SE542699C2

SE542699C2 - A fluid conduit unit for a ventilation system

Info

Publication number: SE542699C2
Application number: SE1751074A
Authority: SE
Inventors: Bengt-Göran Karlsson; Hans Lekeberg; Nils Lekeberg
Original assignee: Enjay Ab Patent
Priority date: 2017-09-06
Filing date: 2017-09-06
Publication date: 2020-06-30
Also published as: WO2019048542A1; SE1751074A1

Abstract

A fluid conduit unit for a ventilation system (1), arranged to receive a flow (F) of exhaust air, configured to extract energy from the flow (F) of exhaust air and capture undesired particles in the exhaust air. The fluid conduit unit (10) has a plurality of conduits through which the exhaust air is arranged to flow, where the conduits are arranged in at least two conduit rows and where the conduits in a first conduit row are arranged to overlap the conduits in a second conduit row. The fluid conduit unit further has a cooling fluid arranged to be transported through the conduits and configured to cool the conduits. Further, the cooling fluid and the arrangement of conduits are configured to extract energy from the flow (F) of exhaust air by cooling the exhaust air, and to simultaneously, due to the physical design of the conduits and due to the cooling of the exhaust air, capture the undesired particles on the conduits.

Description

A FLUID CONDUIT UNIT FOR A VENTILATION SYSTEM TECHNICAL FIELD The present invention relates to a fluid conduit unit for a ventilations system and preferably a ventilation system in a large scale kitchen.

BACKGROUND Most ventilation systems in newer residential and office buildings that contain both exhaust air and supply air deploy energy recycling equipment. The general aim is to extract the energy from the warm exhaust air and, via a heat exchanger device, transfer the energy into the cold supply air to pre-warm it, using recycled energy. Such a part can for example be a cross-stream air-to-air exchanger configured to transfer the inherent energy in the exhaust air to the supply air utilizing metal flanges, or a rotating air-to-air exchanger where the energy exchange is achieved by means of a rotating disc transferring the energy from the exhaust air to the supply air, or a battery device which is configured to extract inherent energy in the exhaust air mainly utilizing the difference in temperature between the warm exhaust air and a cooler refrigerant inside the battery and subsequently reversing the process in the supply air to heat the cool supply air.

Particularly during the cold winter months, regardless of which recycling technology is deployed, this recycled energy cannot raise the temperature of the supply air all the way to the desired temperature needed to keep a comfortable ambient temperature indoors - Therefore, the supply air will be incrementally heated with an extra heating battery, placed downstream of the recycling battery. This battery is connected to the building’s heating system, utilizing whatever means of heating that is deployed, for example district heating, gas or electricity to infuse the supply air with the incremental energy needed to achieve the desired temperature.

To protect the technical equipment designed to extract the energy from the warm exhaust air, the flowing exhaust air is always filtered before it is led into the energy recycling equipment. In residential and office ventilation, this filtration normally consists of bag filters, designed to capture particles that otherwise might get stuck on the recycling equipment and there, as a first detrimental effect, deteriorate the efficiency of the energy exchange. As a second detrimental effect, the particles can start blocking the path of the exhaust air, resulting first in an increased resistance, which means the fans will have to work harder to extract the required air volumes from the building, thus increasing the energy bill. In the extreme case, the particles building up might eventually block up the equipment to an extent that the air flow cannot be maintained, resulting in a seriously deteriorated indoor air quality.

In restaurant, bakery or similar ventilation systems different types of air borne particles, formed during cocking, baking or other activities, create severe issues for the technical equipment designed to extract the energy from the warm exhaust air.

Examples of such particles can be grease, zoot or dust.

The problem with these particles is that they will - very quickly - clog up the traditional bag filters used to protect the recycling equipment in residential and office building ventilation. The ventilation industry has therefore during many years tested other filtration technologies designed specifically to extract or remove grease and zoot from the exhaust air in restaurant and bakery ventilation.

A problem is that the grease, zoot, moisture and warmth from the restaurant kitchens and bakery ovens create a very aggressive environment in the exhaust air. An environment so aggressive that, thus far, no air cleaning technology tested has been able to robustly over time extract or remove enough of the grease and other detrimental particles. Instead the grease escapes through or past the various air cleaning technologies to such an extent that the grease builds up on the heat exchanging areas of the energy recycling equipment. The build-up of grease on the energy recycling equipment leads to the same detrimental effects as for residential and office ventilation: first, deteriorating the energy exchange and secondly increasing the resistance in the duct system, eventually leading to the equipment being totally clogged up by grease, not letting the air pass by, which then means the exhaust air flow cannot be maintained, which in turn means that the indoor air quality is seriously deteriorated.

