Solar heat absorbing system

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Drawing sheet — no readable text.

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SOLAR HEAT ABSORBING SYSTEM SUMMARY OF THE INVENTION

The present application is directed to the recovery of solar heat in a moved system which provides for the use Thus, it may be considered a principal object of the of heat absorbing black body particles in a gaseous present invention to provide a solar heat collecting sys Stream. . . tem providing for an air or other gas stream entrain More particularly, the present application is directed ment of black body heat absorbing particles in a solar to a solar heating system and an operation where the heating zone and the separation of the heated particles heat absorbing black body particles are separated from from the lesser heated fluid medium for transfer to a the carrying stream prior to their being transferred to heat exchange-heat recovery zone. a heat exchange zone so as to reduce the volume of ma O It is also an object of the present invention to provide terial being handled in such zone and resulting cooled for the remixing of the particles and the carrying gas particles are subsequently recombined with the carry after the particles have been passed through a heat ex change zone such that the particles can be rapidly ing gas ahead of the solar heating zone so as to maintain a continuous operation with a more efficient heat ex transferred back to the solar heating zone to provide an change arrangement. 15 efficient continuously operating system. It is a further object of the present invention to pro

BACKGROUND OF THE INVENTION vide means for aerating the particle rich stream within It is recognized that clear gaseous streams will have the heat exchange zone such that there will be a good low heat absorption and low emissivity characteristics heat transfer relationship and enhanced contact of hot and are not efficient for retaining the infrared heat 20 particles with the heat exchange surfaces within the which can be imparted to a moving fluid stream in a heat exchange Zone. The aerating fluid may comprise solar energy heat recovery system. Although air may a portion of the particle free stream or, if desired, a sep have a heat capacity about equal to many black body arately supplied fluidizing medium may be introduced materials on a BTU/1b basis, it is also realized that the into the heat exchange zone for the aeration and for the entrained black body materials will have the far greater 25 enhanced contact with the heat exchange surfaces. weight in a fluidized stream and will thus absorb much Briefly, the present invention provides an improved more heat. For example, the heat capacity (C) of air method for effecting the recovery of solar heat in a at 100 F. is about 0.25 BTU/lb, at one atmosphere of manner which comprises (a) passing a gaseous carrying pressure, while coke or graphite would have a heat ca 30 stream with entrained black body particles to a heating pacity in the range of about 0.20 to 0.39 BTU/lb. How Zone for exposure to solar radiant energy, (b) passing ever, in an operation where fluidized black particles are said stream with resulting heated particles from said carried in a gas stream through solar heating tubes, the heating zone to a particle separation zone and effecting weight of the particulates may be in a range of from a separation to provide a particle stream and a primar about 3 pounds to 20 pounds or more per cubic foot, 35 ily particle free stream, (c) passing the particle stream depending upon the weight of the particular black body from the latter zone to a heat exchange zone and recov material being used and whether there is a " light ering heat therefrom, (d) subsequently passing the re phase' or "heavy phase' density to the aerated flowing sulting cooled particle stream to a mixing zone and stream, while the weight of the air, or other carrying therein combining it with the particle free stream ob gas, would be negligible. In any event, it will be obvious tained from said separation zone, and (e) then recircu that the heat absorbed by the gaseous portion of the 40 lating the recombined particle containing stream to stream will be negligible as compared to the heat which said heating zone for reexposure to the solar energy. will be absorbed into the particulates. It is not intended to limit the present system to the It has been previously suggested and known to make use of any one gaseous carrying medium although air use of black body particles in heat absorbing tubing sys 45 may well be used to advantage to effect the desired tems for solar heat recovery as well as in a heat absorb type of operation. Also, nitrogen, carbon dioxide or ing liquid stream; however, it is believed novel to pro other suitable, generally inert, gaseous medium may vide a system where there is rapid separation of en well be utilized to effect the entrainment and move trained black body particles from a carrying gas such ment of the black body particles in a fluidized manner that a stream of essentially the higher temperature par 50 from one zone or section of the system to the other. ticles only can be used in a heat exchanger means to With respect to black body particles, various types of provide a more efficient solar heat recovery system. materials may well be utilized in the present system, as With a heat exchange means to handle only the re for example carbonaceous materials, which may com duced volumetric flow of the black body particulates, prise carbon black, channel black, oil furnace black, there should be a reduced capacity heat exchanger, as 55 lamp black and the like, or even crushed natural mate compared to means for handling a total stream, and an rials such as coal, coke, charcoal, etc. There also may accompanying lower first cost in such equipment. be utilized pyropolymeric conductive organic Typically, water or other liquids have been used to refractory oxide particles which are formed by the de collect heat in the solar "windows' or tubing and the position of a pyropolymer on the surface of a base ma water then passed to suitable storage or heat exchange 60 terial at a relatively high temperature in the range of zones such that useful heat may be obtained from the 400 as to 750 C. For example, organic substances such aliphatic hydrocarbons, cycloaliphatic hydrocar solar energy. However, in northern climates with both daytime and night-time freezing conditions, it can be of bons, aromatic hydrocarbons, aliphatic halogen deriva particular advantage to have a heat collection system tives, aliphatic oxygen derivatives, carbohydrates, etc., free of any problems with water or other liquids to pre 65 may be pyrolyzed over the surface of a subdivided re clude freezing of outside valves and lines. A gaseous fractory oxide material. The refractory oxide may be system is also of advantage in permitting the use of alumina in various forms, such as gamma-alumina and blowers instead of pumps and their attendant problems. silica-alumina; however, various other refractory ox

