Supercritical carbon dioxide heat exchanger simulation model calibration method based on mechanism model

Abstract

The invention belongs to the technical field of digital twinborn simulation, and particularly relates to a supercritical carbon dioxide heat exchanger simulation model calibration method based on a mechanism model. Comprising the following steps: selecting calibration parameters and target parameters of a heat exchanger simulation model; forming a calibration data set and a test data set; calculating cold and hot side resistance correction coefficients and heat exchange correction coefficients under different cold and hot side inlet temperatures, pressures and flows; fitting a cold and hot side resistance coefficient relational expression and a cold and hot side heat exchange correction coefficient relational expression; heat exchanger simulation model calibration is completed; and the calibrated heat exchanger simulation model is used for twin operation. The method has the beneficial effects that the problems that the simulation precision of a heat exchanger simulation model is high only under a rated working condition and the simulation precision is not ideal under other working conditions can be solved, and the heat exchanger simulation model can simulate the flow heat transfer characteristics of the heat exchanger at high precision under a full-range working condition; and virtual-real synchronous high-precision twinning operation of the heat exchanger and a system where the heat exchanger is located is supported.

Description

Technical Field

[0001] The present invention belongs to the technical field of digital twin simulation, and in particular relates to a supercritical carbon dioxide heat exchanger simulation model calibration method based on a mechanism model. Background Art

[0002] Supercritical carbon dioxide heat exchangers are used in various fields of supercritical carbon dioxide power generation or power. They are key core equipment in power generation or power systems, and their operating characteristics are directly related to system performance.

[0003] Conventional heat exchanger simulation models are developed based on mechanism relationships, which have a certain scope of application. Therefore, there is often a certain deviation between the simulation results of the heat exchanger simulation model and the measured data, such as ±30%. Digital twin simulation modeling requires that the simulation characteristics of the heat exchanger are highly consistent with the actual performance. In order for the heat exchanger to accurately simulate the characteristics of the physical equipment and meet the high precision requirements of the digital twin simulation model, such as ±3%, the heat exchanger simulation model needs to be calibrated with measured data. Calibration is to correct the flow and heat transfer characteristics of the heat exchanger simulation model developed based on the mechanism relationship, so that the heat transfer performance and flow performance of the heat exchanger simulation are consistent with the measured data.

[0004] The conventional calibration method is to correct the heat transfer coefficient and resistance coefficient in the heat exchanger mechanism relationship based on the rated operating data. The correction coefficient is generally a constant, which results in the simulation accuracy of the corrected model meeting the requirements under the rated conditions, but the simulation accuracy under other conditions is often not as ideal as the rated conditions. Summary of the invention

[0005] The purpose of the present invention is to provide a supercritical carbon dioxide heat exchanger simulation model calibration method based on a mechanism model, which improves the traditional fixed value correction method of the heat transfer coefficient and the resistance coefficient of the rated state high-precision simulation to a polynomial correction of the full operating condition parameter range for high-precision simulation, so as to achieve the high-precision requirements of the heat exchanger simulation model in the full operating range with the measured data deviation.

[0006] The technical solution of the present invention is as follows: A method for calibrating a supercritical carbon dioxide heat exchanger simulation model based on a mechanism model comprises the following steps:

[0007] Step 1: Select calibration parameters and target parameters of the heat exchanger simulation model;

[0008] Step 2: Read the unit operation data and pre-process the operation data to obtain the calibration data set and the test data set;

[0009] Step 3: Based on the calibration data set, obtain the calibration coefficient group of the heat exchanger at different inlet temperatures, pressures, and flow rates;

[0010] Step 4: Based on the polynomial regression algorithm, the correction coefficients under different working conditions obtained in the previous step are subjected to polynomial fitting to obtain the relationship between the cold and hot side resistance coefficients and the cold and hot side heat exchange correction coefficients;

[0011] Step 5: Update the correction coefficient in the heat exchanger simulation model to the regression polynomial obtained in step 4 to complete the calibration of the heat exchanger simulation model;

[0012] Step 6: Use the calibrated heat exchanger simulation model for twin operation, that is, transfer the measured boundary parameters of the inlet fluids on the hot and cold sides of the heat exchanger to the simulation model in real time. The heat exchanger model and the physical equipment run synchronously, and the deviation between the simulated value and the measured value of the heat exchanger outlet parameters is displayed in real time. If the model prediction accuracy meets the standard, the twin calibration is completed; if the model accuracy does not meet the standard, the fitting relationship of the correction coefficient is updated again.

