Patent Application
20190086165
The present disclosure relates to a cooling apparatus which is adapted for the prevention of fouling, commonly referred to as anti-fouling. The disclosure specifically relates to anti-fouling of sea box coolers.
Bio-fouling or biological fouling is the accumulation of microorganisms, plants, algae, and/or animals on surfaces. The variety among bio-fouling organisms is highly diverse and extends far beyond attachment of barnacles and seaweeds. According to some estimates, over 1800 species comprising over 4000 organisms are responsible for bio-fouling. Bio-fouling is divided into microfouling which includes biofilm formation and bacterial adhesion, and macrofouling which is the attachment of larger organisms. Due to the distinct chemistry and biology that determine what prevents them from settling, organisms are also classified as hard or soft fouling types. Calcareous (hard) fouling organisms include barnacles, encrusting bryozoans, mollusks, polychaete and other tube worms, and zebra mussels. Examples of non-calcareous (soft) fouling organisms are seaweed, hydroids, algae and biofilm “slime”. Together, these organisms form a fouling community.
In several circumstances bio-fouling creates substantial problems. Machinery stops working, water inlets get clogged, and heat exchangers suffer from reduced performance. Hence the topic of anti-fouling, i.e. the process of removing or preventing bio-fouling from forming, is well known. In industrial processes, bio-dispersants can be used to control bio-fouling. In less controlled environments, organisms are killed or repelled with coatings using biocides, thermal treatments or pulses of energy. Nontoxic mechanical strategies that prevent organisms from attaching include choosing a material or coating with a slippery surface, or creation of nanoscale surface topologies similar to the skin of sharks and dolphins which only offer poor anchor points.
Antifouling arrangements for cooling units that cool the engine fluid of a ship via seawater are known in the art. DE102008029464 relates to a sea box cooler comprising an antifouling system by means of regularly repeatable overheating. Hot water is separately supplied to the heat exchanger tubes so as to minimize the fouling propagation on the tubes.
US2014196745 relates to a system that includes a UV light source and an optical medium coupled to receive UV light from the UV light source. The optical medium is configured to emit UV light proximate to a surface from which biofouling is to be removed once the biofouling has adhered to the protected surface. The system furthermore includes a cleaning mechanism proximate to the protected surface and operable to remove biological material from the protected surface. Additionally or alternatively, the system comprises a degradable layer disposed over and mechanically coupled to the protected surface, wherein selected portions of the degradable layer are removable in response to UV light.
Bio-fouling of box coolers causes severe problems. The main issue is a reduced capacity for heat transfer as the thick layers of bio-fouling are effective heat insulators. As a result, the ship engines have to run at a much lower speed, slowing down the ship itself, or even come to a complete halt, due to over-heating.
There are numerous organisms that contribute to bio-fouling. This includes very small organisms like bacteria and algae, but also very large ones such as crustaceans. The environment, temperature of the water, and purpose of the system all play a role here. The environment of a box cooler is ideally suited for bio-fouling: the fluid to be cooled heats up to a medium temperature and the constant flow of water brings in nutrients and new organisms.
Accordingly methods and apparatus are necessary for anti-fouling. Prior art systems, however, may be inefficient in their use, require regular maintenance and in most cases result in ion discharge to the sea water with possible hazardous effects.
Hence, it is an aspect of the invention to provide a cooling apparatus for the cooling of a ship's machinery with an alternative anti-fouling system according to the appended independent claims. The dependent claims define advantageous embodiments.
Herewith an approach is presented based on optical methods, in particular using ultra-violet light (UV). It appears that most micro-organisms are killed, rendered inactive or unable to reproduce with ‘sufficient’ UV light. This effect is mainly governed by the total dose of UV light. A typical dose to kill 90% of a certain micro-organism is 10 mW-hours per square meter.
