WO2014117860A1 - Tuyau collecteur géothermique - Google Patents

Tuyau collecteur géothermique Download PDF

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Publication number
WO2014117860A1
WO2014117860A1 PCT/EP2013/052045 EP2013052045W WO2014117860A1 WO 2014117860 A1 WO2014117860 A1 WO 2014117860A1 EP 2013052045 W EP2013052045 W EP 2013052045W WO 2014117860 A1 WO2014117860 A1 WO 2014117860A1
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WO
WIPO (PCT)
Prior art keywords
pipe collector
talc
polymer composition
geothermal
pipe
Prior art date
Application number
PCT/EP2013/052045
Other languages
English (en)
Inventor
Adib KALANTAR MEHRJERDI
Mikael Skrifvars
Original Assignee
Muovitech Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Muovitech Ab filed Critical Muovitech Ab
Priority to PCT/EP2013/052045 priority Critical patent/WO2014117860A1/fr
Priority to EP13704897.1A priority patent/EP2951511A1/fr
Priority to CA2937973A priority patent/CA2937973A1/fr
Priority to US14/762,020 priority patent/US20150323264A1/en
Publication of WO2014117860A1 publication Critical patent/WO2014117860A1/fr
Priority to US15/481,000 priority patent/US20170227257A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24T—GEOTHERMAL COLLECTORS; GEOTHERMAL SYSTEMS
    • F24T10/00—Geothermal collectors
    • F24T10/10—Geothermal collectors with circulation of working fluids through underground channels, the working fluids not coming into direct contact with the ground
    • F24T10/13—Geothermal collectors with circulation of working fluids through underground channels, the working fluids not coming into direct contact with the ground using tube assemblies suitable for insertion into boreholes in the ground, e.g. geothermal probes
    • F24T10/15—Geothermal collectors with circulation of working fluids through underground channels, the working fluids not coming into direct contact with the ground using tube assemblies suitable for insertion into boreholes in the ground, e.g. geothermal probes using bent tubes; using tubes assembled with connectors or with return headers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24T—GEOTHERMAL COLLECTORS; GEOTHERMAL SYSTEMS
    • F24T10/00—Geothermal collectors
    • F24T10/10—Geothermal collectors with circulation of working fluids through underground channels, the working fluids not coming into direct contact with the ground
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24T—GEOTHERMAL COLLECTORS; GEOTHERMAL SYSTEMS
    • F24T10/00—Geothermal collectors
    • F24T10/30—Geothermal collectors using underground reservoirs for accumulating working fluids or intermediate fluids
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F1/00—Tubular elements; Assemblies of tubular elements
    • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
    • F28F1/40—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only inside the tubular element
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/10—Geothermal energy

