WO2011055401A2 - Échangeur de chaleur tubulaire, plus particulièrement tube récepteur d'une centrale solaire à concentration - Google Patents

Échangeur de chaleur tubulaire, plus particulièrement tube récepteur d'une centrale solaire à concentration Download PDF

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Publication number
WO2011055401A2
WO2011055401A2 PCT/IT2010/000441 IT2010000441W WO2011055401A2 WO 2011055401 A2 WO2011055401 A2 WO 2011055401A2 IT 2010000441 W IT2010000441 W IT 2010000441W WO 2011055401 A2 WO2011055401 A2 WO 2011055401A2
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WO
WIPO (PCT)
Prior art keywords
tube
heat exchanger
tubular heat
temperature
solar
Prior art date
Application number
PCT/IT2010/000441
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English (en)
Other versions
WO2011055401A8 (fr
WO2011055401A3 (fr
Inventor
Bruno Grindatto
Original Assignee
Advanced Research Consulting S.R.L.
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 Advanced Research Consulting S.R.L. filed Critical Advanced Research Consulting S.R.L.
Priority to US13/505,689 priority Critical patent/US20120312294A1/en
Priority to CN2010800499700A priority patent/CN102741645A/zh
Priority to EP10790684A priority patent/EP2496904A2/fr
Publication of WO2011055401A2 publication Critical patent/WO2011055401A2/fr
Publication of WO2011055401A3 publication Critical patent/WO2011055401A3/fr
Publication of WO2011055401A8 publication Critical patent/WO2011055401A8/fr
Priority to IL219501A priority patent/IL219501A0/en

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Classifications

    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S20/00—Solar heat collectors specially adapted for particular uses or environments
    • F24S20/20—Solar heat collectors for receiving concentrated solar energy, e.g. receivers for solar power plants
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
    • F28F13/14—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by endowing the walls of conduits with zones of different degrees of conduction of heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S80/00—Details, accessories or component parts of solar heat collectors not provided for in groups F24S10/00-F24S70/00
    • F24S2080/03—Arrangements for heat transfer optimization
    • F24S2080/05—Flow guiding means; Inserts inside conduits
    • 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