The cooling apparatus for the cooling of a ship's machinery is suitable to be placed in a box that is defined by the hull of the ship and partition plates. Entry and exit openings are provided on the hull so that sea water can freely enter the box volume, flow over the cooling apparatus and exit via natural flow and/or under the influence of motion of the ship. The cooling apparatus comprises a bundle of tubes through which a fluid to be cooled can be conducted and at least one light source for generating an anti-fouling light, arranged by the tubes so as to emit anti-fouling light over the tubes' exterior surface.
In an embodiment of the cooling apparatus the anti-fouling light emitted by the light source is in the UV or blue wavelength range from about 220 nm to about 420 nm, preferably about 260 nm. Suitable anti-fouling levels are reached by UV or blue light from about 220 nm to about 420 nm, in particular at wavelengths shorter than about 300 nm, e.g. from about 240 nm to about 280 nm which corresponds to what is known as UV-C. Anti-fouling light intensity in the range of 5-10 mW/m2 (milliwatts per square meter) can be used. Obviously higher doses of antifouling light would also achieve the same if not better results.
The light source may be a lamp having a tubular structure in an embodiment of the cooling apparatus. For these light sources as they are rather big the light from a single source is generated over a large area. Accordingly it is possible to achieve the desired level of anti-fouling with a limited number of light sources which render the solution rather cost effective.
A very efficient source for generating UVC is the low-pressure mercury discharge lamp, where on average 35% of input watts is converted to UVC watts. The radiation is generated almost exclusively at 254 nm viz. at 85% of the maximum germicidal effect. Low pressure tubular flourescent ultraviolet (TUV) lamps are known which have an envelope of special glass that filters out ozone-forming radiation.
For various germicidal TUV lamps the electrical and mechanical properties are identical to their lighting equivalents for visible light. This allows them to be operated in the same way i.e. using an electronic or magnetic ballast/starter circuit. As with all low pressure lamps, there is a relationship between lamp operating temperature and output. For example, in low pressure lamps the resonance line at 254 nm is strongest at a certain mercury vapour pressure in the discharge tube. This pressure is determined by the operating temperature and optimises at a tube wall temperature of 40° C., corresponding with an ambient temperature of about 25° C. It should also be recognised that lamp output is affected by air currents (forced or natural) across the lamp, the so called chill factor. The reader should note that, for some lamps, increasing the air flow and/or decreasing the temperature can increase the germicidal output. This is met in high output (HO) lamps viz. lamps with higher wattage than normal for their linear dimension.
A second type of UV source is the medium pressure mercury lamp, here the higher pressure excites more energy levels producing more spectral lines and a continuum (recombined radiation). It should be noted that the quartz envelope transmits below 240 nm so ozone can be formed from air. Advantages of medium pressure sources are:
Further, Dielectric Barrier Discharge (DBD) lamps can be used. These lamps can provide very powerful UV light at various wavelengths and at high electrical-to-optical power efficiencies.
The germicidal doses needed can also easily be achieved with existing low cost, lower power UV LEDs. LEDs can generally be included in relatively smaller packages and consume less power than other types of light sources. LEDs can be manufactured to emit (UV) light of various desired wavelengths and their operating parameters, most notably the output power, can be controlled to a high degree.
In a particular embodiment of the cooling apparatus, the light sources are arranged substantially perpendicular to the orientation of the tubes. Accordingly it is provided that the anti-fouling light generated by the lamp to be scattered over various pipes. Hence the risk of a single pipe which is closer to the light source receiving and absorbing a big percentage of the light and the other pipes remaining in the shade of this first pipe is avoided.
In a further particular embodiment of the cooling apparatus, the light sources are arranged in parallel to each other. Thus similar distribution of light over the entire cooling apparatus is achieved and any missed spots on the pipes are avoided and thus the anti-fouling efficiency is increased.
In a further particular embodiment of the cooling apparatus the light source extends along the full width of the cooling apparatus. Thus the scattering of the emitted anti-fouling light to all the pipes are assured.
In an embodiment of the present invention the cooling apparatus comprises a bundle of tubes wherein the tubes are U-shaped and at least one light source is arranged at the inner side center of the semicircular tube portion.
