JP3197073B2 - Solar heat receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar heat receiver for heating a fluid by solar heat and utilizing the solar heat.

[0002]

2. Description of the Related Art In order to utilize solar heat in solar thermal power generation or a chemical plant utilizing solar heat, the present applicant has previously filed Japanese Patent Application No. 2-1 as a conventional apparatus for heating a fluid by solar heat.
No. 10119 was proposed. In this apparatus, FIGS.
As shown in FIG. 1, sunlight condensed by the reflector 13 is received on the surface of the porous ceramic cylinder 6 and is heated, and a gas to be heated is caused to flow through the ceramic and is heated by radiation from solar heat. The gas is heated from the porous ceramics by convection heat transfer.

[0003] Porous ceramics have a porosity of 80 to 9
As high as 9%, the heat transfer coefficient between the gas and the gas is large, a large heat flow rate is generated with a small temperature difference, and the gas can be easily heated with a small heat transfer area. This porous ceramic is placed in a cylindrical container 9 made of quartz glass, a cool gas before heating is flowed between the porous ceramic and the quartz glass, and the gas heated by the porous ceramic is a porous ceramic. It flows through the inside and is taken out of the heat collector through the pipe of the heat insulation structure.

[0004] In the solar heat receiver configured as described above, light collected by the solar collector having the reflector 13 and received on the surface of the porous ceramic cylinder 6 of the heat collector has a concentrated distribution. Therefore, the temperature is high in the portion where the concentration is high, and a large temperature distribution is generated. The relationship between the temperature and the pressure loss through the fluid in a porous ceramic is generally expressed by the following equation.

[0005]

(Equation 1)

Here, C is a resistance coefficient, and A is a cross-sectional area of the passage. C and A are constants depending on the shape of the passage through which gas flows, and γ and V are variables that change with temperature as follows.

[0007]

(Equation 2)

[0008] Here, the values with the subscript 0 are the values in the standard state. As described above, in the porous ceramics, the pressure loss of the passing fluid increases as the temperature increases.

Therefore, as described above, when a temperature distribution occurs in the porous ceramic cylinder 6 due to the distribution of the degree of concentration of sunlight, the pressure loss of fluid passing through a high temperature becomes large, and the flow through the porous ceramic cylinder 6 increases. There is a distribution in which the heating fluid flow rate decreases as the temperature increases.

For this reason, the gas temperature after passing through the porous ceramic cylinder 6 is proportional to the product of the fluid temperature and the flow rate, so that the gas temperature is close to the fluid temperature of the portion where the flow rate is high and the temperature is low. There is a large difference between the fluid temperatures.

If a porous ceramic having a heat resistance of 1700 ° C. is used, if the difference between the maximum temperature of the ceramic and the fluid temperature after heating is 1000 ° C., the porous ceramic is heated to 1700 ° C. 700 ℃
The gas cannot be heated any more.

[0012]

SUMMARY OF THE INVENTION As described above, according to the present invention, the heating efficiency of the fluid is reduced due to the passing pressure loss to the fluid caused by the distribution of the concentration of light on the collector made of porous ceramics. To improve
It is an object of the present invention to provide a solar heat receiver that can heat a fluid to a temperature close to the heating temperature of porous ceramics.

Another object of the present invention is to make it possible to heat a fluid to near the heat-resistant temperature of porous ceramics by using a solar heat receiver having a simple structure.

[0014]

SUMMARY OF THE INVENTION The present invention is directed to a solar heat receiver in which a fluid to be heated is caused to flow through porous ceramics heated by receiving solar radiation on the surface thereof to heat the fluid. to solve, and comprises a plurality of portions with different least Izure or other of its porosity and thickness of porous ceramic as a heat collector, it the flow resistance is received light intensity with respect to the flow <br/> body Place in inverse proportion structure .

Further, in the present invention, the light receiving surface of the porous ceramics constituting the heat receiver is formed in a concave shape, and at least one of the porosity and the thickness is changed from the peripheral edge toward the bottom to change the fluid. Also, a configuration in which the passage resistance with respect to is reduced.

[0016] In the present invention, one either at least porous ceramics respectively porosity and thickness is adopted a structure in which composed of different plural portions constituting the heat collector.

[0017]

According to the present invention, since the fluid passage resistance of the porous ceramics constituting the solar heat receiver is inversely proportional to the distribution of the light concentration of sunlight, the passage resistance is lower at a portion having a higher concentration of sunlight. A large amount of gas flows in a portion where the degree of concentration is high and the radiant heat flow rate is high, and a large amount of high temperature fluid is obtained.

Conversely, in a portion where the concentration of sunlight is low, the passage resistance is increased, so that the flow rate of gas passing therethrough decreases, and the temperature of the gas passing through this portion increases. Since the heating gas having a small temperature distribution is mixed as described above, the change in temperature is small, and the difference between the gas temperature after heating and the temperature of the porous ceramics is small. Therefore, the gas can be heated to a temperature close to the heat resistant temperature of the porous ceramic.

Further, according to the present invention, the light receiving surface of the porous ceramic constituting the heat receiver is made concave, and the resistance to the passage of the fluid from the periphery to the bottom is reduced. The heat radiation from the hardly leaks to the outside, the radiation loss can be reduced, and the fluid can be efficiently heated.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A solar heat receiver according to the present invention will be specifically described below with reference to the illustrated embodiments. First, a first embodiment shown in FIG. 1 will be described. In FIG. 1, FIG.
The same parts as those of the conventional apparatus shown in FIG. 11 are denoted by the same reference numerals, and description thereof will be omitted.

In the solar heat receiver shown in FIG. 1, the cold gas entering the quartz glass tube 9 from the gas inlet 40 passes through the porous ceramic cylinder 6 heated by the condensed solar heat and the alumina tube 7 and the heat insulating material. The gas is discharged to the outside of the device from the gas outlet 41 through the passage constituted by 71.

The porous ceramic is composed of seven divided parts 61 to 67.
The pore diameters are adjusted as shown in Table 1 so that the passage resistances 1 to 67 are inversely proportional to the concentration of sunlight in the portions 61 to 67 shown in FIG.

[0023]

[Table 1]

In Table 1, the passage resistance ratio indicates the passage resistance of each part when the minimum passage resistance of the porous ceramic is set to 1. When the porous ceramic is composed of seven portions having different passage resistances as shown in Table 1, the mass flow rate is as shown in FIG. For this reason, the temperature of the porous ceramics becomes substantially constant, and it becomes possible to heat the gas to near the heat resistant temperature of the ceramics.

Next, a second embodiment shown in FIGS. 4 and 5 will be described. In FIGS. 4 and 5, the same parts as those of the apparatus shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. 4 and 5, the heat collecting portion is a cavity-type porous ceramic 16 provided inside an alumina tube 7 having a structure insulated by a heat insulating material 71.
It consists of.

The porous ceramic 16 is formed by fastening an O-ring 110 and a holding ring 111 to the first main body 10.
2 covered with quartz glass 9 attached. Second
The heat insulating material 72 is attached to the inner surface of the main body 20, and the first main body 10 and the alumina pipe 7 are connected to the alumina pipe 7 by tightening the O-ring 210 and the holding rings 211 and 212 with bolts 213.

The cold gas that has entered the quartz glass tube 9 from the gas inlet 40 passes through the porous ceramics 16 heated by the condensed solar heat, passes through the alumina tube 7, and passes through the passage formed by the heat insulating material 71. The gas is discharged from the device through the gas outlet 41. The porous ceramic 16 is made up of seven parts 161 to 167 divided as shown in FIG.

When the porous ceramic is composed of seven parts, the concentration ratio of sunlight is as shown in FIG. The pore diameter and thickness are adjusted as shown in Table 2 so that the passage resistance in each of the portions 161 to 167 is inversely proportional to the concentration of sunlight shown in FIG.

[0029]

[Table 2]

For this reason, the temperature of the porous ceramic becomes substantially constant, and it becomes possible to heat the gas to near the heat-resistant temperature of the ceramic. Further, since the light is received by the inner surface of the cavity made of the concave porous ceramics, heat radiation from the heated porous ceramics hardly leaks to the outside and radiation loss is reduced.

Although the embodiments of the solar heat receiver according to the present invention have been specifically described above, the present invention is not limited to these embodiments. For example, in the embodiment, the porosity is changed in order to change the passage resistance of the porous ceramic to the fluid, but instead of the porosity, or by changing the thickness of the porous ceramic in addition to the porosity, the passage resistance to the fluid is changed. Is also good.

[0032]

FIG. 8 shows the temperature distribution of the surface of a conventional heat receiver without controlling the flow rate of the porous ceramics (the surface of the porous ceramics) and the temperature distribution of the heat receiver with the flow rate control according to the present invention. It is a comparison at the same heat receiving gas temperature. According to the present invention, the surface temperature is made uniform by the flow rate control, and the maximum temperature is from 1700 ° C. to 1300 ° C.
Has declined.

FIG. 9 shows a change in the heat receiving efficiency of the heat receiver by the flow rate control. Improvement of heat receiving efficiency is seen by the improvement by the flow control. This is because the heat loss from the heat receiver is mainly caused by the radiation loss on the heat receiving surface, and the radiation loss is reduced by lowering the maximum heat receiving surface temperature.

Further, according to the present invention, the light receiving surface of the porous ceramics is formed in a concave shape, and at least one of the porosity and the thickness is changed from the peripheral edge toward the bottom to reduce the passage resistance to the fluid. With this configuration, in addition to the above-described effects, heat radiation from the porous ceramics hardly leaks to the outside, and more efficient fluid heating can be performed.

Further, according to the present invention, when the porous ceramic is constituted by a plurality of portions having at least one of different porosity and thickness, the production is simple.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a solar heat receiver according to a first embodiment of the present invention.

FIG. 2 is a graph showing the concentration of sunlight on the surface of a porous ceramic in the apparatus of FIG.

FIG. 3 is a graph showing a mass flow rate of gas of porous ceramics in the apparatus of FIG.

FIG. 4 is a longitudinal sectional view of a solar heat receiver according to a second embodiment of the present invention.

FIG. 5 is an enlarged sectional view of a porous ceramic in the apparatus of FIG.

6 is a graph showing the degree of concentration of sunlight on the surface of a porous ceramic in the apparatus shown in FIG.

FIG. 7 is a graph showing a mass flow rate of gas of porous ceramics in the apparatus of FIG.

FIG. 8 is a graph showing a surface temperature distribution of a heat receiver according to the present invention.

FIG. 9 is a graph showing the heat receiving efficiency of the heat receiver according to the present invention.

FIG. 10 is a longitudinal sectional view of a conventional heat receiver.

FIG. 11 is a longitudinal sectional view showing the entire configuration of a conventional solar heat receiver.

[Explanation of symbols]

Reference Signs List 6 Porous ceramic cylinder 7 Alumina tube 9 Quartz glass tube 10 Main body 16 Porous ceramic made of cavity 61-67 Porous ceramic portion forming cylinder 7 161-167 Porous ceramic portion forming cavity type

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-219470 (JP, A) JP-A-4-9549 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F24J 2/48

Claims (3)

(57) [Claims] 1. A solar heat receiver in which a fluid to be heated is caused to flow through porous ceramics which is heated by receiving solar radiation on the surface thereof, and heats the fluid. A solar heat receiver comprising a plurality of portions in which at least one of them is changed , and arranged in a structure in which the passage resistance to the fluid is inversely proportional to the received light intensity. 2. A solar heat receiver in which a fluid to be heated is caused to flow through porous ceramics heated by receiving solar radiation on the surface thereof to heat the fluid, the light receiving surface of the porous ceramics being concave. A solar heat receiver characterized by being formed and having at least one of a porosity and a thickness changed from a peripheral edge toward a bottom to reduce the passage resistance to the fluid. 3. The solar heat receiver according to claim 2, wherein said porous ceramic is constituted by a plurality of portions each having at least one of different porosity and thickness.