Definitions

  • the present invention concerns a tubular heat exchanger, in particular a receiving tube of a concentrating solar plant.
  • the invention concerns a receiving tube for a concentrating solar plant, also known as solar tube or solar boiler, realised with features reducing its average temperature and homogenizing the axial and circumferential temperature gradients originating because of the irradiation produced by the solar power being concentrated, by means of mirrors, usually but not necessarily parabolic mirrors (so called “parabolic through” or Fresnel technology or other technology concentrating sun energy and anyway any case indicated in the following with the expression concentrating thermodynamic solar plant) on a portion of the surface of the sane solar tube or receiver.
  • the invention also allows for obtaining an homogenization of the thermodynamic properties of the heat-carrying fluid flowing inside the solar tube.
  • a concentrating solar plant provides for the amplification of the solar irradiation by concentrating it by means of concentrating mirrors, generally but not necessarily having a parabolic shape, conveying the irradiation on a receiving tube or solar tube, in order to increase the thermal power collected by the tube and favoring it warming up to high temperature, i. e. the increasing of its enthalpy or the change of state of a heat-carrying fluid (i.e. a fluid carrying out energy) flowing inside it or anyway a thermodynamic transformation favouring thermal chemical transformations in the fluid (chemical reformulation of the heat-carrying fluid by means of thermal energy coming from the irradiated tube).
  • a heat-carrying fluid i.e. a fluid carrying out energy
  • the heat-carrying fluid can be subsequently used for a series of applications exploiting such a thermodynamical state, such as for example applications linked to the conversion of thermal energy to electric power by means of transformation plants downstream the solar tube using gas turbines and vapour turbines or combinated cycle plants; applications linked to the water desalting for producing water to be used for irrigation, drinking, industry; applications connected to reforming processes of pure or mixed light hydrocarbons (methane, propane, buthane, liquefied petroleum gas, methanol, etc ..) intended for the enrichment of fuels in fuel fractions having a higher value (hydrogen or lighter hydrocarbons) or for the decomposition or reformulation of fuels from the original chemical formulation to simpler molecular forms.
  • a thermodynamical state such as for example applications linked to the conversion of thermal energy to electric power by means of transformation plants downstream the solar tube using gas turbines and vapour turbines or combinated cycle plants; applications linked to the water desalting for producing water to be used for irrigation, drinking, industry; applications connected to reforming processes of
  • thermodynamic solar plant Since the applications connected to the conversion of thermal energy to electric power are those generally making use of this technology (concentrating thermodynamic solar plant), in the following reference is made, for illustrative non limitative purposes of the invention, to them in particular.
  • thermodynamic solar power The technology allowing for using sun energy for producing electric power, in the following simply called “thermodynamic solar power”, is based on the concentration of sun radiation on a receiving tube positioned at the focus of a parabolic strings of mirrors and inside which a heat- carrying fluid flows (chosen for example amongst diathermic oil, molten salts, etc.) heating up to a high temperature (in current applications 500- 600°C), such thermal power being provided, possibly by means of an intermediate fluid through a thermal energy storage section, for being converted into mechanical-electrical power by means of a motor thermodynamic cycle, such as for example the cycles of Rankine, Hirn, Joule or Ericsson, wherein the heat-carrying fluid or the intermediate fluid represent the high temperature source.
  • the concentration ratio obtained by the parabolic mirrors allows for the tube heating up to a high temperature (with significant circumferential and axial temperature gradients in the solar tube) in order to increase temperature or enthalpy of the heat-carrying fluid with respect to the values that are possible without concentrating the energy of the sun. It is therefore possible to extend the possibility of using the energy of the sun to applications that would not be possible wiyhout concentration, in particular, as already cited, to the thermodynamic conversion powered by sun energy or to total or partial fuel reforming or other applications needing a high temperature.
  • a co-axial tube is provided, suitably thermally insulated from the solar tube and made of a material that is transparent to the solar radiation and absorbs the re-radiated energy from the metallic tube, so that a great part of the re-radiated energy from the solar tube is retrieved.
  • the interspace defined between the metallic tube and the surroinding glass tube is kept under vacuum, with the consequence that also the following must be provided: a static sealing system between the metallic tube and the glass tube; suitable (metallic) elastic bellows allowing for absorbing the great axial expansion of the tube following its temperature and axial temperature gradients increase; a joint working also as a sealing allowing for rotation of parts of the solar tube with respect to others, rotation connected with the need of continuity of great length of the solar tube, the need of bringing to the soil the solar tube itself, quick disconnection or division of the tube or parts thereof.
  • a solar tube in fact, depending on the power needed, can extend for kilometers in terms of length and, therefore, needs portions where it is easy to realise a disconnection of parts.
  • thermodynamic solar energy technology foreste an increase in the dimensions (diametre) of the solar tube, in order to allow for a greater surface collecting the thermal energy and, therefore, a greater power capacity of the plant, for the same tube length (and thus for the same overall extension); a further increase of the sun energy concentration ratio from that available on aplanar surface and that, concentrated by parabolic mirrors, available on the surface of the solar tube; and consequently an increase of the materials and heat-carrying fluids working temperature, with a consequent greater severity of the working conditions of the mechanical sealing system, and of the problem of longitudinal and circumferential thermal distorsions of the tube, of sealing between the metallic tube and the transparent tube, of sealing between adjacent portions of tube, i.
  • connection and disconnection devices of different parts of the plant, and of the structural stability of the treatments of the surface of the tube to improve its behaviour as a black body.
  • gas for example nitrogen, carbon dioxide, water steam, helium, carbon dioxide
