CN110953736B - Fused salt heat absorber thermal efficiency test system and test method - Google Patents
Fused salt heat absorber thermal efficiency test system and test method Download PDFInfo
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- CN110953736B CN110953736B CN201811133184.3A CN201811133184A CN110953736B CN 110953736 B CN110953736 B CN 110953736B CN 201811133184 A CN201811133184 A CN 201811133184A CN 110953736 B CN110953736 B CN 110953736B
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- 150000003839 salts Chemical class 0.000 title claims abstract description 189
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- 238000012360 testing method Methods 0.000 title claims abstract description 67
- 238000010998 test method Methods 0.000 title claims abstract description 14
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention relates to the technical field of solar photo-thermal power generation, and discloses a fused salt heat absorber thermal efficiency test system and a test method, wherein the test system comprises the following steps: an optical path system, a thermal loop system, and a measurement system; the thermal loop system comprises a receiving tower, and converts energy in the optical loop system; the receiving tower is provided with a receiving window, and a fused salt heat absorber is arranged at the receiving window; the light path system comprises an illumination controller, a heliostat field and a reflecting mirror; the receiving tower is arranged between the heliostat field and the reflecting mirror, and the heliostat field reflects light rays to the reflecting mirror; the reflector reflects light to the receiving window, and an illumination controller is arranged between the reflector and the receiving tower, so that the radiation power on the heating surface of the fused salt heat absorber can be regulated; the measuring system comprises a measuring device and external equipment. According to the fused salt heat absorber thermal efficiency testing system and the testing method, the overall thermal efficiency of the heat absorber can be estimated by testing the thermal efficiency of the single tube bank in different temperature ranges, so that the cost is low and the operability is higher.
Description
Technical Field
The invention relates to the technical field of solar photo-thermal power generation, in particular to a fused salt heat absorber thermal efficiency test system and a test method.
Background
The solar power generation technology is an effective means for relieving the energy crisis, has a wide application prospect, and brings new hopes for coping with the global energy crisis. The Chinese solar energy resource is quite rich, and if the solar energy can be reasonably utilized, the Chinese solar energy resource can help to solve the energy problem.
Generally, solar thermal power generation mainly comprises three modes of a trough type, a disc type and a tower type, wherein a tower type photo-thermal power generation system has large capacity, high light concentration ratio, high operating temperature and high efficiency, and is one of the most rapid technologies developed at present. For a tower type solar thermal power generation system, a heat absorber is a key device for photo-thermal conversion. At present, a heat absorber taking molten salt as a working medium is mainly an exposed tube type heat absorber and generally comprises a heat absorption tube, wherein the molten salt working medium is arranged in the tube and is used for bearing solar energy absorbed by the heat absorber.
The thermal efficiency of the molten salt heat absorber is the most critical index, whether it is early design or later performance evaluation. However, in the prior art, one possible thermal efficiency test method is: and (3) placing the processed molten salt heat absorber on an actual solar photo-thermal power station receiving tower for installation, debugging, operation and testing of the thermal efficiency of the molten salt heat absorber, and guiding the optimal design of the molten salt heat absorber according to the test result. Although the scheme has feasibility, in actual operation, the installation position of the fused salt heat absorber is high, and the surface radiation power is high, so that the scheme has extremely large manpower and material resources required to be input, and the accuracy of a test result is difficult to ensure even if an actual test is carried out, so that the scheme is difficult to implement.
Disclosure of Invention
The invention is made in view of the above problems, and an object of the invention is to provide a molten salt heat absorber heat efficiency test system and a test method, which can reduce test cost and test difficulty by designing a miniaturized molten salt heat absorber and a heat efficiency test system thereof. Different working conditions are simulated, so that the thermal efficiency of the fused salt heat absorber under the different working conditions is tested.
Specifically, the invention provides a fused salt heat absorber thermal efficiency test system, which is used for testing the thermal efficiency of a tower type solar photo-thermal power generation fused salt heat absorber, and comprises the following steps: an optical path system, a thermal loop system, and a measurement system; the thermal loop system comprises a receiving tower, a receiving tower and a control unit, wherein the receiving tower is used for converting energy in the optical path system; the receiving tower is provided with a receiving window, a molten salt heat absorber is arranged at the receiving window, and the shape of the receiving window corresponds to the shape of a heating surface of the molten salt heat absorber; the light path system comprises an illumination controller, a heliostat field and a reflecting mirror; the receiving tower is arranged between the heliostat field and the reflecting mirror, and the heliostat field reflects light rays to the reflecting mirror; the reflecting mirror is used for further reflecting light to the receiving window, and the illumination controller is arranged between the reflecting mirror and the receiving tower, so that the radiation power received by the fused salt heat absorber can be regulated; the measuring system comprises a device for measuring the thermal efficiency of the thermal loop system and the optical path system and external equipment.
