Outdoor refrigerant ignition capability prevention

Abstract

Split heat pump with a reduced safety zone of the outdoor unit and method of operation comprising an outdoor unit (1), an indoor unit (2), connecting lines between the indoor unit and the outdoor unit, wherein a refrigerant circuit with a flammable refrigerant is carried in the indoor unit together with the outdoor unit, and wherein an evaporator fan (2), at least one evaporator heat exchanger (3) and at least one refrigerant or leak detection device (10) are provided in the outdoor unit (1), wherein the refrigerant circuit components (4) are arranged in an overflow tank (19), the overflow tank (19) is closed at the bottom and to the sides, the evaporator fan (2) is arranged above the overflow tank (19), and purge openings (23) are arranged on the top of the overflow tank (19) which open directly into the flow path of the fan air of the evaporator fan (2).the outlet of the fan air of the evaporator fan (2) is located above a release height (13) above the ground (18).

Description

[0001] The invention relates to a safety measure that prevents the formation of an ignitable refrigerant-air mixture in the immediate vicinity of an outdoor heat pump. As is known, heat pumps are used to heat and / or cool media, thereby heating and / or cooling houses or other buildings. Using a refrigerant in a refrigeration cycle, environmental energy, e.g., geothermal energy or ambient air, or even waste heat from the heat source, is extracted, raised to a higher and thus usable temperature level, and supplied to the heat sink, for example, the heating system. The refrigerant has the property of absorbing energy from the heat source as an evaporating liquid at low heat source temperatures and was formerly generally non-flammable and non-toxic, but had a considerable global warming potential (GWP).Natural refrigerants have a significantly lower global warming potential, but are flammable and sometimes toxic.

[0002] State of the art includes externally installed heat pumps with flammable, natural refrigerants or split heat pumps with part of the refrigeration circuit located inside the building where they are installed.

[0003] JP 2002 115 939 A teaches that, to prevent hazards such as explosions that could occur as a result of a flammable refrigerant leaking from an outdoor unit in a heat pump system, a sensor for detecting a refrigerant leak should be used, as well as a flap at the bottom of the outer casing of the outdoor unit that can only be opened from the inside to drain any escaping refrigerant. If the sensor detects a refrigerant leak, the direction of the fan, which normally directs airflow to and through the condenser heat exchanger in the outdoor unit, is reversed.Normally, this fan creates a slight positive pressure inside the outer box housing, roughly corresponding to the flow resistance of the condenser heat exchanger. However, reversing the airflow direction results in a slight negative pressure within the housing. This causes the flap on the outside of the housing to open inwards, allowing outside air to enter. This air dilutes the leaked refrigerant and is then vented to the outside by the fan. Once the sensor no longer detects any refrigerant, further action can be taken.

[0004] EP 3 029 397 B1 describes a similar external box where, instead of a flap, a ventilation opening is used for airflow. In the event of a refrigerant concentration measured by a sensor, a leak must be detected, and the fan's direction of airflow is changed from forward to reverse. As with JP 2002 115 939 A, the altered pressure conditions cause the external box to be purged by the fan. This purging is aided by turbulence, which also ensures that the sensor is exposed to airflow, regardless of the leak's location.

[0005] EP 3 943 822 B1 describes a heat pump with an outdoor unit and an indoor unit. The outdoor unit provides an interior space in which the outdoor heat exchanger and the compressor are located, separated by a partition wall. This partition wall has a locking hole and a flap that is coupled to one side of the partition wall and is movable vertically via guide rails and by means of a motor whose control is connected to a refrigerant sensor. Furthermore, the outdoor fan is configured to start a certain time before the compressor is switched on.

[0006] For heat pumps installed outdoors as mono or split systems using a flammable refrigerant, such as R290, special safety measures are required in the event of a refrigerant leak, compared to heat pumps based on conventional flammable gases. It is standard practice to design the electronic components within the unit to be ignition-source-free and to define a protective zone around the heat pump that must not contain any external ignition sources or building openings.

[0007] With the increasing number of equipment replacements in the future, this protected zone can become an obstacle at existing installation sites, often preventing new installations. A well-known countermeasure is to increase the size of the refrigerant outlet. The increased outlet ensures better direct dilution of the refrigerant in the air, preventing the formation of a flammable refrigerant-air mixture. This effect is already utilized when the outdoor unit is wall-mounted, allowing the protected zone to be reduced from a 1 m radius to 0.5 m around the outdoor unit.

