Outdoor unit refrigerant fire prevention

Abstract

A heat pump having a reduced safety area and a method of operation, the heat pump comprising an outdoor unit (1), an indoor unit (14), a connecting line between the indoor unit and the outdoor unit, and a refrigerant circuit having a combustible refrigerant, an evaporator fan (2), at least one evaporator heat exchanger (3) and at least one refrigerant detection device (10) for refrigerant leakage detection are arranged in the outdoor unit (1), a refrigerant circuit component (4) is arranged in an overflow container (19), the bottom and the sides of the overflow container (19) are closed, the evaporator fan (2) is arranged above the overflow container (19), and the evaporator heat exchanger (3) is arranged in the overflow container (19). The top of the overflow container (19) is provided with a purging port (23), the purging port is directly communicated with a flow path of fan air of the evaporator fan (2), and an outlet of the fan air of the evaporator fan (2) is arranged above a release height (13) above the ground (18).

Description

TECHNICAL FIELD

[0001] The present invention relates to a safety measure for preventing the formation of flammable refrigerant-air mixtures in the vicinity of an outdoor installed heat pump. BACKGROUND

[0002] It is known that heat pumps are used for heating and / or cooling a medium, thereby heating and / or cooling a house or other object. By means of a refrigerant in a refrigerant circuit, environmental energy, such as geothermal or ambient air, or waste heat extracted from a heat source, is lifted to a higher utilizable temperature level and delivered to a heat sink, for example a heating device. The refrigerant has the property of absorbing energy from the heat source as an evaporating liquid at a low heat source temperature, is generally not flammable and non-toxic before, but has a considerable Global Warming Potential (GWP). Natural refrigerants have at least significantly lower Global Warming Potential, but are flammable and partly toxic.

[0003] The state of the art is either an outdoor installed heat pump using flammable natural refrigerants or a split heat pump with a part cooling circuit installed within the building where the heat pump is installed.

[0004] To avoid the danger, such as an explosion, that can arise from flammable refrigerants escaping from an outdoor unit in a heat pump system, JP 2002 115 939 A uses a sensor for detecting refrigerant leakage and a flap arranged below the outside of the housing of the outdoor unit, which flap can only open inwardly to discharge the leaking refrigerant. If the sensor detects refrigerant leakage, the delivery direction of a fan, which is normally used for the condenser heat exchanger intake and ventilation of the outdoor unit, is changed. The fan creates a slight overpressure in the housing of the outdoor unit, which is roughly equivalent to the flow resistance of the condenser heat exchanger, and the change in delivery direction results in a slight underpressure in the housing of the outdoor unit, so that the flap on the outside of the outdoor unit housing opens inwardly and external air flows in. The external air dilutes the leaking coolant and is discharged outwardly by the fan. As soon as the sensor no longer detects the coolant, further measures can be taken.

[0005] EP 3 029 397 B1 describes a similar outdoor unit, in which a ventilation opening is used instead of a flap for ventilation, and in the event of a leak inferred from the refrigerant concentration measured by the sensor, the delivery direction of the fan is changed from positive to negative flow. As in JP 2002 115 939 A, the change in pressure conditions results in a blow-off of the outdoor unit by the fan. There, the blow-off is assisted by a vortex, which also ensures that the sensor is passed wherever a leak occurs.

[0006] EP 3 943 822 B1 describes a heat pump having an outdoor unit and an indoor unit, wherein the outdoor unit provides an inner chamber, in which the outdoor heat exchanger and the compressor are arranged and between which a partition wall is provided, which spatially separates the two. The partition wall has a blocking hole and a flap, which is connected with one side of the partition wall and can be moved in vertical direction on a guide rail by means of an electric motor, the controller of which is connected with a refrigerant sensor. Furthermore, an outdoor ventilator is configured to be activated at a certain time before the compressor is activated.

[0007] In comparison to heat pumps using conventional fluorinated gases, special safety measures have to be taken in case of a refrigerant leakage for single or split heat pumps using flammable refrigerants like R290, which are installed outdoors. It is common practice to design the electronic components inside the equipment away from ignition sources and to define a protection zone around the heat pump, in which no external ignition sources or building openings are allowed.

[0008] With an increasing number of future equipment replacements, such protection zones can become an obstacle for existing installation locations. This often hinders new installations. A known countermeasure is to raise the exit position of the leaking refrigerant. The raised exit enables a better direct dilution of the refrigerant proportion in the air to prevent the formation of a flammable refrigerant-air mixture. This effect can be used when installing the outdoor unit on a wall, so that the radius of the protection zone around the outdoor unit can be reduced from 1 m to 0.5 m.

