FR2461212A1 - SOLAR SENSOR AND APPARATUS USING SUCH SENSORS - Google Patents

Abstract

THE SENSOR INCLUDES AN OUTER GLASS TUBE 2 CONTAINING ON THE ONE HAND A REFLECTOR 4, ON THE OTHER HAND A CONDUIT 6 LOCATED AT THE REFLECTOR'S FIREPLACE. THIS LAST IS OF THE DOUBLE PARABOLIC TYPE TO CONCENTRATE ON 6 THE INCIDENT RADIUS FOLLOWING THE RESPECTIVE ANGLES TH AND TH. WHEN AT 6 IT IS PREFERABLY A HEAT TRANSFER TUBE (SEALED TUBE CONTAINING A VOLATILE LIQUID) WITH AN END EXCEEDING 2 TO BE ENGAGED IN A HEAT EXCHANGER. 2 IS SEALED AT ITS TWO ENDS AND ITS VACUUM INNER SPACE.

Description

The present invention relates to solar energy collectors and it aims

  more particularly the tubular vacuum sensors to which

  a parabolic reflector is integrated.

  According to the present invention a solar energy collector comprises an outer glass tube in which are arranged on the one hand a compound parabolic reflector extending substantially over the length of the tube, on the other hand a straight pipe which extends as for it according to the focus of the reflector, the ends of this glass tube

  exterior being sealed and the space it delimits being evacuated.

The external glass tube suitable for use according to the invention can be of any kind, for example made of borosilicate glass, with a

  appropriate diameter and length.

  The reflector used according to the invention is a parabolic reflector

  that compound intended to reflect its home the incident light from the sun. It can advantageously be made of highly polished aluminum and having a high specular reflection power. It is preferably rigid and self-supporting so that it can be held in place in the outer glass tube in a very simple manner by means of clamps

  elastic. It is preferably of the type described in American patents.

ricans 4,002,499 and 4,003,638.

  The pipe can take the form of a tube with open ends, suitable for being inserted into a circuit in which a heat absorption fluid is circulated. It can also be constituted by such a tube with open ends inside which one can mount a heat transfer tube device. Finally, it can directly affect the shape of such a device provided so as to quickly transfer the heat absorbed by the

sensor itself.

  In a first embodiment of the invention, the pipe is constituted by a simple inner glass tube which extends beyond the ends of the above-mentioned outer glass tube, the latter being tightly connected to the surface of the inner glass tube and appropriate means being provided to absorb the differences in expansion between the two tubes. The inner tube is then connected to an appropriate circuit for circulating a heat absorption fluid (heat transfer fluid) in the same way as in known sensors using a

such fluid.

  In a second embodiment of the invention, the pipe takes the form of a device for the heat transfer tube. These devices are well known. We know that they include a tightly closed tube, partially evacuated and containing a small amount of a suitable liquid, while there is provided a tubular wick which extends over the entire length of this tube while being intimately in contact with the inner wall thereof. When heat is applied to one end of the device, the liquid evaporates and the vapor flows along the length of the tube to condense at the cold end of it by heating it. The condensed liquid is brought to the first end via the wick. The use of such a device allows rapid heat transfer from one end

from tube to tube.

According to another embodiment of the invention, the pipe is constituted by an inner glass tube, one open end of which is welded to the outer glass tube, while a heat transfer tube device is engaged in the aforementioned inner glass tube projecting beyond the end thereof welded to the tube

exterior glass.

  In these three embodiments of the invention the device.

  heat transfer tube is arranged so as to have one of its ends inside the external glass tube, while the other protrudes out of this last and is suitable for being introduced into a heat exchanger or into a thermal accumulator. The part of the aforementioned device which is located in the outer glass tube, or else the inner glass tube which encloses this part, is preferably covered with a selective coating with high absorbency and low emission power, in order to '' improve the effectiveness or efficiency of the sensor. The outer glass tube is sealed at one of its ends by means of a suitable cover, while its opposite end

  is tightly connected to the surface of the transfer tube device

heat from the inner glass tube. The interior end of the device rests on a suitable support, other supports being able to be provided along its length, if desired. The other end of this device intended to be introduced into the heat exchanger or the like is preferably covered with a coating capable of radiating heat and it may include fins, if desired. These measures

  itself can be made of glass or of a metal such as copper.

  The appended drawing, given by way of example, will allow a better understanding of the invention, the characteristics which it presents and the advantages which it is capable of providing: FIG. 1 is a cross section of a sensor according to the invention.

  Fig. 2 is a longitudinal section.

  Fig. 3 is a longitudinal section of another embodiment of a sensor according to the invention. In fig. 1 the sensor comprises an external glass tube 2 in which are arranged a compound parabolic reflector 4 made of polished aluminum, as well as a pipe 6 located at the focal point of the reflector, this pipe can be constituted by a tube proper or by a

  heat transfer tube device.