  • heat-carrying fluid in order to overcome the problem of the solidification of presently used heat-carrying fluids (in particular molten salts) at a temperature below 200-250°C, with the consequence of the need for an increase of the pressure of the heat-carrying fluid, in ordert o compensate the low density, with a consequent further worsening of the working conditions of the sealing system.
  • the receiving tube is irradiated only on a emi-cylindrical surface, great circumferential temperature gradients develop on the tube. Such gradients are critical for the static sealing system between the metallic tube (inside which the heat-carrying fluid flows) and the glass tube or the tube of a material that is transparent to sun light and absorbs the light re-radiated from the tube.
  • the heat-carrying fluid flowing inside the receiving tube gradually increases its temperature, consequently temperature gradients develops along the axis of the receiving tube and around the circumference of the same, causing important differential expansions that are critical for the thermo-mechanical stress and for the structural preservation of the treatments of the surface, due to the differential expansions around the circumference and the axis of the tube.
  • the thermal power irradiated by the sun and suitably concentrated on the solar tube being constant, as will be explained in the following, other conditions being the same (for example but not only: geographical position of the site, solar tube dimensions, concentrating system dimensions, solar tube position with respect to the focus of the parabolic mirrors).
  • the overall solar tube is realised by assemblying different materials with surface treatments and housing systems differently reacting to temperature changes and to heat-carrying fluids passing through, this subjects the solar tube to differential extensions of the different parts composing it, which can generate deformations of the structure, as much greater as is the temperature of the tube.
  • the weight if the solar tube represent, at higher temperature, a critical element, since it increases the deflection connected to the deformation due to gravity force and, therefore, the differential deformations, particularly critical, as already said, on the external surface of the tube, where said surface treatments reducing the thermal power the tube radiates towards the exterior are realised.
  • a receiving tube for a concentrating solar plant having structural features (thicknessof the tube suitably circumferentially changing) and/or elements (fins, grooves, inserts, all with radial extension on the side of the heat-carrying fluid) locally changing with a specific aim the (convective and conductive) circumferential and axial thermal resistance (realising changes in the same circumferential and axial direction of the conductive and convective thermal resistance).
  • such elements favor the homogenization of the heat-carrying fluid flowing inside the tube.
  • EP0677715A1 discloses fins arranged in a V shape, intensifying the turbulence and preventing the deposition of particles that would foul the exchanger on the internal side of fluid (exhaust gases of a internal combustion alternative engine being cooled).
  • Patents DE19540683A1 , DE19654367A1 and DE19654368A1 where such elements are realised witha a low cost technology.
  • FR2682747A1 discloses a tubular heat exchanger presenting a non cylindrical thermal exchange surface, that is a thermal surface with irregular shapes, possibly repeated on angular sectors, with the aim of increasing the thermal exchange surface and intensifying the exchanged thermal power.
  • Such internal surface does not have structural elements (fins) but superficial grooves (irregularities).
  • the application referred to is that of the condensation of a fluid and the aim of these irregularities of the surface is that of promoting the intensification of the turbulence and/or the passage from a laminar flow to a turbulent flow.
  • Such grooves favour the formation of drops, acting as promotors of the condensation and, reducing the thickness of the metallic tube, reduce the radial thermal resistance, increasing the convective heat transfer coefficient.
  • the resulting heat exchanger is more efficient and has lower realisation costs.
  • US005655599A discloses a solution according to which the internal surface of a tubular exchanger are provided with fins in order to increase the thermal energy exchanged due to convection and irradiation between a gas (also subject to combustion) flowing inside and the external surface of the tube.
  • the shape of the fins extending realising a sensible reduction of the passage surface for the gas inside is optimised to intensify the radiant thermal exchange between the gas and the exposed surface, thus extending the application of fins of the thermal exchange surfaces (usually referred to the convection) to the case of radiant exchange.
  • the fins being realised along elicoidal lines subjecting the internal fluid to a rotation around the axis of the tube (twisting). The pitch of such elicoidal lines can be changed along the tube.
  • fins provided inside tubular thermal exchangers are also disclosed in DE102004027208A1. According to this patent, fins are arranged internally in order to increase the temperature of the tube heat exchanger and prevent the condensation of water steam that is comprised in exhaust gases deriving from combustion processes, delaying the formation of acidic condensates. In thsi way it is possible to use materials that are less resistant to corrosion and and less expensive. In the claims solution, gas arriving from the combustion process reaches the tubular heat exchanger on the external surface, with a perpendicular direction with respect to the axis of the tube exchanger.
  • h is the gas-wall convective heat transfer coefficient
  • D the diametre of the tube
  • k the internal thermal conductivity of the tube
  • the Reynolds number Re and the Prandtl number Pr are given by:
  • p , ⁇ , v and c p are respectively the fluid density, dynamic viscosity, kinematic viscosity, specific heat at constant gas pressure.
  • the fluid speed u together with the cross section of the tube and with its density, defines the gas mass flow within the solar tube.
  • Equations (1 ), (2) and (3) arevalid for both gas and liquid; between these two possibilities, the option of considering a gas involves a heat transfer coefficient lower of about one order of magnitude.
  • the thermal energy reaching the solar tube and exchanged with the heat-carrying fluid can be represented by the equation:
  • Q jrr is the thermal power reached by the external surface of the tube
  • q irr is the specific thermal flow reached by the external surface of the tube and deriving from the solar irradiation amplified by the amplification ratio of the solar mirrors;
  • S is the irradiated external surface of the tube
  • S INT is the internal surface of the tube in contact with gas
  • T - ⁇ ⁇ is the difference of temperature between the internal wall of the solar tube (lapped by the fluid) and the heat-carrying fluid.