[0013] The calibration parameters in step 1 include the cold side resistance correction coefficient, the hot side resistance correction coefficient, the cold side heat exchange correction coefficient, and the hot side heat exchange correction coefficient. The target parameters include the cold side pressure drop, the hot side pressure drop, the cold side outlet temperature, and the hot side outlet temperature.

[0014] In step 2, the calibration data set and the test data set have the same parameter types but different operating conditions. The calibration data set is used to calibrate the correction coefficient, and the test data set is used to verify the correction effect of the correction coefficient on the heat exchanger simulation model.

[0015] The calibration data set and the test data set in step 2 include operating parameters and result parameters; the boundary parameters include the cold side and hot side fluid inlet temperature, pressure and flow rate, and the result parameters include the cold side and hot side outlet temperature, pressure and flow rate, and the cold and hot side pressure drop.

[0016] The deviation between the simulation value and the actual value in step 3 is calculated as follows:

[0017] Hot side fluid outlet temperature deviation: Err(T ho )=(T ho,calc- T ho ) / T ho

[0018] Cold side fluid outlet temperature deviation: Err(T co )=(T co,calc- T co ) / T co

[0019] Hot side pressure drop deviation: Err(ΔP h )=(ΔP h,calc- ΔP h ) / ΔP h

[0020] Cold side pressure drop deviation: Err(ΔPc )=(ΔP c,calc- ΔP c ) / ΔP c

[0021] Wherein, T represents temperature, °C; P represents pressure, MPa; ΔP represents pressure difference, kPa; subscript h represents hot side, c represents cold side, calc represents simulation value, and no calc represents measured value;

[0022] The parameter calibration logic is: adjust the cold side resistance correction coefficient so that the simulation value of the cold side pressure drop of the heat exchanger is equal to the actual value; adjust the hot side resistance correction coefficient so that the simulation value of the hot side pressure drop of the heat exchanger is equal to the actual value; adjust the cold side heat exchange correction coefficient so that the simulation value of the cold side outlet temperature of the heat exchanger is equal to the actual value; adjust the hot side heat exchange correction coefficient so that the simulation value of the hot side outlet temperature of the heat exchanger is equal to the actual value. Each set of input parameters and result parameters corresponds to a set of calibration parameters, namely the cold and hot side resistance correction coefficients and the cold and hot side heat exchange correction coefficients, and a set of resistance correction coefficients and heat exchange correction coefficients under different operating parameters are obtained.

[0023] The cold side drag coefficient in step 4 is:

[0024] Hot side drag coefficient:

[0025] Cold side heat transfer correction factor:

[0026] Hot side heat transfer correction factor:

[0027] The power of the polynomial fit is selected according to the set accuracy, where m is the dimensionless flow rate, which is the ratio of the measured flow rate to the rated flow rate, the subscript h represents the hot side, and c represents the cold side.

[0028] The step 5 replaces the correction coefficient with the fitting relationship of step 4, and the updated heat exchanger model is tested and verified using the test set. If the deviation is within the allowable range, the calibration is successful. If the deviation exceeds the allowable range, the relationship is refitted until the deviation is met.

[0029] The beneficial effects of the present invention are as follows: the present invention can solve the problem that the simulation accuracy of the heat exchanger simulation model is high only under rated operating conditions, and the simulation accuracy is not ideal under other operating conditions. The present invention can realize that the heat exchanger simulation model can simulate the flow and heat transfer characteristics of the heat exchanger with high accuracy under the full range of operating conditions, and support the high-precision twin operation of the heat exchanger and the system where the heat exchanger is located in virtual and real synchronization. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1This is a flow chart of a method for calibrating a supercritical carbon dioxide heat exchanger simulation model based on a mechanism model provided by the present invention.