  The reflector 4 is an optimized light concentration mirror, which does not form an image. It is of the parabolic type described in American patents 4,002,499 and 4,003,638. This type of device concentrates on the line 6 the incident radiant energy located in an angular range e1 - e2 defined by the lines in broken lines FD and GB. The CD part of the reflector is an expanding part of the circular cross section of the pipe. The part DE is designed to comprise substantially the maximum inclination capable of reflecting on the pipe 6 the incident radiation included in the angle e1. Likewise, the part BC is an involute of the section of the pipe and the part BA also has the maximum inclination with a view to returning the radiation which is located in the angle e2 to the pipe. The reflector is cut at points A and E so that it can be mounted in the outer glass tube 2. We can consider the two symmetrical or asymmetrical configurations so that e1 can be different from G2. In the example shown in fig. 1, e1 = e2 = 35 ', which is a practical value for a fixed solar collector. This results in a concentration ratio C = 1.5 which is suitable for efficient operation at a high temperature. For mechanical and thermal reasons it may be desirable to interpose an intermediate space between the receiver and the reflector at point C. In the vicinity of this space it is possible to capture the radiation by means of a cavity or to provide the developing part in starting from a virtual receiver. So, for example, this virtual receiver can be constituted by the minimal convex surface which surrounds the receiver

  real and by the point of the reflecting wall closest to the re-

  receptor. In the embodiment of the invention illustrated in FIG. 2, line 6 is in the form of a heat transfer tube device. It includes a sealed tube, partially evacuated and containing a small amount of a liquid, such as water, with a wick 40, made for example of copper cloth, which extends over its entire length while being intimately maintained in place against the inner wall of the tube in question. The end 42 of this device (inner end) is

  held in the outer glass tube 2 - by means of a support 44.

  This support 44 is preferably made of a thermally material

  insulation to prevent heat loss by conduction. The extremi-

  tee 45 of the outer glass tube and itself sealed,

  for example by means of an appropriate hat.

  The second end 46 of the heat transfer tube device extends beyond the exterior glass tube 2 in a heat exchanger 47. The tube 2 is sealed in relation to the end of the interior device 6 by means of a weld 48. This device 6 is rectilinear over its entire length so as to ensure maximum efficiency and therefore the weld 48 is not located in the center of the end

of the outer glass tube.

  The exchanger 47 may advantageously include a tube, shown

  in section in fig. 2, through which an absorbent liquid is circulated

  tion of heat or heat transfer liquid. A whole series of sensors can be arranged so that their heat transfer tube devices engage in such a tubular exchanger. The liquid used in the latter can reach it by its two ends to be extracted from it at an intermediate point of its length, this in order to ensure the maximum transfer of heat to the liquid. The exchanger 47 is preferably covered with an insulating material 49. The seal is produced at the point of entry of the device 6 into the exchanger 47 by means of a seal 50

  designed to resist the action of heat and liquid.

  The device 6 can comprise a glass or metal tube; alternatively it may consist of lengths of glass and metal tube. It is preferable to make glass at least the part of this device which is inside the outer glass tube 2, so that the weld 48 can be of the glass on glass type and dtie by

  therefore much easier to achieve than in the case of glass / display.

  The part of the device 6 which is in the outer glass tube 2 preferably comprises a selective coating in order to absorb the maximum of the radiation. As for the part of this device located in

  the exchanger 47, it is made to include a coating capable of radiating the-

heat. If the device 6 is made of glass, a metal sleeve suitable for facilitating heat transfer can be inserted on its end located inside the exchanger. This end of the device 6 located in the exchanger can be equipped with fins, some of which have been shown at 52, in order to ensure faster heat transfer. Although we have shown in fig. 2 an uncovered part of the device 6 between the weld 48 and the joint 50, it should be noted that this was only done for the clarity of the drawing, this part being reduced in practice to a minimum and being isolated if necessary to prevent

heat loss.

  In the example shown in fig. 3, the pipe 6 takes the form of a glass tube, one end 42 of which is closed and is supported inside the external glass tube 2 by a support 44, while the other end is fixed in a sealed manner to this tube 2 by means of a weld 48. A metal device 39 of the heat transfer tube is mounted inside the tube 6 and protrudes beyond it

to engage in a heat exchanger of the type described above in reference

this in fig. 2.

  It should also be understood that the above description has not

  has been given only by way of example and that it in no way limits the field of the invention from which one would not depart by replacing the execution details

  described by all other equivalents.

Claims (9)

R E V E N D I C A T I 0 N S   1. Solar energy collector, characterized in that it comprises an external glass tube (2) containing on the one hand a parabolic reflector compound (4) extending substantially along its length, on the other hand a straight pipe (6) which in turn extends along the focus of said reflector (4), the ends of the outer glass tube (2)   being sealed and the space it delimits being evacuated.   2. Sensor according to claim 1, characterized in that the pipe (6) consists of a tube open at its two ends, which protrude beyond the outer glass tube (2) and are suitable for being connected in a circuit circulation of a fluid heat absorption.   3. Sensor according to claim 1, characterized in that the pipe (6) is constituted by a heat transfer tube device, one end (42) of which is supported inside the tube. outer glass (2), while the other protrudes beyond it.   4. Sensor according to claim 1, characterized in that the pipe (6) consists of a tube with open ends in which is mounted a heat transfer tube device which protrudes   beyond one of said ends.   5. Sensor according to any one of the preceding claims,   characterized in that the outer surface of the part of the pipe (6) which is inside the outer glass tube (2) has a   selective coating to improve heat absorption.   6. Sensor according to any one of claims 3 to 5,   characterized in that the end of the heat transfer tube device (6) which extends beyond the outer glass tube (2) has a   coating capable of radiating heat. 7. Sensor according to any one of claims 3 to 6,   characterized in that the end of the heat transfer tube device (6) which extends beyond the outer glass tube (2) has fins (52).   8. Sensor according to any one of claims 3 to 7,   characterized in that at least the end of the heat transfer tube device (6) which extends beyond the outer glass tube (2) is made of metal.   9. Apparatus for collecting solar energy, characterized in   that it comprises several sensors according to any one of claims   3 to 9, arranged side by side, the ends of their heat transfer tube devices (6) which protrude beyond the outer glass tubes (2) being engaged in a heat exchanger element (47) at   through which a coolant is passed.