Definitions

  • the present application relates to pipe collectors for geothernnal heat exchange and polymer compositions for improving the properties of geothermal pipe collectors.
  • Geothermal energy is energy stored as heat in the ground. This
  • geothermal energy may originate from the hot core of the earth or may be heat generated by the earth surface being exposed to infrared radiation from the sun.
  • Most geothermal installations today use the second category of geothermal energy, i.e. solar energy stored as heat in e.g. water, ground or bedrock.
  • the heat is extracted from the ground (e.g. water or bedrock) using a geothermal pipe collector.
  • the fluid known as heat transfer medium or heat transfer liquid is circulated such that fluid heated by the geothermal energy is extracted in one end of the geothermal pipe collector, the cooled fluid is then returned in the other end of the
  • geothermal pipe collector such that a closed system is created.
  • geothermal energy systems are ground surface heat systems, sea heat systems and borehole heat systems.
  • ground surface heat systems a several hundred meter long geothermal pipe collector is buried in the ground at a frostproof depth.
  • sea heat system a similar pipe collector is placed in the sea water and/or on/in the sea bed.
  • a geothermal pipe collector having two fluid conduits is placed in the bore hole, such that the fluid can be conveyed into the bore hole in a first fluid conduit and conveyed from the bore hole in a second fluid conduit.
  • the geothermal pipe collectors for use in borehole heat systems could be so called U-pipe collectors.
  • a U-pipe collector comprises a separate, closed pipe which is bent such that it forms a U-shape, such that the direction of the fluid conveyed is altered in the bottom of the borehole.
  • An alternative geothermal pipe collector is the so called double U-pipe collector, which comprises two pipes for conveyance of the heat transfer liquid down into the drilled hole which branches off into two pipes that transports the fluid back from the drilled hole and further to a heat pump.
  • coaxial collector Yet another type of collector used in borehole heat systems is the so called coaxial collector.
  • an inner pipe is arranged in an outer pipe.
  • the pipes are welded together, such that a single unit is formed, and subsequently installed in a drilled hole.
  • the fluid is conveyed down into the borehole in the outer pipe and thus absorbs heat from the borehole.
  • the fluid When the fluid reaches the bottom of the borehole it is conveyed up again through the inner pipe. It is desirable to avoid long surface area contact between heated fluid and the cooled fluid, which is why the outer pipe is provided with a larger cross-sectional area, such that a faster flow is achieved in the inner pipe.
  • PE Polyethylene
  • a thermal insulator with low thermal conductivity which is a drawback when the material is used in heat exchange applications.
  • the wall thickness of the pipe collector may be decreased.
  • decreasing the wall thickness affects the mechanical properties of the pipe, which may be a disadvantage for fulfilling the requirements of pipe standards and for the handling of the pipe.
  • EP 2195586 to M. Ojala et al. it is described how the thermal conductivity of a geothermal pipe collector can be increased by creating a turbulent flow of the fluid inside the pipe collector.
  • creating a turbulent flow involves the creation of a groove or recess in the wall of the geothermal pipe collector, which decreases the thickness of the wall of the geothermal pipe collector, again affecting some of the mechanical properties of the pipe.
  • 9 To be able to reduce the length of the pipe used in ground surface heat systems, and reduce the depth of the borehole in borehole heat systems, it would be advantageous to have a design of a geothermal pipe collector with reduced thermal resistance and maintained mechanical properties.
  • a geothermal pipe collector is provided.
  • the geothermal pipe collector is provided.
  • a collector is made from a polymer composition comprising: more than 50wt% Polyethylene (PE), 0.1 wt% - 35wt% talc and 0.5wt% - 10wt% Carbon black (CB).
  • PE Polyethylene
  • CB Carbon black
  • the addition of CB protects the geothermal pipe collector against the natural environment but reduces some of the mechanical properties of the polymer composition.
  • talc increases the performance of a thermal conductivity thus increasing the heat exchanging capabilities of the geothermal pipe collector making it possible to have the same heat exchanging capabilities with a shorter pipe collector.
  • the addition of talc also increases the relevant mechanical properties of the pipe collector, which makes it possible to have thinner walls, which further decreases the thermal resistance of the pipe collector and thus increases the heat exchange.
  • the geothermal pipe collector is
  • talc made from a polymer composition comprising 0.1 wt% - 3wt% talc.
  • the geothermal pipe collector is
  • the geothermal pipe collector is
  • the geothermal pipe collector is made from a polymer composition comprising 8wt% - 15wt% talc. This embodiment has a higher density than water and is still flexible enough to easily be coiled.
  • the geothermal pipe collector is made from a polymer composition comprising 8wt% - 12wt% talc. In the interval 8wt% - 12wt% talc, the polymer composition have some
  • the geothermal pipe collector is
  • compositions made from a polymer composition comprising 0.5wt% - 5wt% CB or 1 .5wt% - 3wt% CB. Both compositions provide sufficient protection against the natural environment, but a polymer compositions comprising 3wt% - 5wt% CB have a higher thermal stability.
  • the talc added to the polymer composition may be talc in which the average aspect ratio is above 1 .2. Talc with a high aspect ratio further increases the thermal conductivity of the polymer composition.
  • the inner surface of the geothermal pipe collector comprises recesses or protrusions for increasing the turbulence of a medium flowing in the pipe collector and thus the heat exchange in the pipe collector.
  • the recesses or protrusions may extend helically on the inner surface of the pipe collector, in relation to the length axis of the pipe collector, such that a turbulent flow is created in the direction of the length axis of the pipe collector.
  • the helically extending recesses or protrusions alter direction at least at some portion along the length axis of the pipe collector, such that the direction of the turbulent flow is altered along the length axis of the pipe collector, which introduces further turbulence of the fluid.
