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CN-121994868-A - Air relative humidity measurement and calibration device

CN121994868ACN 121994868 ACN121994868 ACN 121994868ACN-121994868-A

Abstract

The invention discloses an air relative humidity measurement and calibration device, and belongs to the field of humidity measurement. The device is realized by adopting a Dalton partial pressure law, a wet air enthalpy and humidity calculation theory and an improved dry and wet ball temperature measurement theory, free diffusion of water vapor outside an effective air film is avoided through a closed container, so that wet air in the effective air film of the wet ball sensor is converted into a saturated air state, unsaturated state errors of the effective air film of the traditional dry and wet ball method are eliminated, meanwhile, a cooling device is added to avoid inaccurate wet ball measurement caused by heat transfer limit temperature difference between the dry ball wet ball temperatures, unification of air humidity measurement and Dalton partial pressure law, wet air enthalpy and humidity calculation theory and related thermodynamic theory is realized, and a datum point is found for air relative humidity measurement. The invention can successfully construct the saturation state of the effective air film around the wet bulb temperature sensor, unifies theoretical and practical measurement, has excellent precision, high calibration efficiency and strong suitability, and finds a datum point for measuring the relative humidity of air.

Inventors

  • ZHANG QIANG
  • HU LICUI
  • ZHANG SEN
  • ZHOU FAN

Assignees

  • 河北农业大学

Dates

Publication Date
20260508
Application Date
20260225

Claims (10)

  1. 1. The utility model provides an air relative humidity measures calibrating device, its characterized in that, the device adopts dalton partial pressure law, wet air enthalpy wet calculation theory and modified wet ball temperature measurement principle to realize, avoid vapor free diffusion to outside effective air film through airtight container, make the wet air in the effective air film of wet ball sensor change to saturated air state, eliminate the unsaturated state error of the effective air film of traditional wet ball method, simultaneously, add cooling device in order to avoid the problem that the wet ball measurement that the heat transfer limit difference in temperature between the wet ball temperature of dry ball of traditional wet ball method is inaccurate, realize the unification of air humidity measurement and dalton partial pressure law, wet air enthalpy wet calculation theory and relevant thermodynamic theory, find a datum point for the air relative humidity measurement.
  2. 2. An air relative humidity measurement calibration device according to claim 1, wherein the device comprises: A closed container (4) configured to limit a closed space in which water vapor freely diffuses so as to accumulate humid air in an effective air film of the wet bulb sensor to a thermodynamic saturation state; The wet bulb temperature sensor (1) is arranged in the closed container (4) and is used for measuring the temperature after the water evaporation and heat absorption lead to temperature reduction; The dry bulb temperature sensor (2) is arranged in the closed container (4) side by side with the wet bulb temperature sensor (1) at the same height and is used for reflecting the thermodynamic intrinsic temperature of air; And the temperature control system can ensure that the wet air in the effective air film forms a saturated state which accords with the Dalton partial pressure law and the wet air enthalpy and humidity calculation theory.
  3. 3. The air relative humidity measurement calibration device of claim 2, wherein the temperature control system comprises a closed container micro-environment temperature control system and a wet bulb water supply temperature control system; the closed container micro-environment temperature control system is configured to be capable of controlling the temperature of the inner environment of the closed container (4), and the wet bulb water supply temperature control system is configured to be capable of controlling the water supply temperature of the wet bulb temperature sensor (1).
  4. 4. The air relative humidity measurement and calibration device according to claim 3, wherein the closed container microenvironment temperature control system comprises heat preservation cotton (5), a closed container microenvironment cooling coil (8), a data acquisition controller (12) and a buffer water tank (7), wherein the heat preservation cotton (5) is arranged around the periphery of the closed container (4), the closed container microenvironment cooling coil (8) is arranged in the closed container (4) in a surrounding mode and connected with the buffer water tank (7), and can control the cooling water in the buffer water tank (7) to flow in the closed container microenvironment cooling coil (8) under the action of the data acquisition controller (12) so as to realize temperature control of the environment in the closed container (4).
  5. 5. The air relative humidity measuring and calibrating device according to claim 4, wherein the heat-insulating cotton (5) and the closed container microenvironment cooling coil (8) are used for maintaining the air temperature in the closed container to be constant, and play a role of heat insulation.
  6. 6. The air relative humidity measuring and calibrating device according to claim 4, wherein the inner surface of the heat preservation cotton (5) is provided with an ambient temperature sensor (3), and the ambient temperature sensor (19) and the dry bulb temperature sensor (2) in the closed container are used for judging the influence degree of the external ambient temperature on the closed container in real time.
  7. 7. The air relative humidity measurement and calibration device according to claim 3, wherein the wet bulb water supply temperature control system comprises a water diversion groove (6), a water diversion groove cooling coil (9), a data acquisition controller (12) and a buffer water groove (7), the water diversion groove (6) is connected with the water diversion groove cooling coil (9), the water diversion groove cooling coil (9) is connected with the buffer water groove (7), and the temperature control of wet bulb water supply in the water diversion groove (6) can be realized by controlling cooling water in the buffer water groove (7) to flow in the water diversion groove cooling coil (9) under the action of the data acquisition controller (12).
  8. 8. The air relative humidity measurement and calibration device according to claim 6, wherein the wet bulb temperature sensor (1), the dry bulb temperature sensor (2), the ambient temperature sensor (3), the buffer water tank temperature sensor (17), the water tank temperature sensor (18) and the ambient air sensor (19) are all connected with the data acquisition controller (12), data are transmitted to an upper computer, and the upper computer calculates initial relative humidity of air according to the data of the wet bulb temperature sensor (1), the dry bulb temperature sensor (2), the ambient temperature sensor (3), the buffer water tank temperature sensor (17), the water tank temperature sensor (18) and the ambient air sensor (19) by stably regulating and controlling the air in the closed container and finally calculating the initial relative humidity of the air according to the data of the wet bulb temperature sensor (1) and the dry bulb temperature sensor (2).
  9. 9. The air relative humidity measurement calibration device according to claim 2, wherein the diameter of the closed container (4) is determined in such a way that: Based on molecular motion diffusion and energy conservation theory, the volumes of the sensors with different shapes and sizes and the weather wet bulb gauze are calculated to obtain the volume of the closed container, and then the installation positions of the wet bulb temperature sensor (1) and the dry bulb temperature sensor (2) are determined according to the isotropy theory.
  10. 10. The air relative humidity measurement and calibration device according to claim 2, wherein the wet bulb temperature sensor (1) comprises the wet bulb temperature sensor (1) and a meteorological wet bulb gauze (11), the meteorological wet bulb gauze (11) is covered on a temperature sensing head of the temperature sensor in a single layer mode and extends downwards into a water diversion groove to be in contact connection with water so as to continuously realize wet bulb water supply, and a hollow sleeve (16) is arranged between the lower part of the wet bulb sensor (1) and a central hole at the bottom of the closed container so as to wrap the meteorological wet bulb gauze (11), so that only the water content of the meteorological wet bulb gauze (11) wrapping the wet bulb temperature sensor (1) is guaranteed to evaporate into the closed container, and excessive evaporation is prevented from causing excessive wet bulb temperature.

