EP2635853A1 - A channel arrangement for a solar absorber, a solar absorber, use of a channel arrangement - Google Patents

A channel arrangement for a solar absorber, a solar absorber, use of a channel arrangement

Info

Publication number
EP2635853A1
EP2635853A1 EP10771759.7A EP10771759A EP2635853A1 EP 2635853 A1 EP2635853 A1 EP 2635853A1 EP 10771759 A EP10771759 A EP 10771759A EP 2635853 A1 EP2635853 A1 EP 2635853A1
Authority
EP
European Patent Office
Prior art keywords
channel arrangement
cooling channels
channel
heat
fluid
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP10771759.7A
Other languages
German (de)
French (fr)
Inventor
Hans Keife
Petri Konttinen
Anders Falkenö
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Aurubis AG
Original Assignee
Aurubis AG
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 Aurubis AG filed Critical Aurubis AG
Publication of EP2635853A1 publication Critical patent/EP2635853A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S10/00—Solar heat collectors using working fluids
    • F24S10/70—Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits
    • F24S10/75—Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits with enlarged surfaces, e.g. with protrusions or corrugations
    • F24S10/753—Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits with enlarged surfaces, e.g. with protrusions or corrugations the conduits being parallel to each other
    • 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
    • Y02E10/40—Solar thermal energy, e.g. solar towers
    • Y02E10/44—Heat exchange systems

Definitions

  • the channel arrangement comprises preferably a material with high thermal conductivity, such as copper, alumi num, etcetera, wherein the inner heat conducting parts are adapted to conduct heat to the channels.
  • the channels are adapted to conduct a fluid in form of a cooling medium.
  • the channel arrangement is adapted to be exposed to solar radiation and absorb at least a portion of the energy from the solar radiation, convert the energy of the solar radiation i nto heat and transfer the heat away from the channel arrangement.
  • the size of the cross section of the cooling channels shall be as large as possi ble in order to allow a large quantity of the fluid to stream through the channel .
  • the pressure of the streami ng fl uid shall preferably be as high as possible in order to transfer a large portion of the heat away from the body of the channel arrangement.
  • the object of the present invention is to provide a channel arrangement for solar absorbers with improved heat transfer efficiency.
  • the first ratio is in the range of 0,82 - 0,86.
  • the range of the first ratio provides the most advantageous efficiency in relation to the material consumption of the channel arrangement.
  • a body with a high thermal conductivity is advantageous for the efficiency when the channel arrangement is used in a solar ab- sorber.
  • the high thermal conductivity promotes the heat transfer rate from the inner heat conducting part to the cooling channels.
  • the cooling channels are oval with a certain length of the major axis and the inner heat conducting part separates the cooling channels with a certain distance from each other, wherein a third ratio between the length of the major axis and said distance between the channels is in the range 0,10 - 0,30, preferably in the range 0,15 - 0,20.
  • the body comprises two outer heat conductive parts that are located at a first side respectively a second side of the body, wherein each of the outer heat conductive parts has a certain width that forms the respective side of the body of the channel arrangement.
  • the outer heat conductive parts have the same width.
  • the cross section area of each channel is between 5-15 mm 2 , preferably between 7-10 mm 2 .
  • the strength and rigidity of the inner heat conducting part is increased in relation to the cooling channel .
  • the channel arrangement is constructed by the first and the second material , the strength of the cooling channel can be optimized in relation to both the inner heat conducting part and to the pressure mai ntaining capacity of the cooling channels.
  • the first material is aluminum, or an alloy thereof, and the second material is copper, or an alloy thereof.
  • the first material is iron, or an alloy thereof, and the second material is copper, or an alloy thereof.
  • the first material is stainless steel .
  • the chan nels have an i nternal surface adapted to be in contact with the fluid , wherei n the internal surface comprises a surface enhancement with grooves and projections.
  • Fig. 1-2 shows a channel arrangement for a solar absorber according to a first embodiment of the invention.
  • Fig. 1a shows the channel arrangement in a perspective view.
  • Fig. 1b shows the channel arrangement viewed from above.
  • Fig. 1c shows the channel arrangement viewed from a first side parallel with a longitudinal axis of channels of the channel arrangement.
