Method for judging flow passage blockage of molten salt micro-channel heat exchanger, test platform and method

Abstract

The present disclosure provides a flow channel blockage condition discrimination method in molten salt micro-channel heat exchanger performance test, at the beginning of the test, the initial temperature of the heat transfer fluid in the molten salt micro-channel heat exchanger is obtained, and the initial pressure drop between the inlet and outlet of the heat transfer fluid in the molten salt micro-channel heat exchanger is obtained; the heat transfer fluid is molten salt or steam; at a test time point s, the current temperature of the heat transfer fluid in the molten salt micro-channel heat exchanger is obtained, and the current pressure drop between the inlet and outlet of the heat transfer fluid in the molten salt micro-channel heat exchanger is obtained; according to the relationship between temperature and fluid density, the densities corresponding to the initial temperature and the current temperature are determined; the micro-channel blockage degree of the molten salt micro-channel heat exchanger at the test time point is determined by using the pressure drop and density data. The present disclosure also provides a molten salt micro-channel heat exchanger performance test platform and a test method. Using the present disclosure can realize the discrimination of the blockage condition of the molten salt micro-channel heat exchanger.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of molten salt heat storage, and particularly relates to a molten salt micro-channel heat exchanger performance test platform, a test method, and a molten salt micro-channel heat exchanger flow channel blockage condition discrimination method. BACKGROUND

[0002] The molten salt steam generator in solar thermal power generation and molten salt heat storage is a key link of heat conversion. The micro-channel heat exchanger has the characteristics of large unit volume heat exchange area, compact structure, excellent heat transfer performance, and the like, and can replace the shell-and-tube heat exchanger to be used for heat exchange between molten salt and fluid such as steam and sCO2. The micro-channel heat exchanger usually contains multiple fine flow channels. The heat exchange channel is smaller than the conventional shell-and-tube heat exchanger, and the channel diameter is generally less than 3 mm, which is easy to accumulate particulate impurities. Compared with conventional heat transfer fluid, the molten salt has the characteristics of high melting point, large viscosity and density, and corrosion, and in the heat exchange process, the change of the temperature causes the change of the properties of the molten salt, which causes the molten salt to be partially condensed in the heat exchange channel. After long-term operation, the corrosion scale is generated on the channel wall, which further causes the diameter of the heat exchange channel to be reduced, and even blocked.

[0003] It is very important to build a heat exchanger performance test platform in the design, production and experimental research of the heat exchanger. The existing test platform is mainly used for the heat transfer performance test of the conventional size channel molten salt heat exchanger (such as the shell-and-tube heat exchanger) or the micro-channel heat exchanger of conventional fluid such as water. The test platform for the heat transfer performance of the molten salt micro-channel heat exchanger is not perfect, and has the following problems:

[0004] 1) The existing molten salt micro-channel heat exchanger test platform can only test the heat exchange performance of the heat exchanger, and lacks the test method for the increase of the flow resistance and the channel blockage caused by the condensation of the molten salt, and has no discrimination ability for the channel blockage condition.

[0005] 2) In the actual operation of the molten salt heat storage system, the working condition frequently changes, and the heat exchanger intermittently works, such as 18 hours of operation and 6 hours of shutdown within one day. The existing test system cannot perform the performance test of the heat exchanger in the long time and periodic change.

[0006] 3) In the test process of the micro-channel heat exchanger and other forms of heat exchanger, the energy transferred from the molten salt to the steam is large, the high-temperature steam discharged from the heat exchanger is directly cooled or emptied, and there is a lack of energy recovery unit, which causes the test platform to consume more electric energy and have high operation cost in the long-term operation process. SUMMARY

[0007] Therefore, the application provides a molten salt micro-channel heat exchanger performance test platform, a test scheme and a molten salt micro-channel heat exchanger flow channel blockage condition discrimination method, which can realize the discrimination of the blockage condition of the molten salt micro-channel heat exchanger.

[0008] To solve the above technical problems, the present application is implemented as follows.

[0009] A flow passage blockage condition discrimination method in performance test of a molten salt micro-channel heat exchanger, comprising:

[0010] At the beginning of the test, the initial temperature T0 of the heat transfer fluid in the molten salt micro-channel heat exchanger is obtained, as well as the initial pressure drop ΔP0 between the inlet and outlet of the heat transfer fluid of the molten salt micro-channel heat exchanger; the heat transfer fluid is molten salt or steam;

[0011] At a test time point s, the current temperature T s of the heat transfer fluid in the molten salt micro-channel heat exchanger is obtained, as well as the current pressure drop ΔP s between the inlet and outlet of the heat transfer fluid of the molten salt micro-channel heat exchanger;

[0012] The initial temperature T0 and the current temperature T s are obtained, as well as the corresponding initial density ρ0 and the current density ρ s ;

[0013] The micro-channel blockage degree η of the molten salt micro-channel heat exchanger at the test time point s is determined, and the greater the η value, the more serious the blockage:

[0014]

[0015] Preferably, the initial temperature T0 and the current temperature T s are both the average temperature of the inlet and outlet of the molten salt side or the steam side of the molten salt micro-channel heat exchanger.

[0016] Preferably, the method further comprises: during the test stage, recording the corresponding relationship between various pressure drop values and the micro-channel blockage degree η as the micro-channel pressure drop changes; according to the maximum degree η max of the micro-channel blockage allowed by the molten salt micro-channel heat exchanger, the corresponding relationship is used to find the pressure drop value as the blockage fault pressure drop threshold ΔP 阈值 of the currently tested molten salt micro-channel heat exchanger;

[0017] When the molten salt micro-channel heat exchanger is actually working, if the pressure drop between the inlet and outlet of the heat transfer fluid of the molten salt micro-channel heat exchanger reaches the blockage fault pressure drop threshold ΔP 阈值 , it is determined that a blockage fault occurs.

[0018] Preferably, the method further comprises: obtaining the change relationship of the micro-channel blockage degree η with time, which is used to predict the micro-channel blockage change of the molten salt micro-channel heat exchanger when the molten salt micro-channel heat exchanger is actually working.