There are numerous patents pertaining to this traditional approach of trying to create a robust solution specifically for energy recycling in restaurant, bakery and similar types of ventilation systems: As a first step filter and clean the exhaust air to capture or remove the grease and as a second step subsequently lead the filtered and cleaned and supposedly grease-free exhaust air through energy recycling devices designed for residential and office type ventilation systems. One known prior art is described in for example EP 2149756.

SUMMARY An object has been to find a new technical solution that would enable the industry to extract the inherent energy also in exhaust air from restaurant, bakery and similar ventilation systems, without having to deploy and try to protect energy recycling units that are designed for other types of ventilation systems, i.e. energy recycling units for residential and office ventilation, which cannot survive in the extreme environment. The new technical solution is a totally new type of energy extraction unit, specifically designed to be able to survive in the aggressive environment that ventilation systems in restaurants, bakeries and similar operations represent, without any need for pre-filtration of the exhaust air by means of a separate air cleaning technology and with the inherent, specifically designed- in ability to manage the air borne particles that would clog up the traditional energy recyclers.

This object is achieved by a technique defined in the appended independent claims and where certain embodiments being set forth in the related dependent claims.

In a first aspect, there is provided a fluid conduit unit for a ventilation system, arranged to receive a flow of exhaust air, configured to extract energy from the flow of exhaust air and capture unwanted particles in the exhaust air. The fluid conduit unit comprises a plurality of conduits between which said exhaust air is arranged to flow, wherein said conduits are arranged in at least two conduit rows, said rows being arranged orthogonal with respect to said flow of exhaust air, and wherein the conduits in a first conduit row are arranged to overlap the conduits in a second conduit row, and a cooling fluid arranged to be transported through said conduits and configured to cool said conduits, wherein said cooling fluid and said arrangement of conduits are configured to extract energy from said flow of exhaust air by cooling said exhaust air, and to simultaneously, due to the physical design of the conduits and due to the cooling of said exhaust air, capture said unwanted particles on said conduits, by the plurality of conduits being cooled thereby generating an attracting force between unwanted particles increasing the likelihood of collision between unwanted particles leading to larger particles that are easier to filter; the plurality of conduits being of a round shape in order to generate a low pressure area behind each conduit causing unwanted particles to be attracted into the low pressure area increasing the likelihood of collision between unwanted particles leading to larger particles that are easier to filter, and increase the turbulence also increasing the likelihood of collision between unwanted particles leading to larger particles that are easier to filter; wherein said fluid conduit unit further comprises at least two spaced-apart conduit sections of conduits each comprising at least two conduit rows, wherein the distance (Dl) between a first section and a second section is between 50 and 1000 mm and wherein the distance (D2) between one conduit row and an adjacent conduit row within a section is between 20 and 100 mm in order to allow the unwanted particles time to clump together leading to larger particles that are easier to filter, wherein the distance Dl is larger than the distance D2 and wherein the fluid conduit unit is characterized in that the cooling fluid is configured to cool each conduit such that a layer of ice is created on the outer surface of each conduit, wherein the layer of ice is configured to attract and capture the unwanted particles and to further protects the outer surface of the conduits by letting the unwanted particles stick to the ice instead of to the outer surface.

In an embodiment the fluid conduit unit further comprises a distributing conduit arranged to distribute said cooling fluid to each conduit.

In an embodiment the fluid conduit unit further comprises a collecting conduit arranged to collect the cooling fluid after it has been transported through said conduits.

In an embodiment each conduit row comprises at least 12 conduits respectively.

In an embodiment the fluid conduit unit further comprises a chamber for collecting condensation water forming on said conduits when cooling said flow of exhaust air by means of the cooling fluid in said conduits. In an embodiment the fluid conduit unit further comprises a heating device configured to heat the condensation water to a temperature equal to or above 65°C.

In an embodiment the fluid conduit unit further comprises a water distributing device installed in said fluid conduit unit and configured to laminar sprinkle water on at least said conduits in order to remove particles captured on said conduit, wherein said water has a temperature equal to or above 65°C during sprinkle.

In an embodiment said water distributing device is connected to said chamber containing collected condensation water.