  • Fig. 2b shows an enlargement of a channel of the channel arrangement in fig.2a.
  • Fig. 3a-3d shows a channel arrangement for a solar absorber according to a second embodiment of the invention.
  • Fig.3a shows the channel arrangement in a perspective view.
  • Fig.3b shows the channel arrangement viewed from above.
  • Fig.3c shows the channel arrangement viewed from a first side parallel with a longitudinal axis of channels of the channel arrangement.
  • Fig.3d shows an enlargement of an edge part of the channel arrangement in fig.3a.
  • Fig.4a shows a collective tube with openings for receiving cool- ing channels of the channel arrangement in fig.3a-3d.
  • Fig.4b shows a collective tube with openings for receiving cooling channels of the channel arrangement in fig.3a-3d.
  • Fig.5 shows the channel arrangement in fig.3a-3d attached to the collective tube in fig.4a4b.
  • Figure 1 shows a channel arrangement 1 for a solar absorber according to an embodiment of the invention.
  • the channel arrangement 1 is seen in a perspective view in fig. 1a, in a view from above in fig. 1b, and in a side view in fig. 1c.
  • Each of the three cooling channels 10 extends along a longitudinal axis L1.
  • the body 5 comprises a first side S1, a second side S2, a third side S3 and a forth side S4.
  • the first side S1 and the second side S2 are parallel with the longitudinal axis L1.
  • the third side S3 and the fourth side S4 are perpendicular to the longitudinal axis L1.
  • the body 5 further comprises a plurality of inner heat conducting parts 12 and two outer heat conducting parts 14.
  • the body comprises two inner heat conducting parts 12 and two outer heat conducting parts 14.
  • Each of the two inner heat conducting parts 12 is located between two of the cooling chan- nels 10.
  • the two outer heat conducting parts 14 forms the first side S1 respectively at the second side S2 of the body 5.
  • Each of the i nner heat conducting parts 12 separates two adjacent cooling channels 10 from each other by means of that each of the inner heat conducting parts 1 2 has a width W 1 .
  • the two inner heat conducti ng parts 12 have preferably the same width
  • Each of the outer heat conductive parts 14 has a certai n width W2 that forms the respective side of the body 5 of the channel arrangement 1 .
  • the two outer heat conductive parts 14 have the same width W2.
  • the body 5 of the channel arrangement 1 comprises a first metal profile and a second metal profile.
  • the first and the second metal profile are attached to each other by a plurality of joints 20.
  • Two joints 20 are arranged on opposite sides of each cooling channel 10.
  • Joints are also arranged on the first side S 1 and the second side S2.
  • the joints between the first and the second metal profile are manufactured by means of clad-rolling .
  • Figure 2a shows the channel arrangement 1 in figure 1 a - 1 c viewed from the third side S3.
  • Figure 2b shows an enlargement of a channel of the channel arrangement 1 at the enclosed area in fig . 2a.
  • Fig . 2a-2b comprises dimensional numbers of an embodiment of the invention. It shall be understood that the dimen- sional numbers are merely a preferable embodiment and shall not be interpreted as limiting to the scope of protection.
  • Each of the cooling channels 10 comprises a first cross section area A1 for conducting the fluid.
  • the inner heat conducting parts 12 comprises material with a second cross section area A2.
  • a first ratio between the first cross section area A1 and the second cross section area A2 is in the range of 0,7 - 0,9.
  • the first ratio is in the range of 0,82 - 0,86.
  • the body 5 of the channel arrangement 1 preferably comprises a metal with a high thermal conductivity.
  • the metal is copper or a copper alloy that has a thermal conductivity higher than 340 W/(m K).
  • FIG.2b an enlargement of a cooling channel 10 of the channel ar-rangement 1 in fig. 2a is shown.
  • the cooling channel comprises a an ovality by means of that the channel 10 comprises a major axis "a" and minor axis "b" that are perpendicular to the longitudinal axis L1 and mutually perpendicular to each other.
  • the ovality is defined as the ratio: 2(a-b)/(a+b).
  • the ovality of the cooling channel 10 is between 0,10 and 0,15.