[0031] Figure 2 An example of a heat exchanger simulation model. DETAILED DESCRIPTION

[0032] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the basic implementation principle of the present invention is described below in conjunction with the accompanying drawings. The specific implementation principle described herein is only used to explain the present invention and is not intended to limit the present invention. In the following description, many specific details are set forth in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those within the scope of this description, and therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below. Based on the implementation principle of the present invention, all other implementation cases obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments, as well as the steps in all disclosed methods or processes, except for mutually exclusive features or steps, can be combined, expanded and replaced in any way.

[0033] In view of the problems existing in the prior art described in the background technology, the present invention proposes a supercritical carbon dioxide heat exchanger simulation model calibration method based on a mechanism model, that is, different correction coefficients are used under different operating conditions, and the correction coefficient is a function of the characteristic parameters of the operating condition. This method can achieve that under any operating condition, the deviation between the heat exchanger simulation model and the measured data meets the high-precision simulation requirements.

[0034] Digital twin modeling requires that the simulation characteristics of the heat exchanger and the actual performance are highly consistent. Therefore, twin modeling needs to calibrate the heat exchanger simulation model according to the measured data to ensure that the simulation data and the measured data meet the set twin high-precision requirements under all operating conditions of the heat exchanger. The traditional calibration method of the fixed value correction of the heat exchanger resistance coefficient and the heat transfer coefficient cannot achieve high-precision simulation over the entire operating range. In order to achieve the above purpose, the present invention provides a supercritical carbon dioxide heat exchanger simulation model calibration method based on a mechanism model, which can simulate the working fluid flow and heat transfer characteristics of the heat exchanger over the entire operating range with high precision to meet the requirements of digital twin modeling.

[0035] Combination Figure 1 A supercritical carbon dioxide heat exchanger simulation model calibration method based on a mechanism model comprises the following steps:

[0036] Step 1: Select calibration parameters and target parameters for the heat exchanger simulation model

[0037] The calibration parameters include the cold side resistance correction coefficient, the hot side resistance correction coefficient, the cold side heat exchange correction coefficient, and the hot side heat exchange correction coefficient; the target parameters include the cold side pressure drop, the hot side pressure drop, the cold side outlet temperature, and the hot side outlet temperature.

[0038] Step 2: Read the unit operation data and preprocess the operation data to obtain the calibration data set and the test data set.

[0039] The calibration data set and the test data set have the same parameters, including operating parameters (also called boundary parameters) and result parameters; boundary parameters include the inlet temperature, pressure and flow rate of the fluid on the cold and hot sides of the heat exchanger, and the result parameters include the outlet temperature, pressure and flow rate of the cold and hot sides, as well as the pressure drop on the cold and hot sides. The calibration data set and the test data set have different operating conditions. The former is used to calibrate the correction coefficient, and the latter is used to verify the correction effect of the correction coefficient on the heat exchanger simulation model.

[0040] The unit operation data read is the outlet temperature, pressure and pressure drop of the heat exchanger at different inlet temperatures, pressures and flow rates. The preprocessing of the unit operation data includes noise filtering, missing value filling, and outlier removal to ensure that the data is accurate and available.

[0041] Step 3: Based on the calibration data set, obtain the calibration coefficient group of the heat exchanger at different inlet temperatures, pressures, and flow rates.

[0042] The parameter calibration logic is:

[0043] Adjust the cold side resistance correction coefficient so that the simulated value of the cold side pressure drop of the heat exchanger is equal to the actual value; adjust the hot side resistance correction coefficient so that the simulated value of the hot side pressure drop of the heat exchanger is equal to the actual value; adjust the cold side heat exchange correction coefficient so that the simulated value of the cold side outlet temperature of the heat exchanger is equal to the actual value; adjust the hot side heat exchange correction coefficient so that the simulated value of the hot side outlet temperature of the heat exchanger is equal to the actual value. Each set of input parameters and result parameters corresponds to a set of calibration parameters, namely the cold and hot side resistance correction coefficient and the cold and hot side heat exchange correction coefficient. If the calibration data set has multiple sets of operating parameters, multiple sets of correction coefficients can be obtained.