In an embodiment of the present invention at least one light source is arranged to emit light towards the inner side of the tube bundle and at least one light source is arranged to emit light towards the outer side of the tube bundle. This configuration facilitates anti-fouling of both on the inner and the outer sides of the tubes.
In a further embodiment of the present invention the tube bundle comprises tube layers arranged in parallel along its width such that each tube layer comprises a plurality of hairpin type tubes having two straight tube portions and one semicircular portion so as to form a U-shaped tube and wherein the tubes are disposed with U-shaped tube portions concentrically arranged and straight tube portions arranged in parallel, so that the innermost U-shaped tube portions are of relatively small radius and the outermost U-shaped tube portions are of relatively large radius, with the remaining intermediate U-shaped tube portions are of progressively graduated radius of curvature disposed therebetween.
In a further aspect of the embodiment described above at least one light source is arranged at the inner side center of the innermost semicircular tube portion. Accordingly anti-fouling light is more efficiently scattered on the inner side of the rounding bottom of the U.
In an embodiment of the present invention the tube bundle conforms to a rectangular prism shape with a half cylinder shape connected to the rectangular prism portion at the bottom end and at least one of the light sources is arranged to lie on or in parallel to the axis line of the said cylinder.
In an embodiment of the present invention the tube bundle conforms with an elongated cylindrical shape with a hemispherical shape connected to the cylindrical portion at the bottom end and at least one of the light sources is arranged to lie on or in parallel to the axis line of the said cylinder.
In an embodiment of the present invention at least one light source is arranged in-between each tube. In an embodiment the cooling apparatus comprises a plurality of transverse lamellas on the tube bundle disposed in longitudinally spaced relation with each other and having the straight tube portions extending therethrough, thereby to maintain the tubes in fixed spaced relationship with each other throughout their lengths. Also, assuming that the lamellas are in contact with the tubes, the lamellas may contribute to heat transfer from the tubes so that a similar amount of heat transfer can be achieved with fewer tubes and thus the amount of shadow cast by tubes among other tubes is minimized thereby increasing the antifouling efficiency. The lamellas may be of any suitable shape and may be shaped like plates, for example. It is furthermore possible for the lamellas to be provided with two types of apertures, namely one type of aperture for allowing the tubes to pass through and another type of aperture for realizing that a flow of cooling medium such as water along the tubes is hindered only to a minimum extent by the presence of the lamellas. According to another option, the lamellas may be hollow so as to be capable of communicating with the tubes and transporting the fluid to be cooled in order to achieve an even larger contribution of the lamellas to the heat transfer. According to yet another option, each of the lamellas may be formed as an integral whole with a number of sections of tube portions extending through the lamellas. This option may be advantageous in view of the manufacturing process of the cooling apparatus, as according to this option, putting the lamellas in place with respect to the tubes requires nothing more than stacking the lamellas and interconnecting the sections of the tube portions.
In an embodiment the cooling apparatus comprises a plurality of longitudinal lamellas on the tube bundle extending in between two tube portions or between a tube portion and a light source. Accordingly similar to the embodiment above enhanced heat transfer and antifouling properties are achieved.
In further variation of the above embodiment the light source is positioned at the center, the tubes are positioned in a cylindrical configuration around the light source and the lamellas are extending from each straight tube portion towards the central light source. In this embodiment the cooling apparatus is actually a circular style heat exchanger and the light source is arranged in center of the heat exchanger such that it would lie in parallel with the straight tube portions.
In an embodiment of the cooling apparatus the light sources are arranged such that there exists at least one light source in between each tube. Accordingly the risk of the tubes casting a shade over each other is mitigated and a desired level of anti-fouling is achieved.
In an embodiment of the cooling apparatus the tubes and/or the lamellas are at least partially coated with a light reflective coating. Advantageously, the light reflective coating is adapted to cause the antifouling light to reflect in a diffuse way so that light is distributed more effectively over the tubes.