  • Both the first side S1 and the second side S2 comprise the edge part with the L-shaped flange 30.
  • the flange 35 protrudes perpendicular to the outer heat conducting part 14.
  • Fig.5 shows the channel arrangement 1 in fig.3a-3d attached to a collective tube 30.
  • the forth side S4 of the channel arrangement 1 is attached to the collective tube 30.
  • the attachment between the cooling channels 10 and the collective tube 30 is established by means of soldering, brazing, welding, gluing, shrink fitting, etcetera.
  • the invention is not limited to the disclosed embodiments but may be varied within the scope of the claims.

Abstract

A channel arrangement (1) for a solar absorber. The channel arrangement (1) comprises a surface (3) adapted to be exposed to solar radiation and transform the solar radiation to heat, a body (5) adapted to absorb the heat from the surface (3). The body (5) comprises two or more cooling channels (10) for conducting a fluid, which fluid absorbs heat from the body (5) and transfer the heat away from the body (5), at least one inner heat conducting part (12) between the cooling channels (10), which conducting part is adapted to conduct heat to the cooling channels. Each of the cooling channels has a first cross section area (Al) for conducting the fluid and the at least one inner heat conducting part (12) comprises material with a second cross section area (A2), wherein a first ratio between first cross section area(Al) and the second cross section area (A2) is in the range of 0,7 - 0,9.

Description

A CHAN N E L ARRAN GEM ENT FOR A SOLAR ABSORBER, A SOLAR ABSORBER, USE OF A CHAN N EL ARRANGEM ENT
FI ELD OF TH E I NVENTI ON The present i nvention relates to a channel arrangement for a solar absorber. The channel arrangement comprises a surface adapted to be exposed to solar radiation and transform the solar radiation to heat and a body adapted to absorb the heat from the surface. The body comprises two or more cooling channels for conducting a fl uid , wh ich flu id a bsorbs heat from the body and transfer the heat away from the body and at least one inner heat conducting part between the cooling channels, which conducting part is adapted to conduct heat to the channels. PRIOR ART
A channel arrangement in here defi ned to comprise two or more cooling channels mutually separated by i nner heat conducting parts. The channel arrangement comprises preferably a material with high thermal conductivity, such as copper, alumi num, etcetera, wherein the inner heat conducting parts are adapted to conduct heat to the channels. The channels are adapted to conduct a fluid in form of a cooling medium. The channel arrangement is adapted to be exposed to solar radiation and absorb at least a portion of the energy from the solar radiation, convert the energy of the solar radiation i nto heat and transfer the heat away from the channel arrangement. Preferably, the size of the cross section of the cooling channels shall be as large as possi ble in order to allow a large quantity of the fluid to stream through the channel . Furthermore, the pressure of the streami ng fl uid shall preferably be as high as possible in order to transfer a large portion of the heat away from the body of the channel arrangement.
Preferably, the inner heat conducting parts between the channels shall be of a material with high heat conductivity. Furthermore, a distance of the inner heat conducti ng parts separating the two adjacent cooling channels from each other shall be as short as possi ble in order to efficiently conduct heat to the cooling channels. Furthermore, the i nner heat conducting parts shall preferably provide a high heat conduction capacity.
The above descri bed ideal preferably design of the channel ar- rangement i n respect of performance would however for a certain material result in a heavy channel arrangement requiring a high material consumption for its manufacture. Accordi ngly, the cost of such a channel arrangement would be high. A problem with prior art channel arrangement is thus that, even though the channel arrangement is efficient, the material consumption high , and accordi ngly the cost of the channel arrangement is high.
OBJ ECTS AND SUMMARY OF THE I NVENTION The object of the present invention is to provide a channel arrangement for solar absorbers with improved heat transfer efficiency.
This object is obtained by channel arrangement as defined by the preamble of claim 1 , wherein the channel arrangement is characterized in that the each of the cooling channels has a first cross section area for conducting the fluid and the at least one inner heat conducti ng part comprises material with a second cross section area, wherei n a first ratio between first cross sec- tion area and the second cross section area is i n the range of 0,7 - 0,9. The first ratio between first cross section area and the second cross section area regards the relation between the inner dimensions of the cooling channels and the dimension of the inner heat conducting part. The first ratio relates to a relation between the heat transfer rate from the inner heat conducting part to the cooling channels and the heat transfer rate away from the cooling channels. The first ratio provides a preferable relationship between the dimensions of the cooling channels and the inner heat conducting part that provides a high efficiency in relation to the material consumption when used in a solar absorber.
