An in-situ environment simulated wet-bulb temperature calibration device

Abstract

The in-situ environment simulation wet-bulb temperature calibration device of the present invention is characterized by comprising a shell, a rectangular annular circulation air duct installed in the shell, and an inner shell installed in the central gap of the annular air duct; the calibration device also includes a drying device, a humidifying device, a sensor device, an air circulation device with adjustable wind speed, a constant temperature device and a controller. The present invention also provides a humidity calibration method for an in-situ environment simulation wet-bulb temperature calibration device. The present invention can realize the simultaneous control of wind speed, temperature and humidity in the device. The wind guide plate and the rectifier plate are optimized to ensure the uniformity of wind speed in the measurement area of ​​the device. In this patent scheme, in order to improve the efficiency of humidity control, an optimization algorithm is used to output the required dry / wet gas. The calibration device is efficient and simple to operate. The calibration time is effectively shortened by the optimization algorithm. The measurement results are further verified by simulating the actual use environment, and it can be intuitively judged whether the calibrated wet-bulb platinum resistance is accurate and reliable.

Description

Technical Field

[0001] The invention belongs to the field of household appliance detection equipment and relates to an in-situ environment simulated wet-bulb temperature calibration device. Background Art

[0002] At present, wind tunnels with independently adjustable wind speed and constant temperature and humidity chambers with independently adjustable temperature and humidity are relatively common, but portable calibration devices with both adjustable wind speed and controllable temperature and humidity have not been found on the market.

[0003] During the calibration process of the home appliance enterprise laboratory, it was found that the dry-wet bulb method is a commonly used method to monitor the ambient temperature. This method has the characteristics of high accuracy, good stability, low cost, and convenient maintenance. According to the requirements of various laboratory calibration specifications currently in effect, the dry and wet bulbs need to be placed in a constant temperature furnace for temperature calibration on site, and the accuracy of the temperature measured after the wet bulb is wrapped in gauze is not considered.

[0004] According to the working principle of the wet-dry bulb method, factors such as the matching degree between the gauze size and the wet bulb, the water quality of the water used to soak the wet bulb, and the wind speed flowing through the wet bulb will affect the measurement results. Through long-term laboratory calibration work, it is found that due to the high turnover of corporate personnel, personnel training is sometimes not so timely and in place, resulting in uneven personnel quality, and some irregular operations are inevitable when placing and setting the wet bulb. In addition, as the laboratory's service life increases, the equipment will age to varying degrees, and these factors will have a certain impact on the measurement results. Therefore, for laboratories with high requirements for environmental humidity, it is necessary to perform a verification calibration of the wet bulb temperature under normal working conditions.

[0005] At present, the common practice of verification calibration is: after the dry / wet bulb temperature calibration is completed, the wet bulb is covered with gauze and filled with water, the laboratory is stabilized under the common temperature and humidity conditions, and a standard thermometer and hygrometer are placed next to the dry / wet bulb temperature sampler for data comparison to see whether the ambient temperature and humidity measured by the standard thermometer and hygrometer are consistent with the set values ​​of the calibrated laboratory. However, this method also has the following disadvantages:

[0006] 1) The laboratory takes a long time to stabilize, which increases the time cost of laboratory calibration work;

[0007] 2) The laboratory space is large, with a common area between 10m2 and 40m2. The temperature field has a certain degree of fluctuation, and the sampling cycle of the calibrated laboratory and the standard thermometer and hygrometer cannot be synchronized, which is not conducive to data comparison;

[0008] 3) The standard thermometer and hygrometer is placed next to the temperature and humidity sampler, and can only be as close as possible to the calibrated dry-bulb and wet-bulb. The environment is not exactly the same, so it is not an ideal calibration method. Summary of the invention

[0009] In order to make up for the deficiencies of the prior art, the present invention provides an in-situ environment simulated wet-bulb temperature calibration device with fast calibration and accurate data.

[0010] The in-situ environment simulated wet-bulb temperature calibration device of the present invention is characterized by comprising an outer shell, a rectangular annular circulation air duct installed in the outer shell, and an inner shell installed in the central space of the annular air duct; the calibration device also includes a drying device, a humidifying device, a sensor device, an air circulation device with adjustable wind speed, a constant temperature device and a controller; wherein the drying device and the humidifying device are installed in the inner shell; and the controller is installed on the outer shell;

[0011] 1) Drying device: including a drying chamber, an air pump, a filter, a stirring fan and connecting pipes. An air dryer (i.e., a dehumidifier) ​​and a stirring fan are installed in the drying chamber. An air pump is installed in the air inlet pipe of the drying chamber, and a filter is installed in the air outlet pipe. The air inlet pipe and the air outlet pipe are respectively connected to different positions of the circulating air duct; dry air is provided in the circulating air duct of the calibration device to reduce the relative humidity of the circulating gas, and a specified volume of dry air can be output according to the program design;

[0012] 2) Humidification device: including an ultrasonic humidification chamber, an air pump, a filter, a stirring fan and connecting pipes. The air inlet pipe of the ultrasonic humidification chamber is equipped with an air pump, the air outlet pipe is equipped with a filter, an ultrasonic steam generator (i.e., a humidifier) ​​and a stirring fan are installed in the ultrasonic humidification chamber, and the air inlet pipe and the air outlet pipe are respectively connected to different positions of the circulating air duct; saturated wet steam is provided in the circulating air duct of the calibration device to increase the relative humidity of the circulating gas, and a specified volume of saturated water vapor can be output according to the program design;