In an embodiment of the cooling apparatus the light source is placed in a sleeve to protect the light source from outside effects.
In an embodiment of the cooling apparatus the cooling apparatus comprises a tube plate on which the tubes are mounted, and connected to the tube plate a fluid header comprising one inlet stub and one outlet stub for the entry and the exit of the fluid to and from the tubes respectively. In a version of this embodiment one end of the sleeve is attached to the fluid header. Accordingly when installed in a final usage location the light source will be accessible from the outside as well as the inlet stub and the outlet stub, without a need for demounting the cooling apparatus from the installed position.
In an embodiment of the cooling apparatus the cooling apparatus is arranged for avoiding shadows over substantially the entire submerged portion of the exterior of the tube, so that this portion is protected from fouling.
In a version of the above-mentioned embodiment the shadows are avoided by positioning the light source with respect to the tubes. The shadows may be avoided by positioning the light source substantially perpendicular to the orientation of the tubes and/or when the tubes are U-shaped by the light source being arranged at the inner side center of the rounding bottom of the tubes. Alternatively shadows may also be avoided by decreasing damping of the light, for example by increasing reflection of the light.
The invention furthermore relates to a cooling apparatus as mentioned in the foregoing, in a situation prior to installation of the at least one light source, i.e. a cooling apparatus comprising a bundle of tubes for containing and transporting fluid in their interior, the exterior of the tubes being in operation at least partially submerged in water so as to cool the tube to thereby also cool the fluid, a tube plate on which the tubes are mounted and to which the tubes are connected, a fluid header comprising an inlet stub and an outlet stub for the entry and the exit of the fluid to and from the tubes respectively, the apparatus being adapted to receive at least one light source for producing light that hinders fouling by casting anti-fouling light over the tubes' exterior, preferably the adaptation comprising a sleeve for accommodating the light source, the sleeve being attached to the fluid header so as to allow the light source to be arranged therein to be accessible from the outside.
The invention also provides a ship comprising a cooling apparatus as described above. In such an embodiment the inner surfaces of the box in which the cooling apparatus is placed may be at least partially coated with a light reflective coating. Similarly to the embodiment above as a result of this particular embodiment the anti-fouling light can be made to reflect in a diffuse way so that light is distributed more effectively over the tubes. Furthermore in such an embodiment the light source may be associated with an inner surface of the box in any suitable manner, particularly be part of or connected to or attached to the inner surface of the box.
The term “substantially” herein, such as in “substantially parallel” or in “substantially perpendicular”, will be understood by the person skilled in the art. The term “substantially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term “substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” includes also embodiments wherein the term “comprises” means “consists of”. The term “comprising” may in an embodiment refer to “consisting of” but may in another embodiment also refer to “containing at least the defined species and optionally one or more other species”.
It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.
It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
The invention further applies to a device comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.
The various aspects discussed in this patent can be combined in order to provide additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:
The drawings are not necessarily on scale.
While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the disclosure is not limited to the disclosed embodiments. It is further noted that the drawings are schematic, not necessarily to scale and that details that are not required for understanding the present invention may have been omitted. The terms “inner”, “outer”, “along”, “longitudinal”, “bottom” and the like relate to the embodiments as oriented in the drawings, unless otherwise specified. Further, elements that are at least substantially identical or that perform an at least substantially identical function are denoted by the same numeral.
As shown in
In an embodiment the cooling apparatus comprises a tube bundle comprising tube layers arranged in parallel along its width. Each tube layer comprises a plurality of hairpin type tubes 8 comprising two straight tube portions 18, 28 and one semicircular tube portion 38. The tubes 8 are disposed with their semicircular portions 38 concentrically arranged and their straight portions 18, 28 arranged in parallel, so that the innermost semicircular tube portions 38 are of relatively small radius and the outermost semicircular tube portions 38 are of relatively large radius, with the remaining intermediate semicircular tube portions 38 are of progressively graduated radius of curvature disposed therebetween.