  • Equation (4) The term on the right of the equation (4) is constant and depends only by the exposed surface (external diameter of the solar tube and by the concentration ratio of sun light achieved by the concentrating mirrors and by the insulation features of the site) thus, the equation (4) can be used in the form:
  • T M T P + QIRR (6)
  • T M tends to increase in turn.
  • T FL tends to increase also more and more the fluid proceeds inside solar tube, thus obtaining T M getting bigger in an axial direction.
  • the present invention aims at solving the problems relating to circumferential and axial temperature gradients occurring inside the solar tube by means of the introduction of protruding elements (fins, grooves, inserts, all extending radially on the side of the heat-carrying fluid) on the irradiated portion of the surface, on the internal side of the tube.
  • protruding elements fins, grooves, inserts, all extending radially on the side of the heat-carrying fluid
  • the present invention takes part also in connection with the solution of the problem of mechanical sealing between glass tube (or another transparent material for the direct solar radiation) and the solar tube and with the protection of the integrity of surface treatments realised on the solar tube external surface.
  • thermal resistance requires for increasing the product inl intervening on h and Sj n t, whereas reducing the conductive thermal resistance requires a lowering of the thickness and/or an increase of the section for the passage of thermal energy (in the conductive thermal flow direction).
  • protruding elements fins, grooves, inserts, all extending radially on the side of the heat-carrying fluid
  • changing the thickness of the tube in a circumferential direction for the conductive side corresponds locally an increase of the conductive thermal flow in a circumferential (and axial) direction and, therefore, a homogenization of the temperature circumferential thermal gradients.
  • the purpose of the present invention is therefore that of realising a receiving tube of a concentrating solar plant allowing for overcoming the limits of the solutions of the prior art and for obtaining the previously described technical results.
  • said receiving tube can be manufactured with substantially low costs, as far as both production costs and managing costs is concerned.
  • Not least aim of the invention is that of realising a receiving tube of a concentrating solar plant that is substantially simple safe and reliable.
  • a tubular heat exchanger between a source of radiant heat located externally with respect to said tubular heat exchanger and a heat-carrying fluid flowing inside the exchanger, the radiant heat coming from said source being concentrated on a longitudinal portion of the external surface of said tubular heat exchanger, characterised in that it comprises means for reducing the temperature gradient along the cross section of the walls of the tubular heat exchanger.
  • said means for reducing the temperature gradient along the cross section of the walls of the tubular heat exchanger comprise a plurality of protruding or recessive elements with respect to the internal surface of the tubular heat exchanger, positioned mainly in correspondence of said longitudinal portion of the external surface of the tubular heat exchanger on which the radiant heat coming from said source is concentrated.
  • said protruding or recessive elements are positioned along the cylinder generatrixes of the tubular heat exchanger, or are positioned along curves that do not follow the cylinder generatrixes of the tubular heat exchanger.
  • the number and/or the surface of said protruding or recessive elements change in a circumferential and axial direction.
  • the shape of said protruding or recessive elements can change in a circumferential and axial direction.
  • said means for reducing the temperature gradient along the cross section of the walls of the tubular heat exchanger comprise a thickness of the walls changing in a circumferential direction, between a minimum value in correspondence of said longitudinal portion of the external surface of the tubular heat exchanger on which the radiant heat coming from said source is concentrated, and a maximum value in correspondence of the longitudinal portion of the external surface of the tubular heat exchanger opposed to that on which the radiant heat coming from said source is concentrated.
  • FIG. 1 shows a schematic view of a portion of a concentrating parabolic solar plant
  • FIG. 2 shows a schematic section view of a solar tube, and represents the portion of the cylindric surface of said tube reached by the concentrated irradiation;
  • FIG. 3 shows a schematic section view of a solar tube, and represents the genesis of circumferential temperature gradients
  • FIG. 4 shows a perspective view of a portion of solar tube according to a first embodiment of the present invention
  • FIG. 5 shows a perspective view of a portion of solar tube according to a second embodiment of the present invention
  • FIG. 6 shows a perspective view of a portion of solar tube according to a third embodiment of the present invention.
  • FIG. 7 shows a portion of solar tube according to a fourth embodiment of the present invention.
  • FIG. 8 shows a portion of solar tube according to a fifth embodiment of the present invention.
  • FIG. 9 shows a diagram of the temperature distribution over the solar tube, having a set thickness and irradiation of the emisurface, as a function of the angleon the circumference, for a heat-carrying fluid with a convective heat transfer coefficient of 55 W/m 2o C and a fluid temperature of 290 °C;
  • FIG. 10a and 10b show the distribution of the thermal zones over the circumferential section of two solar tubes according to the present invention, respectively having equispaced fins over all the circumference or in correspondence of a portion thereof, for a heat-carrying fluid having a heat transfer coefficient of 55W/m 2 °C and a fluid temperature of 290 °C;
  • FIG. 11 shows the trends of the maximum, mean and minimum temperature of the solar tube for changes of the circumferential disposition of fins in a solar tube according to the present invention, having fins equispaced, for a heat-carrying fluid having a heat transfer coefficient of 55W/m 2 °C;
  • FIG. 12a and 12b show the distribution of the thermal zones over the circumferential section of two solar tubes according to the present invention, respectively over a tube having constant thickness and over a tube having a changing thickness along its circumference, for a heat- carrying fluid having a heat transfer coefficient of 55W/m 2 °C and a fluid temperature of 290 °C;
  • FIG. 13a and 13b show the distribution of the thermal zones over the circumferential section of two solar tubes according to the present invention, with the section changing in the same way around the circumference, respectively with equispaced fins over all the circumference or in correspondence of a portion thereof, for a heat- carrying fluid having a heat transfer coefficient of 55W/m 2 °C and a fluid temperature of 290 °C;