According to one embodiment of the invention, the first ratio is in the range of 0,82 - 0,86. The range of the first ratio provides the most advantageous efficiency in relation to the material consumption of the channel arrangement.
According to one embodiment of the invention, the body is made of a metal with a thermal conductivity higher than 15 W/(m*K), preferably more than 240 W/(m*K), more preferably higher than 340 W/(m«K).
A body with a high thermal conductivity is advantageous for the efficiency when the channel arrangement is used in a solar ab- sorber. The high thermal conductivity promotes the heat transfer rate from the inner heat conducting part to the cooling channels.
According to one embodiment of the invention, each of the cooling channels is adapted to conduct a flow rate of the fluid in the range of 0,00090 to 0,00120 kg/s. The cooling channels will be provided with thermal energy from the inner heat conducting part, which requires the specified flow rate of the fluid.
According to one embodiment of the invention, the fluid for transferring the heat away from the body of the channel arrangement comprises mainly water. Accordi ng to one embodiment of the invention, the cooling channels are cylindrical with a certain i nner diameter and the at least one inner heat conducting part has a width that separates the cooling chan n els from each other, wherei n a second ratio between the inner diameter of the cooling channels and said width is in the range 0, 10 - 0,30, preferably in the range 0, 1 5 - 0,20. The second ratio between the i n ner d ia meter of the chan nels and the distance between the channels relates to the relation between the distance that absorbed energy shall be conducted and the size of the cooling channel . Furthermore, the second ratio relates to the relationship between the area that absorbs energy from the solar radiation and the area for conducting the fluid that transfers the energy away from the body of the channel arrangement.
Accordi ng to one embodiment of the invention, the cooling channel comprises a major axis and minor axis that are perpendicular to a longitudi nal axis and mutually perpendicular to each other, wherein the length of the major axis and the mi nor axis are arranged so that an ovality of the cooling channel is between 0,01 and 0,20, preferably between 0, 10 and 0, 15.
The major axis is longer than the minor axis. When the major axis is "a" and the minor axis is "b", the ovality is defined as the ratio: 2(a-b)/(a+b). The ovality is the degree of deviation from a perfect circularity of the cooling channel . The ovality of the cool- ing channel enhances the degree of turbulence flow of the fluid in comparison to a perfect circularity of the cooling channel . Accordingly, the heat transfer efficiency from the body to the fluid is improved . Accordi ng to one em bod iment of the i nvention , the major axis extends essentially in parallel with the extension of the inner heat conducting part and the minor axis extends essentially perpendicular to the extension of the inner heat conducting part.
According to one embodiment of the invention, the cooling channels are oval with a certain length of the major axis and the inner heat conducting part separates the cooling channels with a certain distance from each other, wherein a third ratio between the length of the major axis and said distance between the channels is in the range 0,10 - 0,30, preferably in the range 0,15 - 0,20.
According to one embodiment of the invention, the body comprises a plurality of inner heat conductive parts that have the same width.
According to one embodiment of the invention, the body comprises two outer heat conductive parts that are located at a first side respectively a second side of the body, wherein each of the outer heat conductive parts has a certain width that forms the respective side of the body of the channel arrangement. Preferably, the outer heat conductive parts have the same width.
According to one embodiment of the invention, the body is made of one of copper, aluminum and iron, or an alloy thereof. The three elements have the benefits of high or relatively high thermal conductivity and high or relatively high mechanical strength. A preferable iron containing alloy for the body is stainless steel.
According to one embodiment of the invention, the cross section area of each channel is between 5-15 mm2, preferably between 7-10 mm2.
According to one embodiment of the invention, the body of the channel arrangement consists of a single material. Accordi ng to one embodiment of the invention, the inner heat conducting part is mainly made of copper or an alloy thereof, wherei n the material thickness of the inner heat conducti ng part is 0, 10 - 0,25 mm .