Compared with the prior art, the fused salt heat absorber thermal efficiency testing system provided by the invention has the advantages that the structure is simple, the operability is strong, and the overall thermal efficiency of the fused salt heat absorber can be evaluated by testing the thermal efficiency of a single tube bank in different temperature ranges under the condition that the incident power on the heating surface of the heat absorber is not required to be tested. In addition, the test system provided by the invention reduces the size of the molten salt heat absorber by miniaturizing the molten salt heat absorber, is beneficial to designing a simple molten salt heat absorber efficiency test system and is more accurate in obtaining the thermal efficiency of the molten salt heat absorber.
Preferably, the reflecting mirror includes a secondary parabolic reflecting mirror, and the illumination controller and the receiving window are disposed along a direction of an optical axis of the secondary parabolic reflecting mirror; the illumination controller includes a radiation control disc, and the radiation control disc is movable between the receiving window and the secondary parabolic mirror along a direction of an optical axis of the secondary parabolic mirror, and the radiation control disc and the receiving window are disposed on both sides of a focal point of the secondary parabolic mirror, respectively.
The radiation control disc can control the motion of the radiation control disc, and the radiation control disc can shield the light reflected by the secondary parabolic reflector, so that the radiation power reaching the receiving window can be adjusted. And when the radiation disc is used for adjusting radiation power, the energy distribution of the light spots on the surface of the fused salt heat absorber is still uniform.
Further, it is preferable that the radiation control disc is mounted by being parallel to the rotation axis of the receiving tower and is rotatable about the rotation axis.
The radiation control disc is also rotated to block the light reflected by the secondary parabolic mirror, thereby adjusting the power of the thermal radiation reaching the receiving window.
Further, preferably, the radiation control disc is provided with a cooling water passage, and a cooling water inlet and a cooling water outlet.
Because the radiation control disc blocks a part of heat radiation, the radiation control disc is higher in radiation power and temperature, so that the radiation control disc is deformed or even damaged at high temperature, and the normal use of the radiation control disc is affected. The introduced cooling water can exchange heat with the radiation control disc, so that heat is taken away, the temperature of the radiation control disc is reduced, and the radiation control disc is protected.
In addition, preferably, a light-restricting baffle is further arranged at the edge of the receiving window, an air duct is further arranged at the edge of the receiving window, a fan communicated with the air duct is arranged in the receiving tower, and a heating device can be arranged.
The air speed in the air duct is regulated by the fan, the air temperature in the air duct is regulated by the heating equipment, and the air flow reaches the receiving window through the air duct, so that different external environment conditions can be simulated.
Preferably, a heat-insulating device is further provided on a surface of the molten salt heat absorber that does not receive the light reflected by the secondary parabolic mirror.
The heat preservation device is arranged on the side of the heat absorber which does not receive illumination, and the heat preservation device is consistent with the situation in an actual tower type photo-thermal power station, so that the actual situation can be better simulated.
In addition, preferably, the measuring device includes: the first temperature sensor is used for measuring the temperature of the molten salt working medium at the inlet of the molten salt heat absorber, and the second temperature sensor is used for measuring the temperature of the molten salt working medium at the outlet of the molten salt heat absorber; and a flowmeter for measuring the flow rate of the molten salt working medium.
The invention also provides a method for testing the thermal efficiency of the fused salt heat absorber, which mainly comprises the following steps: s1, measuring the temperature of a molten salt working medium through a first temperature sensor arranged at an inflow port of a molten salt heat absorber and a second temperature sensor arranged at an outflow port of the molten salt heat absorber, and measuring the flow rate of the molten salt working medium through a flowmeter; s2, adjusting the distance (d) between the radiation control disc and the heating surface, measuring the temperature of molten salt working media at an inflow port and an outflow port of the molten salt heat absorber, and changing the flow rate of the molten salt working media by adjusting a molten salt pump to enable the measured temperature to be the same as the temperature measured at the inflow port and the outflow port in the S1; s3: measuring the flow of a molten salt working medium of a molten salt heat absorber; s4: and calculating and comparing the measured data to obtain the thermal efficiency of the fused salt heat absorber.
Compared with the prior art, the testing method provided by the invention can evaluate the overall thermal efficiency of the molten salt heat absorber without testing the radiation power of the heating surface of the molten salt heat absorber.
Further, preferably, in step S2, an angle a between the radiation control disc and the heating surface is adjusted, the temperatures of the molten salt working medium of the inflow port and the outflow port of the molten salt heat absorber are measured, and the flow rate of the molten salt working medium is adjusted by the molten salt pump, so that the measured temperatures are the same as the temperatures measured in the inflow port and the outflow port in step S1, and the effect of adjusting the radiation power of the heating surface of the heat absorber can be achieved.