[0013] 3) Sensor device: including hot-bulb anemometer, platinum resistance temperature sensor, dry-wet integrated temperature and humidity sensor (i.e. standard temperature and humidity meter), platinum resistance temperature sensors are installed in the drying chamber and saturated ultrasonic humidification chamber respectively, hot-bulb anemometer, dry-wet integrated temperature and humidity sensor and calibrated wet bulb are installed in the circulating air duct, these three are close to each other in the circulating air duct, used to monitor the temperature, humidity and wind speed in the circulating air duct, dryer and saturated steam generator, and transmit information to the controller in real time; two dry-wet integrated temperature and humidity sensors are set on the same cross section behind the calibrated wet bulb, and the feedback data of the two sensors are compared to verify the accuracy and reliability of the sensor itself and the temperature and humidity in the measuring air duct;

[0014] 4) Wind speed adjustable air circulation device: including air duct, frequency converter, voltage stabilized power supply, fan, guide plate and rectifier plate; the circulating air duct is a rectangular closed annular channel, arc-shaped curved guide plates are installed at each corner of the circulating air duct, and straight pipe section rectifier plates are installed at the straight pipe section near the corner; a fan is installed in the circulating air duct, and the fan is connected to the frequency converter and voltage stabilized power supply; the air circulation device is a closed gas internal circulation, and does not exchange gas with the outside during operation, providing a stable and controllable wind speed environment for the calibrated sensor;

[0015] 5) Constant temperature device: including Peltier, which is installed in the drying chamber, ultrasonic humidification chamber, and circulating air duct respectively; it provides the heat and cooling required for stable temperature for the circulating air duct, dryer and saturated steam generator of the calibration device.

[0016] In the circulating air duct, a foreign body prevention gauze is installed in front of the rectifier plate of the straight pipe section; the drying device, humidifying device, frequency converter, and voltage-stabilized power supply are installed together in the inner shell; the controller adopts a PLC controller or a single-chip microcomputer; a combination of optimization algorithm and PID adjustment is adopted; the corresponding program is calculated and executed according to the measurement information fed back by the wind speed and temperature / humidity sensors to meet the set value requirements.

[0017] In the circulating air duct, the calibration device test area is placed side by side with the wet bulb and the hot bulb anemometer in the same cross section and located in the straight pipe section of the circulating air duct.

[0018] In the circulating air duct, the guide plates at the right-angle bends are designed with a radius of 5cm and a 1 / 4 arc shape, evenly distributed at the bends; the guide plates are made of solid plates with a thickness of 0.5-1 mm.

[0019] When the width of the circulating air duct is 150mm, 5 guide plates are evenly installed at the right-angle bends.

[0020] In the circulating air duct, extension plates with a length equal to the arc radius are installed at both ends of the guide plate, and the extension plates are arranged parallel to the circulating air duct; this can reduce turbulence and simultaneously reduce the pressure difference between the air inlet and outlet ends on both sides of the guide plate, thereby reducing the loss of air volume.

[0021] In the circulating air duct, the straight pipe section rectifier plate adopts a hexagonal cross-section, a hole height of 10mm, and a thickness of 100mm. The cross-section of the rectifier plate is honeycomb-shaped, and the center line of the hole is perpendicular to the plate surface.

[0022] In the circulating air duct, the hexagonal cross-section of the straight pipe section rectifier is a hexagonal unit with holes in the side wall, which plays a role in balancing the pressure between the units when the airflow just enters the rectifier. At the same time, in order to ensure that the airflow does not form new turbulence in the rectifier due to the holes, a certain length of steady flow section is required to ensure that the airflow out of the rectifier is uniform and stable. The length of the opening section accounts for 1 / 3 of the length of the hexagonal unit, that is, the thickness of the plate, and the opening rate (that is, the total area of ​​the unit openings / the cross-sectional area of ​​the unit) is about 40%.

[0023] The beneficial effects of the present invention are:

[0024] 1) This patented solution can achieve simultaneous control of wind speed, temperature and humidity in the device.

[0025] 2) In this patent solution, in order to ensure the uniformity of wind speed in the measuring area of ​​the device, the wind guide plate and the rectifier plate are optimized.

[0026] 3) In order to improve the humidity control efficiency in this patent solution, an optimization algorithm is used to output the required dry / wet gas.

[0027] 4) The calibration device is efficient and easy to operate. The calibration time is effectively shortened by optimizing the algorithm. The measurement results are further verified by simulating the actual use environment, and it can be intuitively judged whether the calibrated wet-bulb platinum resistance is accurate and reliable. At the same time, the calibration device can also be used to simulate different use conditions to check whether the measurement results change linearly under different conditions.

[0028] 5) Through the optimized design of the guide plate and the rectifier plate, the requirements for the length of the straight pipe section can be greatly reduced, and the device volume can be miniaturized, which is convenient for carrying to the site. It can effectively achieve uniform and stable wind speeds at different locations in the test area to meet the calibration requirements. According to the working environment requirements of the calibration object, the main wind speed measurement range of the device is less than 6m / s. For low wind speed calibration, the wind speed uniformity optimization design scheme will have a better effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawing is a schematic structural diagram of the present invention.