Accordi ng to one embodiment of the invention, the inner heat conducting part is mainly made of alumi num or an alloy thereof, wherei n the material thickness of the inner heat conducti ng part is 0,2 - 0,5 mm.
Accordi ng to one embodiment of the invention, the inner heat conducting part is mainly made of iron or an alloy thereof, wherei n the material thickness of the inner heat conducting part is 0,9 - 0, 1 1 mm .
Accordi ng to one embodiment of the invention, a substantial part of the least one i nner heat conducting part consists of a first metal material and a substantial part of the cooling channels consists of a second metal material , wherein the first material has higher mechanical strength than the second material .
By using the first material for the inner heat conducting part and the second material for the cooling channel , the strength and rigidity of the inner heat conducting part is increased in relation to the cooling channel . In addition , by means of that the channel arrangement is constructed by the first and the second material , the strength of the cooling channel can be optimized in relation to both the inner heat conducting part and to the pressure mai ntaining capacity of the cooling channels.
Accordi ng to one embodiment of the invention, the first material is aluminum, or an alloy thereof, and the second material is copper, or an alloy thereof. Accordi ng to one embodiment of the invention, the first material is iron, or an alloy thereof, and the second material is copper, or an alloy thereof. Preferably, the first material is stainless steel . Accordi n g to on e em bod i ment of the i nventi on , the chan nels have an i nternal surface adapted to be in contact with the fluid , wherei n the internal surface comprises a surface enhancement with grooves and projections. By means of the surface en hancement the contact surface between an inner surface of the cooling channels and the fluid is enlarged . Thereby, the heat transfer from the cooling channel to the fluid is improved . Furthermore, the surface enhancement creates turbulence that improves the heat transfer from the cool- ing channels to the fluid .
Accordi ng to one embodiment of the invention, the surface comprises a spectral selective coating , which coating is adapted to, when the coating is exposed to sun light, absorb a su bstantial part of the energy from the sun light and transform the absorbed energy to thermal energy. The spectral selective coating is for example black chrome, selective pai nt, cermet structure.
Accordi ng to one embodiment of the invention, the channels ar- rangements are manufactured by means of rolling two metal profiles toward each other. I n particular for a body of copper or a copper alloy the manufacturing of the channel arrangement by rolling is preferable. Accordi ng to one embodiment of the invention , the channel arrangement comprises an edge part with a flange, which flange comprises a surface that is adapted to accommodate an air-tight connection between the surface and a transparent cover. By means of the air-tight connection between the surface and the transparent cover, the heat radiation from the channel arrangement is reduced . According to one embodiment of the invention, the channels are adapted to be attached to a collective tube by means of one of soldering, brazing, welding, gluing and shrink fitting.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be explained more closely by the description of different embodiments of the invention and with reference to the appended figure.
Fig. 1-2 shows a channel arrangement for a solar absorber according to a first embodiment of the invention.
Fig. 1a shows the channel arrangement in a perspective view. Fig. 1b shows the channel arrangement viewed from above.
Fig. 1c shows the channel arrangement viewed from a first side parallel with a longitudinal axis of channels of the channel arrangement.
Fig.2a shows the channel arrangement in fig. 1a-c viewed from a third side perpendicular to the longitudinal axis of cooling channels of the channel arrangement.
Fig. 2b shows an enlargement of a channel of the channel arrangement in fig.2a. Fig. 3a-3d shows a channel arrangement for a solar absorber according to a second embodiment of the invention.
Fig.3a shows the channel arrangement in a perspective view. Fig.3b shows the channel arrangement viewed from above.
Fig.3c shows the channel arrangement viewed from a first side parallel with a longitudinal axis of channels of the channel arrangement.
Fig.3d shows an enlargement of an edge part of the channel arrangement in fig.3a.
Fig.4a shows a collective tube with openings for receiving cool- ing channels of the channel arrangement in fig.3a-3d. Fig.4b shows a collective tube with openings for receiving cooling channels of the channel arrangement in fig.3a-3d.