[0009] A fire can be prevented by active dilution. The problem is, however, that it is not known in advance where the feared leak will occur and, thus, whether the leak is in gaseous or liquid form. This leads to the question of how to technically compensate for the flammable window between the over- and under-concentration of the refrigerant-air mixture in a safe manner. That is, the possible leak points for liquid and gaseous refrigerant must be considered separately and handled accordingly using safety technology.

[0010] For equipment installed on the outside of a building or the building itself, it is often also necessary to take insulation measures in the area of the outer wall, both at the window, the facade, and in the case of maintenance work, and in this case, it must be taken into account that people are working on scaffolding, without putting them at risk, even if they are using tools, making a phone call or smoking, i.e. using a potential ignition source. Therefore, equipment installed outdoors must be safe even in the switched-off and de-energized state. Animals, in particular birds and rodents, can also be a source of danger, and in addition, vandalism is a risk. SUMMARY

[0011] In view of this, the object of the present application is to take appropriate measures to reduce the protected area, so that an outdoor heat pump or outdoor unit of a split system can be newly installed in a location where it was previously not possible or not allowed.

[0012] The problem is solved by a heat pump with a reduced safety area for the outdoor unit, comprising an outdoor unit, an indoor unit, a connecting line arranged between the indoor unit and the outdoor unit, and a refrigerant circuit with a flammable refrigerant, and in the outdoor unit an evaporator fan, at least one evaporator heat exchanger and at least one refrigerant detection device for refrigerant leakage, wherein

[0013] The refrigerant circuit components are arranged in an overflow container,

[0014] The bottom and the sides of the overflow container are closed,

[0015] The evaporator fan is arranged above the overflow container,

[0016] The top of the overflow container is provided with purge openings which directly communicate with the flow path of the fan air of the evaporator fan,

[0017] The outlet of the fan air of the evaporator fan is arranged above a release height above ground level.

[0018] In terms of refrigerant detection devices or leakage detection devices, not only systems that can directly detect refrigerant, such as known flammable substance sensors in the air, but also all indirect methods, for example by means of ultrasonic pulses to observe the acoustic vibration behavior of the refrigerant circuit.

[0019] In some embodiments, lines with a large amount of refrigerant can be introduced into the indoor unit, in which case the risk of leakage is mainly present in the indoor space. If one wants to avoid the risk of leakage in the indoor space, one can arrange all the components that guide the refrigerant in the outdoor unit, in which case only the heating circuit lines from the indoor unit to the outdoor unit have to be correspondingly insulated.

[0020] The release height can be chosen arbitrarily as long as the outlet of the air flow of the evaporator fan is sufficiently high, the outlet can be raised by a duct or moved to a less dangerous location as appropriate.

[0021] In one embodiment of the heat pump, one of the purge openings is provided with an air deflection cover which deflects the outside air into the overflow container for purging. This is actually equivalent to the landing flaps on an airplane.

[0022] In a further embodiment of the heat pump, a safety module is provided in the overflow container, which safety module comprises activated carbon for adsorption. Only a small amount of activated carbon is required, which temporarily adsorbs the refrigerant at high concentrations, and subsequently desorbs during further ventilation. Thereby, it is possible to prevent the formation and persistence of such air stream streaks in the exhaust air stream under laminar conditions.

[0023] In a further embodiment of the heat pump, a safety module is provided in the overflow container, which safety module can fill the space of the overflow container with an inert gas that is heavier than air. In the case of R290, i.e. propane, as refrigerant, carbon dioxide is suitable as inert gas. This inert gas is heavier than air and is close to propane. In a simple and low-cost implementation, a common gas cylinder, such as used in soda machines, can be used, and the opening of the valve is then controlled by means of a refrigerant detection device.

[0024] In a further embodiment of the heat pump, all components in the overflow container and the evaporator fan are designed to be explosion-proof. Even in the event of a refrigerant leak, the amount of which is not known in advance during the concentration change, it is always ensured that, in the overflow container and when being discharged through the purge port, a fire cannot be ignited, even if a flammable mixture can have formed.

[0025] In a further embodiment of the heat pump, the outdoor unit has a safety valve that discharges gas into the overflow container. The greater the resulting input of refrigerant, the more design reserves have to be provided for the other safety devices.