[0030] Figure 1 This is a top view of the internal structure. Figure 2 This is the laminar and turbulent distribution diagram of a guide plate (quarter arc). Figure 3 The laminar and turbulent distribution diagrams of 5 guide plates (quarter circle) are shown below. Figure 4 This is the laminar and turbulent distribution diagram of 8 guide plates (quarter arc). Figure 5 The laminar and turbulent distribution diagrams of 5 guide plates (with extended plates at both ends of the quarter arc) are shown. Figure 6 To install the guide plate with the extension plate, Figure 7 is the uniformly distributed square hole section of the straight pipe rectifier plate, Figure 8 The uniformly distributed hexagonal hole cross section of the straight pipe rectifier plate, Figures 9 to 13 The flow velocity distribution diagrams of the straight pipe section rectifier schemes 1 to 5 are shown in order. Fig.14 The hexagonal unit of the side wall opening of the hexagonal hole section of the straight pipe rectifier plate, Fig.15 It is the longitudinal wind speed distribution curve after the rectifier.

[0031] In the figure: drying chamber 1, air pump 2, filter 3, stirring fan 4, ultrasonic humidification chamber 5, air pump 6, filter 7, stirring fan 8, air dryer 9, ultrasonic saturated steam generator 10, rectifier plate 11, hot bulb anemometer 12, platinum resistance temperature sensor 13, dry and wet integrated temperature and humidity sensor 14 (standard temperature and humidity meter), circulating air duct 15, inverter 16, stabilized power supply 17, small twist fan 18, anti-foreign matter gauze 19, guide plate 20, Peltier 21, calibrated wet bulb 22, outer shell 23, inner shell 24, controller 25, extension plate 26, hole 27. DETAILED DESCRIPTION

[0032] The accompanying drawings show a specific embodiment of the present invention.

[0033] In order to calibrate the wet bulb under actual working conditions on site more scientifically, accurately and efficiently, a calibration device that can simulate the real working environment has been developed. At present, wind tunnels with independently adjustable wind speed and constant temperature and humidity chambers with independently adjustable temperature and humidity are more common, but there is no portable calibration device with adjustable wind speed and controllable temperature and humidity on the market.

[0034] The in-situ environment simulated wet-bulb temperature calibration device of the present invention comprises a housing 23, a rectangular annular circulation air duct 15 installed in the housing, and an inner housing 24 installed in the central space of the annular air duct; the calibration device also comprises a drying device, a humidifying device, a sensor device, an air circulation device with adjustable wind speed, a constant temperature device and a controller; wherein the drying device and the humidifying device are installed in the inner housing; and the controller 25 is installed on the housing. (See the structural diagram Figure 1 ).

[0035] 1) Dryer: It consists of a drying chamber 1, an air pump 2, a filter 3, a stirring fan 4 and connecting pipes. A stirring fan and an air dryer 9 (i.e., dehumidification) are installed in the drying chamber. The air inlet pipe of the drying chamber is installed with an air pump 2, and the air outlet pipe is installed with a filter 3. The air inlet pipe and the air outlet pipe are respectively connected to different positions of the circulating air duct 15. Dry air is provided in the circulating air duct of the calibration device to reduce the relative humidity of the circulating gas. A specified volume of dry air can be output according to the program design.

[0036] 2) Saturated steam generator: It consists of an ultrasonic humidification chamber 5, an air pump 6, a filter 7, a stirring fan 8 and a connecting pipeline. The stirring fan 8 and the ultrasonic saturated steam generator 10 (i.e., a humidifier) ​​are installed in the ultrasonic humidification chamber. The air inlet pipe of the ultrasonic humidification chamber is installed with an air pump, and the air outlet pipe is installed with a filter. The air inlet pipe and the air outlet pipe are respectively connected to different positions of the circulating air duct 15. Saturated wet steam is provided in the circulating air duct of the calibration device to increase the relative humidity of the circulating gas, and a specified volume of saturated water vapor can be output according to program design.

[0037] 3) Wind speed, temperature / humidity sensor: It consists of a hot-bulb anemometer 12, a platinum resistance temperature sensor 13, and a dry-wet integrated temperature and humidity sensor 14 (standard temperature and humidity meter). The platinum resistance temperature sensor 13 is installed in the drying chamber 1 and the saturated ultrasonic humidification chamber 5 respectively, and the hot-bulb anemometer 12, the dry-wet integrated temperature and humidity sensor 14 and the calibrated wet bulb 22 are installed in the circulating air duct 15. These three are close to each other in the circulating air duct. It is used to monitor the temperature, humidity and wind speed in the circulating air duct, dryer and saturated steam generator, and transmit information to the logic controller in real time. Two dry-wet integrated temperature and humidity sensors are set on the same cross section behind the calibrated wet bulb 22. The feedback data of the two sensors are compared to verify the accuracy and reliability of the sensor itself and the temperature and humidity in the measuring air duct.

[0038] 4) Wind speed adjustable air circulation system: It consists of a circulating air duct 15, a frequency converter 16, a voltage-stabilized power supply 17, a small twist fan 18, a foreign body screen 19, a guide plate 20 and a rectifier 11. The circulating air duct is a rectangular closed annular channel. A small twist fan 18 is installed in the circulating air duct. An arc-shaped curved guide plate 20 is installed at each corner of the circulating air duct. A straight pipe section rectifier 11 is installed in the straight pipe section near the corner (the air outlet end of the corner); a foreign body screen 19 is installed in front of the straight pipe section rectifier. The fan 18 is connected to the frequency converter 16 and the voltage-stabilized power supply 17; the system is a closed gas internal circulation, and no gas exchange is carried out with the outside world during operation, providing a stable and controllable wind speed environment for the calibrated sensor.