In one variation of the above embodiment the tube bundle conforms with a rectangular prism shape with a half cylinder shape connected to the rectangular prism portion at the bottom end, as shown in
In an embodiment the cooling apparatus 1 is further provided with at least one lamella 16 that is at least partly in contact with the tubes 8 so as to increase the heat transfer. In appropriate cases, especially cases in which a plurality of tubes 8 are present in a tube layer, it is preferred for the lamella 16 to be positioned so as to direct the light from the light source 9 towards the sides of the tube portions 18, 28, 38, 118, 228, 338 which otherwise remain in the shadow.
In a version of the above embodiment as shown in
In another variation of the above embodiment the tube bundle conforms with an elongated cylindrical shape with a hemispherical shape connected to the cylindrical portion 38 at the bottom end. Accordingly more tubes 8 are provided in the central layers and the layers above and below the central layers have a gradually decreasing number of tubes 8, as shown in
In an embodiment the tube bundle is provided with a plurality of transverse plate-shaped lamellas 16 disposed in longitudinally spaced relation with each other and having the straight tube portions 18, 28, 118, 228 extending therethrough as shown in
In an embodiment the cooling apparatus 1 as shown in
In comparison with the transverse lamellas 16 as shown in
In the configuration of the cooling apparatus 1 as shown in
The assembly of the light source 9 and the protective sleeve 14 extends through the fluid header 11. In the shown example the protective sleeve 14 has a circular periphery. A portion of the protective sleeve 14 as present in the fluid header 11 may be incorporated in an internal construction 111 of the fluid header 11 which serves for separating the relatively hot fluid to be supplied to the tubes 8 from the relatively cool fluid discharged from the tubes 8. In particular, such a construction 111 may have a cylinder-shaped portion 112 for constituting the portion of the protective sleeve 14, as can be seen in
It is noted that the lamellas 16 may have apertures for allowing the tubes 8 to pass therethrough, as mentioned in the foregoing, but as an alternative, it is possible for the lamellas 16 to be formed as an integral whole with sections of the straight tube portions 18, 28 extending through the lamellas 16, which whole will hereinafter be referred to as lamella element. In that case, during assembly of the cooling apparatus 1, the tubes 8 are realized by connecting a number of lamella elements to a portion of the tubes 8 extending down from the fluid header 11, wherein a first lamella element is attached to the portion of the tubes 8 as mentioned, a second lamella element is attached to the first lamella element, a third lamella element is attached to the second lamella element, etc. A U-shaped portion 38 of the tubes 8 is attached to the last lamella element of the thus obtained stack of lamella elements in order to complete the tubes 8. Hence, when lamella elements as mentioned are applied, a segmented appearance of the tubes 8 is obtained. The application of the lamella elements may contribute to facilitation of the manufacturing process of the cooling apparatus 1.
In a preferred version of this embodiment the light source 9 is positioned at the center, the tubes 8 are positioned in a cylindrical configuration around the light source 9 and the lamellas 16 are extending from each tube portion 18, 28, 118, 228 towards the central light source 9 as shown in
Elements and aspects discussed for or in relation with a particular embodiment may be suitably combined with elements and aspects of other embodiments, unless explicitly stated otherwise. The invention has been described with reference to the preferred embodiments. Modifications and alterations may occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. As fouling may also happen in rivers or lakes or any other area where the cooling apparatus is in contact with water, the invention is generally applicable to cooling by means of water.
| Number | Date | Country | Kind |
|---|---|---|---|
| 14197744.7 | Dec 2014 | EP | regional |
| 15177631.7 | Jul 2015 | EP | regional |
This application is a Divisional of application Ser. No. 15/534,770, filed on Jun. 9, 2017, which is the U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2015/078612, filed on Dec. 4, 2015, which claims the benefit of European Patent Application No. 14197744.7, filed on Dec. 12, 2014 and European Patent Application No. 15177631.7, filed on Jul. 21, 2015. These applications are hereby incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15534770 | Jun 2017 | US |
| Child | 16196725 | US |