[0019] The application further discloses a molten salt micro-channel heat exchanger performance test platform which adopts the above-mentioned method to judge the blocking condition; the test platform comprises a molten salt loop, a steam loop, a heat-conducting oil storage loop and a control module.

[0020] The molten salt loop is led out from a molten salt side outlet of the measured molten salt micro-channel heat exchanger, is sequentially connected with a low-temperature molten salt tank and a high-temperature molten salt tank, and is then connected with a molten salt side inlet of the measured molten salt micro-channel heat exchanger; the high-temperature molten salt tank has a smaller volume than the low-temperature molten salt tank.

[0021] The steam loop is led out from a steam side outlet of the measured molten salt micro-channel heat exchanger, is sequentially connected with a steam pipeline of a molten salt preheater, a steam pipeline of a steam-water-oil heat exchanger and a steam-electric heater, and is then connected with a steam side inlet of the measured molten salt micro-channel heat exchanger; the steam-electric heater is connected with a softened water supply device; the molten salt preheater is connected to a pipeline between the low-temperature molten salt tank and the high-temperature molten salt tank in the molten salt loop, and the recovered steam energy is used to heat the low-temperature molten salt.

[0022] The heat-conducting oil storage loop is led out from a heat-conducting oil side outlet of the steam-water-oil heat exchanger, is connected with a heat-conducting oil supply device, and is then returned to a heat-conducting oil side inlet of the steam-water-oil heat exchanger, so that the remaining steam energy in the steam-water-oil heat exchanger is further recovered into the heat-conducting oil.

[0023] The control module is connected with sensors in the loops, and adopts the above-mentioned flow channel blocking condition judgment method to judge the blocking condition.

[0024] Preferably, a molten salt inlet pressure gauge, a molten salt filter, a molten salt flowmeter and a molten salt inlet temperature gauge are sequentially arranged on a molten salt side inlet pipeline of the measured molten salt micro-channel heat exchanger, and the molten salt inlet pressure gauge is arranged upstream of the molten salt filter; a molten salt outlet temperature gauge and a molten salt outlet pressure gauge are sequentially arranged on a molten salt side outlet pipeline of the measured molten salt micro-channel heat exchanger; and measurement points of a molten salt differential pressure gauge are arranged on the molten salt side inlet pipeline and the outlet pipeline of the measured molten salt micro-channel heat exchanger.

[0025] A steam inlet pressure gauge, a steam filter, a steam flowmeter and a steam inlet temperature gauge are sequentially arranged on a steam side inlet pipeline of the measured molten salt micro-channel heat exchanger, and the steam inlet pressure gauge is arranged upstream of the steam filter; a steam outlet temperature gauge and a steam outlet pressure gauge are sequentially arranged on a steam side outlet pipeline of the measured molten salt micro-channel heat exchanger; and measurement points of a steam differential pressure gauge are arranged on the steam side inlet pipeline and the outlet pipeline of the measured molten salt micro-channel heat exchanger.

[0026] Preferably, a molten salt preheater steam flow meter, a molten salt preheater steam inlet stop valve, and a test module steam outlet stop valve are arranged on the steam circuit between the molten salt preheater and the steam side outlet of the molten salt microchannel heat exchanger under test; a test module steam inlet stop valve is arranged on the steam circuit between the molten salt preheater and the steam side inlet of the molten salt microchannel heat exchanger under test; and a molten salt preheater steam regulating valve is arranged between the steam inlet pipeline and the steam outlet pipeline of the molten salt preheater to regulate the molten salt temperature at the outlet of the molten salt preheater.

[0027] Preferably, a steam evacuation bypass is connected to the steam-water-oil heat exchanger outlet pipeline, and a steam evacuation valve is arranged therein; a steam-water electric heater is arranged on the steam side inlet pipeline of the molten salt microchannel heat exchanger under test to supplement the steam in the circuit when the test platform is running, and a softened water regulating valve is controlled to maintain the stable steam flow at the steam side inlet of the molten salt microchannel heat exchanger under test.

[0028] The application further provides a test method using the molten salt microchannel heat exchanger performance test platform.

[0029] Step 1: Preheat the test system: run the electric heat tracing system arranged around the test platform to heat the molten salt microchannel heat exchanger under test and the pipelines and equipment on the test platform; run the variable-power electric resistance wire heater in the low-temperature molten salt tank to heat the molten salt in the low-temperature molten salt tank to above the melting point; and control the softened water supply device to pass softened water into the steam-water electric heater to preheat the steam side pipeline.

[0030] Step 2: Pump the molten salt stored in the low-temperature molten salt tank into the molten salt circuit, pass it through the molten salt preheater, and then into the high-temperature molten salt tank, and store part of it in the high-temperature molten salt tank; the molten salt flow is automatically adjusted according to the liquid level height of the high-temperature molten salt tank.

[0031] Step 3: The variable-power electric resistance wire heater built in the high-temperature molten salt tank heats the molten salt to a set temperature, which is then pumped into the molten salt side of the molten salt microchannel heat exchanger under test; the steam-water electric heater heats the softened water into steam, which is then passed into the steam side of the molten salt microchannel heat exchanger under test.

[0032] Step 4: Open the molten salt preheater steam inlet stop valve on the pipeline between the molten salt microchannel heat exchanger under test and the molten salt preheater, run the molten salt preheater, and realize heat transfer from high-temperature steam to low-temperature molten salt; run the steam-water-oil heat exchanger to transfer part of the heat of the steam to the heat transfer oil and store it in the heat transfer oil, control the heat transfer oil regulating valve in the heat transfer oil storage circuit to adjust the flow, and control the steam side outlet temperature of the steam-water-oil heat exchanger.

[0033] Step 5: Maintain the constant molten salt side and steam side inlet flow of the molten salt microchannel heat exchanger under test by controlling the opening degree of the regulating valve.

