A live fish tank re-circulation arrangement with high-pressure and low-pressure chambers at opposite ends

Abstract

A live fish tank (1) arrangement with an integrated dedicated water re-circulation arrangement, comprising a fish chamber (8), a low-pressure chamber (9) and a high-pressure chamber (10). The low-pressure chamber is arranged at a first end of the tank and is separated from the fish chamber by a first screen (11). The high-pressure chamber is arranged at a second opposite end of the tank and is separated from the fish chamber by a second screen (12). The low-pressure chamber and the high-pressure chamber are fluidly coupled through at least one channel (13) or duct extending along the tank. At least one circulation pump (18, 19) is coupled to the channel or duct to circulate water from the low-pressure chamber to the high-pressure chamber.

Description

A LIVE FISH TANK RE-CIRCULATION ARRANGEMENT WITH HIGH-PRESSURE AND LOW- PRESSURE CHAMBERS AT OPPOSITE ENDSTechnical Field

[0001] The present invention relates to a live fish tank arrangement with integrated water circulation.

[0002] When fish is to be kept in a tank for any significant period it is necessary to circulate water though the tank. The flow of the water ensures a good environment for fish, in particular to supply the fish with oxygen rich water, and it provides the opportunity to treat the water, such as supplying extra oxygen to the water, removing CO2 and filtering out impurities from the water. It is therefore vital to the fish health to ensure a sufficient flow through the fish tank.Background Art

[0003] Conventionally, the equipment used to provide circulation comprises pipes and pumps that is also used for transferring the fish into and out of the tank, and also lifting the water to a higher level for removal of CO2. The re-circulation system also includes other types of water treatment, such as filtering. This water treatment causes pressure losses in the re-circulation that have to be overcome by the pumps. Moreover, when the same pumps are used for transfer of fish and a huge amount of water, this requires high-capacity pumps, which have a lifting height of about 15m. Typically, the pumps will have an effect of around 60 - 230 kW. When using such a pump for pure re-circulation, it will have to be run at a much lower lifting height than when transferring fish and water. This means that the pump has to operate in a range where it is not very efficient. Consequently, the energy consumption will be substantially higher than what actually is needed to provide the necessary recirculation.

[0004] There exist prior art solutions that uses a pump integrated with the tank. One such solution is described in CN113229185A. Here a circular tank is provided with a centrally arranged sump that is separated from the rest of the tank by a water permeable screen. A circulation pump is arranged within the sump, and pumps water from the sump to a plurality of nozzles that are arranged in a circle along the bottom of the tank.

[0005] This solution may work well for a circular tank, but it is not very convenient to use in a non-circular tank, such as a rectangular or square tank.

[0006] US4211183A describes another solution for a circular fish tank. It has a central part that is separated from the peripheral part by a mesh. An impeller transports water from the central part via a pipe and over a horizontal plate. From this plate the water runs down and into the tank.

[0007] The central part takes up a large portion of the tank and leaves a very reduced space to the fish. Moreover, the pipe and plate extend to above the water level and will hinder access to the tank from above. It is not a convenient solution for a four-sided tank.

[0008] DE202006006832U1 describes a fish accommodation arrangement with water circulation. It has several chambers, including a fish chamber. Water is flowing from the fish chamber to a sediment chamber, which includes a pump compartment. From the pump compartment the water is pumped via a water distribution unit with gas treatment and back again to the fish chamber. A bio reactor is also included in the arrangement.

[0009] The different units of this arrangement are substantially within a single outer box shape. However, the different units seem to take up a large space, which cannot be used to accommodate fish. Moreover, the water is at one point elevated to above the fish chamber. This increases the building height of the arrangement.

[0010] KR100998799B1 relates to an aquarium for decorative purposes. The aquarium is split into two parts, one main tank and one part which is denoted as a reef. The fish may swim freely between the main tank and the reef. A circulation pump is arranged to circulate the water between the main tank and the reef.

