A flow ratio correction method for a split-flow humidity generator

Abstract

The application discloses a flow ratio correction method of a split-flow humidity generator, and belongs to the technical field of humidity measurement and test.The application measures the dew point of dry gas branch outlet gas in real time through a precision dew point instrument, and measures the outlet pressure of the dry gas branch and the saturated pressure of the wet gas branch in real time through a high-precision pressure gauge; the absolute water content of the dry gas branch is calculated through real-time monitoring of the dew point temperature of the dry gas branch; the flow correction value of the dry gas or wet gas branch is calculated through the law of conservation of mass; and the flow ratio error caused by incomplete drying of the dry gas branch is offset through flow ratio correction.The application is different from feedback compensation correction which adjusts flow according to results; the absolute water content of the dry gas branch is compensated in real time through feedforward adjustment of the dew point temperature of the dry gas branch; and the accuracy of the output standard wet gas of the split-flow humidity generator is improved.The application can solve the problem that the split-flow humidity generator causes a large error of the ratio of standard wet gas under non-ideal conditions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of humidity measurement and testing, and relates to a flow ratio correction method for a humidity generator. BACKGROUND

[0002] The split-flow method humidity generator is usually used as a secondary standard humidity generator to calibrate or calibrate the temperature and humidity sensor. The method is to accurately divide a dry air into two streams with a known ratio, one of which is saturated on the surface of pure water or ice in a saturator, and the other of which remains dry, and then the two streams are mixed at a certain flow ratio to obtain the required standard humidity gas. Therefore, the dew point temperature accuracy of the split-flow method humidity generator is closely related to the performance indicators of the dry and wet gas branches.

[0003] The existing correction method of the split-flow method humidity generator at home and abroad is based on feedback control, that is, the dry and wet gas inlet flow or the on-off of the dry and wet gas inlet electromagnetic valve is corrected according to the outlet dew point temperature.

[0004] The dryer is the core component of the dry gas branch, and its drying performance directly affects the ratio result of the split-flow method humidity generator. The flow ratio coefficient of the split-flow method humidity generator is obtained by theoretical calculation based on the ideal state of dry gas, but the actual dryer cannot reach the ideal state, and the outlet dew point of the dry gas branch will affect the lower limit value of the dry and wet gas flow ratio result and the dew point temperature accuracy of the output standard humidity. Therefore, the present application monitors the dew point temperature of the dry gas branch in real time through a dew point sensor, calculates the actual absolute moisture content of the dry gas branch according to the real-time dew point temperature of the dry gas branch, and compensates in real time through the flow of the dry gas branch or the wet gas branch to offset the influence of the actual dry gas branch in a non-ideal state on the flow ratio result. Absolute moisture content can be defined by mass mixing ratio or specific humidity. Mass mixing ratio is defined as the ratio of the mass of water vapor in wet air to the mass of dry air coexisting with it; specific humidity is defined as the ratio of the mass of water vapor in wet air to the total mass of wet air. SUMMARY

[0005] To solve the problem of large error in the ratio of the standard humidity of the dry gas branch of the split-flow method humidity generator in a non-ideal state, the main purpose of the present application is to provide a flow ratio correction method for a split-flow method humidity generator, which monitors the dew point temperature of the dry gas branch in real time, calculates the absolute moisture content of the dry gas branch, calculates the flow correction value of the dry gas or wet gas branch through the law of conservation of mass, and completes the flow ratio correction to offset the flow ratio error caused by the incomplete drying of the dry gas branch, and improve the response speed and accuracy of the dry and wet gas ratio result.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] The application discloses a flow proportioning correction method for a split-flow method humidity generator, which realizes real-time measurement of dry gas branch outlet dew point through a precision dew point instrument, realizes real-time measurement of dry gas branch outlet and wet gas branch saturation pressure through two high-precision pressure gauges, calculates absolute water content of the dry gas branch through real-time monitoring of the dew point temperature of the dry gas branch, calculates a flow correction value of the dry gas or wet gas branch through a mass conservation law, and completes flow proportioning correction, so as to offset flow proportioning error caused by incomplete drying of the dry gas branch, and improve dry gas and wet gas proportioning response speed and proportioning result accuracy.