  • the recesses or protrusions on the inner surface of the pipe collector may extend continuously on the inner surface of the pipe collector, such that the pipe collector can be manufactured by means of continuous extrusion.
  • FIG. 1 shows a geothermal U-pipe collector in a borehole
  • Fig. 2 is a table of polymer compositions on which experiments have been conducted
  • Fig. 3 is a graph showing the density of a polymer composition as a function of the filler contents
  • Fig. 4 is a table showing the tensile strength of different polymer compositions
  • Fig. 5 is graph showing tensile strength of polymer compositions as a function of the filler content in the compositions
  • Fig. 6a is a graph showing impact resistance as a function of filler content in polymer compositions, notched and edgewise
  • Fig. 6b is a graph showing impact resistance as a function of filler content in polymer compositions, un-notched and flatwise,
  • Fig. 7 is a graph showing elongation and impact resistance as a function of the filler content in the polymer composition
  • Fig. 8 is a graph of thermal conductivity and thermal diffusivity of polymer compositions as a function of the filler content in the polymer composition
  • Fig. 9 is a graph of the volumetric heat capacity and specific heat of polymer compositions as a function of the filler content in the polymer composition
  • Fig. 10a is a graph showing the thermal resistance of a pipe
  • Fig. 10b is a graph showing the thermal resistance of a pipe
  • Fig. 1 1 is a table showing the weight loss of different polymer
  • Fig. 12 is a graph showing the weight of a polymer composition as a function of temperatures to which the polymer composition is exposed
  • Fig. 13 is a graph of the particle size of a polymer composition by showing the percent of the volume which is made up of particles having a specific diameter
  • Fig. 14a shows an embodiment of a geothermal pipe collector in which the pipe collector comprise helically extending recesses
  • Fig. 14a shows an embodiment of a geothermal pipe collector, in which the pipe collector comprise helically extending recesses which alter direction at least at some portion along the length axis of the pipe collector.
  • FIG. 1 shows the principle for a conventional U-pipe collector.
  • a continuous, sealed Polyethylene (PE) pipe 1 is arranged in a drilled borehole 2.
  • the pipe 1 is preferably made as a single continuous pipe extruded in a plastic extruder.
  • the pipe 1 forms a U-shaped bend 3 in the end towards the bottom 4 of the borehole, such that the fluid conveyed into the borehole 2 is conveyed up again after reaching the bottom of the borehole 2.
  • This particular system is known as a "U-pipe collector" as the bend forms a U-shape.
  • Fig. 1 only shows the principle, the U-shape of the pipe collector may be a separate part to which a first and second portion 1 ', 1 " of the pipe is welded.
  • the upper part 5 of the collector system is usually terminated in a manhole at ground level 6, from where the collector pipes 1 , 1 ', 1 " are connected to a heat pump (not shown).
  • the pipe is fed into the borehole 2 manually or by means of a pipe feeder.
  • the pipe feeder typically comprises pulleys feeding the pipe, and the feeder thus bends the pipe while pressing it into the borehole. The feeding thus places substantial strain on the pipe and the pipe thus needs to be both flexible and capable of handling considerable strain.
  • the geothermal pipe collector is made from a polymer composition based on PE.
  • a polymer composition is to be understood as any compounded material comprising at least one polymer material in some quantity, and a filler is to be understood as a material in the polymer composition other than the main polymer (herein PE).
  • the fillers described herein are talc and CB, and talc is the filler in instances in the graphs where the filler is not specified.
  • Carbon black is added to the polymer composition.
  • CB is a form of amorphous carbon produced by incomplete combustion of petroleum products.
  • CB is an economic additive which effectively increases the UV resistance of PE even at low
  • CB can also be used to increase the thermal stability of PE, which is important when the pipe collectors are used in high temperature applications.
  • the drawback however, is that CB reduces some of the mechanical properties of PE, making the material hard and brittle.
  • Talc is a mineral composed of hydrated magnesium silicate
  • talc the softest known mineral, measured as 1 on the Mohs hardness scale.
  • the talc's unique characteristics such as softness, chemical inertness, slipping, oil and grease absorption, whiteness, availability, and its rather low price, makes it a promising material to be used as a filler.
  • talc is added to the polymer composition.
  • the talc filled polymer composition decreases the thermal resistance of the geothermal pipe collector by increasing the thermal conductivity of the material and enabling the reduction of the wall thickness of the geothermal pipe collector, thereby increasing the heat exchange.
  • the geothermal pipe collector is made from a PE based polymer composition comprising: 0.1wt% - 35wt% talc and 0.5wt% - 10wt% CB (and the remaining part PE).
  • the CB protects the geothermal pipe collector against the elements of nature, and to have a sufficient protection against UV - radiation, at least 0.5% should be included in the composition.
  • the addition of CB also improves the heat stability of the polymer composition. However, as previously mentioned, the CB negatively affects some of the mechanical properties of PE, in particular the impact resistance.
  • the added talc increases the thermal conductivity of the polymer composition as well as the modulus of elasticity and the tensile strength, and increases the density of the polymer composition. Apart from that, the addition of talc reduces equipment wear during processing, decreases shrinkage, and improves the product machinability. Also, the addition of talc reduces the specific heat capacity of the composition, which makes it possible to increase production speed.
  • Such additives may include Kaolin clay, silica and calcium carbonate, or dye for obtaining a pipe collector of a specific color.
  • the geothermal pipe collector is made from a polymer composition comprising 0.1wt% - 3wt% talc.
  • the conductivity of the polymer composition may be increased at small levels of talc, as the crystallinity of the polymer composition is increased.