In another aspect of the invention there is provided a ventilation system comprising at least one duct and at least one fluid conduit unit as described above.

In an embodiment the ventilation system further comprises a water distributing device installed in the duct and configured to laminar sprinkle water on at least the conduit of the fluid conduit unit in order to remove particles captured on the conduits, wherein the water distributing device is connected to a chamber containing collected condensation water from the fluid conduit unit and wherein the condensation water has a temperature equal to or above 65 °C during sprinkle.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will be described in the following, reference being made to the appended drawings which illustrate non-limiting examples of how the inventive concept can be reduced into practice.

Fig. 1 is a schematic view of a ventilation system according to an embodiment of the invention, Fig. 2 is a schematic front view of a fluid conduit unit according to an embodiment of the invention used in the ventilation system in Fig. 1, Fig. 3 is a schematic side view of the fluid conduit unit in Fig. 2, Fig. 4 is a schematic top view of the fluid conduit unit in Fig. 2, Fig. 4a is a detailed view of a piece of the fluid conduit unit in Fig. 4, Fig. 5 is a schematic top view of the fluid conduit unit in Fig. 2 with a flow of exhaust air, and Fig. 6 is a block diagram of a filtration method used by the fluid conduit unit in Fig. 2.

DETAILED DESCRIPTION OF EMBODIMENTS With reference to the drawings a ventilations system 1 with a duct 2 and a fluid conduit unit 10 arranged within the duct 2 is illustrated. The ventilation system 1 as such can be any known type of ventilation system and is not limiting the features of the fluid conduit unit 10. Advantageously, the ventilation system 1 can be located in an environment where exhaust air contains unwanted particles such as grease, zoot, dust or other types of particles which needs to be effectively managed. Such an environment can for example be a large scale restaurant kitchen, a bakery or any other where unwanted particles are created during use.

These types of particles may be of different sizes and shapes. A typical range of particle sizes for more than 95% of the sample mass of a troublesome pollutant -grease - is from 2 pm up to 25 pm.

The fluid conduit unit 10 is designed and arranged to receive a flow F of exhaust air containing unwanted particles Pa, Pb, Pb’, Pc flowing through the duct 2 of the ventilation system 1. Preferably, the fluid conduit unit 10 is arranged such that no exhaust air flow is allowed to escape the fluid conduit unit 10. The flow F of exhaust air is achieved by a fan unit 3 often located towards the back end of the ventilation duct 2. The fan unit 3 can be any type of fan unit used in ventilation systems today.

The fluid conduit unit 10 presented below is able to both filter the exhaust air by removing unwanted particles and extract energy from the flow due to temperature differences between the flow of exhaust air and the conduits () of the fluid conduit unit 10 that the air passes through. This is explained in more detail below.

In order to achieve the above purposes the fluid conduit unit 10 includes a plurality of conduits 11a-e, 12a-d, 14a-e through which the exhaust air flows. The conduits 11a-e, 12a-d, 14a-e are arranged in at least two conduit rows 11’, 12’ where the conduits 11a-e in a first conduit row 11’ are arranged to overlap the conduits 12a-d in a second conduit row 12’. By arranging the conduits 11a-e, 12a-d to overlap each other the fluid conduit unit 10 forces the exhaust air to move around in order not to collide with the conduits 11a-e, 12a-e. This creates a desired turbulence in the flow of exhaust air. In the shown embodiment, there are six conduit rows 11’-16’ but this number may of course vary. A preferred number of rows is between 2 and 15, and even more preferred is a number of more than 2 rows.

In the shown exemplifying embodiment, there are between four and five conduits in each conduit row 11’-16’, but a preferred number of conduits in each row is between 12 and 150. An even more preferred number of conduits is between 38 and 52. The variation of number of conduits affects the ability to extract energy and capture pollutants, while maintaining a minimal pressure loss over the ventilation duct 2 and/or ventilation system 1 as the air passes by the conduits. Figs 3-5 also show that the conduits 11 a-e, 14a-e can be arranged in spaced apart sections 11”, 14”, where each section 11”, 14” contains a number of conduit rows 11’ , 14’ . A preferred distance D 1 between the last conduit row 13’ of a first section 11” and the first conduit row 14’ of a second section 14” is 150 mm.