Further, it is preferable that the air flow rate and temperature near the heated surface of the molten salt heat absorber are changed throughout the test steps S1 to S4, thereby simulating different external conditions.
Drawings
FIG. 1 is a schematic perspective view of a molten salt heat absorber thermal efficiency test system in accordance with a first embodiment of the invention;
FIG. 2 is a schematic diagram of a molten salt heat absorber thermal efficiency test system according to a first embodiment of the invention;
FIG. 3 is a schematic diagram of a thermal loop system of a molten salt heat sink thermal efficiency test system of a first embodiment of the invention;
FIG. 4 is a schematic view of a receiving window provided with a light-confining barrier in accordance with a first embodiment of the invention;
FIG. 5 is a schematic view of a receiving window with an air duct according to a first embodiment of the present invention;
FIG. 6 is a schematic view of a radiation control disc according to a first embodiment of the present invention;
FIG. 7 is a schematic view of a radiation control disc provided with a slideway and a slider in accordance with a first embodiment of the invention;
FIG. 8 is a schematic diagram of a test performed to adjust the distance d of a radiation control disc from a heated surface in accordance with a first, second or fourth embodiment of the present invention;
fig. 9 is a schematic diagram of a test performed by adjusting the angle a of the radiation control disc to the heated surface according to the first, third or fourth embodiment of the present invention.
Reference numerals illustrate:
1-a receiving tower; 1 a-a receiving window; 1a 1-a light-restricting baffle; 1a 2-air duct; a 2-mirror; 2 a-a secondary parabolic mirror; 3-an illumination controller; 3 a-a radiation control disc; 3 b-a rotating shaft; 3a 1-cooling water inlet; 3a 2-cooling water outlet; 3a 3-a circulating cooling water passage; 4-heliostat field; 5-a molten salt heat absorber; 5 a-heating surface; 5 b-inflow port; 5 c-outflow port; 6 a-a first temperature sensor; 6 b-a second temperature sensor; 6 c-a flow meter; 8-a heat preservation device; 9-a molten salt pump; 10-a molten salt storage tank; 11-a cooling tank; 12-a slideway; 13-a slider; 14-tightening the screw.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings. The structure of the molten salt heat absorber thermal efficiency test system and the like are schematically simplified in the drawings.
Embodiment one
A first embodiment of the present invention provides a molten salt heat absorber thermal efficiency testing system for testing thermal efficiency of a tower solar photo-thermal power generation molten salt heat absorber 5, as described in fig. 1,2 and 3, wherein a straight line with an arrow indicates a direction of light irradiation, and a dashed line in the figure indicates an optical axis of a reflector, including: an optical path system, a thermal loop system and a measurement system.
The thermal circuit system comprises a receiving tower 1 for converting energy in the optical path system, a receiving window 1a is arranged on the receiving tower 1, a molten salt heat absorber 5 is arranged at the receiving window 1a, and the shape of the receiving window 1a corresponds to the shape of a heating surface 5a of the molten salt heat absorber 5. And a molten salt pump 9, a molten salt storage tank 10, and a cooling tank 11 connected to the molten salt heat absorber 5. The molten salt working medium stored in the molten salt storage tank 10 is pumped into the molten salt heat absorber 5 through the heat absorber inflow port 5b by the molten salt pump 9, flows into the cooling tank 11 from the molten salt heat absorber 5 outflow port 5c for cooling after the molten salt working medium is heated to a certain temperature, and finally returns to the molten salt storage tank 10. In order to reduce the test cost, in the embodiment, the molten salt heat absorber 5 may be a tube row, and each test result exactly corresponds to the actual working condition of a single tube row in the molten salt heat absorber 5 of the actual tower type photo-thermal power station, so that the test system is miniaturized.
The light path system comprises an illumination controller 3, a heliostat field 4 and a reflecting mirror 2, and a receiving tower 1 is arranged between the heliostat field 4 and the reflecting mirror 2. The heliostat field 4 is composed of a plurality of heliostats. Light from the heliostat is reflected and focused by the mirror 2 to the receiving window 1 a. Among them, the mirror 2 is preferably a mirror capable of converging light, such as a secondary parabolic mirror. An illumination controller 3 is provided between the reflecting mirror 2 and the receiving tower 1, and the receiving tower 1 and the illumination controller 3 are provided along a straight line where the optical axis of the reflecting mirror 2 is located, the illumination controller 3 being capable of adjusting the intensity of radiation reflected by the secondary parabolic reflecting mirror 2a to the receiving window 1 a.
The measurement system includes a device (not shown) and an external device (not shown) for measuring the thermal efficiency of the thermal circuit system and the optical path system.