[0039] 5) Constant temperature device: composed of Peltier, Peltier 21 is installed in the drying chamber 1, ultrasonic humidification chamber 5, and circulating air duct 15 respectively. It provides the heat and cold required for stable temperature for the circulating air duct, dryer and saturated steam generator of the calibration device.

[0040] 6) Logic controller 25: adopts PLC controller or single chip microcomputer. Adopts the combination of optimization algorithm and PID regulation. Calculates and executes corresponding programs according to the measurement information fed back by wind speed, temperature / humidity sensors to meet the requirements of set values.

[0041] In the circulating air duct 15, a foreign body prevention gauze 19 is installed in front of the straight pipe section rectifier plate 11; the drying device, humidifying device, inverter, and voltage-stabilized power supply are installed together in the inner shell 24; the controller 25 adopts a PLC controller or a single-chip microcomputer, and adopts a combination of optimization algorithm and PID adjustment to calculate and execute corresponding programs according to the measurement information fed back by the wind speed and temperature / humidity sensors to meet the set value requirements.

[0042] In the circulating air duct, the calibration device test area is placed side by side with the wet bulb 22 and the hot bulb anemometer 12 in the same cross section and located in the straight pipe section of the circulating air duct.

[0043] In the circulating air duct, the guide plates 20 at the right-angle bends are designed with a radius of 5 cm and a 1 / 4 arc shape, and are evenly distributed at the bends; the guide plates are made of solid plates with a thickness of 0.5-1 mm.

[0044] When the width of the circulating air duct is 150 mm, five guide plates 20 are evenly installed at the right-angle bends.

[0045] In the circulating air duct, extension plates 26 with a length equal to the arc radius are installed at both ends of the guide plate 20, and the extension plates are arranged parallel to the circulating air duct; this can reduce turbulence and simultaneously reduce the pressure difference between the air inlet and outlet ends on both sides of the guide plate, thereby reducing the loss of air volume.

[0046] In the circulating air duct, the straight pipe section rectifier plate 11 adopts a rectifier plate with a hexagonal cross-section, a hole height of 10 mm, and a thickness of 100 mm. The cross-section of the rectifier plate is honeycomb-shaped, and the center line of the hole is perpendicular to the plate surface.

[0047] In the circulating air duct, the hexagonal cross-section of the straight tube section rectifier plate 11 is a hexagonal unit of the side wall opening 27, which plays a role in balancing the pressure between the units when the airflow just enters the rectifier plate; at the same time, in order to ensure that the airflow does not form new turbulence in the rectifier plate due to the openings, it is necessary to ensure a certain length of steady flow section to ensure that the airflow out of the rectifier plate is uniform and stable. The length of the opening section accounts for 1 / 3 of the length of the hexagonal unit, that is, the thickness of the plate, and the opening rate (that is, the total unit opening area / unit cross-sectional area) is about 40%.

[0048] 1. Wind speed uniformity optimization design

[0049] The calibrated wet-bulb and hot-bulb anemometers in the test area of ​​the calibration device are placed side by side in the same section. In order to ensure that the measured wind speed is the wind speed at the calibrated wet-bulb, it is necessary to have good wind speed uniformity in the section. To achieve this goal, this paper focuses on the optimization design of the right-angle bend guide plate and the straight pipe section rectifier plate.

[0050] The airflow in the duct can be divided into fully developed pipe flow and non-fully developed pipe flow. Since the straight pipe section of the calibration device test area involved in this article is limited in length, it belongs to non-fully developed pipe flow. Affected by various resistances, turbulence will form, making the wind speed uniformity in the same cross section worse.

[0051] 1.1 Optimization design of right-angle bend guide plate

[0052] After the airflow passes through the bend, it will be affected by the inertial force and form turbulence. The flow field will become very complex, and the velocity distribution will be uneven and irregular. The airflow can be guided by adding guide plates to reduce the influence of inertial force, increase the influence of viscous force, and make the velocity distribution present laminar distribution, which will cause the gas flow to be layered, and the direction of each flow layer is parallel to the axis of the air duct.

[0053] To achieve this goal, the deflectors are designed with a radius of 5 cm and a quarter arc shape, evenly distributed at the bends. The following will optimize the design of the deflectors in terms of quantity and style.

[0054] 1.1.1 Number of guide plates

[0055] The guide plates guide the airflow. Too few guide plates will not be effective, while too many will narrow the air duct and block the airflow. Selecting the right number according to the diameter of the air duct can improve the uniformity of wind speed and reduce wind speed loss. The following will compare the laminar and turbulent distribution diagrams of 1, 5, and 8 guide plates to select the best solution. Figure 2 , Figure 3 , Figure 4 .

[0056] Table 1 Pressure difference between the air inlet and air outlet on both sides of the guide plate

[0057]

[0058] It can be seen that after installing 5 guide plates, the turbulence in the test section is significantly less, and the effect of 8 guide plates is not much improved compared to 5 guide plates. Considering the processing cost and difficulty, 5 guide plates are a more ideal choice.

[0059] 1.1.2 Guide plate style

[0060] As can be seen from the figure above, there is still some turbulence in the test section after the guide plate is installed. The guide plate can be further modified. Figure 6 ), the laminar and turbulent distribution diagrams of the five guide plates are as follows Figure 5 .