[0026] In a further embodiment of the heat pump, the outdoor unit has a gas separator that discharges gas into the overflow container. This discharge is necessary in the case of a refrigerant line that does not lead to the indoor unit of the building, but rather to the heating circuit line of the building, in the case of which there is a risk that the refrigerant reaches the heating circuit via the heat exchanger (the heating circuit is usually kept at a lower pressure than the cooling circuit).

[0027] The invention also relates to a method for handling a detected leak. The method is applicable to a device as described above, in which the outdoor unit is provided with the entire refrigerant circuit comprising a compressor and an expansion device. The following steps are carried out in sequence:

[0028] a. detecting the refrigerant by means of a refrigerant detection device,

[0029] b. switching off the refrigerant compressor of the refrigerant circuit,

[0030] c. continuously switching on the evaporator fan,

[0031] d. discharging the refrigerant,

[0032] e. stopping the heat pump,

[0033] f. displaying a fault message,

[0034] g. requesting service.

[0035] It is clear that even in the event of a large-scale power failure, the fan can be operated at least at a reduced power by means of the battery, of course also for the refrigerant detection device and other electronic control equipment. For this reason, the compressor as the main consumer must be the first to be disconnected, otherwise the battery reserve will soon be exhausted.

[0036] In one embodiment of the method, in the step "continuously switching on the evaporator fan", an air deflector is also provided or installed for ventilating the overflow container. Since the fan creates a flow resistance, under the influence of which noise can occur, this air deflector is usually stowed away, without the purge port having to be closed, but instead providing a smooth and laminar flow around the purge port during normal operation, thus avoiding whistling.

[0037] If present, in another embodiment of the method, in addition to the step "discharging the refrigerant", temporary adsorptive storage of the refrigerant and / or inertization is also included. The temporary storage can always be in operation, that is, open as an adsorption bed or only separated from the space of the overflow container by a sieve, while for example the inertization by means of carbon dioxide requires a signal for leak detection, which can also be set so that the inertization is only carried out above a minimum concentration of the refrigerant in the air, which should be kept at a safe distance from the flammable limit. BRIEF DESCRIPTION OF DRAWINGS

[0038] The application will be explained in detail below with reference to four schematic drawings. In which:

[0039] Figure 1 shows a heat pump with an outdoor unit, which comprises the entire refrigerant circuit,

[0040] Figure 2 shows a heat pump with an outdoor unit, which comprises a partial refrigerant circuit,

[0041] Figure 3 is a side view from the perspective of the outer wall,

[0042] Figure 4 is another side view from the perspective of the outer wall,

[0043] Figure 5 is a flow chart of the process. DETAILED DESCRIPTION

[0044] Figure 1A heat pump with an outdoor unit 1 is schematically shown, which comprises the entire refrigerant circuit, which comprises an evaporator fan 2, an evaporator heat exchanger 3 and the remaining refrigerant circuit components 4, such as refrigerant compressor and expansion valve etc. The refrigerant circuit further comprises a safety valve 5, a refrigerant-air separator 6, a condenser 7 and the corresponding connection lines 8a and 8b, which lead to a hydraulic module 9 in an indoor unit 14.

[0045] In the outdoor unit 1 there is also a refrigerant detection device 10, which is usually one or more sensors that measure in different measurement methods. All these refrigerant circuit components, except the evaporator fan 2 and the evaporator heat exchanger 3, are located in an overflow container 19 and are installed in a removable refrigerant circuit module frame 15. That is, if refrigerant leaks, it will overflow from the edge of the overflow container 19 to a release height 13 above the ground 18, where it is blown away by the evaporator fan 2 and thus diluted substantially. From Figure 1 It can be seen that, viewed from the perspective of the view, the air of the evaporator fan 2 enters the evaporator fan 2 and escapes on the opposite side, where the air flow flows along the right and left heat exchanger surfaces of the evaporator heat exchanger. The air flow of the evaporator fan 2 can also flow away from the house outer wall 16, which is the most common case, where the air flow is then guided through the evaporator heat exchanger 3. In this case, the air duct of the evaporator fan is shown here in the form of an axial twist. These two technical variants are technically equivalent.

[0046] Figure 1 An optional safety module 20 is also shown, as well as the house outer wall 16 of the building and the simplified roof 17.

