geoTHERM", Vaillant GmbH 03/2009. Here, heat is obtained from an earth borehole, this earth borehole being traversed by a brine circuit, where it absorbs or gives off heat. The heat pump itself as well as its installations for the users are set up within a building, which results in high demands on safety. Such a system represents the closest prior art.

The thermodynamic cycle processes that are used have been known for a long time, as are the safety problems that can arise when using suitable working fluids. Apart from water, the most well-known 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 damage the ozone layer, 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 promoted the need for replacement.

For this reason, the use of these refrigerants was subject to restrictions, in the European Union for example through the F-gas regulation (EU) 517/2014. As a result, practically all harmless safety refrigerants are banned and only dangerous working fluids and water remain to choose from. In this case, dangerous means that they are either toxic, such as ammonia, or flammable or explosive in connection with atmospheric oxygen, but are hardly harmful to the environment.

The problems that arise in the safety design of such systems are described in the WO 2015/032905 A1 clearly described. The lower ignition limit of R290 as a working fluid is around 1.7 percent by volume in air, which corresponds to 38 g / m ³ in air. If the refrigeration process is carried out in a hermetically sealed, but otherwise air-filled space with the working fluid R290 that surrounds it, the problem arises of recognizing a critical, explosive situation after a fault in which the working fluid escapes into this hermetically sealed space. Electrical sensors for the detection of critical concentrations are difficult to design to be explosion-proof, which is why the propane detection by the sensors themselves increases the risk of explosion considerably, with the exception of infrared sensors. R290 is also toxic if inhaled above a concentration of approx. 2 g / m ^{3 there} are narcotic effects, headaches and nausea. This applies to people who are supposed to solve a recognized problem on site before there is a risk of explosion.

R290 is also heavier than air, so it sinks to the ground in still air and collects there. So if some of the propane collects in a low-flow zone of the closed room in which the disturbed unit is located, the local explosion limits can be reached much faster than the quotient of the total room volume to the leaked R290 amount would lead to expect. The WO 2015/032905 A1 seeks to solve this problem by integrating a generator for electrical current in the opening or locking of this room and, when activated, in a first step generates and provides the electrical energy with which the sensor is activated, and in the event of an alarm the The lock then does not release, but causes ventilation of the locked room, and only allows unlocking and opening in a second step.

The DE 10 2009 029 392 A1 describes an explosion-proof refrigeration system in which a fan evacuates the contaminated air inside a gas-tight housing in the event of a leak after all devices have been switched off. The leak is detected by a gas sensor. The extracted mixture is conveyed into the environment, where it is mixed with ambient air in a very short time and is diluted to such an extent that there is no longer an explosive mixture. The device is intended to be used wherever refrigeration systems are required for cooling and there is a need for heat at the same time, and is preferably used in a supermarket refrigeration system.

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, at least one environmentally hazardous, toxic and / or inflammable Contains or consists of a 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 molded part, a paint, a spray film or a coating. The support structure of the molded part 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 after a threshold value has been reached or if an accident is detected. The adsorption can be carried out inside or outside a closed space.

The DE 20 2016 103 305 U1 describes an explosion-proof device for controlling the temperature of heat transfer fluids at different temperature levels, comprising an enclosure, a base element, a closed refrigerant circuit with the usual apparatus, a suction device with a fan and a gas sensor for the detection of flammable gas. The heat exchangers are positioned outside the housing. If the sensor strikes, a leak is suspected and the fan sucks the mixture out of the housing into a channel that leads to a location outside the housing. The device has its preferred location in a shopping mall.

It is also known to simply discharge flammable and explosive working fluids into the open in the event of a leak. In May 2012, the "Federal College of Refrigeration and Air Conditioning Technology" declared that the influence on global warming with R290 was very small, so draining it was necessary the usual procedure to dispose of this refrigerant into the atmosphere. However, certain safety precautions must be taken to minimize the occurrence of an explosive atmosphere as far as possible.

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

• ein Wärmepumpengehäuse,
• mindestens einen Verdichter für Arbeitsfluid,
• mindestens eine Entspannungseinrichtung für Arbeitsfluid,
• mindestens zwei Wärmeübertrager für Arbeitsfluid mit jeweils mindestens zwei Anschlüssen für Wärmeüberträgerfluide,
• eine Einrichtung zur Zwangsbelüftung,
  wobei
• im Wärmepumpengehäuse ein Kapselgehäuse vorgesehen wird, welches alle Apparate und Armaturen umschließt, die von Arbeitsfluid durchströmt werden,
• mindestens ein Gassensor im Kapselgehäuse angeordnet wird, bei dessen Alarm die Zwangsbelüftung des Kapselgehäuses (107) aktiviert wird,
• ein Außenanschluss mit einem Luftkanal für Spülluft vorgesehen wird, der mit dem Inneren des Kapselgehäuses verbunden ist und an die Umwelt außerhalb des Gebäudes führt.