[0061] Table 2 Pressure difference between the air inlet and air outlet on both sides of the guide plate after transformation

[0062]

[0063] It can be seen that the improvement of the deflector style not only reduces turbulence, but also simultaneously reduces the pressure difference between the air inlet and air outlet on both sides of the deflector, reducing the loss of air volume. Through comparative analysis, it is more ideal to arrange 5 deflectors with extension plates at the right-angle bend.

[0064] 1.2 Optimization design of straight pipe section rectifier

[0065] The installation of the rectifier can further ensure the uniformity and stability of the airflow in the test area. In order to achieve the most ideal effect, we will optimize the design from the aspects of rectifier structure (cross-sectional shape, hole height, thickness), pressure loss, and pressure balance.

[0066] 1.2.1 Rectifier plate structure (cross-sectional shape, hole height, thickness)

[0067] Here we select the most common square cross-section and hexagonal cross-section rectifier plates (such as Figure 7 , Figure 8 ), and selected different hole heights and thicknesses for comparison (see Table 3) to determine the optimal solution.

[0068] Table 3 Rectifier board solution summary

[0069] Cross-sectional shape Hole height / mm Thickness / mm square 20 100 hexagon 10 100 hexagon 20 100 hexagon 40 100 hexagon 10 50

[0070] Flow velocity distribution diagram Figures 9 to 13 .

[0071] Through comparison, it is found that the rectifier plate with hexagonal cross-section is better than the rectifier plate with square cross-section. The smaller the hole height and the thicker the rectifier plate, the better the rectifying effect. Considering the influence of the resistance coefficient on the air supply volume, the hole height cannot be reduced or the thickness cannot be increased indefinitely. According to the size of the calibration device, it is more ideal to select a rectifier plate with a hexagonal cross-section, a hole height of 10mm and a thickness of 100mm.

[0072] 1.2.2 Pressure loss and pressure balance

[0073] When the airflow passes through the rectifier plate, due to the influence of the resistance along the way and the local resistance, a certain pressure loss will be generated to reduce the wind speed, forcing the air supply system to select a fan with higher power, which is neither energy-saving nor conducive to the stability of the internal environment of the air duct.

[0074] Since the wind field is not uniform after the airflow passes through the right-angle bend, the wind speed of the hexagonal units at different positions at the air inlet end of the rectifier plate will be different, and the corresponding wind pressure at the air inlet end will be different. In principle, a longer straight pipe section needs to be placed behind the rectifier plate to stabilize the airflow. Due to the volume limitation of the device, the requirement for the length of the straight pipe section cannot be met. It is necessary to find a way to achieve pressure balance between the hexagonal units of the rectifier plate within a short distance, so as to minimize the wind pressure difference between the hexagonal units at the air outlet end of the rectifier plate and shorten the requirement for the length of the straight pipe section.

[0075] At the same time, if the wind pressure difference between the hexagonal units can be balanced at the air inlet end of the rectifier plate, it will also be beneficial to reduce the influence of the along-the-way resistance and local resistance, and reduce the pressure loss caused by the rectifier plate.

[0076] Here, a hexagonal unit with holes in the sidewall is designed ( Fig.14 ), which can effectively balance the pressure between units when the airflow just enters the rectifier. At the same time, in order to ensure that the airflow does not form new turbulence in the rectifier due to the openings, it is necessary to ensure a certain length of steady flow section to ensure that the airflow out of the rectifier is uniform and stable. Several schemes with different numbers of openings, hole spacing, and hole diameters are selected for comparison. The specific schemes are shown in Table 4, and the flow direction wind speed distribution curve is shown in Fig.15 .

[0077] Table 4 Rectifier board solution summary

[0078]

[0079] As can be seen from the figure, the cross-sectional wind speed distribution is low in the middle and high on both sides. In the case of Scheme 1, the symmetry of the flow direction wind speed distribution is poor. After the perforated rectifier is used, the symmetry is significantly improved, and Scheme 2 has the best effect. Therefore, the length of the perforated section accounts for about 1 / 3 of the length of the hexagonal unit, and the opening ratio (total unit opening area / unit cross-sectional area) is about 40%. For details, see Table 4. Fig.14 .

[0080] In summary, through the optimized design of the guide plate and the rectifier plate, the requirements for the length of the straight pipe section can be greatly reduced, and the device volume can be miniaturized, which is convenient for carrying to the site. It can effectively achieve uniform and stable wind speeds at different locations in the test area to meet the calibration requirements. According to the working environment requirements of the calibration object, the main wind speed measurement range of the device is less than 6m / s. For low wind speed calibration, the wind speed uniformity optimization design scheme will have a better effect.

[0081] 2. Control operation logic

[0082] Wind speed and temperature regulation are relatively simple to implement, and here we will focus on describing the more efficient implementation method of humidity control.

[0083] 2.1 Wind speed control operation logic:

[0084] There are two adjustment modes: automatic and manual:

[0085] a. Use PID regulation to adjust the fan inverter frequency according to the feedback data of the hot-bulb anemometer to achieve the set wind speed value.

[0086] b. Since the household appliance laboratory does not have high requirements for the wind speed in the air sampler (for example, GB / T 7725 requires no less than 5m / s), the wind speed can also be manually adjusted according to the feedback value of the hot bulb anemometer.