  • the geothermal pipe collector is made from a polymer composition comprising 8wt% - 35wt% talc. Above 8wt% talc, the polymer composition has substantially the same impact resistance as PE without the addition of CB (denoted as PEn in the tables and diagrams herein). Above 8% of talc, the polymer composition will have a density of more than 1 (i.e. higher than water), which makes the geothermal pipe collector sink to the bottom of the borehole, which is a clear advantage as no active feeding of the pipe collector is needed. Also, the pipe collector having a density of above 1 could be used in sea heat applications without the need to anchor the pipe collector to the sea bed.
  • Adding more than 35wt% of talc in the polymer composition will create a polymer composition having an elasticity modulus too high for normal extruders, and even if the material could be extruded with high pressure, the finished pipe collector would be difficult to coil or feed into the borehole without the risk of breakage, which will make the material very hard to transport and handle. Also, the risk that the material is not properly compounded increases as the amount of talc is increased, creating a risk that large areas of poorly mixed polymer composition will be created, which increases the risk of breakage.
  • the polymer composition comprises 8wt% - 15wt% talc.
  • the polymer composition (with 0.5wt% - 3wt% CB) has density above 1 and substantially the same impact resistance as PE without CB.
  • the impact resistance of the polymer composition is reduced considerably above 15wt% talc, which makes the polymer composition less suitable for some geothermal pipe collector applications.
  • the polymer composition could comprise 8wt% - 12wt% talc, which is the interval (depending on the amount of CB in the composition) in which the impact strength is highest at the same time as the density is above 1 , making the geothermal pipe collector sink in the borehole or when placed in the sea.
  • the polymer composition comprises approximately 2,5wt% CB, the impact resistance, as measured by the Charpy impact test, is reduced by almost 30% (as can be seen in the graph of fig. 6).
  • PEn For regaining the impact strength of PE without the CB (PEn), between 8wt% - 12wt% of talc needs to be added to the
  • composition which, as stated above, also increases the density of the material such that the material will have a density higher than water.
  • the talc could have a high aspect ratio.
  • the plate-like shape of high aspect ratio talc adds to the enhancement of the impact strength and the thermo-physical characteristics
  • the particles are fractured or altered in shape, which decreases the aspect ratio of the talc particles in the polymer composition.
  • the polymer composition including high aspect talc means that the aspect ratio of the talc particles on average is above 1 .2.
  • the polymer composition including high aspect talc could mean that the aspect ratio of the talc particles on average is above 1 .5, and in yet another
  • the polymer composition including high aspect talc could mean that the aspect ratio of the talc particles on average is above 2.
  • talc has a plate-like shape with a high aspect ratio and the layers of talc can easily slip over each other during the processing, the polymer can easily fill the spaces between the particles this would happen if there is sufficient shear stress during the pipe processing or compounding.
  • Particulates can therefore be oriented in the flow direction parallel to the axis of the pipe surely particle orientation depends on the nature of the flow field, but it is quite clear from SEM images that particles are well dispersed and oriented with the injection moulding direction. This unique organization allows forming kind of heat channels as result heat can be transferred through, although the particulate did touch completely together to make the true heat channel.
  • the polymer composition could therefore, according to one embodiment, comprise 0.5wt% - 5wt% CB (up to 5wt% for increased thermal stability), and for the purpose of providing sufficient UV - protection comprise 1 .5wt% - 3wt% CB.
  • the amount of PE in the finalized composition varies.
  • the polymer composition preferably comprises more than 75wt% PE.
  • HDPE Polyethylene
  • MFI melt flow rate
  • Vicat softening temperature 1 18°C
  • density 952 kg/m314.
  • the HDPE contains 2.5 wt% of Carbon black (CB), which was fully precompounded by the supplier.
  • CB Carbon black
  • PEc HDPE with CB
  • PEn PE neat
  • the neat HDPE has an MFI of 0.4 g/10 min, a Vicat softening temperature of 122°C, and a density of 942 kg/m321 .
  • the PEn was used as a reference to investigate the effect of the CB added on the neat HDPE, and the PEc was used as a reference to study the effect of talc on the HDPE/CB/talc composites.
  • Fig. 2 is a table showing the different compositions and indicating the amount of CB and talc in the respective compositions.
  • compositions shown in the table were prepared by compounding the PEc and the talc at different ratios, in a twin-screw extruder with two side- feeders (ZSK 25 WLE; Cooperion Werner & Pfleiderer, Germany).
  • the temperature profile used was 180-220°C from feed to die (above the melting temperature of HDPE and well below its decomposition
  • the PEc was fed into the main hopper with a screw speed of 230 rpm while the talc was fed into the side-feeder with a screw speed of 18 300 rpm.
  • Two individually controlled gravimetric K-tron feeders were used to control the feeding rate, both for the resin and the filler.
  • the throughput was set to 13.67 kg/h for the main feeder, while the throughput for the side-feeder was set to obtain the desired sample composition.
  • the extruded strand was cooled in a water bath and pelletized. The granules were then oven-dried followed by injection molding in an Engel ES
  • Fig. 3 is a diagram showing specific density as a function of the
  • Fig. 4 shows a table describing the influence of the talc loadings on the tensile strength, elongation at yield, and elongation at break, as well as the E-modulus.
  • Fig. 5 shows a graph of the tensile strength as a function of the filler content. It can be noted that the tensile strength at yield increased gradually with increasing filler content. In contrast, PEc, which had 2.5wt% CB, showed a slight decrease in tensile strength compared to HDPE with no filler (PEn). The increase in tensile strength on incorporation of talc was more evident at higher concentrations. To evaluate the significance of differences observed between different composite formulations, the data (for the six talc concentrations from 5wt% to 35wt% and PEc as control) were analyzed by one-way ANOVA at the 95% confidence level.
