FR2478288A1 - METHOD AND INSTALLATION FOR DISCHARGE OF RADIATION, IN PARTICULAR THERMAL ENERGY, BY RADIATION RADIATION IN A SEALED ENCLOSURE - Google Patents

Abstract

Method for removing by radiation an energy, particularly a thermal energy, confined within a sealed housing. A furnace (1) is provided with glazings (4-5) which are positionned in front of a window (3) and which are transparent to an assembly of radiation wavelengthes including those corresponding to the radiations discharging the energy. An insulating door (7) may be either closed for opposing to the radiation passage or opened for freeing the passage.

Description

Method and installation for evacuating radiation, in particular thermal energy, confined in a sealed enclosure.

 The present invention relates to an installation making it possible to evacuate, by radiation, in particular thermal anergy confined in a possibly isolated sealed enclosure.

 It is known that the various forms of energy can transform one into the other, in particular radiant energy, that is to say energy transported by electromagnetic waves. This kind of energy propagates at the speed of light in transparent bodies for the wavelengths which characterize it (light, infrared, etc.) or in a vacuum. It is an orderly, oriented energy, propagating in a straight line, which can be reflected, possibly refracted.

The present invention relates to all cases where an energy, of whatever nature, confined in a sealed enclosure possibly isolated from the outside, can be transformed into radiant energy, either that it is thus transformed spontaneously, or that is susceptible to be induced to do so by any known means. An interesting particular case is that of heat, or thermal energy, confined for example in atmospheres of controlled composition in a sealed oven. Heat is a totally disordered form of energy, not propagating in a vacuum but only, through material bodies, by a transmission from near to close (conduction) or carried by a moving fluid (convection). cooling a thermal oven without it being possible to open the door, which is a common case, we generally wait for it to cool little by little by conduction because its insulation is not perfect, which requires a very long time. The process can be accelerated by various devices, in particular by causing a flow of gas of controlled composition inside the enclosure, which causes evacuation by convection. But the
cooling time generally stays much longer
as long as we would like.

The present invention overcomes this diffi
culture and, for this purpose, relates to a process for exploiting
ter and evacuate in particular confined thermal energy
in a sealed enclosure, characterized in that one operates
this evacuation by radiation and that, preferably
this, we recover this radiation for reuse.

According to the invention this orocédé5t tst also characterized in
what we combine, in association with the enclosure, of a
share at least one glazing which helps ensure its seal
cheeness, which is able to withstand the internal conditions pro
near the enclosure in activity in particular of temperature,
pressure, corrosion and which is transparent for a set
ble wavelengths of radiation including those eva
costing energy, these functions can be assumed by more
sieurs glazings re.laying successively to transmit
radiation evacuating energy, the resistance of each of these glazings then being adapted to internal conditions
specific to the enclosure as they change as evacuation and on the other hand, at least one pa
removable insulating king which is placed opposite the glazing
to prevent the evacuation of energy during the period of confinement and that is withdrawn at the time of the shift.

The invention also relates to an installation for implementing the above method, characterized in that it
comprises in combination an enclosure in which a window is provided, at least one glazing which must be placed against the window in a sealed manner and which is transparent to a set of wavelengths including
those which correspond to radiation evacuating energy and at least one movable insulating wall between a position
active in which it is placed next to the glazing
to oppose the passage of radiation and a position
inactive in which it is moved away from the glazing to free the passage of radiation.

 In a thermal oven, for example, there is a continuous exchange between heat and radiation, between thermal energy and radiant energy, the materials absorbing the radiation and transforming it into heat, then re-emitting radiation, and so on. The method and the installations according to the invention, in this example, break this continuous exchange by activating a set of panels transparent to the radiation produced in the oven when the time for cooling has arrived. The conditions under which the problem presents itself, in particular in the case of ovens with temperatures that are slightly elevated, make it complex, and no valid solution has been imagined in this way until now.

 The invention will be better understood from the detailed description below, made with reference to the accompanying drawing. Of course, the description and the drawing are given only by way of an indicative and nonlimiting example.

 The single figure of the drawing shows schematically, in section, an enclosure according to the invention.