[0008] ①According to current dew point temperature t d1 measured by the precision dew point instrument, d1 );

[0009] ②According to dry gas branch outlet pressure P1 and the saturation water vapor pressure e(t d1 ) in ①, current mass mixing ratio r1 and specific humidity q1 of the dry gas branch are calculated, and the formula is as follows:

[0010]

[0011]

[0012] ③Saturation water vapor pressure e(t d ) under the set dew point temperature t d is calculated;

[0013] ④Mass mixing ratio r and specific humidity q under the set dew point temperature t d are calculated according to the saturation water vapor pressure e(t d ) in ③ and saturation pressure P2, and the formula is as follows:

[0014]

[0015]

[0016] ⑤Saturation water vapor pressure value e(t s ) in the saturator is calculated according to the saturation temperature t s of the saturator;

[0017] ⑥Relative humidity U and split-flow coefficient F of the set dew point temperature t d at the saturation temperature t s are calculated, and the formula is as follows:

[0018]

[0019]

[0020] ⑦ Calculate the theoretical dry and wet gas flow rates Q based on the flow splitting coefficient F. d With Q w ;

[0021] ⑧ Calculate the total specific humidity q2, mass mixing ratio r2, and actual saturated water vapor pressure e(t) of the actual dry and wet gas mixture. d2 The formula is as follows:

[0022]

[0023]

[0024]

[0025] ⑨ Based on the actual saturated water vapor pressure value e(t) in ⑦ d2 The actual relative humidity U2 and the actual flow splitting coefficient F2 are calculated using the following formulas:

[0026]

[0027]

[0028] ⑩ The actual flow rate Q of pure dry gas is calculated based on the flow splitting coefficient F2. d1 If the moisture in the dry gas branch is transferred to the wet gas branch, then the actual flow rate Q in the wet gas branch is... w1 The formula is as follows:

[0029]

[0030] If the moisture content of the dry gas branch is transferred to the wet gas branch, it is determined that the moisture content of the wet gas branch is higher, and the actual flow rate of the wet gas branch is:

[0031]

[0032] According to the law of conservation of water vapor mass, the reduced flow rate ΔQ in the moist gas branch is... w Or the increased flow rate value △Q of the dry gas branch. d The compensation value is calculated using the following formula:

[0033]

[0034] If the moisture from the dry gas branch is transferred to the wet gas branch, the compensated flow rate for the wet gas branch is:

[0035] ΔQ w =Q w -Q w1 (15)

[0036] The flow ratio is corrected based on the flow rate value of the dry gas branch and the compensated flow rate value of the wet gas branch to offset the flow ratio error caused by the incomplete drying of the dry gas branch, thereby improving the response speed and accuracy of the dry and wet gas ratio.

[0037] Preferably, in the process of calculating the compensation flow rate, the dew point value and pressure value are measured by the corresponding precision dew point meter and high precision pressure gauge, and transmitted to the humidity generator control software. The compensation value of the dry gas branch or the wet gas branch is calculated in real time by the control software, and the corresponding branch is compensated and controlled in real time.

[0038] Beneficial effects:

[0039] 1. To address the issue of significant errors in the standard moisture ratio of the dry gas branch in a split-flow humidity generator under non-ideal conditions, this invention discloses a flow ratio correction method for a split-flow humidity generator. By real-time monitoring of the dew point temperature of the dry gas branch, the absolute moisture content of the dry gas branch is calculated. Using the law of conservation of mass, the flow correction value of the dry or moist gas branch is calculated to complete the flow ratio correction, thereby offsetting the flow ratio error caused by the incomplete drying of the dry gas branch.

[0040] 2. The present invention discloses a flow ratio correction method for a split-flow humidity generator, which differs from the existing feedback compensation correction method that adjusts the flow based on the result. Instead, it uses feedforward adjustment based on the dew point temperature of the dry gas branch to compensate for the absolute moisture content of the dry gas branch in real time, thereby improving the accuracy of the standard humidity output by the split-flow humidity generator. Attached Figure Description

[0041] Figure 1 A schematic diagram of the process for searching space orbital families of binary star systems based on grid search according to the present invention. Detailed Implementation

[0042] To better illustrate the purpose and advantages of the present invention, the invention will be further described below in conjunction with the accompanying drawings and examples.

[0043] Example 1:

[0044] The flow distribution is divided into dry gas branch and wet gas branch. Since the dry gas branch cannot reach the ideal dry state, the flow rate of the dry gas branch or the flow rate of the wet gas branch is corrected to compensate for the dew point temperature deviation caused by the non-ideal state of the dry gas branch.