Fig.5 shows the channel arrangement in fig.3a-3d attached to the collective tube in fig.4a4b.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
Figure 1 shows a channel arrangement 1 for a solar absorber according to an embodiment of the invention. The channel arrangement 1 is seen in a perspective view in fig. 1a, in a view from above in fig. 1b, and in a side view in fig. 1c.
The channel arrangement 1 comprises a surface 3 adapted to be exposed to solar radiation and transform the solar radiation to heat and a body 5 adapted to absorb heat from the surface 3.
The body 5 comprises three cooling channels 10 for conducting a fluid. The fluid is adapted to absorb heat from the body 5 and transfer the heat away from the body 5. The fluid is for example, water, water-antifreeze mixture, carbon dioxide, etcetera.
Each of the three cooling channels 10 extends along a longitudinal axis L1. The body 5 comprises a first side S1, a second side S2, a third side S3 and a forth side S4. The first side S1 and the second side S2 are parallel with the longitudinal axis L1. The third side S3 and the fourth side S4 are perpendicular to the longitudinal axis L1. The body 5 further comprises a plurality of inner heat conducting parts 12 and two outer heat conducting parts 14. In figure 1a - 1c, the body comprises two inner heat conducting parts 12 and two outer heat conducting parts 14. Each of the two inner heat conducting parts 12 is located between two of the cooling chan- nels 10. The two outer heat conducting parts 14 forms the first side S1 respectively at the second side S2 of the body 5. Each of the i nner heat conducting parts 12 separates two adjacent cooling channels 10 from each other by means of that each of the inner heat conducting parts 1 2 has a width W 1 . The two inner heat conducti ng parts 12 have preferably the same width W 1 .
Each of the outer heat conductive parts 14 has a certai n width W2 that forms the respective side of the body 5 of the channel arrangement 1 . Preferably, the two outer heat conductive parts 14 have the same width W2.
The body 5 of the channel arrangement 1 comprises a first metal profile and a second metal profile. The first and the second metal profile are attached to each other by a plurality of joints 20. Two joints 20 are arranged on opposite sides of each cooling channel 10. Joints are also arranged on the first side S 1 and the second side S2. Accordi ng to an embodiment of the invention , the joints between the first and the second metal profile are manufactured by means of clad-rolling .
The surface 3 is located at a side of the body 5. Preferably, the su rface is coveri ng both the cooling chan nels 1 0 and the in ner heat conducti ng parts 12. The surface 3 is a so called spectral selective coating , which is adapted to absorb a substantial part of the energy from the sun light and transform the absorbed energy to thermal energy. According to one embodiment of the i n- vention the surface 3 is black chrome.
Figure 2a shows the channel arrangement 1 in figure 1 a - 1 c viewed from the third side S3. Figure 2b shows an enlargement of a channel of the channel arrangement 1 at the enclosed area in fig . 2a. Fig . 2a-2b comprises dimensional numbers of an embodiment of the invention. It shall be understood that the dimen- sional numbers are merely a preferable embodiment and shall not be interpreted as limiting to the scope of protection.
Each of the cooling channels 10 comprises a first cross section area A1 for conducting the fluid. The inner heat conducting parts 12 comprises material with a second cross section area A2. According to an embodiment of the invention, a first ratio between the first cross section area A1 and the second cross section area A2 is in the range of 0,7 - 0,9. According to a preferred embodiment of the invention the first ratio is in the range of 0,82 - 0,86.
The body 5 of the channel arrangement 1 preferably comprises a metal with a high thermal conductivity. In a preferable em- bodiment the metal is copper or a copper alloy that has a thermal conductivity higher than 340 W/(m K).
The cross section of the cooling channels 10 and the strength of the cooling channels 10 is adapted to conduct a flow rate of the fluid in a range of 0,00090 - 0,0012 kg/s.
In fig.2b an enlargement of a cooling channel 10 of the channel ar-rangement 1 in fig. 2a is shown. The cooling channel comprises a an ovality by means of that the channel 10 comprises a major axis "a" and minor axis "b" that are perpendicular to the longitudinal axis L1 and mutually perpendicular to each other. The ovality is defined as the ratio: 2(a-b)/(a+b). The ovality of the cooling channel 10 is between 0,10 and 0,15. By means of the ovalty of the cooling channel 10 a turbulent flow of the fluid arises. Thereby, the heat transfer efficiency of the channel arrangement is improved.