 It is assumed, beforehand, that the energy confined in the sealed enclosure is transformed, at least partially, into radiant energy, either spontaneously or through the intervention of any known means. For example, in the particular case, mentioned above, of a thermal oven, the energy spontaneously transforms into infrared radiation by an emission phenomenon, the distribution of the radiated energy in the various wavelengths d emission taking place as a function of temperature, according to Planck's law for the "black body" or "integral radiator" and according to a particular approximate law for each absorbing body. The higher the temperature, the shorter the emission wavelengths and vice versa. In the oven enclosure, the walls of which are generally made of absorbent refractory materials, the emitted infrared radiation is continuously absorbed and then re-emitted, so that the energy is constantly changing from the calorific form to the radiant form and vice versa.

 According to other characteristics of the invention - the glazing 4-5 and the insulating wall 7 constitute a double door capable of masking and unmasking the window 3; - The interior walls 2a-2b of the enclosure 1 adjacent to that which includes the window 3 are inclined at least partially relative to the mean axis x normal to the plane of this window 3, forming acute angles with it; - The interior walls of the enclosure 2a-2b adjacent to those which includes the window 3 are, at least in part, provided with grooves 12 - the direction of which is parallel to the mean axis normal to the plane of the window 3 ,, - the glazing is made of silica glass; - The installation comprises at least two movable glazing 4 and 5 capable of being individually placed and removed in front of the window 3 in order to be there either together or separately; - The glazing closest to 1 enclosure 4 is applied in a sealed manner against the interior periphery of the window 3; the glazing 4 and 5 are separated by a space 6 in which can be established, by any known means, a vacuum maintaining the first glazing 4 applied against the periphery of the window 3, an elastic seal possibly being placed between this glazing 4 and this circumference.

It is to put an end to the reciprocal exchange of the calorific form in the radiating form and to allow a removal of the radiation by optical transmission that, according to one of the main characteristics of the invention, at least part insulating walls of the enclosure - you are removable and, in the inactive position, unmask transparent glazing for the wavelengths of the radiation to be evacuated. This is then no longer absorbed but transmitted to the outside as it is emitted by the enclosure. The seal is however maintained by this glazing, the material of which is also chosen for withstand the internal conditions specific to the active enclosure, temperature, pressure, corrosive action, etc. When a single material cannot perform all of these functions (which is
often the case), several glazings are used which take turns, separating them successively to assume the functions of sealing and evacuation of the radiation in bands of successive wavelengths, each resisting internal conditions such as they change as and when evacuated.

 In the particular case of a thermal oven, this involves evacuating the thermal energy to cool the oven from a temperature T1 to a temperature T2. At temperature T1, the enclosure radiates in a certain band of wavelengths, and, at temperature T2, lower, in another band of longer wavelengths. For example, for T1 = 7000C (i.e. 973 "K), the emission of infrared radiation takes place between approximately 1.5 y and 10, the maximum radiant energy emitted being around 3y, and for T2 = 200" C (ie 473 "K), l 'emission takes place between approximately 2.5y and 18 y with a maximum around 6.5.

 Referring to the drawing, a diagram is seen in vertical section of an installation according to the invention relating to a particular example of a thermal oven. The enclosure 1 is surrounded by walls such as 2, insulating and more or less absorbent, in one of which is provided a window 3 here provided with two glazing 4 and 5 separated by a space 6, this window 3 being completely closed by a portion 7 of insulating wall for the duration of activity of the enclosure 1 (position shown 'in dotted lines).

 The wall portion 7 is movable around an axis 8.

When it is desired to cool the enclosure 1, it is placed in the erasing position as shown in solid lines. Thus, the windows 4 and 5 are unmasked, which are thus able to play their role of evacuation by optical transmission.

The first glazing 4 is applied in a sealed manner,
The first glazing 4 is applied in a sealed manner, from the inside, by its entire periphery against the frame of the window 3 forming a shoulder 9; it is slidably mounted parallel to its plan. In the example shown, the temperature T1 of the furnace in activity is assumed to be of the order of 1500 C or 1600 C, and the temperature
T2 which we want to achieve is of the order of room temperature, for example 200 C. The first glazing 4 is made of silica glass, a material which begins to soften only above 1700 C, and which is transparent polish the wavelengths ranging from 0.2 to 4.5y approximately. This glazing 4 effectively removes the radiation emitted by the enclosure 1 at 1500 or 1600 until it emits by cooling to 4500/400 ".