  • An equivalent result i.e. an increase in tensile strength with an increased filler concentration, was obtained for the tensile strength at break, also shown in fig 5.
  • the P-value of ⁇ 0.05 for the tensile strength at break indicated that there were significant differences between the various composites.
  • the PEn pure HDPE
  • Fig. 6a and 6b shows impact resistance measured by a Charpy impact test, as a function of filler content in a notched specimen edgewise (Fig. 6a), and un-notched flatwise (Fig. 6b).
  • the notched specimen includes a small crack such that the specimen shall fail during testing.
  • the Charpy impact test is a test which determines how much energy a material absorbs during fracture. This absorbed energy provides a measure of a given material's notch toughness. At first, with incorporation of 2.5 wt% of CB in the HDPE, the toughness was steeply reduced by 34%.
  • Fig. 7 shows a graph of the impact resistance (Charpy test) and tensile elongation as a function of filler content. As can be seen, the tensile elongation and impact resistance correlate.
  • the toughness was steeply reduced by 34%. Then, in the presence of talc, the toughness gradually improved until at 8wt% loading the highest value for impact resistance was reached, which was very close to the value for pure HDPE (83 kJ/m218 ). After that, the impact resistance dropped gradually with an increase in filler loading.
  • Figs. 8 shows thermal conductivity and thermal diffusivity (thermal conductivity divided by density and specific heat capacity at constant pressure) as a function of filler content. It was found that the thermal conductivity and the thermal diffusivity increased gradually.
  • thermal conductivity indicates that a percolated particle network was not formed, as we could not achieve the thermal conductivity values of pure talc.
  • the fillers would form thermally conductive percolated networks (instead of isolated thermally conductive particles surrounded by the matrix), and heat can therefore flow through these channels.
  • the maximum thermal conductivity was up to 70% higher than for unfilled PEc at a talc concentration of 35wt%.
  • the talc particles were well dispersed throughout the matrix, and the particles could not form a percolated conductive path. So these results show that the heat transfer occurred according to the dispersion mechanism, with no percolation.
  • the interconnectivity of the filler and matrix is thereby of large importance for the thermal conductivity of the compounded polymer composition.
  • Fig. 9 is a graph showing volumetric and specific heat capacity (Cp).
  • Fig. 10a is a graph showing thermal resistance in a geothermal pipe collector as a function of the thermal conductivity of the polymer
  • the thermal resistance of the pipe collector is dependent on the physical properties of the pipe, such as diameter, wall thickness and the occurrence of patterns increasing the heat exchange.
  • Fig. 10b shows the thermal resistance as a function of thermal
  • Fig. 1 1 is a table showing the result of Thermogravimetric analysis showing the CB is an effective additive for increasing thermal stability.
  • a decomposition of PEn of 5% occurred at 395°C while 5% degradation in weight for PEc occurred at 435°C. Additionally, the maximum mass loss temperatures were 448°C and 462°C, respectively.
  • One explanation for the higher thermal stability for PEc might be the moderate enhancement of the thermal conductivity and the uniform heat dissipation.
  • CB has a non-polar surface character, which is more compatible in a matrix like HDPE, as it is also non-polar. Thus, the interfacial heat transfer could be improved, reducing local overheating and hot spots, which can delay the thermal degradation.
  • Fig. 12 shows a graph of thermal degradation (weight as a function of temperature) for PEn, PEc and PE with different amounts of talc.
  • PEn started to degrade at a temperature of 395°C, and decomposition of almost 100% occurred at 570°C.
  • the composition comprising talc has lower thermal stability than the PEc.
  • the mechanism of accelerated degradation can be explained in two ways. Firstly, the ability of the talc particle surface to absorb stabilizers can result in reduced long-term thermal stability. Therefore, as the specific surface area of the filler is increased, this adverse effect can be more pronounced.
  • Fig. 13 shows a graph of the particle size distributions with respect to the cumulative volume and the volume in each size fraction (particle diameter as a function of volume).
  • the mean particle size was 1 1 .14 +/- 0.02 ⁇ .
  • Fig. 14a shows a geothermal pipe collector 12 according to one
  • the inner surface 14 of the pipe collector 12 comprises recesses or protrusions 16 extending helically in relation to the length axis (L in fig. 14b) of the pipe collector 12, such that a turbulent flow is created in the direction of the length axis of the pipe collector.
  • the recesses or protrusions 16, may be continuous or discontinuous in the longitudinal direction of the single pipe collector 12.
  • Usual dimensions for geothermal pipe collectors 12 are within the range 25-63 mm in diameter.
  • the height of the indentations and/or elevations 16, which could be grooves 18 or the grooving, can be varied, but can typically be within the range of 0.2-5 mm depending on the size of the pipes and the wall thickness, and preferably within the range 0.2-2 20 mm, for the most usual dimensions of the collector pipes 12.
  • the grooves 18 are evenly spread around the inner circumferential surface of the pipe, as seen in the cross section of fig. 14a.
  • the creations of grooves on the inner surface of the pipe collector makes the wall of the pipe collector thinner at some portions, which may affect some of the mechanical properties of the pipe collector 12. Thus, when removing material from the wall of the pipe collector, it may be necessary or advantageous to increase the
  • [074] 14b shows one embodiment of the geothermal pipe collector 2 in a longitudinal section.
  • the geothermal pipe collector comprises helically extending recesses or protrusions 16 which alter direction at least at some portion along the length axis L of the pipe collector 2.
  • the direction of the helical shape of the recesses or protrusions 16 can be altered suitably at least every second meter or every meter, in the longitudinal direction L of the pipe.