[0034] Step 6: After the platform is stable, record the flow, temperature, and pressure difference data of the inlet and outlet of the molten salt side and the steam side of the measured molten salt micro-channel heat exchanger; calculate the heat exchange capacity and the degree of micro-channel blockage to obtain the continuous change of the heat exchange performance and the degree of micro-channel blockage with time;

[0035] Step 7: After the test platform runs for M hours, sequentially turn off the built-in molten salt pump, heat-conducting oil supply device, and softened water supply device of the high-temperature molten salt tank and the low-temperature molten salt tank, and open the high-temperature steam in the steam exhaust valve exhaust pipeline set on the steam exhaust bypass; then, high-temperature nitrogen is introduced into the molten salt side of the measured molten salt micro-channel heat exchanger to blow out the residual molten salt in the channel and prevent the molten salt from condensing and blocking the channel;

[0036] Step 8: After the test platform stops running for N hours, run the softened water supply device and the heat-conducting oil supply device to introduce softened water and heat-conducting oil into the steam-water-oil heat exchanger to heat the softened water to a steam state using the heat stored in the heat-conducting oil and preheat the steam pipeline and the measured micro-channel heat exchanger; when the steam temperature is lower than the set value, run the steam electric heater to heat the steam;

[0037] Step 9: Repeat steps 2 to 8 according to the mode cycle of running for M hours and stopping for N hours until the test cycle requirement is met.

[0038] Preferably, the test method further comprises:

[0039] If the heat exchange capacity is insufficient, the measured molten salt micro-channel heat exchanger is optimized in structure by increasing the design allowance of the heat exchange area;

[0040] The corresponding pressure drop of the inlet and outlet of the measured molten salt micro-channel heat exchanger is recorded, and the degree of micro-channel blockage η is calculated; according to the maximum degree of micro-channel blockage η allowed by the molten salt micro-channel heat exchanger max , the corresponding pressure drop is taken as the blockage fault pressure drop threshold value ΔP 阈值 of the currently measured molten salt micro-channel heat exchanger, which is used as a standard for judging whether the blockage fault is reached when the measured molten salt micro-channel heat exchanger is actually working.

[0041] Advantages:

[0042] (1) The molten salt micro-channel heat exchanger performance test platform provided by the present application can realize the blockage condition test of the molten salt micro-channel heat exchanger, continuously detect the pressure difference of the inlet and outlet of the micro-channel heat exchanger by setting a differential pressure gauge, and further obtain the degree of micro-channel blockage and its change trend with time, which is helpful for optimizing the design and improving the reliability and safety of the actual operation of the molten salt micro-channel heat exchanger.

[0043] (2) The application realizes the analysis of the heat transfer performance change and the flow passage blockage condition of the molten salt micro-channel heat exchanger during long-term intermittent operation, and is further used for optimizing design, and improving the reliability and safety of the actual operation of the molten salt micro-channel heat exchanger.

[0044] (3) The molten salt preheater is arranged as a first recovery loop, the high-temperature steam discharged from the measured molten salt micro-channel heat exchanger is used to heat the low-temperature molten salt, the heat in the high-temperature steam is recovered partially, the power consumption is reduced during long-term performance test of the heat exchanger, and the operation cost of the test platform is reduced.

[0045] (4) The heat conducting oil heat storage loop based on the steam-water-oil heat exchanger is arranged as a second recovery loop, is used for transferring and storing part of the heat in the steam at the outlet of the molten salt preheater and the bypass steam into the heat conducting oil, realizes further energy recovery, and heats the feed water during the periodic start of the test system, so that the energy consumption of the system is further reduced.

[0046] (5) In a preferred embodiment, the large-volume low-temperature molten salt tank is used for storing the molten salt, and the small-volume high-temperature molten salt tank is used for adjusting the molten salt flow entering the measured heat exchanger, the liquid level height in the high-temperature molten salt tank is constant, and the storage cost of the high-temperature molten salt and the heat loss during storage are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 The flow chart of the flow passage blockage condition discrimination method of the application;

[0048] Figure 2 The principle diagram of the molten salt micro-channel heat exchanger performance test platform of the application;

[0049] Figure 3 The schematic diagram of the sensor arrangement on the connecting pipeline of the micro-channel heat exchanger in the molten salt micro-channel heat exchanger performance test platform of the application. DETAILED DESCRIPTION

[0050] The application will be described in detail below with reference to the drawings and embodiments.

[0051] The application first provides a flow passage blockage condition discrimination method during performance test of a molten salt micro-channel heat exchanger, and first analyzes the reasons for the micro-channel heat exchanger blockage, including: (1) partial blockage of the micro-channel caused by changes in fluid properties or accumulation of particulate impurities, complete or partial blockage of the flow passage cross section of the micro-channel at a certain section along the way; (2) reduction of the flow passage cross section caused by corrosive fouling of the micro-channel; and (3) the above two situations occur in the micro-channel at the same time.

[0052] Assuming that a certain proportion of the microchannels is completely blocked, the resistance coefficient in the unblocked microchannels is constant. Then the blockage and unblockage can be reflected in the pressure drop of the heat exchanger inlet / outlet. Based on this, the present application determines the microchannel blockage condition according to the pressure drop of the heat exchanger inlet / outlet at the initial time and the pressure drop at the test time, and combines the pressure drop formula. The microchannel blockage condition determination is suitable for the blockage condition determination of the molten salt microchannel and the steam microchannel.

[0053] The pressure drop formula of the channel is:

[0054]

[0055] Wherein, ΔP is the pressure drop of the molten salt microchannel heat exchanger inlet / outlet, unit: Pa; ρ is the fluid density, unit: kg / m 3 ; v is the flow rate, unit: m / s, f is the channel resistance coefficient; D is the hydraulic diameter, unit: m; L is the flow path length, unit: m.

[0056] The measured microchannel heat exchanger molten salt side or steam side inlet / outlet pressure drop is:

[0057]

[0058] Wherein, ΔP s0 is the pressure change caused by the heat exchanger inlet / outlet header, unit: Pa, which is smaller than the pressure drop in the microchannel, so it is ignored; V is the mass flow rate of the molten salt or the steam, kg / s; n is the total number of unblocked microchannels in the heat exchanger; A0 is the cross-sectional area of a single channel, unit: m 2 .