 To cool the enclosure 1 below 400, use is made of the second glazing 5 formed. oar exemole. silver chloride or cerargyrite material which withstands temperatures up to 450 "and is transparent for wavelengths from 0.4 to about 15-208. Silver chloride cannot be polished but can be molded in relatively large dimensions; it is not very fragile and relatively inexpensive.This material can dissipate the radiation emitted by the enclosure 1 Until its internal temperature reaches ambient temperature, for example around 200.

 As the silver chloride can evacuate, also, the radiations emitted since the temperature T1, of the order of 1.500, this second glazing 5 can occupy its active position during the evacuation imparted to the first glazing 4 without disturbing the latter. It is applied from the outside by its entire periphery, in a sealed manner, against the shoulder 9 of the window frame 3.

 A vacuum pushes as much as possible or a draft of air in depression is maintained in the insulation space 6, in order to contribute to protect this second glazing 5 against temperature increases which it could not support, and also in order to perfect the sealing of the enclosure 1 by pressing the first glazing 4 against the window frame 3.

 When the internal temperature of the enclosure 1 drops to 450 -400, the barometric depression or the draft of air in depression in the space 6 is eliminated, which helps to release the first glazing 4 from its adhesion to the frame of window 3, and this glazing 4 is made to slide in a sealed and insulating sheath 10 made projecting outside the enclosure until it is entirely outside the outline of the window 3. The second glazing 5 is thus able to play the evacuation role which is assigned to it. It is maintained, by any known means, applied in a sealed manner against the shoulder 9 of the window frame 3, before removing the barometric depression in space 6.

The second glazing 5 can, in this same example, be made of any transparent optical material for an interval of wavelengths including the pass band from 2 y to 13 approximately required to evacuate the emitted radiation from 400 to 20 C, and capable withstand temperatures of the order of at least 400. For example, cadmium sulfide or greenockite Cd S (transparent from 0.5 to 15, resistant up to 900 C), sodium chloride or rock salt Na Cl (0.2 to 16, 800), potassium chloride or Syl Cl K ne (0.2 to 25 y, 750) potassium bromide KBr (0.25 to 35 700), iodide potassium KI (0.4 to 40, 700), cesium bromu re Cs Br (0.2 to 50 y, 620), cesium iodide
Cs I (0.25 to 70.600); if need be, thallium bromoiodide or KRS-5, TlBr, Tl I, which is transmitted from 0.5 to 40 but whose melting point is very little above 400 (414.5); ; or again, the barium fluoride Ba F2, whose melting point is high (1280) but which only transmits from 0.15 to 12, which makes it possible to descend to around 50 C.

 These various materials, the list of which is by no means exhaustive, are in the same case as the silver chloride cited as an example (not preferential) in the description above. These are materials which do not withstand the temperature T1 of the order of 1500/1600 fixed in the example described, but whose spectral transmission band, chosen to remove the radiation produced from 400 to 20, also allows the evacuation since 1500/16000. In this case, the second glazing can be kept in its active position during llevacuatioí) imparted to the first glazing, which protects the second against the excessively high temperature of the oven. It is not the same with other materials that can use for the second glazing 5, like the gallium arsenive GaAs (2 to 15 y, 1200), indium phosphide InP (2 to 13ii, 1000 "), sintered glass with zinc sulfide or Irtran -2 (2 to 13 y, 800) ... The transmission band of these materials allows them to efficiently dissipate radiant energy only from about 500 to 400. When they are used, removes the second glazing 5 during the first evacuation phase from 1500/1600 to 400 imparted to the first glazing 4. For example, the second glazing is pivoted about an axis 11 to a clearing position (not shown at the end of the first evacuation phase, the second glazing 5 is returned to the active position and it is kept applied qué sealingly against the shoulder 9 of the window frame 3. When the internal temperature of the enclosure 1 has reached the lowest desired level, we can, if desired, remove the second glazing 5 again, this which has the effect of opening window 3 to the open air.