  • FIG. 14 shows on an overall diagram the results of the test performed for a heat-carrying fluid having a heat transfer coefficient of 55W/m 2 °C, the abscissa indicating each tested configuration, changing number, height and disposition of fins and the ordinate showing the corresponding maximum, minimum and mean temperature values;
  • FIG. 15 shows on a diagram the results of the test performed for a heat-carrying fluid having a heat transfer coefficient of 520 W/m 2 °C, the abscissa indicating each tested configuration, changing the number and height of fins (equispaced between one another) and the ordinate showing the corresponding maximum, minimum and mean temperature values;
  • FIG. 16 shows on a diagram the results of the test performed for a heat-carrying fluid having a heat transfer coefficient of 520 W/m 2 °C, the abscissa indicating each tested configuration, keeping fixed the features of the fins and changing their number and position inside the tube and the ordinate showing the corresponding maximum, minimum and mean temperature values;
  • FIG. 17 shows on a diagram the results of the test performed for a heat-carrying fluid having a heat transfer coefficient of 520 W/m 2 °C, abscissa indicating each tested configuration, keeping the features of the fins fixed and changing the position of the zone of the tube having a higher thickness, and the ordinate showing the corresponding maximum, minimum and mean temperature values.
  • FIG 1 it is schematically shown a portion of a concentrating parabolic solar plant, in which two solar tubes 1 are represented and a plurality of parabolic mirrors 2, and the solar rays S deviated by parabolic mirrors 2 and concentrated over the solar tubes 1.
  • Figure 2 shows a schematic section view of a solar tube 1 , and indicates with ⁇ the angle subtending the cylindrical surface portion of said tube reached by the concentrated irradiation (schematised with the arrows indicated with P v ).
  • a solar tube according to a first embodiment of the invention is indicated with the reference numeral 10, and is provided with a plurality of fins 1 in it, arranged in correspondence of the portion 12 of the external surface of the tube irradiated by the solar radiation concentrated by the parabolic mirrors, equispaced between each other in a circumferential direction and positioned along the Irngth of the solar tube.
  • the presence of fins causes a lowering of the convective thermal resistance in the irradiated area, with advantages as far as it concerns the temperature of the tube.
  • the presence of fins in a portion of solar tube allows for locally lowering the thermal resistance of the wall of the tube, thus locally promoting the transit of the thermal flow with a lowering of the circumferential thermal gradients and of temperature.
  • this second embodiment produces a mixing of the heat-carrying fluid reducing the thermal stratification and also an intensification of the convective heat transfer coefficient on the side of the heat-carrying fluid.
  • fins 21 are positioned in a non linear way inside the tube 20, in correspondence of the irradiated portion 22. Fins, therefore, can be realised by following any curve belonging to the internal cylindrical surface of the tube.
  • Figure 6 shows a portion of a solar tube according to a third embodiment of the present invention
  • the change of thickness of the tube in a circumferential direction realises in the same direction a change in the conductive thermal resistance (a lowering of the thickness increase) with advantage on the reduction of circumferential thermal gradients.
  • the embodiment shown in figure 7 shows the surface of the cylinder representing the internal surface 33 of the tube 30 eccentric with respect to the external (cylindrical) surface 34, in order to define a lower thickness of the wall of the tube 30 in correspondence of the irradiated area 32.
  • the changes in thickness can be obviously realised also by modifying the external surface 34 of the solar tube 30.
  • Cases shown in figures 4-8 can also be provided with fins changing their thickness in the direction of the radius and along their directrixes (straight or having any shape).
  • the portions of solar tube reported can be repeated to reproduce the overall length of the solar tube or spaced out or alternated (portions with straight fins followed by portions with fins following any curve).
  • Eurther embodiments of the present invention are represented by cross section of the heat-carrying fluid according to any other shape, for example with cross sections realised by means of eccentric cylindrical holes partially intersecating or elliptical cross sections or any other shape realising changes in the conductive thermal resistance around the circumferential direction.
  • the section of the tube can also be variable along the axis of the tube thus realising, for example, frustoconical holes.
  • Figure 9 shows a diagram of the temperature distribution over the solar tube, having a set thickness and irradiation on the emisurface, in a circumferential direction, for a heat-carrying fluid having a convective heat transfer coefficient of 55 W/m 2o C and a fluid temperature of 290 °C.
  • the upper curve makes reference to the temperature distribution without fins, the lower one to the presenceof fins with a set thickness, height and angular frequence.
  • the presence of fins concentrate in a restricted angular sector makes the temperature trend approximatively constant around the circumferential anglr. It is also evident the advantage of the fins on the decreasing temperature mean value of the tube.
  • Figures 10a and 10b show the distribution of the thermal zones over the circumferential section of two solar tubes according to the present invention, respectively having fins equispaced over all the circumference or only over a portion of the circumference, as shown in the figure, for a heat-carrying fluid having a heat transfer coefficient of 55W/m 2 °C and a fluid temperature of 290 °C.
  • Figures 10a and 10b show therefore the thermal level on the thickness of the tube.
  • the minimum temperature is of 330°C
  • the maximum of 505°C the temperature intervals in the thermal levels are 9, equispaced. All the geometric parametres of the tube and irradiation conditions on the emisurface are definite for calculation.
  • the minimum temperature is of 378°C, the maximum of 440°C, the temperature intervals in the thermal levels are 9, equispaced.
  • the figure makes also evident the beneficial effect of concentrating the fins on the side of the irradiated surface.
  • it is outlined the reduction of the temperature mean value of the solar tube and the reduction of the circumferential thermal gradients.
  • the solutions shown for example in figures 10a and 10b refer to fins arranged in the axial direction of the solar tube.
  • Figure 1 1 shows the trends of the maximum, mean and minimum temperature of the solar tube obtained by introducing the same number of fins differently spaced over angular sectors.