[0008] Preventing ignition can be achieved through active dilution. However, a problem arises because the precise location of the anticipated leak is unknown beforehand, making it impossible to know for certain whether the escape will be in gaseous or liquid form. This raises the question of how to safely bridge the ignition window between an excessively rich and a too-lean refrigerant-air mixture—that is, between the lower and upper ignition limits. Therefore, the potential leak points of liquid refrigerant and those of gaseous refrigerant must be considered separately and addressed with appropriate safety measures.

[0009] For equipment installed outside buildings or attached to the buildings themselves, the additional factor is that insulation work often needs to be carried out on the exterior walls, whether it involves work on windows or the facade, or maintenance work. In such cases, scaffolding must be used, and people working on it must not be endangered, even when they are using tools, talking on the phone, or smoking—in other words, when they are using potential ignition sources. Therefore, the equipment installed outside must be safe even when switched off and unpowered. Animals, especially birds and rodents, can also pose a danger, and vandalism is another risk.

[0010] The object of the invention is therefore to reduce the protection zone by suitable measures to such an extent that new installations of externally placed heat pumps or external boxes of split devices can be carried out in places where this has not previously been possible or permitted.

[0011] The problem is solved by a split heat pump with a reduced safety zone of the outdoor unit, comprising an outdoor unit, an indoor unit, connecting lines between the indoor unit and the outdoor unit, wherein a refrigeration circuit with a flammable refrigerant is carried in the indoor unit together with the outdoor unit, and wherein an evaporator fan, at least one evaporator heat exchanger and at least one refrigerant or leak detection device are provided in the outdoor unit, wherein The refrigeration circuit equipment is arranged in an overflow tank, the overflow tank is closed at the bottom and sides, the evaporator fan is arranged above the overflow tank, purge openings are arranged on the top of the overflow tank which open directly into the flow path of the evaporator fan's air, and the outlet of the evaporator fan's air is located above a release height above the ground.

[0012] With regard to refrigerant or leak detection equipment, this includes not only systems that can directly detect refrigerants, such as the well-known sensors for flammable substances in air, but also all indirect methods that observe, for example, the acoustic vibration behavior of the refrigeration circuit, e.g., using ultrasound pulses.

[0013] In practice, this means that a large number of refrigerant lines can be routed to the indoor unit, in which case the risk of leakage is primarily located indoors. If the goal is to keep the risk of leakage away from the indoor area, all refrigerant-carrying components can be located in the outdoor unit. In this case, only heating circuits run from the indoor unit to the outdoor unit, and these must be appropriately insulated.

[0014] The release height can be chosen arbitrarily, provided that the airflow from the evaporator fan exits high enough; if necessary, the air outlet can be increased by an air duct or moved to a less hazardous location.

[0015] In one embodiment of the split heat pump, an air deflector flap is provided at one of the purge openings, which directs outside air into the overflow tank for purging. This is practically equivalent to the familiar landing flaps on aircraft.

[0016] In a further embodiment of the split heat pump, a safety module containing activated carbon for adsorption is integrated into the overflow tank. Small quantities are sufficient for this purpose; only at high concentrations does refrigerant become temporarily adsorbed, which is then desorbed during subsequent ventilation. This prevents the formation of clumps of refrigerant that would otherwise persist in the exhaust air stream, assuming a laminar flow.

[0017] In a further embodiment of the split heat pump, a safety module is provided in the overflow tank. This module can fill the tank's volume with an inert gas that is heavier than air. If the refrigerant is R290 (propane), carbon dioxide would be a suitable inert gas. Carbon dioxide is heavier than air and similar to propane in this respect. In a simple and cost-effective design, a standard cartridge, such as those used in water dispensers, can be used for this purpose. The opening valve is then controlled by the refrigerant detection system.

[0018] In a further embodiment of the split heat pump, all components in the overflow tank and the evaporator fan are designed to be explosion-proof. Even during the course of a refrigerant leak, the extent of which is unknown in advance, it is ensured that no ignitable mixture, should one even form, can ignite in the overflow tank or at the outlet through the purge ports.

[0019] In another embodiment of the split heat pump, the outdoor unit is equipped with a safety valve that vents into the overflow tank. The greater the potential refrigerant release resulting from this valve, the more design margin must be provided for the other safety devices.