 As for the material constituting the first glazing unit 4, silica glass, a material of current manufacture even in large dimensions, of relatively low price, resistant, it is optimal for the implementation of the invention in thermal ovens. in certain cases to call upon other materials, for example: magnesium oxide or periclase, Mg 0 also existing in sintered material transmitting from 0,25 to 8,5, resistant up to 2,800 and allowing to evacuate the radiant energy at least in the first phase by cooling the enclosure 1 up to approximately 2000 to 1500; alumina or corundum Al203 (0.2 to 6y, 2000 to 300/250), barium titanate Ba Ti 03, which exists in the form of ceramic (0.5 to 7, 16000 to 250).

When the temperature T1 of the active furnace is of the order of at most 1300, calcium fluoride or fluorite Ca F2 is used (0.13 to 9/10, 1300 to 1500/1000). For a temperature T1 of the order of 1100 at most, cadmium fluoride
Cd F2 (0.2 to 10, 1100 to 100), with then the possibility of using for the second glazing 5 the glass of pentase arsenic lenide As2 Ses (2 to 18, 100 to 20). For a temperature T1 = 950 at most, sodium fluoride or villiaumite NaF (02 to 10, 950 to 100) with the possibility of relaying by arsenic pentaselenide. For a temperature T1 = 850 at most, lithium fluoride Li F (0.2 to 6, 850 to 300/250).

 It is also possible, according to the invention, to use a single material to constitute the transparent evacuating glazing, in all cases where the temperature T1 of the furnace in activity does not reach the softening or transformation temperature of this material and where the transmitted bandwidth includes all the radiations emitted substantially between the temperature T1 and the lowest temperature T2 that we want to reach. All the materials cited, without limitation, in the present description, may be suitable within the limits which are specific to them.

Finally, according to the invention, it is possible to use three or more glazings. In the example described above of the thermal oven with a temperature T1 = 15000 to 1600 and a temperature T2 = 20, it is possible to use successively - a first glazing of silica glass (0.2 to 4.5 *, 1600
at around 400); - a second glazing in germanium oxide glass or
VIR-3 (0.3 to 6 y, 4500 to 300/250), or in sintered glass
magnesium fluoride or Irtran-1 (1 to 74; 13500 to 2500/2000);
- a third glazing in arsenic trisulfide glass (0.6 to 10M ;;
200 to 100), or in amorphous selenium (1 to 25p 2200 to 20), or in
core of a glass sintered with zinc sulfide or Irtran-2 (2 to 138; 8000
to 300/200).

 Optionally, a fourth glazing can be put. in use, for example in arsenic pentaselenide glass (2 to 18, 100 to 20).

 Connections can be facilitated between successive intervals of acceptable temperatures, by cooling externally such or such glazing as the case may be.

The erasure and activation conditions are those which have been described for the combination of two panes.

 In the drawing, the removable insulating wall portion 7, as well as the second transparent glazing 5, have been shown pivoting around horizontal axes 8 and 11, because this arrangement is the most convenient to represent in vertical section. The axes of rotation may preferably be vertical and the removable portion of insulating wall 7 as well as the second transparent glazing 5 may constitute the door itself of the oven, in the form of a double door opening and closing laterally as this is usually the case.

 In order to facilitate the evacuation of the radiation emitted in the enclosure 1, the interior walls such as 2a and 2b which are adjacent with respect to the wall which comprises the window 3, are inclined with respect to the mean axis x normal to this window by forming acute angles with the plane thereof. In this way, the radiation emitted by these walls are, on average, directed more directly towards the window 3. In addition, to further promote the evacuation of radiation and increase the emissive surface, the walls such as 2a and 2b, are , at least in part, with grooves not shown but whose situation is shown in dotted lines at 12, dug in directions as close as possible to that of the average axis x of window 3; and these walls, with their grooves, as well as the wall 2c opposite the window 3, are optionally provided with small reliefs and small hollows or with a granular structure.

 Finally, in order to facilitate the emission of radiant energy as a function of the temperature of the oven, the inside surface of the enclosure 1 is either made up or coated with a substance having properties which are as close as possible to those of the "black body" or "integral radiator".