The invention solves this problem for the safe implementation of a counterclockwise thermodynamic cycle in a brine-water heat pump by means of a dangerous working fluid, which is guided in a closed, hermetically sealed working fluid circuit, suitable for installation in a building

• 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,
  in which
• a capsule housing is provided in the heat pump housing, which encloses all apparatus and fittings through which the working fluid flows,
• at least one gas sensor is arranged in the capsule housing, in the event of which the forced ventilation of the capsule housing (107) is activated,
• an external connection with an air duct for scavenging air is provided, which is connected to the interior of the capsule housing and leads to the environment outside the building.

So if a leak occurs, the resulting overpressure means that the air mixture can escape from the capsule housing directly to the environment.

In one embodiment, it is provided that a flow grille is used in the air duct for scavenging air, the flow ducts of which have duct widths that prevent ignitability by being smaller than the quenching diameter of an ignitable mixture, the diameter being the hydraulic diameter. The quenching diameter corresponds to the boundary layer of the flow as it would occur in an air duct without a flow grille. The grids themselves can be formed from thin sheets or from honeycombs or from spirals of corrugated sheet metal or segmented sheet metal, the design depends on the shape of the air duct for scavenging air, which can be designed as a flat duct, for example.

In a further embodiment it is provided that a conveying fan is provided in the air duct for scavenging air, which is designed to be explosion-proof. For this purpose, the capsule housing must have an air inlet that is either integrated in the air duct or that is 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.

In a further embodiment it is provided that an ejector and a pressurized gas container are connected to the air duct (103) for scavenging air as a device for forced ventilation, the ejector being operated with the pressurized gas from the pressurized gas container as propellant gas. In an advantageous embodiment it is provided that the Pressurized gas container is filled with air or with inert gas or with oxygen-depleted air. This means that in the event of a malfunction, the ignitable gas mixture is diluted or rendered inert. This option is useful in the case of major leakages that rarely occur.

In a further embodiment it is provided that an air stream is led out of the capsule housing and directed into an adsorber by means of a conveying fan. This adsorber can either vent into the room where the heat pump is installed or back into the capsule housing. In a further variant, the adsorber is also used as an upstream filter when venting into the outside area of the building; this avoids concentration peaks of gaseous working fluid in the gas mixture to be discharged, but venting must then take longer, with the adsorber being slowly desorbed or discharged. This results in an equalization.

Depending on the detected gas concentration, either the forced ventilation to the outside can be activated, which is to be carried out for larger concentrations or rapid increases in concentration, or only the forced ventilation by the adsorber for low concentrations of working fluid, or the equalization by the adsorber as an upstream filter.

• Fig. 1 schematisch eine Wärmepumpe nach dem Stand der Technik, die in einem Wohngebäude steht,
• Fig. 2 dieselbe Wärmepumpe mit Sicherheitsausstattung,
• Fig. 3 die Wärmepumpe mit einem Ejektor,
• Fig. 4 die Wärmepumpe mit dem Adsorber als Vorschaltfilter,
• Fig. 5a und 5b zwei Strömungsgitter im Querschnitt des Spülkanals.

The invention is explained in more detail below with the aid of examples. Show:

• Fig. 1 schematically a heat pump according to the state of the art, which is located in a residential building,
• Fig. 2 the same heat pump with safety equipment,
• Fig. 3 the heat pump with an ejector,
• Fig. 4 the heat pump with the adsorber as an upstream filter,
• Figures 5a and 5b two flow grids in the cross section of the flushing channel.

Fig. 1 shows a residential building 100, which is equipped with a brine-water heat pump 101, which is also used as a hot water device. In the upper part, the brine-water heat pump 101 has the hot water elements, such as the drinking water storage tank 2, the additional electrical heater 7, as well as the safety temperature limiter 6 and a conduit 1. An electrical switch box 3 with a controller board 4 and a connection for the voltage supply 5 are provided on the front.

In the lower part, the thermodynamic devices are arranged that lead the working fluid in the refrigeration circuit, these are the compressor 12, the expansion valve 14, the evaporator 18, the condenser 19 and the 3-way valve 8, plus 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 draining valves for the heating circuit 10 and the brine circuit 16.

You can freely choose whether these arrangements are made in the manner described above, or whether the hot water part and the refrigeration circuit are arranged next to one another or exactly the other way around, one above the other. The type plate 11, the recessed grips 13 and the condensate pan 15 are located in the floor area.

Fig. 2 shows the changes made by the security concept. First, the part in which the thermodynamic apparatus is located is encapsulated by a capsule housing 107. On the one hand, this encapsulation is tight to the outside, but air can flow in from the outside. An air duct 103 leads from the capsule housing 107 through a wall opening as an external connection 104 directly to the outside. Compared to the outside area, only protective grids or similar protective devices against the ingress of animals or dirt are provided at the outside outlet 105 of the air duct 103. It is useful if the air duct 103 is short and the heat pump 101 is set up directly on an outer wall 102.

At the inner inlet of the air channel, which is located in the capsule housing 107, a non-return valve can be arranged to prevent the inflow of outside air during normal operation, otherwise a large amount of air can quickly escape in the event of a severe leak and a pressure build-up in the capsule housing 107 as well as in the entire housing of the heat pump 101 is certainly omitted. This venting can be supported by the explosion-proof conveyor fan 106 if necessary. In such cases, the heat pump is stopped immediately.