[0059] The microchannel blockage degree of the heat exchanger molten salt side or steam side at a certain time s is η, the larger the η value, the more serious the blockage:

[0060]

[0061] Wherein, ΔP0 is the pressure drop between the inlet and outlet of the molten salt microchannel heat exchanger at the beginning of the test, unit: Pa; ΔP s is the pressure drop of the molten salt microchannel heat exchanger inlet / outlet at a certain time s, unit: Pa; according to the flow channel blockage determination object, the inlet / outlet pressure drop can be the molten salt side inlet / outlet pressure drop, or the steam side inlet / outlet pressure drop; ρ0 is the molten salt / steam density at the beginning of the test, unit: kg / m 3 ; ρ s is the molten salt / steam density at a certain time s, unit: kg / m 3 . The densities ρ0 and ρ s are obtained based on the corresponding relationship between the temperature and the fluid property (fluid density). In a specific embodiment, in order to facilitate the value, the temperature T0 corresponding to the density ρ0 and the temperature T s corresponding to the density ρs Both can be simplified as the average temperature of the molten salt micro-channel heat exchanger molten salt side / steam side inlet and outlet at the corresponding time.

[0062] Based on the above formula, the flow channel blockage condition discrimination method of the molten salt micro-channel heat exchanger performance test of the present application comprises the following steps:

[0063] Step 1: At the beginning of the test, the initial temperature T0 of the heat transfer fluid in the molten salt micro-channel heat exchanger is obtained, as well as the initial pressure drop ΔP0 between the inlet and outlet of the heat transfer fluid of the molten salt micro-channel heat exchanger; the heat transfer fluid is molten salt or steam.

[0064] Step 2: At a test time point s, the current temperature T s of the heat transfer fluid in the molten salt micro-channel heat exchanger is obtained, as well as the current pressure drop ΔP s between the inlet and outlet of the heat transfer fluid of the molten salt micro-channel heat exchanger.

[0065] Step 3: According to the relationship between temperature and fluid density, the initial temperature T0 and the current temperature T s corresponding densities: initial density ρ0 and current density ρ s are determined.

[0066] Step 4: Determine the degree of micro-channel blockage η of the molten salt micro-channel heat exchanger at the test time point s, the greater the η value, the more serious the blockage:

[0067]

[0068] In a preferred embodiment, the test stage can determine the blockage fault pressure drop threshold. Specifically, in the test stage, with the change of the micro-channel pressure drop, the micro-channel blockage degree η corresponding to various pressure drop values is recorded; according to the maximum degree of micro-channel blockage η max allowed by the molten salt micro-channel heat exchanger, the corresponding pressure drop value is found as the blockage fault pressure drop threshold ΔP 阈值 of the currently tested molten salt micro-channel heat exchanger;

[0069] When the molten salt micro-channel heat exchanger is actually working, if the pressure drop between the inlet and outlet of the molten salt micro-channel heat exchanger reaches the corresponding blockage fault pressure drop threshold ΔP 阈值 , it is determined that a blockage fault occurs.

[0070] In a preferred embodiment, the relationship between the degree of micro-channel blockage η and time can also be obtained, which is used to predict the change of the micro-channel blockage of the molten salt micro-channel heat exchanger when the molten salt micro-channel heat exchanger is actually working. The user can determine the maintenance or replacement of the micro-channel heat exchanger core according to the blockage prediction.

[0071] The present invention also provides a performance testing platform for molten salt microchannel heat exchangers, which can not only perform the above-mentioned clogging condition identification, but also features two-stage energy recovery and supports long-term operation.

[0072] like Figure 1 As shown, the molten salt microchannel heat exchanger performance testing platform includes a molten salt circuit, a steam circuit, a thermal oil storage circuit, and a control module. In this invention, the steam circuit includes a primary energy recovery device, and the thermal oil storage circuit is a secondary energy recovery device.

[0073] Molten salt circuit: Starting from the molten salt side outlet of the molten salt microchannel heat exchanger 1 under test, the pipeline connects sequentially to the low-temperature molten salt tank 2, the molten salt preheater 4 (also part of the steam circuit), and the high-temperature molten salt tank 6, and then connects to the molten salt side inlet of the molten salt microchannel heat exchanger 1 under test. A molten salt main pipeline flow meter 5 is installed on the outlet pipeline of the molten salt preheater 4. The test module molten salt inlet shut-off valve 8 and the test module molten salt outlet shut-off valve 9 are respectively installed on the molten salt side inlet and outlet pipelines of the molten salt microchannel heat exchanger 1 under test, and their function is to connect / isolate the molten salt microchannel heat exchanger 1 under test from the test platform during operation / stop.

[0074] The cryogenic molten salt tank 2 is connected to the molten salt side outlet of the microchannel heat exchanger 1 for the molten salt being tested. After heat exchange, the cryogenic molten salt flows into and is stored in the tank. The variable power resistance wire heater and thermometer built into the cryogenic molten salt tank 2 maintain a constant temperature of the molten salt inside the tank. The variable frequency submersible molten salt pump built into the cryogenic molten salt tank 2 is used to pump the cryogenic molten salt into the main pipeline. The main pipeline connected to the cryogenic molten salt tank 2 is equipped with a bypass pipeline, and the bypass pipeline is equipped with a cryogenic molten salt tank bypass regulating valve 3. Its function is to control the flow rate of molten salt entering the molten salt preheater 4 in the main pipeline, and automatically adjusts according to the liquid level height of the high-temperature molten salt tank 6 and the reading of the molten salt main pipeline flow meter 5.

[0075] Molten salt preheater 4 is located on the main outlet pipeline of the cryogenic molten salt tank 2. Molten salt preheater 4 is a key component of the steam circuit. The energy of molten salt preheater 4 comes from the high-temperature steam discharged from the microchannel heat exchanger 1 of the molten salt under test. The function of molten salt preheater 4 is to use the high-temperature steam discharged from the microchannel heat exchanger 1 of the molten salt under test to heat the cryogenic molten salt. By partially recovering the heat in the high-temperature steam, the energy consumption of the electric heater during the operation of the test platform is reduced.