[0087] 2.2 Temperature control operation logic:

[0088] Using PID regulation, according to the feedback data from the temperature sensor, the required heat and cooling generated by the Peltier has reached the set temperature value.

[0089] 2.3 Humidity control operation logic:

[0090] By using the optimization algorithm, the difference ρ′ between the unsaturated water vapor density at the current temperature and humidity and the set temperature and humidity is calculated through the results measured by the standard temperature and humidity sensor, and the number of grams of water vapor missing or extra per cubic meter can be obtained. Since the volume V of the air duct of the calibration device is fixed and the value can be measured, the mass m1 of the water vapor missing or extra in the air duct can be calculated using the volume V and the density difference ρ′.

[0091] When the measured value is lower than the set value, since the device is a closed cavity, the volume of gas output by the saturated steam generator must be inhaled from the air duct. The saturated water vapor density ρ qb Subtract the unsaturated water vapor density ρ under the measured temperature and humidity conditions q1 , it can be concluded that the saturated steam generator exchanges 1m 3 The mass of water vapor added by the gas is m2, and m1 / m2 gives the volume of saturated water vapor that needs to be output in the air duct with a volume of V;

[0092] When the measured value is higher than the set value, since the device is a closed cavity, the volume of gas output by the dryer must be inhaled from the air duct. 3 The mass m2 of water vapor reduced by the gas is numerically equal to the unsaturated water vapor density ρ under the measured state q1 , m1 / m2 is the volume of dry air that needs to be output in the air duct with a volume of V.

[0093] 3 Theoretical basis of humidity control optimization algorithm

[0094] At normal temperature and pressure, dry air can be regarded as an ideal gas, while water vapor in wet air is generally in an overheated state and has a very small content, so it can be approximately regarded as an ideal gas. In this way, the state equation of ideal gas can be used to express the relationship between the main state parameters of dry air and water vapor - pressure, temperature, specific volume, etc., that is:

[0095] P g V=m g R g T or P g v g =R g T

[0096] P q V=m q R q T or P q v q =R q T

[0097] Where:

[0098] P g , P q ——Pressure of dry air and water vapor, Pa;

[0099] V——Total volume of moist air, m 3 ;

[0100] m g 、m q ——Mass of dry air and water vapor, kg;

[0101] R g , R q ——Gas constant for dry air and water vapor, R g =287J / (kg·K), R q =461 J / (kg·K);

[0102] v g ——Specific volume of dry air, m 3 / kg;

[0103] v q ——Specific volume of water vapor, m 3 / kg;

[0104] T——Thermodynamic temperature of dry air, (273.15+t)℃. t is the measured temperature.

[0105] The specific volumes of dry air and water vapor are:

[0106]

[0107]

[0108] The density of dry air and water vapor is equal to the reciprocal of the specific volume:

[0109]

[0110]

[0111] Where:

[0112] ρ g ——Dry air density, kg / m 3 ;

[0113] ρ q ——Water vapor density, kg / m 3 .

[0114] According to Dalton's law, the pressure of moist air should be equal to the sum of the pressure of dry air and the pressure of water vapor, that is:

[0115] B=P g +P q

[0116] Where:

[0117] B——generally known as atmospheric pressure. The standard atmospheric pressure at sea level is 101325Pa.

[0118] The density of moist air ρ is equal to the sum of the density of dry air and the density of water vapor, that is:

[0119]

[0120] Where:

[0121] ρ——Density of moist air, kg / m 3 .

[0122] Relative humidity It is defined as the ratio of the water vapor pressure of moist air to the water vapor pressure of saturated moist air at the same temperature, that is:

[0123]

[0124] Where:

[0125] P q·b ——Saturated water vapor pressure, Pa.

[0126] P can be calculated using the following Hyland-Wexler empirical formula: q·b , when t=(0~200)℃

[0127] Time: (t is the measured temperature of the air duct)

[0128]

[0129] Where:

[0130] c1——-5800.2206, constant;

[0131] c2——1.3914993, constant;

[0132] c3——-0.048640239, constant;

[0133] c4——0.000041764768, constant;

[0134] c5——-1.4452093×10 -8 ,constant;

[0135] c6——6.5459673, constant.

[0136]

[0137]

[0138] The simplified calculation formula can be obtained from the above control operation logic and formula:

[0139] The calculation formula for the output saturated water vapor volume required to increase humidity is:

[0140]

[0141] The formula for calculating the volume of dry air required to reduce humidity is:

[0142]

[0143] Where:

[0144] V′1——Required output saturated water vapor volume, m 3 ;

[0145] V'2——Required output dry air volume, m 3 ;

[0146] V——the volume of the air duct of the calibration device, m 3 ;

[0147] m1——the mass of saturated water vapor required to be added to the space with volume V, kg;

[0148] m2——1m per exchange 3 The mass of water vapor added by the gas, kg;

[0149] m3——The mass of saturated water vapor that needs to be reduced in a space with a volume of V, kg;

[0150] m4——1m per exchange 3 The mass of water vapor reduced by the current gas, kg;

[0151] ρ′——Difference in density between unsaturated water vapor at current temperature and humidity and at set temperature and humidity, kg / m 3 ;

[0152] ρ qb ——Saturated water vapor density, kg / m 3 ;

[0153] ρ q0 ——Unsaturated water vapor density at set state, kg / m 3 ;

[0154] ρ q1 ——Unsaturated water vapor density at current state, kg / m 3 ;

[0155] ——Relative humidity of unsaturated moist air in set state, %RH;

[0156] ——Relative humidity of unsaturated moist air in the current state, %RH.