[0045] This invention monitors the dew point and pressure at the outlet of the dry gas branch and the saturation pressure at the outlet of the wet gas branch in real time, and calculates the compensation flow rate based on the real-time measurement values.

[0046] To set the dew point temperature td The temperature is -30℃, and the saturation temperature is t. s The temperature is 40℃, at which point the dew point temperature t of the dry gas branch outlet is... d1 Taking the case where the temperature is -55℃ and both the dry gas outlet pressure P1 and the saturation pressure P2 are 101325 Pa as an example. Figure 1 As shown in the figure, this embodiment discloses a flow ratio correction method for a split-flow humidity generator, and the specific implementation steps are as follows:

[0047] ① Current dew point temperature t of dry gas branch d1 The corresponding saturated water vapor pressure value e(t) d1 The Pa can be calculated using Wexler's empirical formula, yielding a result of 2.09264 Pa. The specific calculation formula is as follows:

[0048]

[0049] ② Based on the pressure P1 at the outlet of the dry gas branch and the saturated water vapor pressure e(t) in ① d1 The calculated mass mixing ratio r1 of the dry gas branch is 1.28462 × 10⁻⁶. -5 The calculated specific humidity q1 is 1.28461 × 10⁻⁶. -5 The specific calculation formula is as follows:

[0050]

[0051]

[0052] ③ Set the dew point temperature t d The saturated water vapor pressure value e(t) d The value can be calculated using the Wexler empirical formula, resulting in a value of 37.99867 Pa. The specific calculation formula is as follows:

[0053]

[0054] ④ Based on the saturated water vapor pressure e(t) d The dew point temperature t is calculated based on the saturation pressure P2. d The mass mixing ratio r was 2.33349 × 10⁻⁶. -4 The calculated specific humidity q is 2.33294 × 10⁻⁶. -4 The specific calculation formula is as follows:

[0055]

[0056]

[0057] ⑤ The saturator at saturation temperature t s The saturated water vapor pressure value e(t)s The Pa can be calculated using Wexler's empirical formula, yielding a result of 7385.299073 Pa. The specific calculation formula is as follows:

[0058]

[0059] ⑥ Set the dew point temperature t d At saturation temperature t s The calculated relative humidity U is 51.45177%, and the calculated flow splitting coefficient F is 4.77195 × 10⁻⁶. -3 The specific calculation formula is as follows:

[0060]

[0061]

[0062] ⑦ Based on the splitting coefficient F, the theoretical dry gas mass flow rate Q d The result was set to 5.16 × 10 -3 kg / min, theoretical moisture mass flow rate Q w The calculation result is 2.47413 × 10 -5 kg / min, the specific calculation formula is as follows:

[0063]

[0064] ⑧ The calculated total specific humidity q2 of the actual dry and wet gas mixture is 2.46079 × 10⁻⁶. -4 The calculated mass mixing ratio r2 is 2.46139 × 10⁻⁶. -4 The actual saturated water vapor pressure e(t) d2 The calculated result is 40.08073 Pa;

[0065]

[0066]

[0067]

[0068] ⑨ The calculated actual relative humidity U2 is 54.27096%, and the calculated actual flow splitting coefficient F2 is 5.03352 × 10⁻⁶. -3 The specific calculation formula is as follows:

[0069]

[0070]

[0071] ⑩ Actual flow rate of pure dry gas Q d1The calculation result is 4.89057 × 10 -3 kg / min, the specific calculation formula is as follows:

[0072]

[0073] Based on the conservation of water vapor mass, the mass flow correction value △Q for the dry gas branch is... d It should be equal to the sum of the mass flow rate of pure dry gas and the water content of the dry gas branch. The increased dry gas branch flow rate value ΔQ d The calculation result is 2.69434 × 10 -4 kg / min, the specific calculation formula is as follows:

[0074]

[0075] Based on the conservation of water vapor mass, corrections can be made for either the dry gas or wet gas branch, i.e., the increase in the flow rate ΔQ of the dry gas branch. d Or reduce the flow rate ΔQ of the moisture branch. w △Q d The mass flow correction value △Q for the wet branch can be calculated from equation (32). w It should be equal to the difference between the theoretical mass flow rate of the moisture branch and the actual mass flow rate of the moisture branch. The actual flow rate of the moisture branch is Q. w1 The calculation result is 2.61044 × 10 -5 kg / min, the specific calculation formula is as follows:

[0076]

[0077] According to the law of conservation of mass, the compensating flow rate ΔQ in the moisture branch is... w The calculation result is -1.36305 × 10 -6 kg / min, the specific calculation formula is as follows:

[0078] ΔQ w =Q w -Q w1 (34)

[0079] All flow rates involved in the prediction results are mass flow rates. The saturated water vapor pressure involved in the prediction process can be obtained by looking up tables or by calculating the empirical formula for saturated water vapor pressure. The specific humidity can be derived from the mass mixing ratio. Finally, the compensation flow rate is obtained based on the mass conservation of water vapor.