According to an embodiment of the invention, the cooling chan- nels 10 are cylindrical with a certain inner diameter D1. The inner heat conducting parts each has a certain width W1 that separates two adjacent cooling channels 10 from each other. A second ratio between the inner diameter D1 and the distance W1 between the channels is in the range 0,10 - 0,30. Preferably the second ratio is in the range 0,15 - 0,20.
The distance W1 of the cooling channels 10 is preferably 20 - 30 mm, preferably 24 - 26 mm.
Preferably the first cross section area A1 of the cooling chan- nels that is adapted to conduct the fluid has a cross section area of 5 - 15 mm2 preferably between 7 - 10 mm2.
According to one embodiment of the invention, the inner heat conducting part 12 consists of a first metal material and each cooling channels 10 consists of a second metal material. The first material has higher mechanical strength than the second material.
According to an embodiment of the invention, the first metal ma- terial is copper or an alloy thereof and the second metal material is aluminum or an alloy thereof.
According to an embodiment of the invention, the cooling channels 10 have an internal surface that is adapted to be in contact with the fluid. The internal surface comprises a surface enhancement comprising grooves and projection in order to enhance the contact between the fluid and the cooling channel 10.
The surface 3 of the channel arrangement 1 preferably com- prises a spectral selective coating. The spectral selective coating is adapted to absorb a substantial part of energy from the sunlight and transform the absorbed energy into thermal energy.
Fig. 3a-3d shows a channel arrangement 1 for a solar absorber according to a second embodiment of the invention. The cooling channels 10 have been exposed at the third side S3 and at the forth side S4 by means of a plurality of cutouts at the inner heat conducting parts 12 and outer heat conducting parts 14. Thereby, the cooling channels 10 protrudes along the longitudinal axis L1 away from the third side S3 respectively the forth side S4.
The exposed cooling channels 10 enable establishing a connection of the cooling channels 10 to a collective tube 30, see fig. 3d. The cooling channels 10 are inserted into openings 31 at the collective tube 30 and an attachment between the cooling channels 10 and the collective tube 30 is established.
Fig.3d shows an enlargement of the encircled area in fig. 3a. The channel arrangement 1 comprises an edge part with an L- shaped flange 35.
Both the first side S1 and the second side S2 comprise the edge part with the L-shaped flange 30. The flange 35 protrudes perpendicular to the outer heat conducting part 14.
The flange 35 comprises a lip 37 that protrudes essentially parallel with the outer heat conducting part 14. The lip 37 forms a connection surface 39 essentially parallel with the surface 3 of the outer heat conducting parts 14. The connection surface 39 is adapted to accommodate an air tight connection between the connection surface 39 and a transparent cover. By means of air tight connection between the connection surface 39 and the transparent cover, the heat radiation from the channel arrangement 1 is reduced.
Fig.4a shows a collective tube 30 with openings for receiving cooling channels 10 of the channel arrangement 1 in fig.3a-3d. The collective tube 30 comprises three openings 31 adapted to receive exposes cooling channels 10 as seen in fig.3a-3d. Fig.4b shows a collective tube with openings for receiving the cooling channels 10 of the channel arrangement in fig. 3a-3d. Each opening 31 has a form that conforms to the form of the exposed channel including the joints on both side of the cooling channels 10.
It shall be understood that the invention is not limited to the form of the opening in fig.4a-4b. Other forms such as circular, rectangular, etcetera, are possible.
Fig.5 shows the channel arrangement 1 in fig.3a-3d attached to a collective tube 30. The forth side S4 of the channel arrangement 1 is attached to the collective tube 30. According to an embodiment the attachment between the cooling channels 10 and the collective tube 30 is established by means of soldering, brazing, welding, gluing, shrink fitting, etcetera. The invention is not limited to the disclosed embodiments but may be varied within the scope of the claims.