[0076] The high-temperature molten salt tank 6 uses a small tank to store a small amount of high-temperature molten salt, aiming to reduce the electrical energy consumed in maintaining the high temperature of the molten salt. The high-temperature molten salt tank 6 has a built-in variable power resistance wire heater and thermometer to maintain a constant temperature of the molten salt inside the tank. The high-temperature molten salt tank 6 has a built-in variable frequency submersible molten salt pump to pump the high-temperature molten salt into the main pipeline. The main pipeline connected to the high-temperature molten salt tank 6 is equipped with a bypass pipeline, which has a molten salt regulating valve 7. Its function is to regulate the molten salt flow rate returning to the high-temperature molten salt tank 6 according to the molten salt flow meter 104, so as to precisely control the molten salt flow rate entering the microchannel heat exchanger 1 of the molten salt being measured.

[0077] Various sensors are installed on the molten salt side outlet and inlet pipes of the molten salt microchannel heat exchanger 1 under test. For example... Figure 2 As shown, the molten salt inlet pipe of the tested molten salt microchannel heat exchanger 1 is sequentially equipped with a molten salt inlet pressure gauge 102, a molten salt filter 103, a molten salt flow meter 104, and a molten salt inlet thermometer 105, with the molten salt inlet pressure gauge 102 located upstream of the molten salt filter 103. The molten salt outlet pipe is sequentially equipped with a molten salt outlet thermometer 107 and a molten salt outlet pressure gauge 108. The measuring points of the molten salt differential pressure gauge 106 are respectively set on the inlet and outlet pipes of the tested molten salt microchannel heat exchanger 1 on the molten salt side, and are used to obtain the inlet and outlet pressure difference of the tested molten salt microchannel heat exchanger. Using this pressure difference, the microchannel blockage status can be obtained using the aforementioned microchannel blockage formula.

[0078] The steam circuit of this invention is as follows: starting from the steam-side outlet of the molten salt microchannel heat exchanger 1 under test, the pipeline sequentially connects to the steam outlet shut-off valve 10 of the test module, the steam inlet shut-off valve 11 of the molten salt preheater, the steam flow meter 12 of the molten salt preheater, the steam side of the molten salt preheater 4, the steam pipeline of the steam-water-oil heat exchanger 14, the steam-water electric heater 15, and the steam inlet shut-off valve 16 of the test module, and then connects to the steam-side inlet of the molten salt microchannel heat exchanger 1 under test. It can be seen that the steam inlet of the molten salt preheater 4 is connected to the steam-side outlet of the molten salt microchannel heat exchanger 1 under test, and the steam-water-oil heat exchanger 14 is connected to the steam outlet of the molten salt preheater 4 and the steam-side inlet of the molten salt microchannel heat exchanger 1 under test, thus forming a steam circulation loop. High-temperature steam is utilized in the molten salt preheater 4, and the remaining steam energy is transferred to the heat transfer oil storage circuit in the steam-water-oil heat exchanger 14.

[0079] A steam inlet shut-off valve 11 and a steam flow meter 12 for the molten salt preheater are sequentially installed on the steam-side inlet pipe of the molten salt preheater 4. The inlet pipe of the steam inlet shut-off valve 11 is connected to the steam outlet pipe of the molten salt preheater 4. A steam regulating valve 13 is installed between the steam inlet pipe and the steam outlet pipe of the molten salt preheater 4 to control the steam flow rate entering the molten salt preheater, thereby regulating the molten salt temperature at the preheater outlet.

[0080] The function of the steam-water-oil heat exchanger 14 is to transfer and store part of the heat from the steam at the outlet of the molten salt preheater 4 and the bypass steam into the heat transfer oil, thereby achieving energy recovery. It also heats the feedwater during the periodic startup of the test system to reduce system energy consumption. The outlet pipe of the steam-water-oil heat exchanger 14 is connected to a steam venting bypass and is equipped with a steam venting valve 17, which is used to discharge excess steam in the circuit when the system stops or the heat transfer oil overheats. The steam-water-oil heat exchanger 14 is equipped with a softened water bypass, connected to a softened water supply device 18. When the system starts, the feedwater shut-off valve 20 is opened to inject softened water into the steam-water-oil heat exchanger 14 to heat the softened water.

[0081] A steam-water electric heater 15 is installed on the steam-side inlet pipe of the molten salt microchannel heat exchanger 1 under test to maintain a constant steam temperature entering the molten salt microchannel heat exchanger 1. The steam-water electric heater 15 is also connected to a softened water supply device 18, which replenishes the steam in the circuit during test platform operation and controls the softened water regulating valve 19 to maintain a stable inlet steam flow rate of the molten salt microchannel heat exchanger 1 under test.

[0082] The test module steam inlet shut-off valve 16 and the test module steam outlet shut-off valve 10 are respectively installed on the inlet and outlet pipelines of the steam side of the molten salt microchannel heat exchanger 1 under test. Their function is to connect / isolate the molten salt microchannel heat exchanger 1 under test to the main system during the operation / stop of the test platform.

[0083] Various sensors are installed on the steam-side outlet and inlet pipes of the molten salt microchannel heat exchanger 1 under test. For example... Figure 2 As shown, the steam inlet pipe of the molten salt microchannel heat exchanger 1 under test is sequentially equipped with a steam inlet pressure gauge 110, a steam filter 111, a steam flow meter 112, and a steam inlet thermometer 113, with the steam inlet pressure gauge 110 located upstream of the steam filter 111. The steam outlet pipe is sequentially equipped with a steam outlet thermometer 115 and a steam outlet pressure gauge 116. The measuring points of the steam differential pressure gauge 114 are located on both the steam inlet and outlet pipes of the molten salt microchannel heat exchanger 1 under test.

[0084] The heat transfer oil storage circuit is the second energy recovery device of this invention: starting from the outlet of the heat transfer oil channel of the steam-water-oil heat exchanger 14, it is sequentially connected to the heat transfer oil supply device 21, the heat transfer oil regulating valve 22, and the heat transfer oil flow meter 23, and then connected to the inlet of the heat transfer oil channel of the steam-water-oil heat exchanger 14. The function of the heat transfer oil storage circuit is to store the heat of steam in the heat transfer oil, heat the softened water to a steam state when the test platform is turned on, and provide a hot steam preheating heat exchanger and steam pipeline.