[0044] Specifically, a simulation model of the heat exchanger is constructed in the NUMAP system simulation software, and the inlet pressure boundary and the outlet flow boundary are set. The inlet pressure boundary is input with the actual measured value of the inlet parameter in the calibration data table, and the outlet flow boundary is input with the actual measured value of the flow in the calibration data table, and then the simulation is performed. During the simulation process, the correction coefficient is adjusted according to the above calibration logic through online parameter adjustment until the outlet temperature, pressure, and pressure drop of the cold and hot sides are consistent with the measured values, that is, the correction coefficient under a set of specific operating parameters is determined.

[0045] The relationship between heat transfer correction coefficient and heat transfer correction is:

[0046] h′=h·γ1

[0047] h′ is the heat transfer coefficient after correction, h is the heat transfer coefficient before correction, and γ1 is the heat transfer correction coefficient.

[0048] The relationship between the resistance correction coefficient and the resistance correction coefficient is:

[0049]

[0050] Where Δp is the corrected pressure drop on the cold or hot side of the heat exchanger, Pa; ζ is the resistance correction factor, f is the friction resistance coefficient, L is the length of the heat exchange channel, m; D is the diameter of the heat exchange channel, m; ρ is the fluid density, kg / m 3 ; u is the fluid velocity, m / s.

[0051] The deviation between the simulated value and the measured value is calculated as follows:

[0052] Hot side fluid outlet temperature deviation: Err(T ho )=(T ho,calc- T ho ) / T ho

[0053] Cold side fluid outlet temperature deviation: Err(T co )=(T co,calc- T co ) / T co

[0054] Hot side pressure drop deviation: Err(ΔP h )=(ΔP h,calc- ΔP h ) / ΔP h

[0055] Cold side pressure drop deviation: Err(ΔP c )=(ΔP c,calc- ΔP c ) / ΔP c

[0056] Wherein, T represents temperature, °C; P represents pressure, MPa; ΔP represents pressure difference, kPa; subscript h represents hot side, c represents cold side, calc represents simulation value, and no calc represents measured value.

[0057] Step 4: Based on the polynomial regression algorithm, the correction coefficients under different working conditions obtained in the previous step are subjected to polynomial fitting to obtain the relationship between the cold and hot side resistance coefficients and the cold and hot side heat exchange correction coefficients;

[0058] Cold side drag coefficient:

[0059] Hot side drag coefficient:

[0060] Cold side heat transfer correction factor:

[0061] Hot side heat transfer correction factor:

[0062] The power of the polynomial fit is intelligently selected according to the set accuracy. Where m is the dimensionless flow rate, which is the ratio of the measured flow rate to the rated flow rate, the subscript h represents the hot side, and c represents the cold side.

[0063] Step 5: Update the correction coefficient in the heat exchanger simulation model to the regression polynomial obtained in step 4 to complete the calibration of the heat exchanger simulation model.

[0064] By modifying the correction coefficient in the heat exchanger simulation model, the previous fixed value correction is changed to a correction based on a polynomial, that is, the correction coefficient is replaced with the fitting relationship in the previous step 4, and the updated heat exchanger model is tested and verified using the test set. If the deviation is within the allowable range, the calibration is successful. If the deviation exceeds the allowable range, the relationship is re-fitted, that is, the coefficients of each polynomial in step 4 are re-fitted to improve the fitting accuracy of the polynomial until the calibration deviation requirements of this step are met.

[0065] Step 6: Use the calibrated heat exchanger simulation model for twin operation, that is, transfer the measured boundary parameters of the fluid at the hot and cold sides of the heat exchanger to the simulation model in real time, and the heat exchanger model and the physical equipment will run synchronously, and the deviation between the simulated value and the measured value of the heat exchanger outlet parameter will be displayed in real time. If the model prediction accuracy meets the standard, the twin calibration is completed; if the model accuracy does not meet the standard, re-update the fitting relationship of the correction coefficient. The model accuracy is given by humans.