[0047] Figure 2 A heat pump with an outdoor unit 1 is schematically shown, which does not comprise the entire refrigerant circuit, but comprises an evaporator fan 2, an evaporator heat exchanger 3 and the remaining refrigerant circuit components 4. In the indoor unit, in addition to the hydraulic module 9, there is a safety valve 5, a refrigerant-air separator 6 and a condenser 7. Instead of connection lines, the outdoor unit 1 and the indoor unit 14 are connected by refrigerant shunt lines 11a and 11b, of which refrigerant shunt connectors 12a and 12b are also shown in the figure. The disadvantage of this is that the refrigerant inventory increases due to the volume of the refrigerant shunt lines 11a and 11b, but the advantage is that Figure 1 The connection lines 8a and 8b in do not require frost protection. The choice between these two solutions must be optimized according to the site conditions. The other installation conditions of the outdoor unit 1 are in line with the description in Figure 1

[0048] Figure 3 ​A side view of the outdoor unit 1 is shown as seen from the outer wall 16. As indicated by the arrows, when the evaporator fan 2 is running, outside air 21 is drawn in from the left and air from the overflow vessel 19 is carried away through the purge opening 23 on the left. Subsequently, the air flows over the heat exchanger surfaces of the evaporator heat exchanger 3 to the evaporator fan 2 (here shown with its blades), in the process of which dilution is achieved by mixing. Mixing is produced by the fact that, in the design, always turbulent flow is striven for in order to achieve good heat transfer, this turbulent flow also produces good mixing and prevents the formation of air flow streaks.

[0049] The air-refrigerant gas mixture flowing from the overflow vessel 19 forms a negative pressure, which causes a suction effect at the purge opening 23 on the right, which is further enhanced by the air deflection flap 22. Figure 3 The connecting lines, the overpressure valve and the gas-air separator are not shown in the middle, but, depending on the embodiment, are likewise in the overflow vessel 19, as shown in Figure 1 and Figure 2 . The remaining description is the same as in Figure 1 and Figure 2 .

[0050] Figure 4 A further side view of the outdoor unit 1 is shown as seen from the outer wall 16. As indicated by the arrows, outside air 21 is likewise drawn in from the left, but instead of carrying away air from the overflow vessel 19 through the purge opening 23 on the left, it is sucked into the overflow vessel 19 through the purge opening 23 on the left. But subsequently, the air does not flow over the heat exchanger surfaces of the evaporator heat exchanger 3 to the evaporator fan 2, but instead enters the area between the evaporator and the fan (here shown with its blades) through the purge opening 23 on the right. The negative pressure is higher here than in the surroundings, and therefore the flow of air for ventilation is greater than in the ventilation solution shown in Figure 3 .

[0051] When mixing, the person skilled in the art will take into account that a sufficiently large mixing distance is produced in the design and that sufficient turbulent flow is produced. In this connection, the suction effect at the purge opening on the left, which is further enhanced by the air deflection flap 22, can produce the turbulent flow required for rapid and complete mixing, preventing the formation of streaks, which the person skilled in the art will take into account when selecting these two technical variants in individual cases. The remaining description is the same as in Figure 1 , Figure 2 and Figure 3 .

[0052] Figure 5The process flow is shown when a leak or other source of refrigerant in the air in the overflow container 19 is detected. After the detection 101 of refrigerant, such as R290, the compressor of the refrigerant circuit is first switched off in a step "switch off 102" to ensure that there is still enough energy reserve in the battery of the outdoor unit to maintain the operation of the evaporator fan even in the event of a power failure. Subsequently, the evaporator fan 2 is switched on in a step "switch on evaporator fan 2 103" or, if the evaporator fan is already running or is still running, the evaporator fan 2 is prevented from being switched off even if there is no heat dissipation in the evaporator heat exchanger 3. This ensures that the exhaust 104 of refrigerant can be completed. Subsequently, the heat pump operation is stopped 105, at the same time, a fault is displayed 106 and "request for service 107" is requested in order to assess whether there is still a risk on site by an expert.

[0053] With the switching on of the evaporator fan 2, the air deflector flap 22 is adjusted if this technical variant is present. Depending on the specific case, the safety module 20 can also be activated when the refrigerant detection device detects a critical concentration.

[0054] If the heat pump is used for air conditioning in summer, the proposed solution for the device and the method also applies analogously to air conditioning operation. In addition, the air flow of the evaporator heat exchanger can not only be horizontal, but also vertical or inclined, the essential thing being that the gas-air mixture diluted with outside air is discharged as high as possible and also well dispersed on site, i.e. not towards the window or aligned with the neighbours. If such site conditions are taken into account, the safety distance can actually be cancelled or kept to a minimum.