Claims

1. A channel arrangement (1) for a solar absorber, wherein the channel arrangement (1) comprises:
- a surface (3) adapted to be exposed to solar radiation and transform the solar radiation to heat,
- a body (5) adapted to absorb the heat from the surface (3), wherein the body (5) comprises:
- two or more cooling channels (10) for conducting a fluid, which fluid absorbs heat from the body (5) and transfer the heat away from the body (5),
- at least one inner heat conducting part (12) between the cooling channels (10), which conducting part is adapted to conduct heat to the cooling channels (10),
characterized in that
each of the cooling channels (10) has a first cross section area (A1) for conducting the fluid and the at least one inner heat conducting part (12) comprises material with a second cross section area (A2), wherein a first ratio between first cross section area (A1) and the second cross section area (A2) is in the range of 0,7 - 0,9.
2. A channel arrangement (1) according to claim 1, characterized in that the first ratio is in the range of 0,82 - 0,86.
3. A channel arrangement (1) according to any of claim 1 and 2, characterized in that each of the cooling channels (10) is adapted to conduct a flow rate of the fluid in the range of 0,00090 to 0,00120 kg/s.
4. A channel arrangement (1 ) according to any of the preceding claims, characterized in that the cooling channels (10) are cylindrical with a certain inner diameter (D1) and the at least one inner heat conducting part (12) has a width (W1) that separates the cooling channels (10) from each other, wherein a second ratio between the inner diameter (D1) of the cooling channels (1 0) and said width (W1 ) is in the range 0, 1 0 - 0,30, preferably in the range 0, 15 - 0,20.
5. A channel arrangement ( 1 ) according to any of claim 1 -3, characterized i n that the cooling channel (10) comprises a major axis (a) and mi nor axis (b) that are perpendicular to a longitudinal axis (L1 ) and mutually perpendicular to each other, wherein the length of the major axis (a) and the minor axis (b) are arranged so that an ovality of the cooling channel (10) is between 0,01 and 0,20, preferably between 0, 10 and 0, 15.
6. A channel arrangement (1 ) according to any of the preceding claims, characterized i n that the inner heat conducti ng part ( 12) separates the cooling channels ( 10) with a certain distance from each other, which distance is 20-30 mm, preferably, 24-26 mm .
7. A channel arrangement (1 ) according to any of the preced- ing claims, characterized in that the body (5) is made of one of copper, alumi num and iron, or an alloy thereof.
8. A channel arrangement (1 ) according to any of the preceding claims, characterized in that the first cross section area (A1 ) of each channel is between 5- 15 mm2, preferably between 7-10 mm2.
9. A channel arrangement (1 ) according to any of the preceding claims, characterized in that a substantial part of the least one i nner heat conducting part ( 12) consists of a first metal material and a substantial part of the cooling channels (10) consists of a second metal material , wherei n the first material has higher mechanical strength than the second material .
10. A channel arrangement ( 1 ) according to claim 9, characterized i n th at the first material is aluminum, or an alloy thereof, and the second material is copper, or an alloy thereof.
11. A channel arrangement (1) according to claim 9, charac- terized in that the first material is iron, or an alloy thereof, and the second material is copper, or an alloy thereof.
12. A channel arrangement (1) according to any of the preceding claims, characterized in that the channels (10) have an internal surface adapted to be in contact with the fluid, wherein the internal surface comprises a surface enhancement with grooves and projections.
13. A channel arrangement (1) according to any of the pre- ceding claims, characterized in that the surface (3) comprises a spectral selective coating, which coating is adapted to, when the coating is exposed to sun light, absorb a substantial part of the energy from the sun light and transform the absorbed energy to thermal energy.
14. A solar absorber comprising the channel arrangement (1) according to any of claim 1-13.
15. Use of a channel arrangement (1) in a solar absorber ac- cording to any of claim 1 -13.
EP10771759.7A 2010-11-02 2010-11-02 A channel arrangement for a solar absorber, a solar absorber, use of a channel arrangement Withdrawn EP2635853A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2010/066576 WO2012059123A1 (en) 2010-11-02 2010-11-02 A channel arrangement for a solar absorber, a solar absorber, use of a channel arrangement

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EP2635853A1 true EP2635853A1 (en) 2013-09-11

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US4083093A (en) * 1975-08-08 1978-04-11 Chertok Burton Z Multiple material solar panel and method and apparatus for manufacturing the same
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