[0066] Example

[0067] A method for calibrating a supercritical carbon dioxide heat exchanger equipment simulation model based on a mechanism model comprises the following steps:

[0068] Step 1: Select the calibration parameters and target parameters of the heat exchanger equipment. The calibration parameters include high and low temperature heat exchange correction coefficients JH_high and JH_low, high and low temperature resistance correction coefficients PH_high and PH_low, and the target parameters include high and low temperature side outlet temperature Tout and inlet pressure Pin;

[0069] Step 2: Read the unit operation data according to the set data table, including boundary parameters, result parameters and target parameters; boundary parameters include the high and low temperature side design inlet flow m of the heat exchanger high =201kg / s,m low =136.2kg / s, design outlet pressure p high=8.3MPa,p low =22.9MPa, design inlet temperature t high =248.4℃,t low =235.5℃ and variable operating flow data, the result parameters include the outlet temperature and inlet pressure on both sides, and the target parameters are the measured data table of fluid temperature and pressure on both sides calculated based on the boundary data and result data;

[0070] Step 3: In the calibration mode, based on the measured data and theoretical data of the unit, calculate the heat exchange correction coefficient and resistance correction coefficient at different high and low temperature side inlet and outlet flow rates, pressures and temperatures;

[0071] Step 4: According to the polynomial regression algorithm, the relationship between the heat transfer correction coefficient and the resistance correction coefficient under different flow rates is automatically fitted. The heat transfer correction coefficient of the high temperature side = f (flow rate, temperature), the specific formula is JH_high = JH_high_a + JH_high_b*(1-m_cor) + JH_high_c*(1-m_cor)**2, and the resistance correction coefficient = f (flow rate, temperature), the specific formula is PH_high = PH_high_a + PH_high_b*(1-m_cor) + PH_high_c*(1-m_cor)**2; where m_cor = m_in*np.sqrt(t_in_0) / (m_0*np.sqrt(t_in)), m_in and m_0 are the fluid inlet flow rates and design values, and t_in and t_in_0 are the fluid inlet temperatures and design values;

[0072] The calculation method of outlet temperature simulation accuracy is: (actual outlet temperature - theoretical outlet temperature) / actual outlet temperature, the calculation results are: ① high temperature side (70.2281-69.6258) / 70.2281 = 0.0086 ② low temperature side (237.623-238.9992) / 237.623 = -0.00579;

[0073] The calculation method of inlet pressure simulation accuracy is: (actual inlet pressure - theoretical inlet pressure) / actual inlet pressure. The calculation result is ① High temperature side (8333357.35-8336292.58) / 8333357.35 = -3.522e -4 ② Low temperature side (22931562.56-22934416.61) / 22931562.56=-1.245e -4 ;

[0074] Step 5: Update the correction coefficient in the model to a regression polynomial, which becomes part of the simulation model, and perform parameter simulation calculations. At this point, the thermal characteristics of the heat exchanger at different flow ratios and temperatures are calculated as follows: when the high-temperature side flow is 201 kg / s and the low-temperature side flow is 136.2 kg / s:

[0075] The simulation calculation result of the high temperature side inlet pressure is 8333357.35pa, and the simulation calculation result of the outlet temperature is 70.2281℃;

[0076] The simulation calculation result of the low temperature side inlet pressure is 22931562.56pa, and the simulation calculation result of the outlet temperature is 237.623℃;

[0077] Step 6: In the operation mode, carry out virtual-real synchronous twin operation simulation of the heat exchange equipment. If the model prediction accuracy reaches the set value, the calibration is completed; if the model accuracy does not reach the set value, re-perform the polynomial regression fitting of the correction coefficient until the set simulation accuracy is reached.

Claims

1. A supercritical carbon dioxide heat exchanger simulation model calibration method based on a mechanism model, characterized in that: The following steps are involved: Step 1: Select calibration parameters and target parameters of the heat exchanger simulation model; Step 2: Read the unit operation data and pre-process the operation data to obtain the calibration data set and the test data set; Step 3: Based on the calibration data set, obtain the calibration coefficient group of the heat exchanger at different inlet temperatures, pressures, and flow rates; Step 4: Based on the polynomial regression algorithm, the correction coefficients under different working conditions obtained in the previous step are subjected to polynomial fitting to obtain the relationship between the cold and hot side resistance coefficients and the cold and hot side heat exchange correction coefficients; Step 5: Update the correction coefficient in the heat exchanger simulation model to the regression polynomial obtained in step 4 to complete the calibration of the heat exchanger simulation model; Step 6: Use the calibrated heat exchanger simulation model for twin operation, that is, transfer the measured boundary parameters of the inlet fluids on the hot and cold sides of the heat exchanger to the simulation model in real time. The heat exchanger model and the physical equipment run synchronously, and the deviation between the simulated value and the measured value of the heat exchanger outlet parameters is displayed in real time. If the model prediction accuracy meets the standard, the twin calibration is completed; if the model accuracy does not meet the standard, the fitting relationship of the correction coefficient is updated again.