 According to a characteristic of the invention, the installation comprises a screen capable of opposing, at least partially, the transmission of radiation through the window, this screen being mounted movable between an active position in which it can obscure the radiation and an erased position in which it is inoperative, in order to be able to modulate the discharge of the radiation out of the enclosure.

 The screen, or grid, or any other modulating optical system (not shown in the drawing), may be partially opaque and / or partially reflecting towards the interior of the enclosure 1 for the wavelengths of radiation discharged. This screen (or grid) can be made mobile, for example by sliding in a housing provided in the sheath 10 or in the insulation space 6.

 Thus the screen (or grid) can occupy a variable part of the surface of window 3 and modulate the optical transmission by which the evacuation takes place, either to increase it or to decrease it progressively depending on whether at the start of its movement the screen (or grid) occupies the surface of window 3 or is, on the contrary erased.

 More generally, the optical modulator system is made mobile or variable by any suitable means between an active position and an inactive position in order to optically scale and modulate the discharge of radiant energy.

 As for the movable part 7 of the insulating wall, which is designed to evacuate the radiation during the active phase of the enclosure 1, it can be made of the same materials as the fixed walls 2 of this enclosure 1.

 It can also, according to one of the characteristics of the invention, operate its role of confinement by an optical means of spectral selection opposing the transmission to the outside of radiation in the bandwidths corresponding to the energy emitted, re-emitted or produced in enclosure 1. This optical means of spectral selection can, on the other hand, allow the transmission in the opposite direction, towards enclosure 1, in other bandwidths, of radiation received outside. This is an interesting variant of the invention, because the installation then assumes a function of capstation and confinement when the removable portion 7 of insulating wall closes the window 3 of the enclosure 1 and a discharge function. confined energy when this removable insulating wall 7 is erased.

 In particular, for the exploitation of radiant solar energy, the installation according to this variant of the invention constitutes a thermal oven heated then cooled optically by radiation. The removable insulating wall portion is, for example, made of ordinary glass, suitable for the "greenhouse" effect, possibly coated with a selective reflective treatment in a thin layer of tin or indium oxide.

It can also be made of any transparent optical material between 0.3 and 1.5 P and opposing transmission above about 1.58. The glazing or the evacuating glazing system is one of those which have been described above, with the proviso that they do not constitute an obstacle or a hindrance to the capture of solar radiation whose bandwidth is situated on the ground between 0 , 3 and 1.5 y. This is absolutely imperative for the glazing ensuring the sealing of the window 3 of the enclosure 1 in activity. Silica glass, chosen in many cases as the optimal material, is suitable in this respect since it transmits radiation from 0.2 to 4.5 p.

On the other hand, for the other possible glazing panes coming in second or third position, we can leave them in front of the window when their spectral transmission band includes the interval 0.3 to 1.5 p, and we discard them in the case on the contrary, by placing them in an active position in front of the window only when they have to play, in their turn, their evacuating role.

Furthermore, it is advisable to protect against any damaging temperature rise the glazing acting as a removable insulating wall portion, for example when it is made of ordinary glass, possibly treated, resistant only to a temperature of order of 550 "C This sensor glazing is isolated from the evacuating glazing by a space in which a vacuum is produced as high as possible, or a current of air, or even a current of water or liquid whose bandwidth of spectral transmission is compatible, at least approximately, with the interval 0.3 - 1.5 y
Finally, an installation according to the invention also provides an advantage. In fact, when the confined energy is discharged slowly as is the case in the installations known until then, it is practically impossible to recover it; it diffuses almost imperceptibly. In particular, during the slow cooling of a thermal oven, the door of which cannot be opened (the internal environment of the oven having to remain confined), the evacuated heat is lost. On the contrary, when the energy is evacuated quickly, as is the case in an installation according to the invention, it becomes possible to reuse it, all the more since this energy is evacuated in radiant form and that there are sensor-receivers for this form of energy, in the various wavelength ranges. The radiated energy evacuated is taken up by one of these sensors either directly or via an appropriate optical system. An interesting variant of direct recovery is as follows: the radiant energy evacuated by the installation is directly taken up by a similar installation during its preliminary activity phase during which its enclosure begins by storing energy. in the case of thermal ovens,
the radiant energy evacuated by a fnur during its cooling
dissement according to the invention is directly taken up by a
another oven, cold, in which one wishes to store energy
For this purpose, in front of the transparent glazing evacuating the radiant energy from the oven during cooling, in a given wavelength band, and as close as possible to this glazing, the transparent glazing (or glazing system) of the cold oven transmitting radiation in an interval including the same band of wavelengths. This glazing then plays a sensor role, transmitting to the enclosure of the cold oven part of the radiant energy discharged from the hot oven. When several transparent panes take turns to evacuate the radiant energy from the hot oven, care is taken, by an adequate set of deactivations and activations of the panes of the cold oven, that the transmission is not impeded. The operation is stopped when the enclosures are in the optimal equilibrium by moving the two installations apart from one another and by replacing the removable insulating wall of the sensor oven in the obturating position of its transparent glazing system.
The oven is thus pre-heated by a sort of "electromagnetic mouth to mouth" allowing optical energy recovery.