[0085] Temperature measuring points are installed at the inlet and outlet of the molten salt preheater 4 on the molten salt side and the steam side, and at the inlet and outlet of the steam side and the heat transfer oil of the steam-water-oil heat exchanger 14.

[0086] The quartz cotton heat insulation is arranged outside the molten salt pipeline and the steam pipeline to reduce heat loss. In order to prevent the molten salt from being frozen and blocked, the molten salt side pipeline, the valve, the pump, the flow meter, and the measured molten salt micro-channel heat exchanger 1 are all provided with electric heating, and at least six temperature measuring points (for example, two on the upper and lower surfaces and two on the side surface) are arranged on the outer wall of the measured molten salt micro-channel heat exchanger 1 to realize real-time monitoring of the temperature value of the outer wall surface of the heat exchanger. When the temperature of the measuring point is lower than the melting point of the molten salt, the electric heating is automatically started. When the average temperature is higher than the melting point of the molten salt by 10 DEG C, the electric heating is automatically turned off.

[0087] The control module in the test platform is connected with the sensors and controlled components in each loop to realize parameter acquisition and state control, and the acquired parameters can be used to calculate the flow channel blocking condition.

[0088] The working process of the molten salt micro-channel heat exchanger performance test platform is as follows:

[0089] Step 1: Before starting the test task, the system state needs to be checked to ensure that the monitoring instruments, valves and the like can normally operate.

[0090] Step 2: Preheat the test system: run the electric heating system, heat the measured molten salt micro-channel heat exchanger 1 and the pipelines and equipment such as the valve, the pump, the flow meter, the molten salt side pipeline and the like on the test platform; run the variable-power electric resistance wire heater in the low-temperature molten salt tank 2 to heat the molten salt in the low-temperature molten salt tank 2 to above the melting point by 10 DEG C; control the softened water supply device 18 to pass the softened water into the steam-water electric heater 15 to heat it into high-temperature steam, and preheat the steam side pipeline.

[0091] Step 3: Pump the molten salt stored in the low-temperature molten salt tank 2 into the main pipeline, pass it through the molten salt preheater 4, and then into the high-temperature molten salt tank 6, and store a small amount of molten salt in the high-temperature molten salt tank 6. The molten salt flow is automatically adjusted according to the liquid level height of the high-temperature molten salt tank 6.

[0092] Step 4: The variable-power electric resistance wire heater built in the high-temperature molten salt tank 6 heats the molten salt to the set temperature, and then pumps it into the molten salt side of the measured molten salt micro-channel heat exchanger 1. The steam-water electric heater 15 heats the softened water into steam and passes it into the steam side of the measured molten salt micro-channel heat exchanger 1.

[0093] Step 5: Open the molten salt preheater steam inlet stop valve 11, run the molten salt preheater 4, realize the heat transfer from the high-temperature steam to the low-temperature molten salt, run the steam-oil heat exchanger 14 to transfer part of the heat of the steam to the heat-conducting oil and store it in the heat-conducting oil, control the heat-conducting oil regulating valve 22 to adjust the flow, and control the steam outlet temperature of the steam-oil heat exchanger 14.

[0094] Step 6: Control the opening degrees of the molten salt regulating valve 7 and the softened water regulating valve 19 according to the indications of the molten salt flow meter 104 and the steam flow meter 112 to maintain the constant inlet flow of the molten salt side and the steam side of the measured molten salt micro-channel heat exchanger 1.

[0095] Step 7: After the test platform is stable, record the flow rate, temperature, pressure difference, etc. of the inlet and outlet of the molten salt side and the steam side of the measured molten salt micro-channel heat exchanger 1.

[0096] According to the formula Q = mC P ΔT to calculate the heat exchange amount and obtain the heat exchange performance of the measured molten salt micro-channel heat exchanger, wherein Q is the heat exchange amount, unit: kJ; m is the mass, unit: kg; c P is the constant-pressure specific heat capacity, unit: kJ / (kg·℃); and ΔT is the inlet / outlet temperature difference, unit: ℃.

[0097] This step also calculates the micro-channel blockage degree using the above formula.

[0098] Further, through long-term testing, the continuity of the micro-channel blockage degree and the heat exchange performance over time can be obtained. When the measured molten salt micro-channel heat exchanger is applied to actual work, the performance of the micro-channel blockage degree changing over time can be used to predict the change of the micro-channel blockage of the molten salt micro-channel heat exchanger, helping users to plan maintenance or replacement in advance.

[0099] During the test phase, as the micro-channel pressure drop changes, the micro-channel blockage degree η constantly changes. The micro-channel blockage degree η corresponding to various pressure drops can be recorded, and according to the maximum degree of micro-channel blockage η max allowed by the molten salt micro-channel heat exchanger, the corresponding pressure drop value is found as the blockage fault pressure drop threshold ΔP 阈值 of the currently tested molten salt micro-channel heat exchanger. Then, when the measured molten salt micro-channel heat exchanger is applied to actual work, the micro-channel inlet and outlet pressure drop can be monitored, and when the real-time micro-channel inlet and outlet pressure drop reaches the blockage fault pressure drop threshold ΔP 阈值 , it is determined that a blockage fault occurs.

[0100] In addition, the heat exchange amount can also determine whether the heat exchanger meets the design requirements. If the heat exchange amount is not enough, the structure of the measured molten salt micro-channel heat exchanger 1 can be optimized by increasing the heat exchange area design margin, such as increasing by 10% to 20% (which can be regarded as a margin of the number of cross-sectional micro-channels).