The adsorber 111, which is connected directly to the capsule housing 107 via the suction connection 109, serves as a further safety measure. Furthermore, a gas sensor 108 is provided which switches on the conveyor fan 110 when working fluid is detected in the capsule housing 107. In this case, purified air is discharged into the interior at the interior outlet 112. This type of ventilation is selected for small leaks; in such cases the heat pump can continue to run in emergency mode for a while.

In many applications, however, the heat pump cannot be installed directly on an external wall. If the air duct is longer, the formation of an ignitable mixture in the air duct must also be taken into account and prevented. The following options are available for this.

Fig. 3 shows the air duct (103) for purging air and, as a device for forced ventilation, an ejector (114) and a pressurized gas container (115) connected to it, the ejector being operated with the pressurized gas from the pressurized gas container as a propellant. In this way, a dilution of the gas mixture can be achieved. The measures with the conveyor fan 106 and the ejector 114 can also be used in combination.

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

In the case of larger air duct cross-sections, however, it is difficult to prevent larger quantities of working fluid from collecting in the air duct if this air duct has to be routed over a long distance due to the installation. In order to reliably prevent ignition in the air duct, the air duct is equipped with flow grids made of very thin sheet metal with sheet thicknesses in the tenths of a millimeter range.

Figure 5a shows such an arrangement for a rectangular channel which can be connected to an activated carbon adsorber in a flat design in a space-saving manner. The flushing pipe grids 113 are inserted into the rectangular duct in a rectangular manner; the grid widths depend on the expected concentrations and the respective design speed of the gas flow.

Figure 5b shows a corresponding arrangement for a round channel, the flow grids can be formed by a spiral sheet or by several nested round sheets, which are held by sector boundaries or made of corrugated sheets, as they are also known for flame protection devices.

It goes without saying that those in the Figures 2 to 5 The measures shown can also be used in combination.

List of reference symbols

1

Cable duct

2

Drinking water storage

3

Electrical switch box

4th

Controller board

5

Power supply connection

6th

Safety temperature limiter STB of the additional heating

7th

Electric auxiliary heating

8th

3-way valve

9

Heating circuit pump

10

Filling and draining valve heating circuit

11

type label

12th

compressor

13th

Recessed grips

14th

Expansion valve

15th

Condensate pan

16

Filling and draining valve, brine circuit

17th

Brine pump

18th

Evaporator

19th

Condenser

100

Residential buildings

101

Heat pump

102

Outer wall

103

Air duct

104

External connection

105

External outlet

106

Conveyor blower

107

Capsule housing

108

Gas sensor

109

Suction connection

110

Conveyor blower

111

Activated carbon adsorber

112

Inner outlet

113

Flush pipe grille

114

Ejector

115

Pressurized gas container

Claims (9)

Brine-water heat pump for the safe implementation of a counterclockwise thermodynamic cycle 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 - 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),
characterized in that - 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), in the event of whose alarm the forced ventilation of the capsule housing (107) is activated, - An external connection (104) with an air duct (103) for scavenging air is provided, which is connected to the interior of the capsule housing (107) and leads to the environment outside the building. Brine-to-water heat pump according to claim 1, characterized in that a flow grille (113) is used in the air duct (103) for scavenging air, the flow ducts of which have duct widths which prevent ignitability by being smaller than the quenching diameter of an ignitable mixture are chosen. Brine-to-water heat pump according to Claim 1, characterized in that a conveying fan (106), which is designed to be explosion-proof, is provided in the air duct (103) for scavenging air as a device for forced ventilation. Brine-to-water heat pump according to claim 1, characterized in that an ejector (114) and a pressurized gas container (115) are connected to the air duct (103) for scavenging air as a device for forced ventilation, the ejector using the pressurized gas from the pressurized gas container as propellant gas is operated. Brine-water heat pump according to Claim 4, characterized in that the pressurized gas container (115) is filled with air or with inert gas or with oxygen-depleted air. Brine-water heat pump according to one of Claims 1 to 5, characterized in that an activated carbon adsorber (111) with a conveying fan (110) is connected to the capsule housing (107), the outlet of the activated carbon adsorber (111) either into the capsule housing ( 103) or to the installation site of the air-brine-water heat pump or to a connection that leads out of the building. Method for flushing a capsule housing of a brine-water heat pump according to the preceding claim 6, characterized in that, depending on the detected gas concentration of working fluid, either the forced ventilation to the outside or the forced ventilation through the activated carbon adsorber is activated. A method according to claim 7, characterized in that with larger concentrations of working fluid or rapid increases in concentration the Forced ventilation to the outside and at low concentrations of working fluid the forced ventilation is carried out by the activated carbon adsorber. Method according to Claim 7, characterized in that in the case of larger concentrations of working fluid or rapid increases in concentration, the forced ventilation to the outside and beforehand is carried out by the activated carbon adsorber.

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