Compared with the prior art, the fused salt heat absorber thermal efficiency testing system provided by the invention is simple in structure and strong in operability, and can evaluate the overall thermal efficiency of the fused salt heat absorber 5 by testing the thermal efficiency of a single tube bank in different temperature ranges under the condition that radiant power on a heating surface of the heat absorber is not required to be tested. In addition, the testing system provided by the invention miniaturizes the fused salt heat absorber and the thermal efficiency testing system thereof, is beneficial to reducing the testing cost and accurately obtaining the thermal efficiency of the fused salt heat absorber 5, and has stronger operability.
In the present embodiment, as shown in fig. 2, the illumination controller 3 includes a radiation control disc 3a, and the radiation control disc 3a is movable between the receiving window 1a and the secondary parabolic mirror 2a in the direction of the optical axis of the secondary parabolic mirror 2a, and the radiation control disc 3a and the receiving window 1a are disposed on both sides of the focal point of the secondary parabolic mirror 2a, respectively. The radiation control disc 3a is provided to be able to regulate the radiation power incident on the heated face 5a of the molten salt heat absorber 5. And the energy distribution of the light spots on the surface of the molten salt heat absorber 5 is still uniform when the radiation control disc 3a is put into use. Of course, the illumination controller 3 may take other shapes as long as the adjustment of the radiation power can be achieved without affecting the energy distribution uniformity of the heating surface 5a of the molten salt heat absorber 5.
More preferably, in the present embodiment, the radiation control disk 3a is mounted by being parallel to the rotation axis 3b of the receiving tower 1, and the radiation control disk 3a can be rotated about the rotation axis 3b, the effect of adjusting the radiation power on the heating surface 5a of the molten salt heat absorber 5 can also be achieved.
The radiation control disc 3a is able to control its own movement, shielding the light reflected by the secondary parabolic mirror 2a, and thus regulating the radiation power reaching the heating surface 5 a. And when the radiation disc is adopted for simulation, the uniformity of the light spot energy distribution on the heating surface 5a of the fused salt heat absorber 5 is not affected.
Specifically, in the present embodiment, as shown in fig. 6, a slide 12 may be provided between the secondary parabolic mirror 2a and the receiving window 1a in the direction of the optical axis of the secondary parabolic mirror 2a, and a slider 13 may be installed in the slide 12, and the radiation control disk 3a may be connected to the slider 13 through a rotation shaft 3b, and when the slider 13 moves, the radiation control disk 3a also moves by the same distance.
And in the present embodiment, the inventors of the present invention found the effective adjustment range of the radiation control disc 3a by simulation. Specific simulation conditions are as follows.
Location: 30.3 ° north latitude, spring day, 11 am: 00.
Heliostat: the dimensions are 5.0m by 4.0m, the curvature is 0.009,8 plane heliostats, and the frontal reflectivity is 0.93.
Secondary parabolic mirror: the parabolic equation is: The cross-sectional diameter was 10.0m, the focal length was 6.0m, and the front reflectance was 0.93.
Light-restricting baffle: the width is 0.4m, 4 total, two light restraint baffles about and the plane that the receiver plane is located are 75 angles, and two upper and lower light restraint baffles are arranged horizontally, and the front reflectivity is 0.93.
The heating surface 5a of the molten salt heat absorber 5: the shape is rectangular, the size is 0.4mx1.0m, and solar radiation with the distance of 6.2m from the center of the parabola is taken as a spring festival day-to-day average dni=750w/m 2.
The diameter of the radiation control disc 3a is 0.3m.
Firstly, simulating a control group without the radiation control disc 3a to obtain various data of the heating surface 5a at the moment:
Total radiated power: p total = 43.6906kW
Average fluence density: p average＝109.226kW/m2
Peak fluence: p peak＝164.963kW/m2
Minimum fluence: p min＝32.8164kW/m2
The distance d between the radiation control disc 3a and the heated surface 5a is adjusted to obtain the result shown in the following table, wherein P total is the total radiation power, P average is the average fluence, P peak is the peak fluence, P min is the lowest fluence, uniformity is the non-uniformity of the radiation energy distribution on the heated surface of the heat absorber, and χ is the ratio of the actual radiation power to the radiation power on the heated surface of the heat absorber when the radiation control disc 3a is not used.
When the distance between the radiation control disc 3a and the heated surface 5a is smaller than 0.6m, the energy distribution of the heated surface 5a is less uniform, so that a local high-temperature area appears on the heated surface 5a of the molten salt heat absorber 5, and the molten salt heat absorber 5 is possibly damaged by local overheating. Therefore, the adjustment range of the distance d between the radiation control disc 3a and the heating surface 5a needs to be 0.6m or more.
The angle a between the radiation control disc 3a and the plane of the heating surface 5a is adjusted with d=0.6m and the following table is obtained:
from the table, when the angle a between the radiation control disc 3a and the plane of the heating surface 5a is adjusted to be larger than 60 °, the rotation of the radiation control disc 3a has little influence on the percentage of the total energy on the heating surface 5a, and basically has no adjusting function, so the adjusting range of the angle a is (0-60 °).