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ides may be used. This type of material is described in which permit solar radiation to reheat the black body U.S. Pat. No. 3,651,386, issued Mar. 21, 1972. Certain particles being entrained in the combined stream. of the carbonized refractory oxide materials may be of In a modified form of system, as hereinbefore briefly advantage over other black body materials by reason of noted, there may be the use of a part of the carrying gas greater surface area for exposure to the solar radia to effect aeration within the heat exchange zone such tions. that the heated black body particles can effect a turbu Preferably, the black body particles will be non lent improved heat relationship with heat transfer pas packing and of a relatively uniform size such that the sageway provided in the particular heat exchange appa material may be readily entrained and separated from ratuS.

the carrying fluid stream. It is also of advantage to have 10 DESCRIPTION OF THE DRAWING particulates that will move in a descending gravity flow from a separator means as well as through the heat ex The present invention may be further described and change zone. Actually, it may be of advantage to pro explained by reference to the accompanying diagram vide specially prepared black body particles which are 5 matic drawing and the following description thereof. of a generally spherical nature such that they will flow In the present drawing, there is indicated diagram readily in a non-packing manner. In addition to the matically the utilization of a plurality of tubular mem aforementioned carbonaceous materials it may be of trained bers 1 to provide a solar heating section where en advantage to utilizc fine, small spherical beads from black body particles may be exposed to solar black body particles, where the particles are formed of O the particles.permit energy and the absorption of infrared heat into dark colored glass or from various of the resin or plastic encompassed by parabolic1 are

The tubes also indicated as being reflector members 2 such types of material. that there may be a concentration of radiant heat onto Inasmuch as the infrared radiation from the solar en each of the tubes and into the particulates being ergy in the heating zone will be primarily absorbed into passed the black body particles and very little heat retained by 25 of a fluidtherethrough.

distributor

There is further indicated the use header 3 receiving entrained black the generally transparent carrying stream, whether it be body particles from line 4 such that there may be a suit air, or other fluid medium, it is generally of advantage able distribution of the particles and the carrying to effect the separation of the carrying fluid from the black body particles soon after the heating stream is the collection of heated streams, thereofisconduits stream into and through the plurality 1. For indicated the passed from the solar zone such as to minimize heat 30 utilization of a header means 5 along the other ends of transfer between the black body particles and the car the tubular members 1 and positioned to discharge a rying medium. The type of separation zone may vary resulting elevated temperature particle stream by way with the nature of the entrained particles; however, of line 6 into a particle separator means 7 whereby the typically the combined stream may well be introduced higher temperature particulates can be separated from into one or more stages of a centrifugal form of particle 35 the lower temperature gaseous carrying medium. separator such that a substantially particle free gaseous As shown by the drawing, the carrying medium will stream will be discharged from the upper portion of the be withdrawn from the upper portion of the separator separator and separated particles withdrawn from the 7 by way of line 8 and blower means 9 while separated lower portion of the separator. Electrostatic precipita heated particles will fall to the lower end of the separa tor means may also be used; however, such devices are 40 tor and be discharged by way of transfer conduit 10 and quite costly as compared to mechanical centrifugal sep valve means 11 into the upper portion of the heat ex arator means and the efficiency of separation from the change 12. Preferably, where the heated particles can latter should be quite adequate for the present system. flow by gravity, there will be the continuous downward In any event, the particle rich stream from the lower movement of the particles through the height of the portion of the separator means will be discharged into 45 heat exchange means 12 to thus flow around and be in a heat exchange zone such that the heat of the particles indirect heat exchange relationship with an internal can be imparted to a suitable heat exchange medium coil 13 or other suitable fluid carrying passageway which will then pass recovered heat along to a storage means. The latter is indicated diagrammatically as ac zone or directly to a zone of heat usage. commodating a fluid stream which enters the heat ex In a simplified form of system, there may be down 50 changer by way of inlet means 14 and is discharged as ward gravity flow of the separated heat particles a heated fluid stream at 15. The resulting substantially through the heat exchange zone such that there is di cooled black body particles are continuously dis rect contact between the particles and the multiple charged at the lower end of the heat exchanger by way heat exchange surfaces provided in the particular heat 55 of an outlet line 16 and valve means 17 to enter a mix exchange apparatus. The resulting cooled particles may ing section 20 and the transfer conduit 4 for recycle also be permitted to flow by gravity from the lower por back to the solar heating tubes 1. tion of the heat exchange zone to be passed to a suit In a preferred operation as shown by the drawing, the able mixing zone for re-entrainment with the carrying particle carrying air or other gas stream will be trans fluid. Actually, there may be the direct intermixing be 60 fered from the blower means 9 through a conduit tween the separated carrying gas and the cooled parti means 18 and a control valve means 19 to the mixing cles at a zone directly below the heat exchange means zone 20 below conduit 16 whereby there may be the by blowing the substantially particle-free carrying resulting re-entrainment of the particles with the carry stream to the standpipe or outlet means below the heat ing fluid and the transfer of the mixture by way of con exchanger means such that there is a direct intermixing 65 duit 4 to the solar heating zone. of particles and the carrying medium. The mixture is Normally there can be the mixing and the re then recycled back to the solar heating zone to pass entrainment of the particles from line 16 into line 4 through the various passageways or conduit means through the use of a typical Tee or a Y arrangement at