[0080] The humidity generator control software monitors the dew point temperature and pressure of the dry gas branch outlet and the pressure of the saturator in real time, and substitutes the measured values ​​into the system calculation to finally obtain the compensated flow value of the dry gas branch or the wet gas branch. The system can set specific compensation branches and compensate the flow set value of the branch in real time, thereby improving the performance indicators of the humidity generator and outputting standard humidity gas with higher accuracy.

[0081] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for correcting the flow ratio in a split-flow humidity generator, characterized in that: The dew point of the dry gas branch is measured in real time using a precision dew point meter. The outlet pressure of the dry gas branch and the saturation pressure of the wet gas branch are measured in real time using two high-precision pressure gauges. The absolute moisture content of the dry gas branch is calculated by monitoring the dew point temperature of the dry gas branch in real time. The flow correction value of the dry gas or wet gas branch is calculated by applying the law of conservation of mass. The flow ratio correction is completed to offset the flow ratio error caused by the incomplete drying of the dry gas branch, thereby improving the response speed and accuracy of the dry and wet gas ratio. The method includes the following steps. ①Based on the current dew point temperature t measured by a precision dew point meter d1 Calculate the current saturated water vapor pressure e(t) of the dry gas branch. d1 ); ② Based on the pressure P1 at the outlet of the dry gas branch and the saturated water vapor pressure e(t) in ① d1 The current mass mixing ratio r1 and specific humidity q1 of the dry gas branch are calculated using the following formulas: ③ Calculate the set dew point temperature t d The saturated water vapor pressure e(t) d ); ④ Based on the saturated water vapor pressure e(t) in ③ d The dew point temperature t is calculated based on the saturation pressure P2. d The mass mixing ratio r and specific humidity q are given by the following formulas: ⑤ Based on the saturation temperature t of the saturator s Calculate the saturated water vapor pressure e(t) inside the saturator. s ); ⑥ Calculate the set dew point temperature t d At saturation temperature t s The relative humidity U and the splitting coefficient F are given by the following formula: ⑦ Calculate the theoretical dry gas flow rate Q based on the splitting coefficient F. d With moisture flow rate Q w ; ⑧ Calculate the total specific humidity q2, mass mixing ratio r2, and actual saturated water vapor pressure e(t) of the actual dry and wet gas mixture. d2 The formula is as follows: ⑨ Based on the actual saturated water vapor pressure value e(t) in ⑧ d2 The actual relative humidity U2 and the actual flow splitting coefficient F2 are calculated using the following formulas: ⑩ The actual flow rate Q of pure dry gas is calculated based on the flow splitting coefficient F2. d1 If the moisture in the dry gas branch is transferred to the wet gas branch, then the actual flow rate Q in the wet gas branch is... w1 The formula is as follows: If the moisture content of the dry gas branch is transferred to the wet gas branch, it is determined that the moisture content of the wet gas branch is higher, and the actual flow rate of the wet gas branch is: According to the law of conservation of water vapor mass, the reduced flow rate ΔQ in the moist gas branch is... w Or the increased flow rate value △Q of the dry gas branch. d The compensation value is calculated using the following formula: If the moisture from the dry gas branch is transferred to the wet gas branch, the compensated flow rate for the wet gas branch is: ΔQ w =Q w -Q w1 (15) The flow ratio is corrected based on the flow rate value of the dry gas branch and the compensated flow rate value of the wet gas branch to offset the flow ratio error caused by the incomplete drying of the dry gas branch, thereby improving the response speed and accuracy of the dry-wet gas ratio.

2. The flow ratio correction method for a split-flow humidity generator as described in claim 1, characterized in that: In the process of calculating the compensation flow rate, the dew point value and pressure value are measured by the corresponding precision dew point meter and high precision pressure gauge, and transmitted to the humidity generator control software. The compensation value of the dry gas branch or the wet gas branch is calculated in real time by the control software, and the corresponding branch is compensated and controlled in real time.

Images