For more convenient measurement and improved measurement accuracy, as shown in fig. 6, graduations are further provided on the slide 12, and stoppers such as fastening screws 14 and the like are provided on the slider 13. When the slider 13 moves to a preset test position, the radiation control disc 3a is fixed by tightening the fastening screw 14, so that the movement of the radiation control disc 3a in the test process is reduced, and the accuracy of the test result is ensured. Preferably, the radiation control disc 3a is integrally formed with the rotation shaft 3b, and a fastener is further provided at a lower portion of the rotation shaft to fix an angle of each rotation of the radiation control disc 3 a.
Moreover, since the radiation control disc 3a blocks a part of the heat radiation, it can be found from the above table that the radiation power on the surface of the radiation control disc 3a is large and the temperature is high, so that the radiation control disc 3a is easily damaged at high temperature, and the normal use of the radiation control disc 3a is affected. For protection of the radiation control disc 3a, in the present embodiment, referring to fig. 7, the radiation control disc 3a is provided with a cooling water channel 3a3 and a cooling water inlet 3a1 and a cooling water outlet 3a2, so that cooling water can flow in the cooling water channel 3a3 in the radiation control disc 3a, thereby performing heat exchange with the radiation control disc 3a more sufficiently, taking away heat of the radiation control disc 3a, reducing temperature of the radiation control disc 3a, and playing a role in protecting the radiation control disc.
In addition, in this embodiment, referring to fig. 4 and 5, the shape of the receiving window 1a in this embodiment is rectangular, a light-restricting baffle 1a1 is further disposed at the edge of the receiving window 1a, the light-restricting baffle 1a1 reflects the incident light to reflect the light to the molten salt absorber 5, so that the shape of a light spot formed at the receiving window 1a is the same as the shape of the heated surface 5a of the molten salt absorber 5, so that the heat radiation distribution of the heated surface 5a of the molten salt absorber 5 is uniform, and damage to the molten salt absorber 5 caused by too high local heat flux density can be effectively prevented. The inventor of the present invention found that under the above simulation conditions, when the included angle between the left and right light-restricting baffles 1a1 and the plane where the heating surface 5a is located is 75 °, the upper and lower light-restricting baffles 1a1 are horizontally arranged, a better effect of reflecting light can be achieved.
An air duct 1a2 is also provided at the edge of the receiving window 1a, and a fan (not shown) communicating with the air duct 1a2 is provided on the receiving window 1 a. Air is supplied by a fan, and air is conveyed to the heating surface 5a of the fused salt heat absorber 5 through the air duct 1a2 and air holes arranged at the edge of the receiving window 1a, so that different working conditions are simulated.
It should be noted that in this embodiment, the fan further includes a temperature regulator (not shown). The device is used for adjusting the temperature of the wind sent out by the air duct 1a2 and further simulating the corresponding working conditions in different seasons.
In the present embodiment, a heat insulating device 8 is further provided on a surface of the molten salt heat absorber 5 that does not receive the light reflected by the secondary parabolic mirror 2a.
A thermal insulation device 8 is arranged for simulating the working environment of the molten salt heat absorber 5a in the actual photo-thermal power station. Wherein, the common heat preservation device 8 is heat preservation cotton.
In order to be able to obtain accurate data for calculating the thermal efficiency of the molten salt heat absorber 5, in the present embodiment, as shown in fig. 3, the measuring device includes: a first temperature sensor 6a and a second temperature sensor 6b, the first temperature sensor 6a is used for measuring the temperature of the molten salt working medium of the inflow port 5b of the molten salt heat absorber 5, and the second temperature sensor 6b is used for measuring the temperature of the molten salt working medium of the outflow port 5c of the molten salt heat absorber 5; a flow meter 6c for measuring the flow rate of the molten salt working medium. Among them, a common temperature sensor is a thermocouple.
In view of the above, the fused salt heat absorber system of the present embodiment is a miniaturized concentrating heat collecting platform, and uses heliostats, secondary parabolic reflectors 2a, and light-restricting baffles 1a1 comprehensively to collect solar radiation energy, so that the fused salt heat absorber system has higher accuracy and operability.