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Abstract

L'invention porte sur un tuyau collecteur géothermique. Le tuyau collecteur géothermique est formé à partir d'une composition de polymère comprenant : plus de 50 % en poids de polyéthylène, de 0,1 % en poids à 35 % en poids de talc et de 0,5 % en poids à 10 % en poids de noir de carbone.
PCT/EP2013/052045 2013-02-01 2013-02-01 Tuyau collecteur géothermique WO2014117860A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
PCT/EP2013/052045 WO2014117860A1 (fr) 2013-02-01 2013-02-01 Tuyau collecteur géothermique
EP13704897.1A EP2951511A1 (fr) 2013-02-01 2013-02-01 Tuyau collecteur géothermique
CA2937973A CA2937973A1 (fr) 2013-02-01 2013-02-01 Tuyau collecteur geothermique
US14/762,020 US20150323264A1 (en) 2013-02-01 2013-02-01 Geothermal pipe collector
US15/481,000 US20170227257A1 (en) 2013-02-01 2017-04-06 Geothermal pipe collector

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Application Number Priority Date Filing Date Title
PCT/EP2013/052045 WO2014117860A1 (fr) 2013-02-01 2013-02-01 Tuyau collecteur géothermique

Related Child Applications (2)

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US14/762,020 A-371-Of-International US20150323264A1 (en) 2013-02-01 2013-02-01 Geothermal pipe collector
US15/481,000 Continuation US20170227257A1 (en) 2013-02-01 2017-04-06 Geothermal pipe collector

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US20170227257A1 (en) 2017-08-10

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