  • the case indicated with “1 " on the abscissa corresponds to an angular distribution over all the circumference; the following cases ("2", “3", “4", 7) refer to a reduction of the angular sector.
  • Data concerning the boundary conditions are those of figures 10a and 10b, for a set geometry of the tube and fins.
  • Figures 12a and 12b show the temperature distribution obtained for a tube having constant thickness (12a) and for a tube having variable thickness (12b) around the circumference.
  • the thermal level over the thickness of the tube of figure 1 a shows a minimum temperature of 551 °C and a maximum temperature of 826°C, the temperature intervals in the thermal levels are 9, equispaced.
  • the thermal level over the thickness of the tube shows a minimum temperature of 646°C; a maximum of 728°C, the temperature intervals in the thermal levels are 9, equispaced.
  • the minimum thickness of the tube is the same as for figure 10a and 10b due to needs of resistance to the internal pressure. The advamtages in terms of reduction of the circumferential gradients are evident.
  • Figures 13a and 13b show the distribution of the thermal zones over the circumferential section of two solar tubes according to the present invention, fora tube with eccentric hole, the size of the cross section of the heat-carrying fluid being the same in the two cases, with the same number of fins, respectively equispaced over all the circumference (figure 13a) or over part of the circumference (figure 13b).
  • the thermal boundary conditions are those of figures 10a and 10b.
  • the minimum thickness of the tube is that of figures 10a, 10b, defined by the need of resistance to the set internal pressure of the heat-carrying fluid.
  • therlam level presents a minimum temperature of 366°C and a maximum of 460°C, the temperature intervals in the thermal levels are 9, equispaced.
  • the minimum temperature is of 384°C and the maximum of 434X, the temperature intervals in the thermal levels are 9, equispaced.
  • Figure 14 shows the results of the analysis of sensitivity made on the data of table 1.
  • the convective heat transfer coefficient on the side of the heat-carrying fluid is of 55W/m 2 °C with the heat-carrying fluid at 290°C.
  • Figure 14 presents a synthesis of all the cases.
  • Eash segment 1-2, 2-3, 3-4, ... 30-31 is comprised of 12 points reporting the dituation from 230° to 90° angular.
  • the ordinate reports the temperature of the fins.
  • the lower curves represent the minimum temperature of the tube, the upper curves represent the maximum temperature of the tube and the intermediate thin curves reppresent the mean temperature of the tube (in each interval 1-2, 2-3, 3-4, ...): values are referred to the disposition of the same number of fins as a function of the angle.
  • the intermediate thick curves represent the average temperature calculated on the base of an analytical formulation.
  • the increase in the number of fins reduces the average temperature of the tube. For example from case 1 (8 fins) to case 5 (24 fins) the average temperature passes from 580°C to 480°C.
  • the increase of the length of the fins gives its contribution in a selective way (the temperature reduction is much more sensible passing from 5mm (cases 1-2-3-4-5) ro 10mm (cases 6-7-8-9- 0) than from 10mm to 15mm (cases 11-12-13-14-15).
  • Figure 15 shows the results due to the presence of fins in a case with a fluid having high heat transfer coefficient (520 W/m 2 °C).
  • a fluid having high heat transfer coefficient 520 W/m 2 °C.
  • maximum temperature upper curve
  • minimum temperature lower curve
  • average temperature intermediate upper curve
  • intermediate lower curve average temperature calculated in analytical form
  • the fourth section refers to a case with 40 fins of 2mm height. From the study it can be seen that: a so high heat transfer coefficient implies temperature of the cold wall (non radiated area) closet o the fluid temperature; the maximum temperature passes from 370°C in absence of fins down to a temperature of 330°C obtained using 40 fins 6mm long and
  • Figure 16 introduces the further possibilita of arranging the fins concentrating them in an angular sector.
  • the three sections of the figure refer to the cases of 12, 24 and 40 fins.
  • For each of these cases 12 configurations were studied with as many distribution angular intervals of the fins themselves: from the right to the left passing from 310° to 90° with an interspace of 20°.
  • the convective heat transfer coefficient heat-carrying fluid wall is of 520 W/m 2o C.
  • the height and thickness of the fins are of 5 mm and 2 mm respectively.
  • the efficacy of the proposed solutions can be verified.
  • the maximum temperature passes from 370°C without fins down to the temperature of 328°C obtained using 24 fins 5mm long and 2mm thick, distributed in an arc of 150°, thus reducing the temperature gradient of about 60 %.
  • the temperature of the cold wall (non radiated zone) is close to the fluid temperature (290°C).
  • the maximum temperature passes from 370°C in absence of fins down to the temperature of 323°C obtained using 24 fins 5mm long distributed over an arc of 150° (the minimum value in figure 11 , right section) thus reducing the temperature gradient of 70 %.
  • FIG 17 it is shown the situation observed with an eccentric hole (variable thickness of the tube along the circumferential direction), for a set number of fins (24), with a fin distribution angle varying from 310° to 130°.
  • the figure shows three sections representing three different construction solution all providing for an eccentric hole in the solar tube: on the left with a minimum thickness on the side of the solar irradiation, on the right with a minimum thickness on the side of the non radiated surface, on the center with a constant thickness (no hole eccentricity).
  • the temperature of the cold wall (non radiated zone) is close to the fluid temperature (290°C); the maximum temperature passes from 370°C without fins down to the temperature of 323°C obtained using 24 fins 5mm long and distributed over an arc of 150° (minimum value of figure 12, right section) thus reducing the temperature gradient of 70%.
  • table 1 reports the variations on the inner diameter of the solar tube (ADEXT), for the two situations condsidered, with reference to convective heat transfer coefficient between heat-carrying fluid and wall and with a linear thermal extension coefficient a of 12e-6 m/°C. in case of a high heat transfer coefficient (520W/m 2 K), the presence of fins reduces the deformations of 10%, whereas for a low thermal exchange coefficient (55W/m 2 K) the contribution to the reduction of the deformation of the section is much more sensible (about 50% in the presence of fins, compared to the case without fins).
  • ADXT the variations on the inner diameter of the solar tube
  • the proposed solution can be applied to all the tubes used as heat exchangers between an external source of heat non homogeneously distributed around the tube and a fluid flowing inside the tube.