Second embodiment
The second embodiment of the invention also provides a method for testing the thermal efficiency of the molten salt heat absorber, which comprises the following steps:
S1, adjusting the distance d between a radiation control disc 3a and a molten salt heat absorber 5, respectively measuring the temperature of molten salt working media at an inflow port 5b and an outflow port 5c of the molten salt heat absorber 5 by a first temperature sensor 6a and a second temperature sensor 6b, and measuring the flow rate of the molten salt working media by a flowmeter 6 c;
S2, moving the radiation control disc 3a, adjusting the distance d between the radiation control disc 3a and the heating surface 5a, and adjusting the molten salt pump 9 to change the flow rate of molten salt working medium, so that the temperature of the inflow port 5b and the outflow port 5c of the molten salt heat absorber 5 is the same as the temperature measured in the step S1;
S3: measuring the flow of molten salt working medium in the molten salt heat absorber;
s4: and calculating the measured data to obtain the thermal efficiency of the fused salt heat absorber 5.
Compared with the prior art, the test method provided by the invention can evaluate the overall thermal efficiency of the molten salt heat absorber 5 without testing the radiation power of the heating surface 5a of the molten salt heat absorber 5.
Specifically, in the present embodiment, referring to fig. 8, a specific method for performing the test includes:
The data to be tested in the actual test are as follows: the first temperature sensor 6a measures the temperature T in of the inflow opening 5b of the molten salt heat absorber 5, the second temperature sensor 6b measures the temperature T out of the outflow opening 5c of the molten salt heat absorber 5, and the flowmeter 6c measures the flow of molten salt working medium
Under the condition that the molten salt heat absorber 5 is in thermal balance, the radiation power P inc on the heating surface 5a of the molten salt heat absorber is equal to the sum of the reflection power (ρP inc) of the molten salt heat absorber 5, the absorption power (P abs) of molten salt working medium and the heat loss power (P los), wherein alpha is the absorptivity of a heat absorption pipe of the molten salt heat absorber 5, ρ is the reflectivity of the heat absorption pipe surface of the molten salt heat absorber 5, and since the transmissivity of the heat absorption pipe is negligible, ρ=1-alpha has the following relation:
Pinc＝ρPinc+Pαbs+Plos
αPinc＝Pabs+Plos
Thus, the molten salt endothermic power can be obtained:
Wherein, H out、Hin is the enthalpy value of molten salt at the inflow port 5b and the outflow port 5c of the molten salt heat absorber 5, and c is the specific heat capacity of the molten salt working medium:
(Hout-Hin)＝c(Tout-Tin)。
The radiation power of the heated surface 5a of the fused salt heat absorber 5 in a specific time period is P inc, the radiation power of the heated surface 5a of the fused salt heat absorber 5 can be changed into χP inc by adjusting the distance d between the radiation control disc 3a and the heated surface 5a of the fused salt heat absorber 5, wherein χ is the ratio of the actual radiation power incident on the heated surface 5a of the fused salt heat absorber 5 after the radiation control disc 3a is adopted to the radiation power when the radiation control disc 3a is not adopted, and is χ - χ (d) and χ=0-1.
When 12 with respect to the local sun according to solar radiation: symmetry of 00, two are chosen with respect to 12: a time period of 00 symmetry was tested. In this embodiment, group a and group B were selected for comparison. Wherein:
group a:11:40-12:00, at this time, the distance d between the radiation control disc 3a and the heating surface 5a of the molten salt heat absorber 5 is adjusted to be a, and the incident power is as follows:
Pinc,A＝χA·PincA
group B:12:00-12:20, at this time, the distance d between the radiation control disc 3a and the heated surface 5a of the molten salt heat absorber 5 is adjusted to b, and the incident power is:
Pinc,B＝χB·PincB
the following is obtained:
αχAPincA＝Pabs,A+Plos,A
αχBPincB＝Pabs,B+Plos,B
Considering the symmetry in time, the following relationship can be considered:
PincA＝PincB
When the inlet and outlet temperatures and external conditions of the fused salt heat absorber 5 are unchanged, the temperature distribution on the surface of the fused salt heat absorber 5 is irrelevant to the radiation power received by the fused salt heat absorber 5 no matter how the mass flow of the working medium is changed, so that the total heat loss power is unchanged. Thus, there are:
Plos,A＝Plos,B＝Plos
It is then possible to obtain:
thus, the first and second substrates are bonded together,
Thus, the thermal efficiency is expressed as:
The efficiency η A、ηB of the two time periods can be calculated separately, and the overall efficiency can then be calculated as the arithmetic mean:
The thermal efficiency of the molten salt heat absorber 5 corresponding to the environmental conditions is obtained.
It should be noted that the above test method requires that the sky be clear and cloudless during the test.
Embodiment III
In the third embodiment of the present invention, a method for testing the thermal efficiency of a molten salt heat absorber is provided, which is a further improvement of the second embodiment, and the main improvement is that in step S2 of the present embodiment, the distance d between the radiation control disc 3a and the heating surface 5a is kept unchanged, the radiation control disc 3a is rotated, and the angle a formed by the radiation control disc 3a and the plane of the heating surface 5a is adjusted.