In a preferred embodiment, the distance D2 between one conduit row 11’ and an adjacent conduit row 12’ is between 20 and 100 mm. The distance between each conduit row 11’-16’ does not have to be the same but can vary between each conduit row 11’-16’. The variation or the continuity of the distances D2 between the conduit rows 11’-16’ can be adapted to specific situations and environments. Further, it is preferred that a distance D3 between one conduit 13d and an adjacent conduit 13e in the same conduit row 13’ is between 4 and 20 mm. Also, the distance between different conduits 11a-e, 12a-d, 13a-e may vary.

As can be seen in Figs 4 and 5, the conduits 11a-e in a first conduit row 11’ are arranged to overlap the conduits 12a-d in a second conduit row 12’ such that the conduits are blocking the way and such that the particles of the flow F of exhaust air needs to move in a non-linear way to avoid collision with the conduits. This is especially efficient for particles Pa of a certain size that is too large to effectively travel between the conduits 11a-e, 12a-d, 13a-e, 14a-e. Since it is preferred for particles Pa to collide with and stick to a conduit 11a-e, 12a-d, 13 a-e, 14a-e in order to be filtered from the exhaust air this arrangement of conduits 11a-e, 12a-d, 13a-e, 14a-e is advantageous. The first and second row 11’, 12’ is in the shown embodiment adjacent rows but may in other embodiments be arranged differently. So, a first way I of removing unwanted particles Pa from the exhaust air by the fluid conduit unit 10 is to make the particles collide with and stick to a conduit 11a-e, 12a-d, 13a-e, 14a-e.

Particles Pb of a smaller size (the exact size being of course dependent on the diameter of the pipes and the distances between the pipes in each direction) may travel between the conduits 11a-e, 12a-d, 13a-e, 14a-e, both due to its smaller size, but also due to turbulent flow in the flow F. Such particles Pb may be filtered in the optional subsequent section of conduits 14” but to increase the likelihood of that happening the turbulence of the flow and a cooling of the particles (explained below) increases the chance of two or more particles Pb colliding, forming larger particles Pb’ which will easier collide with a conduit 12a-d, 13a-e, 14a-e. Thus, the second way II of removing unwanted particles from the exhaust air by the fluid conduit unit 10 is to make the particles Pb collide with each other thereby increasing the chances of the newly formed larger particle Pb’ to collide with and stick to a conduit 12a-d, 13a-e, 14a-e.

The fluid conduit unit 10 further comprises a cooling fluid 20 arranged to be transported through the conduits 11a-e, 12a-d, 13a-e, 14a-e. The cooling fluid is configured to cool the conduits 11a-e, 12a-d, 13a-e, 14a-e which in turn will cool the surrounding exhaust air. A common temperature of such a flow F of exhaust air is between 20°C and 32°C and a common temperature of the transported cooling fluid 20 is between -10°C and 20°C which means that a temperature drop of between 4°C and 18°C of the exhaust air can be achieved. Thus, the cooling fluid 20 and the arrangement of conduits 11a-e, 12a-d, 13a-e, 14a-e are configured to extract energy from the flow F of exhaust air by cooling the exhaust air, and also by extracting the energy released as parts of the water content in the exhaust air condensates, and to simultaneously, due to the cooling of the exhaust air, capture, as explained below, the unwanted particles Pa, Pb, Pb’, Pc on the conduits 11a-e, 12a-d, 13a-e, 14a-e. The cooling effect of the conduits 11a-e, 12a-d, 13a-e, 14a-e on the flow F of exhaust air is used for attracting particles Pc in the flow F. So, a third way III of removing particles Pc from the exhaust air by the fluid conduit unit 10 and making them collide with and stick to the conduits 11a-e, 12a-d, 13a-e, 14a-e is to cool each conduit 11a-e, 12a-d, 13a-e, 14a-e creating a temperature drop between the exhaust air and the conduit 11a-e, 12a-d, 13a-e, 14a-e, thereby cooling the particles Pc and creating an attracting force acting on the particles and pulling them in towards the conduits 11a-e, 12a-d, 13a-e, 14a-e. Also, due to the flow of air F past the conduits 11a-e, 12a-d, 13a-e, 14a-e a low pressure region LP is formed behind the conduit 11a-e, 12a-d, 13a-e, 14a-e, where the word behind is with respect to the direction of the flow F. A low pressure region LP is a region having a lower pressure than the surrounding areas or volumes, with a pressure that is (significantly) lower than that in the flow F. Also, due to the cooling effect, the likelihood of a particle being sucked into the LP region increases as the particles Pc will be attracted to the cool conduits. The three ways I, II, III of filtration are thus distinct but also cooperative and enforcing each other.