[0157] 4 Examples

[0158] Table 5 Assumed experimental conditions

[0159]

[0160] Table 6 Example 1: When humidity needs to be increased

[0161]

[0162] Table 7 Example 2: When humidity needs to be reduced

[0163]

Claims

1. An in-situ environment simulated wet-bulb temperature calibration device, characterized in that: The calibration device comprises an outer shell, a rectangular annular circulation air duct installed in the outer shell, and an inner shell installed in the central space of the annular air duct; the calibration device also comprises a drying device, a humidifying device, a sensor device, an air circulation device with adjustable wind speed, a constant temperature device and a controller; wherein the drying device and the humidifying device are installed in the inner shell; and the controller is installed on the outer shell; 1) Drying device: including a drying chamber, an air pump, a filter, a stirring fan and connecting pipes. An air dryer, i.e. a dehumidifier and a stirring fan are installed in the drying chamber. An air pump is installed in the air inlet pipe of the drying chamber, and a filter is installed in the air outlet pipe. The air inlet pipe and the air outlet pipe are respectively connected to different positions of the circulating air duct. Dry air is provided in the circulating air duct of the calibration device to reduce the relative humidity of the circulating gas, and a specified volume of dry air can be output according to the program design. 2) Humidification device: including an ultrasonic humidification chamber, an air pump, a filter, a stirring fan and connecting pipes. The air inlet pipe of the ultrasonic humidification chamber is equipped with an air pump, the air outlet pipe is equipped with a filter, an ultrasonic steam generator, i.e. a humidifier and a stirring fan are installed in the ultrasonic humidification chamber, and the air inlet pipe and the air outlet pipe are respectively connected to different positions of the circulating air duct; saturated wet steam is provided in the circulating air duct of the calibration device to increase the relative humidity of the circulating gas, and a specified volume of saturated water vapor can be output according to program design; 3) Sensor device: including hot-bulb anemometer, platinum resistance temperature sensor, dry-wet integrated temperature and humidity sensor. Platinum resistance temperature sensors are installed in the drying chamber and saturated ultrasonic humidification chamber respectively. Hot-bulb anemometer, dry-wet integrated temperature and humidity sensor and calibrated wet bulb are installed in the circulating air duct. These three are close to each other in the circulating air duct to monitor the temperature, humidity and wind speed in the circulating air duct, dryer and saturated steam generator, and transmit information to the controller in real time. Two dry-wet integrated temperature and humidity sensors are set on the same cross section behind the calibrated wet bulb. The feedback data of the two sensors are compared to verify the accuracy and reliability of the sensor itself and the temperature and humidity in the measuring air duct. 4) Wind speed adjustable air circulation device: including air duct, frequency converter, voltage stabilized power supply, fan, guide plate and rectifier plate; the circulating air duct is a rectangular closed annular channel, arc-shaped curved guide plates are installed at each corner of the circulating air duct, and straight pipe section rectifier plates are installed at the straight pipe section near the corner; a fan is installed in the circulating air duct, and the fan is connected to the frequency converter and voltage stabilized power supply; the air circulation device is a closed gas internal circulation, and does not exchange gas with the outside during operation, providing a stable and controllable wind speed environment for the calibrated sensor; 5) Constant temperature device: including Peltier, which is installed in the drying chamber, ultrasonic humidification chamber and circulating air duct respectively; providing the heat and cooling required for stable temperature for the circulating air duct, dryer and saturated steam generator of the calibration device.

2. The in-situ environment simulated wet-bulb temperature calibration device according to claim 1, characterized in that: In the circulating air duct, a foreign body-proof gauze is installed in front of the rectifier plate of the straight pipe section; the drying device, humidifying device, frequency converter, and voltage-stabilized power supply are installed together in the inner shell; the controller adopts a PLC controller or a single-chip microcomputer.

3. The in-situ environment simulated wet-bulb temperature calibration device according to claim 1 or 2, characterized in that: In the circulating air duct, the calibration device test area is placed side by side with the wet bulb and the hot bulb anemometer in the same cross section and located in the straight pipe section of the circulating air duct.

4. The in-situ environment simulated wet-bulb temperature calibration device according to claim 1 or 2, characterized in that: In the circulating air duct, the guide plates at the right-angle bends are designed with a radius of 5cm and a 1 / 4 arc shape, evenly distributed at the bends; the guide plates are made of solid plates with a thickness of 0.5-1 mm.

5. The in-situ environment simulated wet-bulb temperature calibration device according to claim 1 or 2, characterized in that: When the width of the circulating air duct is 150mm, 5 guide plates are evenly installed at the right-angle bends.

6. The in-situ environment simulated wet-bulb temperature calibration device according to claim 1 or 2, characterized in that: In the circulating air duct, extension plates with a length equal to the arc radius are installed at both ends of the guide plate, and the extension plates are arranged parallel to the circulating air duct; this can reduce turbulence and simultaneously reduce the pressure difference between the air inlet and outlet ends on both sides of the guide plate, thereby reducing the loss of air volume.

7. The in-situ environment simulated wet-bulb temperature calibration device according to claim 1 or 2, characterized in that: In the circulating air duct, the straight pipe section rectifier plate adopts a hexagonal cross-section, a hole height of 10mm and a thickness of 100mm. The cross-section of the rectifier plate is honeycomb-shaped, and the center line of the hole is perpendicular to the plate surface.