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  • Sustainable Development (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geometry (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
  • Heat Treatment Of Water, Waste Water Or Sewage (AREA)
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Abstract

L'invention concerne un échangeur de chaleur tubulaire entre une source de chaleur rayonnante placée à l'extérieur de l'échangeur de chaleur tubulaire et un fluide caloporteur circulant à l'intérieur de l'échangeur, la chaleur rayonnante issue de la source étant concentrée sur une partie longitudinale de la surface externe de l'échangeur de chaleur tubulaire, comprenant des moyens de réduction du gradient de température le long de la section transversale des parois de l'échangeur de chaleur thermique.
PCT/IT2010/000441 2009-11-03 2010-11-03 Échangeur de chaleur tubulaire, plus particulièrement tube récepteur d'une centrale solaire à concentration WO2011055401A2 (fr)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US13/505,689 US20120312294A1 (en) 2009-11-03 2010-11-03 Tubular heat exchanger, in particular receiving tube of a concentrating solar plant
CN2010800499700A CN102741645A (zh) 2009-11-03 2010-11-03 管状热交换器、特别是聚集式太阳能电站的接收管
EP10790684A EP2496904A2 (fr) 2009-11-03 2010-11-03 Échangeur de chaleur tubulaire, plus particulièrement tube récepteur d'une centrale solaire à concentration
IL219501A IL219501A0 (en) 2009-11-03 2012-04-30 Tubular heat exchanger, in particular receiving tube of a concentrating solar plant