 The invention is not limited only to the embodiments described and shown but on the contrary embraces all variants.

Claims (12)

1 - Process for exploiting and discharging notably energy  thermal confined in a sealed enclosure, characterized  in that one operates this evacuation by radiation and  that, preferably, this radiation is recovered in view: g reuse. 2 - Method according to claim 1, characterized in that  one combines in association with the enclosure, on the one hand  at least one glazing which contributes to ensuring its watertightness  ity, which is able to withstand internal conditions pro  near the enclosure in activity, in particular temperature,  of pressure, corrosion and which is transparent for a  set of wavelengths of radiation including cel  discharging energy, these functions can be assumed  by several windows successively taking turns to  transmit radiation evacuating energy, resistance  tance of each of these glazings then being adapted to  internal conditions specific to the enclosure as they  changes as the evacuation progresses, and  share, at least one removable insulating wall which is placed  opposite the glazing to prevent the evacuation of the energy  during the confinement period and which is removed  at the time of evacuation. 3 - Installation for implementing the method according to one  any of claims 1 and 2 above, character  see in that it comprises in combination an enclosure (1)  in which a window (3) is provided, at least one vi  trage (4-5) which must be placed against the window (3) of  sealed and transparent to a set of  wavelengths including those that correspond to  radiation evacuating energy and at least one wall  insulator (7) movable between an active position in the  which it is placed opposite the glazing (5) to op  pose in the passage of radiation and an inactive position  in which it is moved away from the glazing (5) to release  the passage of radiation. 4 - Installation according to claim 3, characterized in that  that the glazing (4-5) and the insulating wall (7) constitute  a double door capable of masking and unmasking  the window (3). 5 - Installation according to claim 3, characterized in that  that the interior walls (2a-2b) of the enclosure (1)  adjacent to that which includes the window (3) are in  at least partially cleaved from the middle axis  (x) normal to the plane of this window (3) forming with  this one from acute angles. 6 - Installation according to claim 3, characterized in that  that the interior walls of the enclosure (2a-2b) adjacent  to that which includes the window (3) are, at least in par  tie, with grooves (12) whose direction is parallel  to the average axis normal to the plane of the window (3). 7 - Installation according to claim 3, characterized in  that the glazing (4) is made of silica glass. 8 - Installation according to claim 3, characterized in that  that it includes at least two movable panes (4-5)  not likely to be individually placed and removed from  in front of window (3) in order to be there either together or  separately. 9 - Installation according to claim 8, characterized in that  that the glazing closest to the enclosure (4) is ap  plies tightly against the inner perimeter  window (3). 10 - Installai ton according to claim 9, characterized in  that the windows (4 and 5) are separated by a space (6)  in which can be established, by any known means, a  now empty the first window (4) applied against  around the window (3), an elastic seal being  possibly placed between this glazing (4) and this periphery. 11 - Installation according to revenufacturing 9, characterized in  that said glazing (4) is slidably mounted parallel  to his plan. 12 - Installation according to any one of claims 3  to II above, characterized in that it comprises at  minus a screen likely to oppose, at least partial  also the transmission of radiation through the fe  beech (3); this screen being mounted movable between a position  active in which it can obscure the radiation and  an erased position in which it is inoperative, in order to be able to modulate the evacuation of the radiation from  the enclosure (1)