[0101] Step 8: After the system has been running stably for M = 18 hours, the built-in molten salt pump of the high-temperature molten salt tank 6 and the low-temperature molten salt tank 2, the heat-conducting oil supply device 21, and the softened water supply device 18 are sequentially closed, and the steam exhaust valve 17 provided on the heat-conducting oil heat storage circuit is opened to exhaust the high-temperature steam in the pipeline; then, high-temperature nitrogen gas is introduced into the molten salt side of the measured molten salt micro-channel heat exchanger 1 to blow out the residual molten salt in the channel, preventing the molten salt from condensing and blocking the channel. The exhaust operation is opened after the heat-conducting oil supply system is closed, so that the high-temperature steam in the water vapor circuit is exhausted and no longer circulates into the measured heat exchanger.

[0102] Step 9: After the system stops for N = 6 hours, run the softened water supply device 18 and the heat conducting oil supply device 21 to pass the softened water and the heat conducting oil into the steam-water-oil heat exchanger 14. The function is to heat the softened water to steam state by using the heat stored in the heat conducting oil, and to preheat the steam pipeline and the heat exchanger to be tested. When the steam temperature is low, run the steam-water electric heater 15 to heat the steam.

[0103] Step 10: Repeat steps 3 to 9, and execute in the mode of running for M hours and stopping for N hours periodically until the test period requirement is reached.

[0104] The above specific embodiments only describe the design principles of the present application, and the shapes and names of the components in the description can be different and are not limited. Therefore, the skilled in the art of the present application can modify or equivalently replace the technical solutions described in the foregoing embodiments; and these modifications and replacements do not deviate from the purpose and technical solutions of the present application, and should all belong to the protection scope of the present application.

Claims

1. A molten salt microchannel heat exchanger performance test platform, characterized in that, The test platform comprises a molten salt loop, a steam loop, a heat conducting oil storage loop and a control module; The molten salt loop is led out from the molten salt side outlet of the measured molten salt microchannel heat exchanger (1), is sequentially connected with a low temperature molten salt tank (2) and a high temperature molten salt tank (6), and is connected with the molten salt side inlet of the measured molten salt microchannel heat exchanger (1); the volume of the high temperature molten salt tank (6) is smaller than that of the low temperature molten salt tank (2); The steam loop is led out from the steam side outlet of the measured molten salt microchannel heat exchanger (1), is sequentially connected with a steam pipeline of a molten salt preheater (4), a steam pipeline of a steam-water-oil heat exchanger (14) and a steam-water electric heater (15), and is connected with the steam side inlet of the measured molten salt microchannel heat exchanger (1); the steam-water electric heater (15) is connected with a softened water supply device (18); the molten salt preheater (4) is connected to the pipeline between the low temperature molten salt tank (2) and the high temperature molten salt tank (6) in the molten salt loop, and the recovered steam energy is used to heat the low temperature molten salt; The heat conducting oil storage loop is led out from the heat conducting oil side outlet of the steam-water-oil heat exchanger (14), is connected with a heat conducting oil supply device (21), and is returned to the heat conducting oil side inlet of the steam-water-oil heat exchanger (14), so that the residual steam energy in the steam-water-oil heat exchanger (14) is further recovered into the heat conducting oil; The control module is connected with sensors in each loop, and is used for judging the heat exchange performance and the blocking condition of the microchannel heat exchanger; The flow channel blocking condition judging mode for judging the blocking condition is as follows: At the beginning of the test, the initial temperature T0 of the heat transfer fluid in the measured molten salt microchannel heat exchanger (1) and the initial pressure drop ΔP0 between the inlet and the outlet of the heat transfer fluid in the measured molten salt microchannel heat exchanger (1) are obtained; the heat transfer fluid is molten salt or steam; At a test time point s, the current temperature T of the heat transfer fluid in the measured molten salt micro-channel heat exchanger (1) is acquired s , and the current pressure drop ΔP between the heat transfer fluid inlet and outlet of the measured molten salt micro-channel heat exchanger (1) is acquired s ; Obtaining an initial temperature T0 and a current temperature T s A corresponding initial density p0 and a current density p s ; The microchannel blocking degree η of the measured molten salt microchannel heat exchanger (1) at a test time point s is determined; the greater the η value, the more serious the blocking is:

2. The molten salt microchannel heat exchanger performance test platform of claim 1, wherein, A molten salt inlet pressure gauge (102), a molten salt filter (103), a molten salt flowmeter (104) and a molten salt inlet temperature gauge (105) are sequentially arranged on the molten salt side inlet pipeline of the measured molten salt microchannel heat exchanger (1), and the molten salt inlet pressure gauge (102) is arranged upstream of the molten salt filter (103); a molten salt outlet temperature gauge (107) and a molten salt outlet pressure gauge (108) are sequentially arranged on the molten salt side outlet pipeline of the measured molten salt microchannel heat exchanger (1); the measuring points of a molten salt differential pressure gauge (106) are arranged on the molten salt side inlet pipeline and the outlet pipeline of the measured molten salt microchannel heat exchanger (1); A steam inlet pressure gauge (110), a steam filter (111), a steam flowmeter (112) and a steam inlet temperature gauge (113) are sequentially arranged on the steam side inlet pipeline of the measured molten salt microchannel heat exchanger (1), and the steam inlet pressure gauge (110) is arranged upstream of the steam filter (111); a steam outlet temperature gauge (115) and a steam outlet pressure gauge (116) are sequentially arranged on the steam side outlet pipeline of the measured molten salt microchannel heat exchanger (1); the measuring points of a steam differential pressure gauge (114) are arranged on the steam side inlet pipeline and the outlet pipeline of the measured molten salt microchannel heat exchanger (1).

3. The molten salt microchannel heat exchanger performance test platform of claim 2, wherein, A molten salt preheater (4) and a steam side outlet of a molten salt microchannel heat exchanger (1) are provided with a molten salt preheater steam flow meter (12), a molten salt preheater steam inlet stop valve (11), and a test module steam outlet stop valve (10); a steam circuit between the molten salt preheater (4) and a steam side inlet of the molten salt microchannel heat exchanger (1) is provided with a test module steam inlet stop valve (16); a steam inlet pipeline and a steam outlet pipeline of the molten salt preheater (4) are provided with a molten salt preheater steam regulating valve (13) to regulate the outlet molten salt temperature of the molten salt preheater (4).