The cooling fluid 20 is arranged to run in a closed loop between the conduits 11a-e, 12a-d, 13a-e, 14a-e of the fluid conduit unit 10 and an optional thereto connected pump 40 by means of two ducts 21a, 21b. The pump 40 can be replaced by for example a heat exchanger, a heat pump or any other suitable device but for now we will refer to it as a pump 40. The first duct 21a connects the pump 40 with the fluid conduit unit 10 and feeds the cooling fluid 20 which has been cooled to the right temperature. A preferred temperature of the cooling fluid 20 when entering the fluid conduit unit 10 is between -10°C and 20°C. The second duct 21b connects the fluid conduit unit 10 with the pump 20 and transports the cooling fluid 20 back to the pump 20. The cooling fluid 20 has passed through the conduits 11a-e, 12a-d, 13a-e, 14a-e of the fluid conduit unit 10 and cooled the conduits 11a-e, 12a-d, 13a-e, 14a-e, which means that the cooling fluid 20 returning in the second duct 21b has a higher temperature than the cooling fluid 20 transported in the first duct 21a. The cooling fluid is, within the closed loop, again cooled to the right temperature by any suitable device before returning to the fluid conduit unit 10 and the conduits 11a-e, 12a-d, 13a-e, 14a-e through the first duct 21a. The difference in temperature between the cooling fluid 20 in the first duct 21a and the returning cooling fluid 20 in the second duct 21b can be between 4°C and 18°C. The extracted energy from the flowing exhaust air can be used to, for example, heat the building or room in which the ventilation system 1 operates.

The fluid conduit unit 10 further has a distributing conduit 24 arranged to receive the cooling fluid 20 from the pump 40 via the first duct 21a. The distributing conduit 24 is arranged to distribute the cooling fluid 20 to each one of the conduits 1 lae, 12a-d, 13a-e, 14a-e. Further, the fluid conduit unit 10 includes a collecting conduit 25 arranged to receive the cooling fluid 20 after it has been transported through the conduits 11a-e, 12a-d, 13a-e, 14a-e and return it to the pump 40 via the second duct 21b.

The cooling fluid 20 may also be configured to cool each conduit 11a-e, 12a-d, 13a-e, 14a-e such that a layer of ice 27 is created on the outer surface 28 of each conduit 11a-e, 12a-d, 13a-e, 14a-e. What happens then is that due to the temperature drop between the exhaust air and the cooled conduit 11a-e, 12a-d, 13a-e, 14a-e, condense water is obtained from the exhaust air. When the condense water comes in contact with the cooled conduit 11a-e, 12a-d, 13a-e, 14a-e it freezes forming a layer of ice 27 on the outer surface 28 of the conduit 11a-e, 12a-d, 13a-e, 14a-e. In order for this to happen, the cooling fluid 20 needs to be at least below 0°C when entering the conduits 11a-e, 12a-d, 13a-e, 14a-e. The layer of ice 27 is configured to even better attract and capture the unwanted particles Pa, Pb, Pb’, Pc of the flow F of exhaust air. The layer of ice 27 further protects the outer surface 28 of the conduits 11a-e, 12a-d, 13a-e, 14a-e by letting unwanted particles to stick to the ice instead of on the outer surface 28. When cleaning the fluid conduit unit 10, the flow of cooling fluid 20 is stopped and the temperature of the conduits 11a-e, 12a-d, 13a-e, 14a-e increases making the ice melt. The unwanted particles Pa, Pb, Pb’, Pc, which are captured by the ice, follows the melting ice to a container (explained below). This action is then often enough to clean the conduits 11ae, 12a-d, 13a-e, 14a-e of the fluid conduit unit 10.