[0011] KR101555973B1 describes a circulation arrangement that is placed outside of the fish tank. It comprises a lower low-pressure chamber and an upper high- pressure chamber. A pump pumps the water from the lower to the upper chamber. As the arrangement is a separate unit from the fish tank, it requires substantial extra space.

[0012] Other examples of prior art are shown in WO2018151605, WO8803363, NO344668 and US2015342161 . None of these fulfil the objectives of the present invention.Summary of invention

[0013] The present invention has the following objectives:• Provide the possibility to use a pump having pump characteristics, such as an optimal effect range, suitable for circulation at low pressure and high flow.• Limit the required space of the fish tank and the circulation arrangement, so that the required space is as little as possible beyond the space required for the fish tank as such. The invention reduces the amount of pipes and valves external of the fish tank, and it provides the possibility to place pumps within the fish hold instead of in an external pump room. This is in particular an advantage for fish tanks installed in a floating vessel, such as a live fish carrier.• Provide easy access for cleaning and maintenance.

[0014] In a conventional system there is a substantial pressure loss when water has to be pumped through lengths of pipe, a plurality of valves, filters, UV treatment units etc. In the present invention, only the screens will contribute to a small pressure loss in the circulation system, but the pressure loss in other parts of the system is negligible.

[0015] This is an important factor that makes it possible to use low-effect pumps in the present invention. A conventional multi-function pump has a low efficiency when used for recirculation. It is difficult to get below an effect of 60 kW when the pump is set to recirculate a water amount of, e.g., 3000 m3 / hour. According to the invention a low-effect pump is used, which, e.g., can circulate the same amount of water at an effect of around 6 kW.

[0016] A key feature of the present invention is that the re-circulation arrangement is dedicated to the task of re-circulating. The water will recirculate a short distance and with as little resistance as possible. Any branching off of water for treatment will be done by a different system than the system of the present invention. Thereby the re-circulation pumps of the present invention can be run continuously independent of the need for water treatment.

[0017] Other objectives achieved by the invention will be clear from the description below.

[0018] The above objectives are met by the arrangement according to claim 1 or the method according to claim 10.Detailed description of the invention

[0019] Figure 1 a shows a first embodiment of a fish tank with circulation arrangement according to the invention in an isometric view,Figure 1 b shows the fish tank of figure 1 a in planar view,Figure 1 c shows the fish tank of figure 1 a in front elevation view,Figure 2a shows a second embodiment of a fish tank with circulation arrangement according to the invention in an isometric view, andFigure 2b shows the fish tank of figure 2a in front elevation view.

[0020] Referring to figure 1 a, a fish tank 1 is shown in isometric view. The fish tank is generally box shaped, such as having a cuboid shape. The shape may also deviate somewhat from a cuboid. For example, the tank may be narrower at one end, and it may be narrower or wider at the upper end than the bottom end. One or more of the side walls may also be slightly curved. The deviation from a cuboid may be due to the available space on board the vessel. The tank is in the following referred to as “substantially cuboid”.

[0021] A substantially cuboid shape is advantageous as it facilitates the use of a slidable bulkhead inside the tank to crowd fish. If the fish chamber of the tank has the same cross section along its length, the slidable bulkhead may have the same fixed cross section. If the cross section of the fish chamber varies somewhat, the bulkhead may be designed with telescopic parts to accommodate to the varying cross section of the chamber. The closer the cross section is to a rectangle, the easier it will be to use a sliding bulkhead therein.

[0022] If it is not necessary to implement a sliding bulkhead inside the tank, the tank may very well have a different shape, depending on the available space.

[0023] Figures 1 b and 1 c show the tank seen from above and from one end, respectively.

[0024] The tank comprises an outer shell with a four-sided wall, consisting of four sides 2, 3, 4, 5, and a bottom 6. At the top, the tank has a lid 7 that may be opened to provide access to the tank 1 . The tank 1 has a length that is longer than its width but may also be square in footprint.