4. The molten salt microchannel heat exchanger performance test platform of claim 3, wherein, The outlet pipeline of the steam-water-oil heat exchanger (14) is communicated with a steam exhaust bypass and provided with a steam exhaust valve (17); the steam-water electric heater (15) is arranged on a steam side inlet pipeline of the molten salt microchannel heat exchanger (1) and used for supplementing steam in the circuit when the test platform is running; and a softened water regulating valve (19) is used for maintaining the steam flow stability of the steam side inlet of the molten salt microchannel heat exchanger (1).

5. The molten salt microchannel heat exchanger performance test platform of claim 4, wherein, The initial temperature T0 and the current temperature T s Both the initial temperature T0 and the current temperature T are the average temperatures of the molten salt side or steam side inlet and outlet of the measured molten salt micro-channel heat exchanger (1).

6. The molten salt microchannel heat exchanger performance test platform of claim 4, wherein, In the test phase, the correspondence between various pressure drop values and the degree of micro-channel blockage η is recorded as the micro-channel pressure drop changes; according to the maximum degree of micro-channel blockage η allowed by the molten salt micro-channel heat exchanger max , the corresponding relationship is used to find the pressure drop value as the blockage fault pressure drop threshold ΔP of the current molten salt micro-channel heat exchanger (1) 阈值 ; In the actual work of the measured molten salt micro-channel heat exchanger (1), when the pressure drop between the inlet and outlet of the heat transfer fluid of the measured molten salt micro-channel heat exchanger (1) reaches the blockage fault pressure drop threshold ΔP 阈值 , it is determined that a blockage fault occurs.

7. The molten salt microchannel heat exchanger performance test platform of any of claims 4-6, wherein, The change relationship of the microchannel blockage degree η with time is obtained, which is used for predicting the change of the microchannel blockage of the molten salt microchannel heat exchanger when the molten salt microchannel heat exchanger is actually working.

8. A test method of the molten salt micro-channel heat exchanger performance test platform according to any one of claims 4-6, characterized in that, The method comprises the following steps: Step 1: preheat the test system; run the electric heat tracing system arranged around the test platform to heat the molten salt microchannel heat exchanger (1) and the pipelines and equipment on the test platform; run the variable-power electric resistance wire heater in the low-temperature molten salt tank (2) to heat the molten salt in the low-temperature molten salt tank (2) to above the melting point; and control the softened water supply device (18) to pass the softened water into the steam-water electric heater (15) to heat, so as to preheat the steam side pipeline; Step 2: pump the molten salt stored in the low-temperature molten salt tank (2) into the molten salt circuit, pass the molten salt through the molten salt preheater (4), and then enter the high-temperature molten salt tank (6) and be partially stored in the high-temperature molten salt tank (6); the molten salt flow is automatically adjusted according to the liquid level height of the high-temperature molten salt tank (6); Step 3: the variable-power electric resistance wire heater arranged in the high-temperature molten salt tank (6) heats the molten salt to a set temperature, and then the molten salt is pumped into the molten salt side of the molten salt microchannel heat exchanger (1); the steam-water electric heater (15) heats the softened water into steam and passes the steam into the steam side of the molten salt microchannel heat exchanger (1); Step 4: open the molten salt preheater steam inlet stop valve (11) on the pipeline between the molten salt microchannel heat exchanger (1) and the molten salt preheater (4), run the molten salt preheater (4), realize the heat transfer from high-temperature steam to low-temperature molten salt, run the steam-water-oil heat exchanger (14), transfer part of the heat of the steam to the heat storage oil, control the heat storage oil regulating valve (22) in the heat storage oil circuit to adjust the flow, and control the steam side outlet temperature of the steam-water-oil heat exchanger (14); Step 5: maintain the constant molten salt side and steam side inlet flow of the molten salt microchannel heat exchanger (1) by controlling the opening degree of the heat storage oil regulating valve (22). Step 6: After the platform is stable, record the flow, temperature, and pressure difference data of the inlet and outlet of the molten salt side and the steam side of the measured molten salt microchannel heat exchanger (1); calculate the heat exchange capacity and the degree of microchannel blockage, and obtain the continuous change of the heat exchange performance and the degree of microchannel blockage with time; Step 7: After the test platform has been running for M hours, sequentially turn off the built-in molten salt pump of the high-temperature molten salt tank (6) and the low-temperature molten salt tank (2), the heat conducting oil supply device (21), and the softened water supply device (18), and open the steam vent valve (17) on the steam vent bypass to discharge the high-temperature steam in the pipeline; Subsequently, high-temperature nitrogen gas is introduced into the molten salt side of the measured molten salt microchannel heat exchanger (1) to blow out the residual molten salt in the channel and prevent the molten salt from condensing and blocking the channel; Step 8: After the test platform has been stopped for N hours, run the softened water supply device (18) and the heat conducting oil supply device (21) to introduce softened water and heat conducting oil into the steam-water-oil heat exchanger (14) to heat the softened water to a steam state using the heat stored in the heat conducting oil, and preheat the steam pipeline and the measured microchannel heat exchanger; when the steam temperature is lower than the set value, run the steam electric heater (15) to heat the steam; Step 9: Repeat steps 2 to 8 according to the mode cycle of running for M hours and stopping for N hours until the test cycle requirement is met.

9. The test method of claim 8, wherein, The test method further comprises: determining whether the heat exchange capacity obtained in step 6 meets the design requirements, and if the heat exchange capacity is insufficient, optimizing the structure of the measured molten salt microchannel heat exchanger (1) by increasing the design allowance of the heat exchange area; Corresponding record the measured molten salt micro-channel heat exchanger (1) molten salt side import and export pressure drop and the degree of micro-channel blockage η; According to the maximum degree of micro-channel blockage η allowed by the measured molten salt micro-channel heat exchanger (1) max , the corresponding pressure drop is taken as the blockage fault pressure drop threshold ΔP of the current measured molten salt micro-channel heat exchanger (1) 阈值 , which is used as a standard for judging whether the blockage fault is reached when the measured molten salt micro-channel heat exchanger (1) is actually working.

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