[0020] In a further embodiment of the split heat pump, the outdoor unit is equipped with a gas separator that vents into the overflow tank. Such venting is necessary when the heating circuit lines, rather than the refrigerant lines, are routed into the building containing the indoor unit, and there is a residual risk that refrigerant could have entered the heating circuit via a heat exchanger. The heating circuit is typically maintained at a lower pressure than the refrigeration circuit. The gas separator can also be coupled with a refrigerant air separator.

[0021] The invention also relates to a method for the event that a leak is detected. The method relates to a device as described above, in which the entire refrigeration circuit, including the compressor and expansion device, is arranged in the outdoor unit. The following steps are carried out sequentially: a. Detection of the refrigerant by the refrigerant detection device, b. Switching off the refrigerant compressor of the refrigerant circuit, c. Permanent activation of the evaporator fan, d. Venting of the refrigerant, e. Stopping of the heat pump, f. Display of an error message, g. Service request.

[0022] It is clear that even in the event of a general power outage, the fan can still be operated at reduced power via a battery; the same applies, of course, to the refrigerant detection system and the other control electronics. For this reason, the compressor, as the main consumer of electrical energy, must be switched off first, otherwise the battery reserve will be depleted too quickly.

[0023] In one embodiment of the process, it is provided that, in the step of "permanent activation of the evaporator fan," additional air deflection flaps are installed to ventilate the overflow tank. Since these flaps create flow resistance for the fan, which can also generate noise when exposed to airflow, they are normally retracted. In this configuration, they do not need to close the purge ports, but rather ensure a smooth and laminar flow around the purge ports during normal operation, thus preventing whistling noises.

[0024] If applicable, a further embodiment of the process provides for the addition of temporary adsorptive storage of refrigerant and / or inerting to the "venting of the refrigerant" step. While the temporary storage can be continuously operational, i.e., open as an adsorption layer or separated from the overflow tank volume only by a sieve, inerting with, for example, carbon dioxide requires a leak detection signal. This signal can also be configured so that inerting only occurs above a minimum refrigerant concentration in the air, and this minimum concentration can and should be a safe margin above the ignition limit.

[0025] The invention is explained in more detail below with reference to four sketches. These show: Fig. 1 a split heat pump with an outdoor unit containing the entire refrigeration circuit, Fig. 2 a split heat pump with an outdoor unit that partially contains the refrigerant circuit, Fig. 3 a side view from the perspective of the outer wall, Fig. 4 an alternative side view from the perspective of the outer wall, Fig. 5 a flowchart of the procedure

[0026] Fig. 1 The figure schematically shows a split heat pump with an outdoor unit 1, which contains the entire refrigeration circuit with the evaporator fan 2, the evaporator heat exchanger 3, and the remaining refrigerant circuit 4, as well as a safety valve 5, a refrigerant air separator 6, the condenser 7, and the associated heating water lines 8a and 8b, which lead to the hydraulic module 9 in the indoor unit 14.

[0027] The outdoor unit 1 also contains the refrigerant detection device (10), which typically consists of one or more sensors using different measuring methods. All these components, except for the evaporator fan 2 and the evaporator heat exchanger 3, are located in the overflow tank 19 and are mounted in the removable refrigeration circuit module frame 15. Therefore, should refrigerant leak, it would overflow the edge of the overflow tank 19 at the release height 13 above ground level 18 and be blown away by the evaporator fan 2, becoming significantly diluted in the process. Fig. 1 The air from the evaporator fan 2 enters the fan and exits on the opposite side, flowing along the heat exchanger surfaces of the evaporator heat exchanger located on the right and left sides. The airflow from the evaporator fan 2 can also be directed away from the wall 16, which is the most common scenario, in which case the airflow passes through the evaporator heat exchanger 3. In this case, the fan duct of the evaporator fan is shown with an axial twist. Both variants are technically equivalent.

[0028] Fig. 1 It also shows the optional security module 20, the outer wall 16 of the building, and the suggested roof 17.