2. The method for calibrating a supercritical carbon dioxide heat exchanger simulation model based on a mechanism model according to claim 1, characterized in that: The calibration parameters in step 1 include the cold side resistance correction coefficient, the hot side resistance correction coefficient, the cold side heat exchange correction coefficient, and the hot side heat exchange correction coefficient. The target parameters include the cold side pressure drop, the hot side pressure drop, the cold side outlet temperature, and the hot side outlet temperature.

3. The method for calibrating a supercritical carbon dioxide heat exchanger simulation model based on a mechanism model according to claim 1, characterized in that: In step 2, the calibration data set and the test data set have the same parameter types but different operating conditions. The calibration data set is used to calibrate the correction coefficient, and the test data set is used to verify the correction effect of the correction coefficient on the heat exchanger simulation model.

4. The method for calibrating a supercritical carbon dioxide heat exchanger simulation model based on a mechanism model as claimed in claim 3, characterized in that: The calibration data set and the test data set in step 2 include operating parameters and result parameters; the boundary parameters include the cold side and hot side fluid inlet temperature, pressure and flow rate, and the result parameters include the cold side and hot side outlet temperature, pressure and flow rate, and the cold and hot side pressure drop.

5. The method for calibrating a supercritical carbon dioxide heat exchanger simulation model based on a mechanism model according to claim 1, characterized in that: The deviation between the simulation value and the actual value in step 3 is calculated as follows: Hot side fluid outlet temperature deviation: Err(T ho )=(T ho,calc- T ho ) / T ho Cold side fluid outlet temperature deviation: Err(T co )=(T co,calc- T co ) / T co Hot side pressure drop deviation: Err(ΔP h )=(ΔP h,calc- ΔP h ) / ΔP h Cold side pressure drop deviation: Err(ΔP c )=(ΔP c,calc- ΔP c ) / ΔP c Wherein, T represents temperature, °C; P represents pressure, MPa; ΔP represents pressure difference, kPa; subscript h represents hot side, c represents cold side, calc represents simulation value, and no calc represents measured value; The parameter calibration logic is: adjust the cold side resistance correction coefficient so that the simulation value of the cold side pressure drop of the heat exchanger is equal to the actual value; adjust the hot side resistance correction coefficient so that the simulation value of the hot side pressure drop of the heat exchanger is equal to the actual value; adjust the cold side heat exchange correction coefficient so that the simulation value of the cold side outlet temperature of the heat exchanger is equal to the actual value; adjust the hot side heat exchange correction coefficient so that the simulation value of the hot side outlet temperature of the heat exchanger is equal to the actual value. Each set of input parameters and result parameters corresponds to a set of calibration parameters, namely the cold and hot side resistance correction coefficients and the cold and hot side heat exchange correction coefficients, and a set of resistance correction coefficients and heat exchange correction coefficients under different operating parameters are obtained.

6. The method for calibrating a supercritical carbon dioxide heat exchanger simulation model based on a mechanism model according to claim 1, characterized in that: The cold side drag coefficient in step 4 is: Hot side drag coefficient: Cold side heat transfer correction factor: Hot side heat transfer correction factor: The power of the polynomial fit is selected according to the set accuracy, where m is the dimensionless flow rate, which is the ratio of the measured flow rate to the rated flow rate, the subscript h represents the hot side, and c represents the cold side.

7. The method for calibrating a supercritical carbon dioxide heat exchanger simulation model based on a mechanism model according to claim 1, characterized in that: The step 5 replaces the correction coefficient with the fitting relationship of step 4, and the updated heat exchanger model is tested and verified using the test set. If the deviation is within the allowable range, the calibration is successful. If the deviation exceeds the allowable range, the relationship is refitted until the deviation is met.

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