[0055] Legend of the figures

[0056] 1 outdoor unit

[0057] 2 evaporator fan

[0058] 3 evaporator heat exchanger

[0059] 4 refrigerant circuit components

[0060] 5 safety valve

[0061] 6 refrigerant-air separator

[0062] 7 condenser

[0063] 8a, 8b connecting lines

[0064] 9 hydraulic module

[0065] 10 refrigerant detection device

[0066] 11a, 11b refrigerant bypass line

[0067] 12a, 12b refrigerant split connector

[0068] 13 relief height

[0069] 14 indoor unit

[0070] 15 refrigerant circuit module frame

[0071] 16 outer wall

[0072] 17 roof

[0073] 18 ground

[0074] 19 overflow container

[0075] 20 safety module

[0076] 21 outside air

[0077] 22 air deflection cap

[0078] 23 purge port

[0079] 101 detect refrigerant (R290)

[0080] 102 shut down compressor

[0081] 103 turn on evaporator fan

[0082] 104 vent refrigerant (R290)

[0083] 105 shut down heat pump

[0084] 106 display fault information

[0085] 107 request service

Claims

1. Heat pump with reduced safety area, comprising an outdoor unit (1), an indoor unit (14), connecting lines (8a, 8b) arranged between the indoor unit (14) and the outdoor unit (1), a refrigerant circuit with a flammable refrigerant, and in the outdoor unit (1) an evaporator fan (2), at least one evaporator heat exchanger (3) and at least one refrigerant detection device (10) for detecting a refrigerant leakage, characterized in that the refrigerant circuit components (4) are arranged in an overflow container (19), the bottom and the sides of the overflow container (19) are closed, the evaporator fan (2) is arranged above the overflow container (19), the top of the overflow container (19) is provided with purge openings (23) which directly communicate with the flow path of the fan air of the evaporator fan (2), the outlet of the fan air of the evaporator fan (2) is arranged above a release height (13) above the ground (18).

2. Heat pump according to claim 1, characterized in that one of the purge openings (23) is provided with an air deflection cap (22) which deflects external air (21) into the overflow container (19) for purging.

3. Heat pump according to claim 1 or 2, characterized in that the overflow container (19) is provided with a safety module (20) which temporarily stores part of the refrigerant in an adsorbed manner in the event of a refrigerant leakage.

4. Heat pump according to any one of claims 1 to 3, characterized in that the overflow container (19) is provided with a safety module (20) which fills the space of the overflow container with an inert gas which is heavier than air.

5. Heat pump according to any one of claims 1 to 4, characterized in that all components of the overflow container (19) and the evaporator fan (2) are designed in an explosion-proof manner.

6. Heat pump according to any one of claims 1 to 5, characterized in that the outdoor unit (1) has a safety valve (5) which vents into the overflow container (19).

7. Heat pump according to any of claims 1 to 6, characterized in that the outdoor unit (1) has a gas separator or refrigerant-air separator (6) which vents into the overflow container (19).

8. Venting method for an outdoor unit (1) of a heat pump, the heat pump comprising an outdoor unit (1), an indoor unit (14), connecting lines arranged between the indoor unit (14) and the outdoor unit (1), and a refrigerant circuit with a flammable refrigerant, the outdoor unit (1) is provided with refrigerant circuit components (4) comprising a refrigerant compressor and an expansion valve, and optionally a gas separator or refrigerant-air separator (6) and / or a safety valve (5), and in the outdoor unit (1) an evaporator fan (2), at least one evaporator heat exchanger (3) and at least one refrigerant detection device (10), and wherein the refrigerant circuit components (4) are arranged in an overflow container (19), the bottom and the sides of the overflow container (19) are closed, the evaporator fan (2) is arranged above the overflow container (19), the top of the overflow container (19) is provided with purge openings (23) which directly communicate with the flow path of the fan air of the evaporator fan (2), and the outlet of the fan air of the evaporator fan (2) is arranged above a release height (13) above the ground (18), characterized in that the venting method comprises the following steps: the venting method comprises the following steps: detecting (101) the refrigerant by means of the refrigerant detection device (10), switching off (102) the refrigerant compressor of the refrigerant circuit, continuously switching on (103) the evaporator fan (2), discharging (104) the refrigerant, stopping (105) the heat pump, displaying (106) a fault message, requesting (107) a service.

9. The method of claim 8, wherein, In the step "continuously switching on (103) the evaporator fan", an air deflector cap (22) for ventilating the overflow container (19) is also provided or installed.

10. The method according to claim 8 or 9, characterized in that, As a supplement to the step "discharging (104) the refrigerant", temporary adsorptive storage of the refrigerant and / or inertization of the overflow container (19) are also included.

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