[0025] The interior of the tank is divided into three chambers. In the middle is the largest chamber 8, which serves as a fish chamber. At a first end is a low-pressure chamber 9, and at a second opposite end is a high-pressure chamber 10. The chambers 9 and 10 are separated from the fish chamber 8 by a respective water permeable barrier, such as a strainer or screen 11 , 12, which will hereinafter be referred to as screens. The low-pressure chamber and the high-pressure chamber extend substantially across the whole height and width of the tank. The screens have two functions: Keeping the fish away from the water pumps and providing an even distribution of the water flow.

[0026] The size of the low- and high-pressure chambers 9, 10 is exaggerated in the drawings. They should take as little space from the fish tank 8 as possible.

[0027] A channel 13 extend from the low-pressure chamber 9 to the high-pressure chamber 10. It may extend on the outside of the tank 1 , as shown in the figures, but it may also be arranged as a channel on the inside of the tank. The channel may be located close to the bottom of the tank, as shown, but may also be arranged at a higher level.

[0028] Pipes 14, 15; 16, 17 extend from the inside of each chamber 9, 10 to the channel 13. One of the pipes 14, 16 extends further into the chamber 9, 10 than the other pipe 15, 16. The number of pipes for each chamber depends on the width of the tank and chamber. For smaller tanks it may be sufficient to have only one pipe, or possibly only an outlet and inlet opening, respectively, to the chamber. For wider tanks more than two pipes of different lengths for each chamber may be an advantage. The differing length of pipe ensures that the whole volume of water of the chambers 9, 10 is exchanged continuously.

[0029] A small circulation pump 18, 19 is arranged at the outer end of each of the pipes 14, 15 in the low-pressure chamber 9. The pumps 18, 19 may be arranged elsewhere in the flow, such as in the channel 13, but it has been found that a good circulation is achieved by arranging the pumps as shown.

[0030] Both the end chambers 9, 10 and the fish chamber 8 are airtight. During operation of the circulation arrangement alle three chambers will normally have a higher than atmospheric pressure. The low-pressure chamber 9 will have a lower pressure than the fish chamber 8 and the high-pressure chamber 10 will have a higher pressure than the fish chamber 8.

[0031] The screens 11 , 12 have openings having a total area small enough to provide a pressure drop across the screen when the water is circulated. Water is continuously pumped out of the low-pressure chamber 9 through the channel 13, as indicated by the arrow 20, and into the high-pressure chamber 10. Due to the pressure difference created between each of the low- and high-pressure chamber 9, 10 and the fish chamber 8, water will flow through the fish chamber 8 in the direction of the arrows 21 . The flow will be an even flow across the height and width of the fish chamber 8, as the flow is driven by pressure differences across the screens 11 , 12. To prevent local effects around the outer ends of the pipes 14, 15, 16, 17 from influencing the flow along the fish chamber 8, the screens 11 , 12 may have smaller or fewer openings in the vicinity of the pipe ends. The pressure difference between the high-pressure and the low-pressure chambers is conveniently less than a pressure corresponding to a pressure exerted by a water column of 1 meter (i.e. 10 kPa), preferably less than 0,5 meter (i.e 5 kPa).

[0032] All the water will flow through the channel 13 from the low-pressure to the high-pressure chamber. If water treatment external of the fish tank is needed, such as CO2 removal, filtering, heating, cooling etc., this will be handled by a different system than the present invention.

[0033] Despite the above, the water may be oxygenated by supplying oxygen into the high-pressure chamber 9 via nozzles 22, which is supplied from an oxygen source (not shown) via a header pipe 23. This is possible since such addition of oxygen will not add any resistance to the flow of water. The oxygen may be supplied as pure oxygen, as oxygen enriched air or as air.

[0034] Alternatively, the oxygen may be supplied into the channel 13 or into the high- pressure chamber 10. It is an advantage to supply the oxygen into the high-pressure side of the recirculation arrangement to avoid compression of bubbles when the oxygen is subjected to an increased pressure, which would be the case if the oxygen had been supplied at the low-pressure side.