[0029] Fig. 2 Figure 1 schematically shows a split heat pump with an outdoor unit 1, which does not contain the entire refrigerant circuit, but does contain the evaporator fan 2, the evaporator heat exchanger 3, and the remaining refrigerant circuit 4. The indoor unit contains, in addition to the hydraulic module 9, the safety valve 5, the refrigerant air separator 6, and the condenser 7. Instead of the heating water lines, the outdoor unit 1 and the indoor unit 14 are connected by the refrigerant split lines 11a and 11b; the refrigerant split connectors 12a and 12b are also shown. This has the disadvantage that the refrigerant inventory increases by the volume of the refrigerant split lines 11a and 11b, but the advantage that the heating water lines 8a and 8b are made of Fig. 1 They do not need to be protected against frost. The selection of the two variants must be made on-site based on optimization. The remaining installations of outdoor unit 1 correspond to those in Fig. 1 described.

[0030] Fig. 3 Figure 1 shows a side view of the outdoor unit 1 as seen from the outer wall 16. Here, outside air 21, indicated by arrows, flows in from the left and draws air from the overflow tank 19 through the left purge opening 23. The air then flows past the heat exchanger surfaces of the evaporator heat exchanger 3 to the evaporator fan 2, whose blades are indicated here, resulting in dilution through mixing. This mixing also results from the fact that turbulent flow is always aimed for in the design to achieve good heat transfer; this turbulence also ensures good mixing and prevents the formation of streaks.

[0031] The outflowing air-refrigerant gas mixture from the overflow tank 19 creates a negative pressure, which leads to a suction effect at the right purge opening 23, further intensified by the air deflector flap 22. Not shown in Fig. 3 The connecting lines, pressure relief valve, and gas-air separator are located as shown in the diagram, depending on the design variant. Fig. 1 and Fig. 2 shown, also in overflow container 19. Otherwise, the description is identical to that of the Fig. 1 and Fig. 2 .

[0032] Fig. 4 Figure 1 shows an alternative side view of the outdoor unit 1 as seen from the outer wall 16. Here too, outside air 21, indicated by arrows, flows in from the left, but does not draw in air from the overflow tank 19 through the left purge opening 23. Instead, the air is drawn into the overflow tank 19 through the left purge opening 23. The air then does not flow past the heat exchanger surfaces of the evaporator heat exchanger 3 to the evaporator fan 2, but is introduced through the right purge opening 23 directly in front of the area between the evaporator and the fan, whose blades are indicated here. The negative pressure relative to the surroundings is higher there, and therefore the volume flow rate of the air passed through for ventilation is higher than in the figure shown in Figure 2. Fig. 3 ventilation variant shown.

[0033] When mixing, the person skilled in the art must take into account that the design creates a sufficiently large mixing path and sufficient turbulence. The stronger suction effect at the left rinsing opening, which is further enhanced by the air deflector flap 22, counteracts the generation of the necessary turbulence for rapid mixing to prevent clumping, a factor the person skilled in the art considers when selecting the two variants in each individual case. Otherwise, the description is identical to that of the Fig. 1 , Fig. 2 and Fig. 3 .

[0034] Fig. 5This shows the sequence of events when a leak or other source of refrigerant in the air in the overflow tank 19 is detected. After "Detection 101" for refrigerant, for example R290, the compressor of the refrigerant circuit is first switched off in step "Shutdown 102" to ensure that even in the event of a power failure, sufficient energy reserves remain in the outdoor unit's battery to keep the evaporator fan running as long as necessary. The evaporator fan 2 is then switched on in step "103 Switch-on Evaporator Fan 2" or, if it is already running, the shutdown of the evaporator fan 2 is blocked, even without heat being drawn from the evaporator heat exchangers 3. This ensures that the refrigerant is completely vented 204.At the same time, the fault is displayed in step "106 Display error message" and a "Service request 107" takes place so that a specialist on site can assess whether there is still a danger.

[0035] When the evaporator fan 2 is switched on, the air deflection flaps 22 are also positioned, if this variant is provided. Depending on the configuration, the safety module 20 may also be activated if the refrigerant detection device detects a critical concentration.