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITRM2009A000556 2009-11-03
ITRM2009A000556A IT1399246B1 (it) 2009-11-03 2009-11-03 Scambiatore di calore tubolare, in particolare tubo ricevitore per un impianto solare a concentrazione.

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WO2011055401A2 true WO2011055401A2 (fr) 2011-05-12
WO2011055401A3 WO2011055401A3 (fr) 2011-06-30
WO2011055401A8 WO2011055401A8 (fr) 2011-08-18

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US (1) US20120312294A1 (fr)
EP (1) EP2496904A2 (fr)
CN (1) CN102741645A (fr)
IL (1) IL219501A0 (fr)
IT (1) IT1399246B1 (fr)
WO (1) WO2011055401A2 (fr)

Cited By (4)

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Publication number Priority date Publication date Assignee Title
WO2013144406A1 (fr) * 2012-03-30 2013-10-03 Acs Servicios, Comunicaciones Y Energía S.L. Capteur linéaire d'énergie solaire et collecteur
WO2013168074A1 (fr) 2012-05-11 2013-11-14 Eni S.P.A. Installation thermodynamique solaire à concentration
EP2827079A1 (fr) 2013-07-19 2015-01-21 Commissariat A L'energie Atomique Et Aux Energies Alternatives Corps d'absorbeur solaire pour un système de concentration d'énergie solaire et procédé de fabrication d'un corps d'absorption solaire
CN112033183A (zh) * 2020-08-31 2020-12-04 安徽诚铭热能技术有限公司 一种管式辐射换热器

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US20140209070A1 (en) * 2013-01-25 2014-07-31 Woodward, Inc. Heat Exchange in a Vehicle Engine System
US10422552B2 (en) * 2015-12-24 2019-09-24 Alliance For Sustainable Energy, Llc Receivers for concentrating solar power generation

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US5409675A (en) 1994-04-22 1995-04-25 Narayanan; Swami Hydrocarbon pyrolysis reactor with reduced pressure drop and increased olefin yield and selectivity
EP0677715A1 (fr) 1994-04-14 1995-10-18 Behr GmbH & Co. Exchangeur de chaleur pour le refroidissement du gaz d'échappement d'un moteur de véhicule automobile
DE19540683A1 (de) 1995-11-01 1997-05-07 Behr Gmbh & Co Wärmeüberträger zum Kühlen von Abgas
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DE19654367A1 (de) 1996-12-24 1998-06-25 Behr Gmbh & Co Verfahren zum Anbringen von Laschen und/oder Vorsprüngen an einem Feinblech und Feinblech mit Laschen und/oder Vorrichtungen sowie Rechteckrohr aus Feinblechen
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EP0677715A1 (fr) 1994-04-14 1995-10-18 Behr GmbH & Co. Exchangeur de chaleur pour le refroidissement du gaz d'échappement d'un moteur de véhicule automobile
US5409675A (en) 1994-04-22 1995-04-25 Narayanan; Swami Hydrocarbon pyrolysis reactor with reduced pressure drop and increased olefin yield and selectivity
US5655599A (en) 1995-06-21 1997-08-12 Gas Research Institute Radiant tubes having internal fins
DE19540683A1 (de) 1995-11-01 1997-05-07 Behr Gmbh & Co Wärmeüberträger zum Kühlen von Abgas
DE19654367A1 (de) 1996-12-24 1998-06-25 Behr Gmbh & Co Verfahren zum Anbringen von Laschen und/oder Vorsprüngen an einem Feinblech und Feinblech mit Laschen und/oder Vorrichtungen sowie Rechteckrohr aus Feinblechen
DE19654368A1 (de) 1996-12-24 1998-06-25 Behr Gmbh & Co Wärmeübertrager, insbesondere Abgaswärmeübertrager
EP1061319A1 (fr) 1999-06-18 2000-12-20 Valeo Engine Cooling AB Tube transporteur de fluides et refroidisseur de véhicule comportant ledit tube
DE10227084A1 (de) 2002-06-18 2004-01-08 Tesa Ag Verfahren zur Herstellung einer Großrolle Etikettenmaterial sowie Verfahren zur Herstellung von Etiketten aus der Großrolle
DE102004027208A1 (de) 2004-06-03 2005-12-22 Robert Bosch Gmbh Wärmeübertrager
DE102005029321A1 (de) 2005-06-24 2006-12-28 Behr Gmbh & Co. Kg Wärmeübertrager
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013144406A1 (fr) * 2012-03-30 2013-10-03 Acs Servicios, Comunicaciones Y Energía S.L. Capteur linéaire d'énergie solaire et collecteur
WO2013168074A1 (fr) 2012-05-11 2013-11-14 Eni S.P.A. Installation thermodynamique solaire à concentration
EP2827079A1 (fr) 2013-07-19 2015-01-21 Commissariat A L'energie Atomique Et Aux Energies Alternatives Corps d'absorbeur solaire pour un système de concentration d'énergie solaire et procédé de fabrication d'un corps d'absorption solaire
US10533775B2 (en) 2013-07-19 2020-01-14 Commissariat à l'Energie Atomique et aux Energies Alternatives Solar absorber body for a concentrating solar power system and a method for manufacturing a solar absorber body
CN112033183A (zh) * 2020-08-31 2020-12-04 安徽诚铭热能技术有限公司 一种管式辐射换热器

Also Published As

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US20120312294A1 (en) 2012-12-13
WO2011055401A8 (fr) 2011-08-18
EP2496904A2 (fr) 2012-09-12
IL219501A0 (en) 2012-06-28
WO2011055401A3 (fr) 2011-06-30
ITRM20090556A1 (it) 2011-05-04
CN102741645A (zh) 2012-10-17
IT1399246B1 (it) 2013-04-11

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