The fluid conduit unit 10 can further include a chamber 29 for collecting condensation water forming in the fluid conduit unit 10 and on the conduits 3 la-e during use when the flow F of exhaust air is cooled by the cooled conduits 3 la-e or for collecting the melted ice layer 27 with the unwanted particles Pa, Pb, Pb’, Pc when cleaning the fluid conduit unit 10. The gathered water, especially the condensation water can be used during a cleaning process of the fluid conduit unit 10. In order to use the condensation water during cleaning the chamber 29 is connected to a heating device 42 arranged to heat the condensation water to a temperature equal to or above 65°C. The condensation water can then be sprinkled or sprayed on the conduits 11a-e, 12a-d, 13a-e, 14a-e in order to wash away the particles stuck on the outer surface of the conduits 11a-e, 12a-d, 13a-e, 14a-e and/or on the layer of ice 27 formed on the outer surface 28 of the conduits 11a-e, 12a-d, 13a-e, 14a-e. The temperature of 65°C is preferred since particles of grease emulates with the warm water at that temperature, thus letting the grease and water emulsion run off the outer surfaces 28 of the conduits 11a-e, 12a-d, 13a-e, 14a-e. Thus, making it easier to get rid of all the unwanted particles stuck on the conduits 11a-e, 12a-d, 13a-e, 14a-e. Also, the ice layer 27 will melt more quickly if sprinkled or sprayed with water of a temperature of 65°C or above.

A water distribution device, here called a sprinkler device 30 may further be included in either the fluid conduit unit 10 and/or in the ventilation system 1.

Advantageously, the sprinkler device 30 can gather heated water from chamber 29 for cleaning the fluid conduit unit 10. If the heated water from the chamber 29 is not enough for a cleaning process it can be connected and use water from any other suitable water source (not shown), for example the tap in the room where the ventilation system 1 is in use. The sprinkler device 30 consist of one or several sprinkler elements 32a-d which are arranged to direct the water to the desired areas, for example the number of conduits 11a-e, 12a-d, 13a-e, 14a-e. The sprinkler device 30 and optionally the above described heating device 42 may be connected to any regular water source as well if more water is needed during cleaning. It is however an advantage to be able to use condensation water first and then top up with water from another source in order to reuse as much of the created resources as possible.

The fluid conduit unit 10 as described above has many advantages. The fluid conduit unit 10 may both filter the exhaust air and extract energy to be further used. In known ventilation systems these two features are often separate, using two different units to accomplish both filtering and energy extracting. This has not been beneficial since, for example, the amount of necessary cleaning and maintenance work that needs to be done regularly is too extensive and not as efficient as with the fluid conduit unit 10 presented above. Often the unit enabling the energy extraction is not suited to handle unwanted particles such as grease, zoot and similar which, if they stick to the unit, also can affect the efficiency of it. Further, the filter units used today are not able to filter the flow of exhaust air such that the energy extracting unit is totally protected from the unwanted particles. By being able to remove the energy extracting unit, not only the efficiency of the ventilations system can be increased but also a less energy demanding fan unit can be used in the ventilation system. This is because the previously used energy extracting unit has created an obstacle in the course in which the exhaust air flows which in turn demands a stronger fan to create the desired flow.

Although the present invention has been described above with reference to specific embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims.

In the claims, the term “comprises/comprising” does not exclude the presence of other elements or steps. Additionally, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality. The terms “a”, “an”, “first”, “second” etc. do not preclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.