Referring to fig. 9, by adjusting the angle a formed by the radiation control disc 3a and the plane of the heating surface 5a, the radiation power received by the heating surface 5a is changed.
Specifically, in the present embodiment, the control group in which the radiation control disc 3a is not provided is also measured and the corresponding data is obtained. The specific calculation steps are the same as those of the second embodiment, and will not be described herein. The radiation control disc 3a is then rotated and the angle a between the radiation control disc 3a and the heated surface 5a is adjusted.
The radiation power of the heated surface 5a of the fused salt heat absorber 5 in a specific time period is P inc, the power incident on the heated surface 5a of the fused salt heat absorber 5 is changed into χ ' P inc by adjusting the included angle A between the radiation control disc 3a and the heated surface 5a, wherein χ ' is the ratio of the actual radiation power incident on the heated surface 5a of the fused salt heat absorber 5 after the radiation control disc 3a is adopted to the radiation power when the radiation control disc 3a is not adopted, and χ ' to χ ' (A) and χ ' =0 to 1.
When 12 with respect to the local sun according to solar radiation: symmetry of 00, two are chosen with respect to 12: a time period of 00 symmetry was tested. For example:
group a:11:40-12:00, at this time, the angle a between the rotating radiation control disc 3a and the heating surface 5a is a', and the incident power is:
Pinc,A＝χ′A·PincA
group B:12:00-12:20, at this time, the angle a between the rotating radiation control disc 3a and the heating surface 5a is b', and the incident power is:
Pinc,B＝χ′B·PincB
The thermal efficiency is then calculated according to the calculation method in the second embodiment. Similarly, in the present embodiment, the sky is required to be clear and cloudless when the test is performed by the above-described test method.
Of course, in this embodiment, the distance d between the radiation control disc 3a and the heating surface 5a may be adjusted while the angle a between the radiation control disc 3a and the heating surface 5a is adjusted, so as to obtain a larger adjustment range of radiation power, and improve accuracy of the test result.
Fourth embodiment
A fourth embodiment of the present invention provides a method of testing the thermal efficiency of a molten salt absorber 5, which is an improvement over the second and third embodiments, the main improvement being that in the second and third embodiments, the default group a and group B times are relative to the local solar time 12:00 symmetry, when the sky is clear and cloudless, the solar irradiance (DNI) values are the same, and thus P incA＝PincB is considered. In practice, the weather condition is more demanding, and in the embodiment, slight cloud shielding and scattering of particles such as atmospheric dust are considered, so that the influence of weather condition fluctuation on a test result can be reduced by the test method provided by the embodiment.
Because the scale of the test system is smaller, a radiometer is additionally arranged beside the heliostat to monitor DNI change in real time, and finally, integral time averaging is carried out on measurement data of the radiometer to obtain an actual solar radiation average DNI value. The ratio of the obtained average DNI value to the radiation value DNI 0 value calculated according to the astronomical data corresponding to the latitude of the placeThat is to say,
Wherein,Less than 1.
Under ideal weather conditions, the ideal radiation power of the heated surface 5a of the molten salt heat absorber 5 in a specific time period is P inc, and the power incident on the heated surface 5a of the molten salt heat absorber 5 is changed into
When 12 with respect to the local sun according to solar radiation: symmetry of 00, two are chosen with respect to 12: a time period of 00 symmetry was tested. For example:
Group a:11:40-12:00, at this time, the distance d between the radiation control disc 3a and the heating surface 5a of the molten salt heat absorber 5 is adjusted to be a ", and the incident power is as follows:
Group B:12:00-12:20, at this time, the distance d between the radiation control disc 3a and the heated surface 5a of the molten salt heat absorber 5 is adjusted to b ", and the incident power is:
The remaining steps are exactly the same as those of the second embodiment.
Finally, the following relationship is obtained:
Similarly, when the temperature of the inflow port 5b and the outflow port 5c of the molten salt heat absorber 5 and the external conditions are unchanged, the temperature distribution on the surface of the molten salt heat absorber 5 is independent of the radiant power received by the molten salt heat absorber 5 regardless of the change of the mass flow rate of the working medium, so that the total heat loss power is unchanged. Thus, there are:
Plos,A＝Plos,B＝Plos
It is then possible to obtain:
thus, the first and second substrates are bonded together,
Thereby obtaining the following steps:
the efficiencies η A、ηB of the four time periods can be respectively calculated, and the overall efficiency can be calculated as an arithmetic average value:
The thermal efficiency of the molten salt heat absorber 5 is derived taking into account DNI variations.