[0035] Figures 2a and 2b shows an alternative embodiment of the fish tank circulation arrangement. The tank 1 as such is similar to the tank of the embodiment in figures 1 a-c, and the similar features will not be explained further. The difference is that instead of having a channel 13 at the side of the tank 1 , the present embodiment has ducts 13a and 13b that extend above the tank 1 , the ducts are at one end coupled to pipes 14a, 15a that extend into the low-pressure chamber 9, and at the opposite end coupled to the high-pressure chamber 10, optionally through not shown pipes. Low effect pumps 18a, 19a, such as propeller pumps, are coupled to the lower ends of the pipes 14a, 15a to pump water up through the pipes 14a, 15a, along the ducts 13a, 13b to the high-pressure chamber 10.

[0036] Figure 2b shows the tank 1 arranged in a hold 25 in a sea vessel. The vessel has a deck 24 above the hold.

[0037] It is also conceivable to arrange a channel or ducts along the underside of the tank 1 .

Claims

Claims1 . A live fish tank (1 ) arrangement with an integrated dedicated water re-circulation arrangement, comprising a fish chamber (8), a low-pressure chamber (9) and a high-pressure chamber (10), said low-pressure chamber (9) being arranged at a first end of said tank (1 ) and being separated from said fish chamber (8) by a first screen (11 ), said high-pressure chamber (10) being arranged at a second opposite end of said tank (1 ) and being separated from said fish chamber (8) by a second screen (12); said low-pressure chamber (9) and said high-pressure chamber (10) being fluidly coupled through at least one channel (13) or duct extending along said tank (1 ); at least one circulation pump (18, 19) being coupled to said channel (13) or duct to circulate water from said low-pressure chamber (9) to said high-pressure chamber (10).

2. The live fish tank arrangement of claim 1 , wherein said at least one channel (13) or duct is coupled to a pipe (14, 15) that extends into the interior of said low-pressure chamber (9).

3. The live fish tank arrangement of claim 2, wherein said circulation pump (18, 19) is arranged at an inlet end of said pipe (14, 14).

4. The live fish tank arrangement of claim 2, wherein said circulation pump (18, 19) is arranged within said channel (13) or duct.

5. The live fish tank arrangement of any of the preceding claims, wherein an oxygen source (23) is coupled to said high-pressure chamber (10).

6. The live fish tank arrangement of claim 6, wherein at least one oxygen nozzle (22) is arranged within the high-pressure chamber (10) and being coupled to said oxygen source (23).

7. The live fish tank arrangement of any of the preceding claims, wherein said channel (13) or duct extends along one side of said tank (1 ).

8. The live fish tank arrangement of any of the preceding claims 1 - 7, wherein said duct or channel (13) extends above the tank (1 ).

9. The live fish tank arrangement of any of the preceding claims, wherein said chambers (8, 9, 10) are arranged within an outer substantially cuboid shell of said tank (1 ).

10. A method of providing a dedicated water re-circulation in a live fish tank (1 ), comprising: a. providing a low-pressure chamber (9) at a first end of said tank (1 ), b. providing a high-pressure chamber (10) at an opposite second end of said tank (10), c. providing a fish chamber (8) between said low-pressure chamber (9) and said high-pressure chamber (10), said fish chamber (8) being separated from said low-pressure chamber (9) and said high-pressure chamber (10) by a respective screen (11 , 12), d. maintaining a pressure difference between said low-pressure chamber (9) and said high pressure chamber (10), and e. letting water flow from said high-pressure chamber (10) to said low- pressure chamber (9) through said screens (11 , 12) and said fish chamber (8).11 . The method of claim 10, wherein said pressure difference is less than a pressure corresponding to a pressure exerted by a water column of 1 meter, preferably less than 0,5 meter.

12. The method of claim 10 or 11 , wherein oxygen is supplied into said high-pressure chamber.

13. The method of claim 10, 11 or 12, wherein said pressure difference between said low-pressure chamber (9) and said high-pressure chamber (10) is maintained by at least one pump (18, 19) arranged between said chambers (9, 10).

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