Claims

1. A fluid conduit unit for a ventilation system (1), arranged to receive a flow (F) of exhaust air, configured to extract energy from said flow (F) of exhaust air and capture unwanted particles (Pa, Pb, Pb’, Pc) in said exhaust air, said fluid conduit unit (10) comprises: a plurality of conduits (11a-e, 12a-d, 13a-e, 14a-e) between which said exhaust air is arranged to flow, wherein said conduits (11a-e, 12a-d, 13a-e, 14a-e) are arranged in at least two conduit rows (11', 12’, 13’, 14’, 15’, 16’), said rows being arranged orthogonal with respect to said flow of exhaust air (F), and wherein the conduits (11a-e) in a first conduit row (11') are arranged to overlap the conduits (12a-d) in a second conduit row (12’), and a cooling fluid (20) arranged to be transported through said conduits (11a-e, 12a-d, 13a-e, 14a-e) and configured to cool said conduits (11a-e, 12a-d, 13a-e, 14a-e), wherein said cooling fluid (20) and said arrangement of conduits (11a-e, 12a-d, 13a-e, 14a-e) are configured to extract energy from said flow (F) of exhaust air by cooling said exhaust air, and to simultaneously, due to the physical design of the conduits and due to the cooling of said exhaust air, capture said unwanted particles (Pa, Pb, Pb’, Pc) on said conduits (11a-e, 12a-d, 13a-e, 14a-e), by the plurality of conduits (11a-e, 12a-d, 13a-e, 14a-e) being cooled thereby generating an attracting force between unwanted particles (Pa, Pb, Pb’, Pc) increasing the likelihood of collision between unwanted particles (Pa, Pb, Pb’, Pc) leading to larger particles that are easier to filter; the plurality of conduits (11a-e, 12a-d, 13a-e, 14a-e) being of a round shape in order to generate a low pressure area behind each conduit causing unwanted particles (Pa, Pb, Pb’, Pc) to be attracted into the low pressure area increasing the likelihood of collision between unwanted particles (Pa, Pb, Pb’, Pc) leading to larger particles that are easier to filter, and increase the turbulence also increasing the likelihood of collision between unwanted particles (Pa, Pb, Pb’, Pc) leading to larger particles that are easier to filter; wherein said fluid conduit unit further comprises at least two spacedapart conduit sections (11”, 14”) of conduits (11a-e, 12a-d, 13a-e, 14a-e) each comprising at least two conduit rows (11’, 12’, 13 ’, 14’, 15 ’,16’), wherein the distance (Dl) between a first section (11”) and a second section (14”) is between 50 and 1000 mm and wherein the distance (D2) between one conduit row (11’) and an adjacent conduit row (12’) within a section is between 20 and 100 mm in order to allow the unwanted particles time to clump together leading to larger particles that are easier to filter, wherein the distance Dl is larger than the distance D2 and wherein the fluid conduit unit is characterized in that the cooling fluid is configured to cool each conduit (11a-e, 12a-d, 30 13a-e, 14a-e) such that a layer of ice (27) is created on the outer surface (28) of each conduit (11a-e, 12a-d, 30 13a-e, 14a-e), wherein the layer of ice (27) is configured to attract and capture the unwanted particles (Pa, Pb, Pb ’, Pc) and to further protect the outer surfaces (28) of the conduits (11a-e, 12a-d, 13a-e, 14a-e) by letting the unwanted particles (Pa, Pb, Pb ’, Pc) stick to the ice instead of to the outer surfaces (28).

2. The fluid conduit unit according to claim 1, further comprising a distributing conduit (24) arranged to distribute said cooling fluid (20) to each conduit (11a-e, 12a-d, 13a-e, 14a-e).

3. The fluid conduit unit according to any one of the preceding claims, further comprising a collecting conduit (25) arranged to collect the cooling fluid (20) after it has been transported through said conduits (11a-e, 12a-d, 13a-e, 14a-e).

4. The fluid conduit unit according to any one of the preceding claims, wherein each conduit row (11', 12’, 13’, 14’, 15’, 16’) comprises at least 12 conduits (11a-e, 12a-d, 13a-e, 14a-e) respectively.

5. The fluid conduit unit according to any one of the preceding claims, further comprises a chamber (29) for collecting condensation water forming on said conduits (1 la-e, 12a-d, 13a-e, 14a-e) when cooling said flow (F) of exhaust air by means of the cooling fluid (20) in said conduits (11a-e, 12a-d, 13a-e, 14a-e).

6. The fluid conduit unit according to claim 5, further comprising a heating device (42) configured to heat the condensation water to a temperature equal to or above 65 °C.

7. The fluid conduit unit according to any one of the preceding claims, further comprising a water distributing device (30) installed in said fluid conduit unit (10) and configured to laminar sprinkle water on at least said conduits (11a-e, 12a-d, 13a-e, 14ae)in order to remove particles (Pa, Pb, Pb’, Pc) captured on said conduit ( 11 a-e, 12a-d, 10 13a-e, 14a-e), wherein said water has a temperature equal to or above 65°C during sprinkle.

8. The fluid conduit unit according to claim 7 as dependent on claim 5, wherein said water distributing device (30) is connected to said chamber (29) containing collected condensation water.

9. A ventilation system comprising at least one duct (2) and at least one fluid conduit unit (10) according to any one of the preceding claims.

10. The ventilation system according to claim 9 further comprising a water distributing device (30) installed in said duct (2) and configured to laminar sprinkle water on at least said conduit (11a-e, 12a-d, 13a-e, 14a-e) of said fluid conduit unit (10) in order to remove particles (Pa, Pb, Pb’, Pc) captured on said conduits (11a-e, 12a-d, 13a-e, 14ae), wherein said water distributing device (30) is connected to a chamber (29) containing collected condensation water from said fluid conduit unit (10) and wherein said condensation water has a temperature equal to or above 65 °C during sprinkle.