Fifth embodiment
The fourth embodiment of the present invention provides a method for testing the thermal efficiency of a molten salt heat absorber, which is a further improvement of any one of the second, third and fourth embodiments, and is mainly improved in that in any one of the foregoing second, third and fourth test schemes, besides the foregoing necessary test steps, the working state of a fan can be adjusted during the whole test process, so as to change the air flow rate near the molten salt heat absorber 5. In addition, the seasonal variation is considered, and the air sent by the fan can be heated or cooled by the temperature regulator, so that weather conditions corresponding to different seasons are simulated, and the heat absorber thermal efficiency under different external environment conditions is obtained.
The specific calculation step is the same as that of the second embodiment.
Those skilled in the art will appreciate that in the foregoing embodiments, numerous technical details have been set forth in order to provide a thorough understanding of the present application. The technical solutions claimed in the claims of the present application can be basically implemented without these technical details and various changes and modifications based on the above embodiments. Accordingly, in actual practice, various changes may be made in the form and details of the above-described embodiments without departing from the spirit and scope of the application.
Claims (8)
1. The utility model provides a fused salt heat absorber thermal efficiency test system for test tower solar photo-thermal power generation fused salt heat absorber thermal efficiency, its characterized in that includes: an optical path system, a thermal loop system, and a measurement system;
The thermal loop system comprises a receiving tower for converting energy in the optical path system;
The receiving tower is provided with a receiving window, a molten salt heat absorber is arranged at the receiving window, and the shape of the receiving window corresponds to the shape of a heating surface of the molten salt heat absorber;
the hot loop system further comprises a molten salt pump, and the molten salt pump is connected with the molten salt heat absorber through a pipeline and can adjust the flow of molten salt working medium in the hot loop system;
the light path system comprises an illumination controller, a heliostat field and a reflecting mirror;
The receiving tower is arranged between the heliostat field and the reflecting mirror, and the heliostat field reflects light rays to the reflecting mirror; the reflecting mirror is used for reflecting light to the receiving window, and the illumination controller is arranged between the reflecting mirror and the receiving tower and can adjust the radiation power on the heating surface of the fused salt heat absorber;
The measuring system comprises a device for measuring the thermal efficiency of the thermal loop system and the optical path system and an external device,
The reflecting mirror comprises a secondary parabolic reflecting mirror, and the illumination controller and the receiving window are arranged along the direction of the optical axis of the secondary parabolic reflecting mirror; the illumination controller comprises a radiation control disc, the radiation control disc can move along the direction of the optical axis of the secondary parabolic reflector between the receiving window and the secondary parabolic reflector, the radiation control disc and the receiving window are respectively arranged at two sides of the focus of the secondary parabolic reflector,
The radiation control disc is mounted by a rotation axis parallel to the receiving tower and is rotatable about the rotation axis.
2. The molten salt heat sink thermal efficiency test system of claim 1 wherein the radiation control disk is provided with a circulating cooling water channel and cooling water inlet and outlet.
3. The molten salt heat sink thermal efficiency testing system of claim 1, wherein a light-confining baffle is provided at an edge of the receiving window for reflecting light on the receiving window.
4. A molten salt heat absorber thermal efficiency test system according to claim 1 or 3, wherein an air duct is provided at the edge of the receiving window, and a fan is provided in the receiving tower in communication with the air duct.
5. The molten salt heat absorber thermal efficiency test system of claim 1, wherein a thermal insulation device is further arranged on a surface of the molten salt heat absorber, which does not receive the illumination reflected by the secondary parabolic reflector.
6. A molten salt heat absorber efficiency test method, tested by the molten salt heat absorber thermal efficiency test system according to any one of claims 1-5, comprising the steps of:
S1, measuring the temperature of a molten salt working medium through a first temperature sensor arranged at an inflow port of the molten salt heat absorber and a second temperature sensor arranged at an outflow port of the molten salt heat absorber, and measuring the flow of the molten salt working medium through a flowmeter;
s2, adjusting the distance (d) between the radiation control disc and the heating surface, measuring the temperature of molten salt working media of the inflow port and the outflow port of the molten salt heat absorber, and changing the flow rate of the molten salt working media by adjusting a molten salt pump to enable the measured temperature to be the same as the temperature measured at the inflow port and the outflow port in the S1;
S3: measuring the flow of molten salt working medium of the molten salt heat absorber;
S4: and calculating and comparing the measured data to obtain the thermal efficiency of the fused salt heat absorber.
7. The molten salt heat absorber efficiency test method according to claim 6, wherein in step S2, an angle a between a radiation control disk and a heated surface is adjusted, temperatures of molten salt working media of the inflow port and the outflow port of the molten salt heat absorber are measured, and flow rates of the molten salt working media are changed by adjusting a molten salt pump so that the measured temperatures are the same as temperatures measured at the inflow port and the outflow port in S1.
8. The molten salt heat sink efficiency test method according to claim 6 or 7, characterized in that the air flow rate and temperature near the heated surface of the molten salt heat sink are changed throughout the test steps S1-S4, thereby simulating different external conditions.
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