8. The in-situ environment simulated wet-bulb temperature calibration device according to claim 1 or 2, characterized in that: In the circulating air duct, the hexagonal cross-section of the straight pipe section rectifier is a hexagonal unit with holes on the side wall, which plays a role in balancing the pressure between the units when the airflow just enters the rectifier. At the same time, in order to ensure that the airflow does not form new turbulence in the rectifier due to the holes, a certain length of steady flow section is required to ensure that the airflow out of the rectifier is uniform and stable. The length of the opening section accounts for 1 / 3 of the length of the hexagonal unit, that is, the thickness of the plate, and the opening rate, that is, the total opening area of ​​the unit / the cross-sectional area of ​​the unit, is about 40%.

9. A humidity calibration method for the in-situ environment simulated wet-bulb temperature calibration device according to claim 1, characterized in that: The following steps are involved: (1) The difference ρ′ between the unsaturated water vapor density at the current temperature and humidity and the set temperature and humidity is calculated using the results measured by the standard temperature and humidity sensor to obtain the number of grams of water vapor missing or extra per cubic meter. Since the volume V of the air duct of the calibration device is fixed and its value can be measured, the mass m1 of the water vapor missing or extra in the air duct can be calculated using the volume V and the density difference ρ′. (2) When the measured value is lower than the set value, since the device is a closed cavity, the volume of gas output by the saturated steam generator must be the same as the volume of gas inhaled from the air duct. The saturated water vapor density ρ qb Subtract the unsaturated water vapor density ρ under the measured temperature and humidity conditions q1 , it is concluded that the saturated steam generator exchanges 1m 3 The mass of water vapor added by the gas is m2, and m1 / m2 gives the volume of saturated water vapor that needs to be output in the air duct with a volume of V; (3) When the measured value is higher than the set value, since the device is a closed cavity, the volume of gas output by the dryer must be inhaled from the air duct. 3 The mass m2 of water vapor reduced by the gas is numerically equal to the unsaturated water vapor density ρ under the measured state q1 , m1 / m2 is the volume of dry air that needs to be output in the air duct with a volume of V.

10. The humidity calibration method of the in-situ environment simulated wet-bulb temperature calibration device according to claim 9, characterized in that: The following steps are involved: The state equation of ideal gas is used to express the relationship between the main state parameters of dry air and water vapor - pressure, temperature, and specific volume, namely: P g V=m g R g T or P g v g =R g T P q V=m q R q T or P q v q =R q T Where: P g , P q ——Pressure of dry air and water vapor, Pa; V——Total volume of moist air, m 3 ; m g 、m q ——Mass of dry air and water vapor, kg; R g , R q ——Gas constant for dry air and water vapor, R g =287J / (kg·K), R q =461 J / (kg·K); v g ——Specific volume of dry air, m 3 / kg; v q ——Specific volume of water vapor, m 3 / kg; T——dry air thermodynamic temperature, (273.15+t)℃; The specific volumes of dry air and water vapor are: The density of dry air and water vapor is equal to the reciprocal of the specific volume: Where: ρ g ——Dry air density, kg / m 3 ; ρ q ——Water vapor density, kg / m 3 ; According to Dalton's law, the pressure of moist air should be equal to the sum of the pressure of dry air and the pressure of water vapor, that is: B=P g +P q Where: B——Generally known as atmospheric pressure, the standard atmospheric pressure at sea level is 101325Pa; The density of moist air ρ is equal to the sum of the density of dry air and the density of water vapor, that is: Where: ρ——Density of moist air, kg / m 3 ; Relative humidity It is defined as the ratio of the water vapor pressure of moist air to the water vapor pressure of saturated moist air at the same temperature, that is: Where: P q·b ——saturated water vapor pressure, Pa; The Hyland-Wexler empirical formula can be used to calculate P q·b , when t=(0~200)℃: Where: c1——-5800.2206, constant; c2——1.3914993, constant; c3——-0.048640239, constant; c4——0.000041764768, constant; c5——-1.4452093×10 -8 ,constant; c6——6.5459673, constant; Where: ρ q0 ——Unsaturated water vapor density at set state, kg / m 3 ; ρ q1 ——Unsaturated water vapor density at current state, kg / m 3 ; ρ qb ——Saturated water vapor density, kg / m 3 ; ——Relative humidity of unsaturated moist air in set state, %RH; ——Relative humidity of unsaturated moist air in the current state, %RH; The simplified calculation formula can be obtained from the above control operation logic and formula: The calculation formula for the output saturated water vapor volume required to increase humidity is: The formula for calculating the volume of dry air required to reduce humidity is: Where: V1′——Required output saturated water vapor volume, m 3 ; V2′——Required output dry air volume, m 3 ; V——the volume of the air duct of the calibration device, m 3 ; m1——the mass of saturated water vapor to be added in the space with volume V, kg; m2——the mass of saturated water vapor to be added per 1m 3 The mass of water vapor added by the gas, kg; m3——The mass of saturated water vapor that needs to be reduced in a space with a volume of V, kg; m4——1m per exchange 3 The mass of water vapor reduced by the current gas, kg; ρ′——Difference in density between unsaturated water vapor at current temperature and humidity and at set temperature and humidity, kg / m 3 .

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