[0036] The presented solution for the device and the method also applies analogously to air conditioning operation when the split heat pump is used for air conditioning in the summer. Furthermore, the flow through the evaporator heat exchanger can be directed not only horizontally, but also vertically or at an angle. It is important that the gas-air mixture, diluted by the outside air, is discharged as high as possible and can disperse well on site, i.e., not directed into a window or towards a neighbor. If such local conditions are taken into account, the safety distance can be practically eliminated or kept to a minimum. Reference symbol list

[0037] 1 Outdoor unit 2 Evaporator fan 3 Evaporator heat exchanger 4 Refrigerant circuit 5 Safety valve 6 Refrigerant air separator 7 Condenser 8a, 8b Heating water lines 9 Hydraulic module 10 Refrigerant detection device 11a, 11b Refrigerant split lines 12a, 12b Refrigerant split connector 13 Release height 14 Indoor unit 15 Refrigeration circuit module frame 16 Exterior wall 17 Roof 18 Ground 19 Overflow tank 20 Safety module 21 Outside air 22 Air deflector flap 23 Flushing port 101 Refrigerant detection (R290) 102 Compressor shutdown 103 Evaporator fan activation 104 Refrigerant venting (R290) 105 Heat pump stop 106 Fault message display 107 Request Service

Claims

1. Split heat pump with a reduced safety zone of the outdoor unit, comprising an outdoor unit (1), an indoor unit (14), connecting lines (8a, 8b) between the indoor unit (14) and the outdoor unit (1), wherein a refrigerant circuit with a flammable refrigerant is carried in the indoor unit (14) together with the outdoor unit (1), and the outdoor unit (1) includes an evaporator fan (2), at least one evaporator heat exchanger (3), and at least one refrigerant or leak detection device (10). characterized by the fact that- the refrigeration circuit equipment (4) is arranged in an overflow tank (19), - the overflow tank (19) is closed at the bottom and to the sides, - the evaporator fan (2) is arranged above the overflow tank (19), - purge openings (23) are arranged on the top of the overflow tank (19) which open directly into the flow path of the fan air of the evaporator fan (2), - the outlet of the fan air of the evaporator fan (2) is located above a release height (13) above the ground (18).

2. Split heat pump according to claim 1, characterized by the fact that An air deflection flap (22) is provided at one of the flushing openings (23), which directs outside air (21) into the overflow container (19) for flushing.

3. Split heat pump according to one of claims 1 or 2, characterized by the fact that a safety module (20) is provided in the overflow tank (19) which can temporarily store part of the refrigerant in the event of a refrigerant leakage by adsorption.

4. Split heat pump according to one of claims 1 to 3, characterized by the fact that a safety module (20) is provided in the overflow tank (19) which can fill the volume of the overflow tank with an inert gas that is heavier than air.

5. Split heat pump according to one of claims 1 to 4, characterized by the fact that all components in the overflow tank (19) and in the evaporator fan (2) are designed to be explosion-proof.

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

7. Split heat pump according to one of claims 1 to 6, characterized by the fact that the outdoor unit (1) has a gas separator or a refrigerant air separator (6) which vents into the overflow tank (19).

8. Method for venting an outdoor unit (1) of a split heat pump, comprising an indoor unit (14), connecting lines between the indoor unit (14) and the outdoor unit (1), further comprising in the outdoor unit (1) a refrigerant compressor and an expansion valve and optionally a gas separator or a refrigerant-air separator (6) and / or a safety valve (5), and wherein in the indoor unit (14) together with the outdoor unit (1) a refrigerant circuit (4) with a flammable refrigerant is carried out, and wherein in the outdoor unit (1) an evaporator fan (2), at least one evaporator heat exchanger (3) and at least one refrigerant detection device (10) are provided, and wherein the components of the refrigerant circuit (4) are arranged in an overflow tank (19), the overflow tank (19) is closed at the bottom and on the sides, and the evaporator fan (2) is located above the overflow tank. (19) is ordered,- Flushing openings (23) are arranged on the top of the overflow tank (19), which open directly into 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 located above a release height (13) above the ground (18). characterized by The sequence of steps - detection (101) of the refrigerant by the refrigerant detection device (10), - shutdown (102) of the refrigerant compressor of the refrigerant circuit, - permanent activation (103) of the evaporator fan (2), - venting (104) of the refrigerant, - stop (105) of the heat pump, - display (106) of an error message, - request (107) of the service.

9. Method according to claim 8, characterized by the fact that In the step "permanent activation (103) of the evaporator fan", additional air deflection flaps (22) are installed for the ventilation of the overflow container (19).

10. Method according to one of claims 8 or 9, characterized by the fact that In addition to the step "Ventilation (104) of refrigerant", a temporary adsorptive intermediate storage of refrigerant and / or inerting of air deflection flaps (22) is carried out.

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