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S 6 20; however, where deemed suitable, special venturi a. passing a gaseous carrying stream with entrained type mixing means or eductor means may well be uti black body particles to a heating zone for exposure lized to effect the desired intermixing of the separated to solar radiant energy, particles with the carrying fluid such that a well mixed, b. passing said stream with resulting heated particles uniform entrainment of particles will result in the com 5 from said heating zone to a particle separation zone bined stream carrying to header means 3 and the solar and effecting a separation to provide a particle heating tubes 1. stream and a primarily particle free stream, There is also indicated in the drawing that there may c. passing the particle stream from the latter zone to be the provision of a conduit 21 with valve means 22, a heat exchange zone and recovering heat there branching from line 18 that will provide for the intro O from, duction of the controlled amount of aeration fluid into d. subsequently passing the resulting cooled particle the lower end of the heat exchange section 12. In con stream to a mixing zone and therein combining it nection with dry particulates moving in a descending with the particle free stream obtained from said gravity flow, it may be of particular advantage to pro separation Zone, and vide for some movement and turbulence of particles 5 e. then recirculating the recombined particle con within the interior of the heat exchanger 12 such that taining stream to said heating zone for reexposure there is enhanced contact between heated particles and to the solar energy.

the coil 13 (or whatever type of heat exchange surfaces 2. The method of claim 1 further characterized in may be utilized within heat exchanger means 12). Gen that said gaseous carrying stream is air. erally, it will be of advantage to use a portion of the 20 3. The method of claim 1 further characterized in particle carrying gas for the aeration operation; how that said particle separation zone is of a centrifugal ever, where deemed preferable in any particular opera type permitting the centrifugal separation of the heated tion, there may be the use of the separate introduction particles from the carrying stream. of aerating fluid by way of line 23 and valve 24 into line 4. The method of claim 1 further characterized in 21 and the lower portion of heat exchanger 12. For ex 25 that particles from the particle separation zone are ample, it may be desired to introduce another inert me passed in a descending gravity flow through said heat dium such as nitrogen, carbon dioxide, dry steam, etc., exchange Zone.

in lieu of a particular carrying fluid, for the desired tur 5. The method of claim 4 still further characterized bulent movement within heat exchanger 12. in that an aerating medium is introduced into the lower It is to be understood that the present drawing is dia 30 portion of said heat exchange zone to provide for grammatic and should not be considered limited in any movement and turbulence of particles within such zone way as to the configuration or particular nature of any to enhance contact thereof with heat exchange surfaces one portion of the heating and heat recovery system. therein.

As heretofore noted, the particle separator may be 6. The method of claim 4 still further characterized other than the centrifugal type as indicated in the draw 35 in that a portion of the separated particle free stream ing, and the heat exchange design may comprise any is introduced to said heat exchange zone to effect one of several different forms and need not be limited movement and turbulence of particles in said zone to to a downward flow of particles therethrough. Actually, enhance contact with heat exchange surfaces therein. with a fluidized movement of particles in a gaseous 7. The method of claim 1 further characterized in stream or with particles concentrated in a liquid carry 40 that resulting cooled particles from said heat exchange ing medium in a particle rich stream, there may be the zone are withdrawn by gravity therefrom and pass into upward or lateral flow of particles through a heat ex a standpipe means to be intermixed with the separated change device. particle free stream from said separation zone at a mix In still another aspect, there can be modifications in ing zone maintained below the outlet from said heat ex placement of a blower, or the use of additional blowers, 45 change zone and the resulting intermixed entrained as may be required in any particular system. For exam particles are recycled back to the heating zone for reex ple, in the present drawing there has been merely the posure to the solar radiant energy.

indication of one blower means, following the particle 8. The method claim 1 further characterized in that separator means, to provide for the movement of the said black body particles are of a carbonaceous nature. carrying medium and the particles being entrained 9. The method of claim 1 further characterized in therewith. that said black body particles are of substantially uni I claim as my invention: form size and of a generally spherical form whereby 1. A method for effecting the recovery of solar heat they can move in a :knon-compacting

manner.

which comprises: