CN109856182B - Method for measuring relative absorption rate of tube panel of fused salt heat absorber - Google Patents
Method for measuring relative absorption rate of tube panel of fused salt heat absorber Download PDFInfo
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- CN109856182B CN109856182B CN201910114324.0A CN201910114324A CN109856182B CN 109856182 B CN109856182 B CN 109856182B CN 201910114324 A CN201910114324 A CN 201910114324A CN 109856182 B CN109856182 B CN 109856182B
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- 150000003839 salts Chemical class 0.000 title claims abstract description 163
- 239000006096 absorbing agent Substances 0.000 title claims abstract description 107
- 238000010521 absorption reaction Methods 0.000 title claims abstract description 64
- 238000000034 method Methods 0.000 title claims abstract description 21
- 238000004088 simulation Methods 0.000 claims abstract description 26
- 230000017525 heat dissipation Effects 0.000 claims abstract description 21
- 238000005259 measurement Methods 0.000 claims abstract description 14
- 238000000691 measurement method Methods 0.000 claims abstract description 8
- 230000004907 flux Effects 0.000 claims abstract description 3
- 238000012360 testing method Methods 0.000 claims description 32
- 238000004364 calculation method Methods 0.000 claims description 29
- 238000002834 transmittance Methods 0.000 claims description 12
- 239000011248 coating agent Substances 0.000 claims description 11
- 238000000576 coating method Methods 0.000 claims description 11
- 230000003749 cleanliness Effects 0.000 claims description 9
- 238000002310 reflectometry Methods 0.000 claims description 8
- 230000005855 radiation Effects 0.000 claims description 7
- 238000012546 transfer Methods 0.000 claims description 6
- 238000004422 calculation algorithm Methods 0.000 claims description 3
- 238000004140 cleaning Methods 0.000 claims 1
- 229940060587 alpha e Drugs 0.000 abstract description 2
- 238000010248 power generation Methods 0.000 description 8
- 239000011241 protective layer Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 241000282414 Homo sapiens Species 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 238000005338 heat storage Methods 0.000 description 1
- 229910001338 liquidmetal Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a method and a system for measuring the absorption rate of a single tube panel of a fused salt heat absorber. The measurement method comprises the following steps: for a certain tube panel to be detected, the absorption rate alpha is assumed, and when the molten salt heat absorber operates normally, the energy E projected onto the tube panel of the heat absorber is obtained through the energy flow density simulation subsystemtTherefore, the total energy alpha E received by the heat absorber tube panel can be obtainedtObtaining the temperature distribution on the tube panel of the heat absorber through an infrared thermometer, calculating the total heat dissipation loss L on the fused salt heat absorber by adding the measured ambient wind speed and ambient temperature, and obtaining the flux of the fused salt in the tube panel of the heat absorber through the measurement of a fused salt flowmeter
The actual absorbed energy E of the molten salt in the single heat absorber tube panel can be calculated by adding the inlet and outlet temperatures of the heat absorber tube panelrAnd the measured absorption rate alpha of the tube panel of the fused salt heat absorber is equal to (E)r+L)/Et。
Description
Technical Field
The invention relates to a solar tower type molten salt thermal power generation system, in particular to measurement of tube panel absorption rate of a molten salt heat absorber.
Background
The solar high-temperature thermal power generation technology is an important development direction for large-scale utilization of solar energy and has profound significance for solving the problems of fossil energy crisis, air pollution and the like for human beings. There are various technical directions for solar high-temperature thermal power generation: according to the difference of focusing modes, the method can be divided into a tower mode, a groove mode and a disc mode. Among them, the tower type and the tank type are mainly used in large-scale commercial application. Compared with the groove type, the tower type solar cell has higher light gathering ratio, can reach higher use temperature and has higher general power generation efficiency. In addition, in the aspect of energy storage, if the fused salt is adopted for heat storage, the temperature utilization interval of the tower type is about 3 times of that of the tank type, so that the cost of the tower type energy storage is lower. The working medium of the tower-type heat absorber mainly comprises water (steam), molten salt, air, liquid metal and the like. The fused salt can absorb heat and store heat integrally, and the commercial operation of the foreign fused salt power station is realized at present, so the fused salt tower type solar power station is an important direction for large-scale commercial application in the field of solar thermal power generation in the future.
The molten salt heat absorber is a key device for converting solar radiation energy into molten salt heat energy. In order to improve the heat absorption efficiency of the molten salt, a high-absorptivity coating is plated on the surface of the heat absorber. The existing mature fused salt heat absorber coating mainly comprises Pyromark 2500, the service temperature of the coating can reach over 1000 ℃, and the absorptivity of the fused salt heat absorber coated by a strict process can reach over 0.95. The high absorption rate can greatly improve the overall heat efficiency of the molten salt heat absorber, and the absorption rate index is one of core indexes of the molten salt heat absorber.
The absorptivity of the coating of the fused salt heat absorber can be reduced along with the increase of the service life, and in addition, the fused salt heat absorber which runs outdoors for a long time cannot avoid being stained with dust, abraded and eroded, so that the absorptivity is reduced. In addition, the fused salt valve occasionally has salt leakage accidents and stains the light receiving surface of the heat absorption tube panel due to reasons such as reduced sealing performance, the heat absorption tube can also have tube explosion accidents to stain the light receiving surface of the heat absorption tube panel, and the absorption rate of the contaminated heat absorption tube panel can be rapidly reduced, so that the heat absorption efficiency is influenced.
Measuring the absorption rate of the tube panel of the fused salt heat absorber is an important and extremely difficult work. The absorption rate of a heat absorption pipe with small pipe diameter and certain curvature cannot be measured by a conventional measuring instrument; in addition, high-altitude and large-area measurement operation has great safety risk and measurement difficulty. Therefore, developing a simple-to-operate method for measuring the tube panel absorption rate of the molten salt heat absorber is an important and urgent task in a solar tower-type molten salt heat power generation system.
Disclosure of Invention
The invention provides a method and a system for measuring the tube panel absorption rate of a molten salt heat absorber. The measuring method and the measuring system can indirectly measure the absorption rate of a single tube panel of the molten salt heat absorber, so that an accurate basis is provided for the coating replacement period and the heat absorber efficiency calculation.
The technical scheme of the invention is as follows:
a method for measuring the tube panel absorption rate of a molten salt heat absorber comprises the steps of providing a measuring system, wherein the system comprises a power flow density simulation subsystem, a molten salt flowmeter, a molten salt temperature measuring device at an inlet/outlet of a tube panel of the molten salt heat absorber, an infrared thermometer and a wind speed and temperature measuring device, wherein the power flow density simulation subsystem is used for calculating energy projected to a single tube panel; the mass flow of the molten salt is measured through the molten salt flowmeter, the temperature of the molten salt at the outlet and the inlet of the heat absorber is measured through the molten salt temperature measuring device at the inlet/outlet of the tube panel of the molten salt heat absorber, so that the enthalpy value of the molten salt is obtained, and the data measured by the molten salt flowmeter and the molten salt temperature measuring device at the inlet/outlet of the tube panel of the molten salt heat absorber are used for calculating to obtain the energy absorbed by the molten salt in the tube panel; measuring the average temperature of the light side wall surface of the measured tube panel by the infrared thermometer, measuring the ambient wind speed and temperature by the wind speed and temperature measuring device, and calculating the data measured by the infrared thermometer and the wind speed and temperature measuring device to obtain the total heat dissipation loss of the tube panel; the measuring method obtains the absorptivity of the tube panel to be measured through calculation of the energy projected to a single tube panel, the energy absorbed by molten salt in the tube panel and the total heat dissipation loss of the tube panel.
The calculation formula of the energy absorbed by the molten salt is as follows:
wherein
The mass flow of the molten salt at the inlet of the molten salt heat absorber is measured by a molten salt flowmeter; h isoutThe enthalpy value of fused salt at the outlet of the heat absorber; h is a total ofinThe enthalpy value of fused salt at the inlet of the fused salt heat absorber is obtained by a fused salt temperature measuring device at the inlet/outlet of a tube panel of the fused salt heat absorber.
In order to obtain accurate molten salt absorbed energy, the flow rate of the molten salt and the temperature of the molten salt at the inlet/outlet of the heat absorber need to be relatively stable. Therefore, the fluctuation of the flow of the molten salt in the testing period needs to be less than 15%, and the fluctuation of the temperature of the molten salt at the inlet and the outlet of the tube panel of the molten salt heat absorber needs to be less than 15 ℃.
In order to keep the energy supply and heat dissipation losses of the mirror field relatively stable, it is necessary to ensure that the DNI during the test is greater than 700KW/m in consideration of the relation between the projection energy of the mirror field and the direct radiation energy DNI, the availability of the mirror field and the efficiency of the mirror field2And the fluctuation range is not suitable to exceed 50KW/m2(ii) a The availability ratio of the mirror field during the test is more than 90 percent; the mirror field efficiency is generally stable within 3 hours around noon, so the recommended test time period is within 3 hours around noon. The heat dissipation loss of the heat absorber is mainly related to the wind speed, and in order to reduce the test error, the wind speed during the test is required to be less than 6 m/s.
Generally, the greater the energy absorbed by the heat sink, the greater the accuracy of the test, and therefore it is recommended that the energy absorbed by the heat sink during the test be maintained at least above 85% of the rated energy. Therefore, a specular cleanliness of greater than 85% is recommended when testing.
The mirror field of a certain region of the heat absorption tower shadow can be greatly reduced to project energy, so that the mirror field of the heat absorber tube panel corresponding to the region can project energy which does not meet the test requirement, and therefore the absorption rate of the heat absorber tube panel is not measured when the heat absorber tube panel is shielded by the heat absorption tower shadow. Since the position of the sun changes over time, the absorptance of all heat absorber tube panels can be measured by adjusting the test time period.
The energy flow density simulation subsystem can calculate the energy E projected to a single tube paneltThe calculation formula is as follows:
Et＝DNI×S×N×ηt×ηcos×ηs×ηb×ηc×ηr×ηtruc
wherein DNI is direct radiant energy, which can be measured directly by a DNI instrument; s is the area of a single heliostat capable of reflecting solar energy; n is the total number of heliostats projected to the measured tube panel; etatIs the atmospheric transmittance; etacosIs the cosine efficiency; etasIs the shadow efficiency; etabTo the shading efficiency; etacThe cleanliness of the mirror surface is obtained; etarIs the mirror field reflectivity; etatrucThe cutoff efficiency of the tube panel to be measured.
Wherein the atmospheric transmittance etatCosine efficiency ηcosShadow efficiency ηsShielding efficiency etabAnd a cutoff efficiency ηtrucCan be directly simulated and calculated by a mature algorithm, and the main input parameters of the simulation calculation method are the coordinates of all heliostats in a heliostat field, the vertex coordinates of a measured tube panel and the cleanliness eta of a mirror surfacecAnd mirror field reflectivity ηrIt needs to be measured.
In general, the cosine efficiency, the shadow efficiency and the shielding efficiency can be subjected to more accurate simulation calculation through verified codes; the cleanliness of the mirror surface and the reflectivity of the mirror field need to be obtained through measurement; the atmospheric transmittance and the truncation efficiency can only be obtained through simulation calculation at present, but the accuracy is difficult to verify, the atmospheric transmittance is related to particles and gas components in the air, the truncation efficiency is related to the mean error of the heliostat, and the two efficiencies are usually reflected to be larger or smaller as a whole when the calculation is carried out through given parameters.
The total heat dissipation loss includes convection loss, radiation loss and heat conduction loss. Wherein the heat conduction loss is negligible due to the small occupation ratio. The calculation formula of the total heat dissipation loss is as follows:
wherein: h is a convective heat transfer coefficient, mainly related to the ambient wind speed and the normal angle of the tested tube panel, and needs to be actually measured, if actual measurement data are lacked, the convective heat transfer coefficient can be 10-60W/(m) when the wind speed is less than 6m/s during the test period 2K) A value in between; a is the light receiving area of the tube screen to be measured, and the unit m2；
The average temperature of the illuminated surface of the tube screen is measured in K, and the average temperature can be directly measured by an infrared thermometer; t is0Is ambient temperature, in K; epsilon is the emissivity of the tube screen to be measured, needs to be provided by a coating manufacturer, and can be 0.90 when no data exists; σ is Boltzmann constant.
The absorption rate calculation formula of the tube panel to be detected is as follows: α ═ E (E)r+L)/Et
The sub-efficiency of the mirror field inevitably has certain error in the simulation calculation, thereby causing certain error in the absorption rate measurement result. In this case, the method provided by the invention is particularly suitable for measuring the relative absorption rate of the tube panel of the molten salt heat absorber.
The invention provides a method for measuring the relative absorption rate of a tube panel of a molten salt heat absorber, wherein the absorption rates of 2 tube panels measured by the molten salt heat absorber are respectively set to be alpha and alpha ', alpha and alpha ' are respectively calculated by the method, and then the relative absorption rates of the 2 tube panels are calculated by alpha/alpha '. As described above, the simulation result of the atmospheric transmittance and the truncation efficiency tends to show an overall larger or smaller value, but when the two absorptances are compared, the calculation error is greatly reduced, so that the relative absorptance of the tube panel can be calculated more accurately.
The invention also provides a system for measuring the tube panel absorption rate of the molten salt heat absorber, which comprises an energy flow density simulation subsystem, a molten salt flowmeter, a molten salt temperature measuring device at the inlet/outlet of the tube panel of the molten salt heat absorber, an infrared thermometer and a wind speed and temperature measuring device, wherein the energy flow density simulation subsystem is used for calculating to obtain the energy projected to a single tube panel; the molten salt flowmeter is used for measuring the mass flow of molten salt, the molten salt temperature measuring device at the inlet/outlet of the tube panel of the molten salt heat absorber is used for measuring the temperature of molten salt at the outlet and the inlet of the heat absorber so as to obtain an enthalpy value, and data measured by the molten salt flowmeter and the molten salt temperature measuring device at the inlet/outlet of the tube panel of the molten salt heat absorber are used for calculating to obtain the energy absorbed by the molten salt in the tube panel; the infrared thermometer is used for measuring the wall surface temperature of the heat absorber, the wind speed and temperature measuring device is respectively used for measuring the ambient wind speed and the ambient temperature, and data measured by the infrared thermometer and the wind speed and temperature measuring device are used for calculating to obtain the total heat dissipation loss of the tube panel; the absorption rate of the tube panel to be detected can be calculated through the energy projected to the single tube panel, the energy absorbed by the fused salt in the tube panel and the total heat dissipation loss of the tube panel.
Compared with the prior art, the invention has the following beneficial effects:
the measuring method and the measuring system provided by the invention can indirectly measure the absorption rate of a single tube panel of the molten salt heat absorber, thereby providing an accurate basis for the replacement cycle of the coating and the efficiency calculation of the heat absorber.
Of course, it is not necessary for any product in which the invention is practiced to achieve all of the above-described advantages at the same time.
Drawings
FIG. 1 is a schematic diagram of a tower-type solar thermal power generation system;
FIG. 2 is a profile view of an external molten salt heat absorber;
FIG. 3 is a profile view of a cavity-type molten salt heat absorber;
FIG. 4 is a schematic view of a single tube panel;
FIG. 5 is a flowchart of measuring absorption rate of the panel in example 1 of the present invention;
reference numerals: 1. an upper protective layer; 2. combining the heat absorber tube panels; 3. a lower protective layer; 4. feeding a molten salt header; 5, a heat absorption pipe; 6. and (4) a lower molten salt header.
Detailed Description
The invention discloses a method and a system for measuring the absorption rate of a single tube panel of a fused salt heat absorber. The measurement method comprises the following steps: for a certain tube panel to be detected, assuming the absorption rate alpha, when the fused salt heat absorber operates normally, the energy E projected onto the tube panel of the heat absorber is obtained through the energy flow density simulation subsystem tTherefore, the total energy alpha E received by the heat absorber tube panel can be obtainedtObtaining the temperature distribution on the tube panel of the heat absorber through an infrared thermometer, calculating the total heat dissipation loss L on the fused salt heat absorber by adding the measured ambient wind speed and ambient temperature, and obtaining the flux of the fused salt in the tube panel of the heat absorber through the measurement of a fused salt flowmeter
The temperature of the inlet and the outlet of the heat absorber tube panel can be calculated to obtain the energy E actually absorbed by the molten salt in the single heat absorber tube panelr. The measured absorption rate alpha of the tube panel of the fused salt heat absorber is equal to (E)r+L)/Et。
For a better understanding of the present invention, reference is made to the following detailed description of the invention taken in conjunction with the accompanying drawings.
Example 1
As shown in fig. 1, a tower-type solar thermal power station drives a large number of heliostats to track sunlight, so that the sunlight is collected on the surface of a heat absorber positioned at the top end of the heat absorber, and heats a heat absorbing medium, so that light energy is converted into heat energy, and the heat energy is converted into electric energy, thereby realizing solar thermal power generation.
As shown in fig. 2, the external structure of the conventional external molten salt heat absorber mainly comprises an upper protective layer (1), a heat absorbing panel (2) and a lower protective layer (3). The heat absorption panel (2) is surrounded to form 360 degrees, and can receive solar radiation energy reflected all around.
Fig. 3 shows the outline of the cavity molten salt heat absorber. The cavity absorber is generally open downward and thus the acceptance angle is somewhat limited.
A schematic of a single tube panel is shown in fig. 4. The single tube panel comprises an upper molten salt header (4), a heat absorption tube combination (5), a lower molten salt header (6) and the like (the tube panel also comprises structures such as electric heat tracing, heat preservation, an oven and a supporting steel frame, which are not shown in the figure). The molten salt can flow into the lower molten salt header from the upper molten salt header or can flow in the reverse direction. The fused salt temperature of the inlet and the outlet of the tube panel can be measured through the fused salt header.
Fig. 5 is a block diagram of a method for measuring the absorption of a panel, including blocks S1, S2, S3, and S4, wherein,
step S1 is: simulating energy E projected onto a single tube panel of a heat absorbert；
Step S2 is: calculating the total heat dissipation loss L according to the temperature measured by the light-receiving side wall surface of the tube panel, the ambient wind speed and the temperature;
step S3 is: calculating the actual absorption energy E of the molten salt in the tube panel through the flow rate of the molten salt measured by the tube panel and the temperature of the inlet and the outlet saltr；
Step S4 is: and calculating the tube panel absorptivity according to the listed formula according to the parameters obtained in the steps S1, S2 and S3.
Wherein, step S1 specifically includes:
calculated according to the following calculation formula:
Et＝DNI×S×N×ηt×ηcos×ηs×ηb×ηc×ηr×ηtruc
wherein DNI is direct radiant energy; s is the area of the single heliostat capable of reflecting solar energy; n is the total number of heliostats projected to the measured tube panel; eta tIs atmospheric transmittance; etacosIs the cosine efficiency; etasIs the shadow efficiency; etabTo the shading efficiency; etacThe cleanliness of the mirror surface; etarIs the mirror field reflectivity; etatrucThe cutoff efficiency of the tube panel to be measured.
Wherein,
DNI can be measured directly by a DNI meter; s and N can be directly obtained through monitoring software.
Atmospheric transmittance, cosine efficiency, shadow efficiency, shielding efficiency and truncation efficiency can be directly calculated by simulation through a mature algorithm, and the main input parameters of the simulation are coordinates of all heliostats in a mirror field and vertex coordinates of a measured tube panel; the cleanness of the mirror surface and the reflectivity of the mirror field can be directly measured by related instruments.
In general, the cosine efficiency, the shadow efficiency and the shielding efficiency can be subjected to more accurate simulation calculation through verified codes; the cleanliness of the mirror surface and the reflectivity of the mirror field need to be obtained through measurement; the atmospheric transmittance and the truncation efficiency can only be obtained through simulation calculation at present, but the accuracy is difficult to verify, the atmospheric transmittance is related to particles and gas components in the air, the truncation efficiency is related to the mean error of the heliostat, and the two efficiencies are usually reflected to be larger or smaller as a whole when the calculation is carried out through given parameters.
Step S2 specifically includes:
the total heat dissipation loss includes convection loss, radiation loss and heat conduction loss. Wherein the heat conduction loss is negligible due to the small occupation ratio. The calculation formula of the total heat dissipation loss is as follows:
wherein: h is a convective heat transfer coefficient which is mainly related to the ambient wind speed and the normal angle of the tested tube panel, actual measurement is needed, and if actual measurement data is lacked, the convective heat transfer coefficient can be 10-60W/(m/s) when the wind speed is less than 6m/s during testing2K) A value in between; a is the light receiving area of the tube screen to be measured, and the unit m2；
The average temperature of the light-receiving side wall surface of the tube panel to be measured is in unit K, and the average temperature can be directly measured by an infrared thermometer; t is0Is ambient temperature, in K; epsilon is the emissivity of the tube panel to be measured, and is provided by the coating manufacturer, and epsilon can be used in the absence of dataTaking 0.90; σ is Boltzmann constant. Wherein,
the ambient wind speed can be measured by a wind speed measuring device, the ambient temperature can be measured by a temperature measuring device, and the wind speed measuring device and the temperature measuring device can be integrated or arranged separately.
Step S3 specifically includes:
the energy absorbed by the molten salt is calculated according to the following calculation formula:
wherein
Measuring the mass flow of molten salt at the inlet of the molten salt heat absorber by using a molten salt flowmeter; h is outThe enthalpy value of fused salt at the outlet of the heat absorber; h is a total ofinThe enthalpy value of fused salt at the inlet of the fused salt heat absorber is measured by a fused salt temperature measuring device at the inlet/outlet of a tube panel of the fused salt heat absorber.
In order to obtain accurate molten salt absorbed energy, the flow rate of the molten salt and the temperature of the molten salt at the inlet/outlet of the heat absorber need to be relatively stable. Therefore, the fluctuation of the molten salt flow in the test period needs to be less than 15%, and the fluctuation of the molten salt temperature of the inlet and the outlet of the tube panel of the molten salt heat absorber needs to be less than 15 ℃.
In order to keep the energy supply and heat dissipation losses of the mirror field relatively stable, it is necessary to ensure that the DNI needs to be greater than 700KW/m during the test period in consideration of the relation between the projection energy of the mirror field and the DNI, the availability of the mirror field and the efficiency of the mirror field2And the fluctuation range is not suitable to exceed 50KW/m2(ii) a The availability ratio of the mirror field during the test is more than 90 percent; the mirror field efficiency is generally stable within 3 hours around noon, so the recommended test time period is within 3 hours around noon. The heat dissipation loss of the heat absorber is mainly related to the wind speed, and in order to reduce the test error, the wind speed during the test is required to be less than 6 m/s.
Generally, the greater the energy absorbed by the heat sink, the greater the accuracy of the test, and therefore it is recommended that the energy absorbed by the heat sink during the test be maintained at least above 85% of the rated energy. Therefore, a specular cleanliness of greater than 85% is recommended when testing.
The mirror field of a certain region of the heat absorption tower shadow can be greatly reduced to project energy, so that the mirror field of the heat absorber tube panel corresponding to the region can project energy which does not meet the test requirement, and therefore the absorption rate of the heat absorber tube panel is not measured when the heat absorber tube panel is shielded by the heat absorption tower shadow. Since the position of the sun changes over time, the absorptance of all heat absorber tube panels can be measured by adjusting the test time period.
Step S4 includes:
and calculating the tube panel absorption rate according to the calculation formula: α ═ E (E)r+L)/Et
Particularly, certain errors inevitably exist in the mirror field fractional efficiency during simulation calculation, so that certain errors exist in the absorption rate measurement result. In this case, the method provided by the invention is particularly suitable for measuring the relative absorption rate of the tube panel of the molten salt heat absorber.
The method for measuring the relative absorption rate of the tube panel of the molten salt heat absorber provided by the embodiment specifically comprises the following steps: the absorption rates of the 2 tube panels measured by the molten salt heat absorbers are set to be alpha and alpha ', respectively, alpha and alpha ' are calculated through the method, and then the relative absorption rates of the 2 tube panels are calculated through alpha/alpha '. Indeed, as described above, the simulation results of the atmospheric transmittance and the truncation efficiency tend to show a larger or smaller overall value, but when the two absorptances are compared, the calculation error is greatly reduced, so that the relative absorptance of the tube panel can be calculated more accurately.
Example 2
The embodiment provides a system for measuring tube panel absorption rate of a fused salt heat absorber, which comprises a power flow density simulation subsystem, a fused salt flowmeter, a fused salt temperature measuring device for an inlet/outlet of a fused salt heat absorber tube panel, an infrared thermometer and a wind speed and temperature measuring device, wherein the power flow density simulation subsystem is used for calculating to obtain energy projected to a single tube panel; the molten salt flow meter is used for measuring the mass flow of molten salt, the molten salt temperature measuring device at the inlet/outlet of the tube panel of the molten salt heat absorber is used for measuring the enthalpy values of the molten salt at the outlet and the inlet of the heat absorber, and data measured by the molten salt flow meter and the molten salt temperature measuring device at the inlet/outlet of the tube panel of the molten salt heat absorber are used for calculating to obtain the energy absorbed by the molten salt in the tube panel; the infrared thermometer is used for measuring the wall surface temperature of the heat absorber, the wind speed and temperature measuring device is respectively used for measuring the ambient wind speed and the ambient temperature, and data measured by the infrared thermometer and the wind speed and temperature measuring device are used for calculating to obtain the total heat dissipation loss of the tube panel; the absorption rate of the tube panel to be detected can be calculated through the energy projected to the single tube panel, the energy absorbed by the fused salt in the tube panel and the total heat dissipation loss of the tube panel.
The measuring method and the measuring system provided by the invention can indirectly measure the absorption rate of a single tube panel of the molten salt heat absorber, thereby providing an accurate basis for the coating replacement period and the efficiency calculation of the heat absorber.
The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims (7)
1. The method for measuring the relative absorption rate of the tube panel of the molten salt heat absorber is characterized by comprising the following steps of: the absorption rates of 2 tube panels measured by the molten salt heat absorber are respectively set as alpha and alpha ', alpha and alpha ' are respectively calculated, then the relative absorption rates of the 2 tube panels are calculated through alpha/alpha ', a basis is provided for coating replacement, and the calculation method of the absorption rates of the tube panels comprises the following steps:
Providing a test system, wherein the test system comprises an energy flow density simulation subsystem, a molten salt flowmeter, a molten salt temperature measuring device for an inlet and an outlet of a tube panel of a molten salt heat absorber, an infrared thermometer and a wind speed and temperature measuring device;
calculating energy projected to a single tube panel through the energy flow density simulation subsystem, wherein the energy flow density simulation subsystem must consider the influence of the shadow of the heat absorption tower, and does not measure the tube panel absorption rate of the heat absorber in the period when the heat absorber tube panel is shielded by the shadow of the heat absorption tower;
measuring mass flow of molten salt through the molten salt flowmeter, measuring the temperature of an outlet and an inlet of the heat absorber through the molten salt temperature measuring device at the inlet/outlet of the tube panel of the molten salt heat absorber to obtain an enthalpy value of the molten salt, and calculating the energy absorbed by the molten salt in the tube panel through the data measured by the molten salt flowmeter and the molten salt temperature measuring device at the inlet/outlet of the tube panel of the molten salt heat absorber;
measuring the average temperature of the light side wall surface of the measured tube panel by the infrared thermometer, measuring the ambient wind speed and temperature by the wind speed and temperature measuring device, and calculating the total heat dissipation loss of the tube panel by the data measured by the infrared thermometer and the wind speed and temperature measuring device;
the absorption rate of the tube panel is obtained through calculation of the energy projected to the single tube panel, the energy absorbed by the fused salt in the tube panel and the total heat dissipation loss of the tube panel, and the absorption rate of the measured tube panel is calculated through the following formula:
α＝(Er+L)/EtWherein, EtFor said energy projected onto a single tube panel, ErIs the energy absorbed by the molten salt in the tube panel, and L is the total heat dissipation loss of the tube panel.
2. The measurement method according to claim 1, wherein the energy absorbed by the molten salt in the tube panel is calculated as follows:
wherein,
the mass flow of the molten salt at the inlet of the molten salt heat absorber is measured by the molten salt flowmeter; h isoutFor heat absorberEnthalpy of outlet molten salt, hinThe enthalpy value of fused salt at the inlet of the fused salt heat absorber is obtained by the fused salt temperature measuring device at the inlet and the outlet of the tube panel of the fused salt heat absorber.
3. The measurement method according to claim 1, characterized in that the following requirements are placed on the test environment: direct radiation energy requirement during testing of more than 700KW/m2And needs to remain substantially stable; the wind speed during the test is required to be less than 6 m/s.
4. The measurement method according to claim 1, characterized in that the following requirements are placed on the stability of the test data: in the test period, the fluctuation of the molten salt flow is required to be less than 15%, and the fluctuation of the molten salt temperature of the inlet and outlet of the tube panel of the molten salt heat absorber is required to be less than 15 ℃.
5. The measurement method of claim 2, wherein the energy flux density simulation subsystem calculates the energy projected to a single tube panel using the following calculation:
Et＝DNI×S×N×ηt×ηcos×ηs×ηb×ηc×ηr×ηtruc
Wherein DNI is direct radiation energy, and S is the area of the solar energy which can be reflected by a single heliostat; n is the total number of heliostats projected onto the measured tube panel; etatIs the atmospheric transmittance; etacosIs the cosine efficiency; etasIs the shadow efficiency; etabTo the shading efficiency; etacThe cleanliness of the mirror surface; etarIs the mirror field reflectivity; etatrucThe truncation efficiency of the measured tube panel;
wherein the atmospheric transmittance etatCosine efficiency ηcosShadow efficiency ηsShielding efficiency etabAnd a cutoff efficiency ηtrucDirect simulation calculation is carried out through a mature algorithm, main input parameters of the direct simulation calculation are coordinates of all heliostats in a heliostat field and coordinates of four corners and vertexes of a measured tube panel, and DNI is directly measured through a DNI measuring instrument; the total number N of heliostats projected to the measured tube panel is directly read through monitoring software(ii) a Degree of mirror surface cleaning etacAnd mirror field reflectivity ηrAre obtained for the measurement.
6. The measurement method according to claim 5, wherein the degree of cleanliness η for the mirror surfacecThe following requirements are met: the cleanness of the mirror surface is more than 85 percent.
7. The measurement method according to claim 5, wherein the calculation formula of the total heat dissipation loss is as follows:
wherein: h is a convective heat transfer coefficient, mainly related to the ambient wind speed and the normal angle of the tested tube panel, and needs to be actually measured, if actual measurement data is lacked, the wind speed during the test needs to be less than 6m/s, and the convective heat transfer coefficient can be 10-60W/(m/m) 2K) A value in between; a is the light receiving area of the tube panel to be measured in unit m2；
The average temperature of the light-receiving side wall surface of the tube panel is measured in a unit K, and the unit K is directly measured by an infrared thermometer; t is a unit of0Is ambient temperature, in units of K; epsilon is the emissivity of the tube screen to be measured and is provided by a coating manufacturer, or can be 0.90 when no data exists; σ is Boltzmann constant.
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