Description

Air relative humidity measurement and calibration device Technical Field The invention belongs to the technical field of humidity measurement, and particularly relates to a brand-new air relative humidity measurement calibration device conforming to Dalton partial pressure law and wet air enthalpy and humidity calculation theory. Background The accurate measurement of humidity parameters is of great importance in various fields such as industrial process control, meteorological observation, medical health, warehouse logistics, scientific research and the like, and the performance stability and measurement accuracy of a core device, namely a humidity sensor, are highly dependent on regular and reliable calibration. Currently, the humidity sensor calibration field mainly depends on three basic methods with traceability, namely a dew point method, a thermogravimetric method and a brine method. However, in practice, there are significant limitations and disadvantages to the three prior humidity sensor calibration techniques described above. Dew point method: The equipment is complex and expensive, and the purchase and maintenance cost of the whole calibration system is extremely high due to a high-precision cold mirror dew point meter or a precise dew point probe, a high-stability temperature control system, a high-purity air source, a complex air path control and the like. Dew condensation judgment dependence and pollution risk are that a cold mirror dew point meter relies on an optical system to detect dew formation, subjective performance or technical difficulty (particularly ultralow dew point) exists, and a mirror surface is extremely easy to be polluted by pollutants in sample gas, so that measurement errors and even failure are caused, and frequent cleaning and maintenance are needed. Dew point hysteresis, namely supercooling phenomenon possibly occurs in the cooling process, and hysteresis possibly occurs in the heating and dew removing process, so that the measuring precision and speed are affected. Thermal gravimetric method: The measurement period is extremely long, the drying process can be realized in a few hours or even more, and the calibration efficiency is low. The principle defect is that the thermogravimetric absorbent cannot completely absorb the water vapor in the air. The environment requirements are strict, the precision requirement on the balance is extremely high, and an extremely stable environment is required, so that the method is difficult to implement in a common laboratory or on site. Brine method: The balance time is long, the stable gas-liquid balance in the closed container needs several hours or even days, and the calibration speed is low. Salt solution stability and contamination risk-saturation of the salt solution must be strictly maintained (undissolved or precipitated salts cannot be present), the solution is volatile, crystallised or contaminates the sensor probe. Long-term use can result in concentration changes or contamination requiring frequent replacement and verification. In addition, the existing dry and wet ball humidity measurement method has the problem that the theory and practice of the existing dry and wet ball humidity measurement method are contradictory. The dynamic balance of evaporation and condensation is realized on the basis of Dalton theorem when the surface of the wet bulb is saturated with ambient air, namely the net mass transfer is zero, however, in actual measurement, the wet bulb is always in an unsaturated quasi-steady state, and the continuous evaporation phenomenon of the wet bulb and the local saturation condition preset by theory form fundamental conflict. Microscopic mechanical studies show that the contradiction is caused by the complex dynamic behavior of wet-bulb gauze-gas interface, namely that water molecules adsorbed on the surface of the fiber need to overcome the binding barrier formed by a hydrogen bond network (inhibiting the thermal motion of the molecules), the high-frequency collision barrier of gas-phase molecules (blocking desorption paths) and the energy barrier formed by surface tension (increasing the phase change activation energy through cohesive force). These microscopic effects (which make it difficult for the gas-liquid interface to reach theoretical saturation, making the classical mass transfer model ineffective in describing the dynamic process of the unsaturated effective gas film, ultimately resulting in systematic deviations of the Relative Humidity (RH) calculated by the traditional formulas from true atmospheric humidity). The forced convection scheme (wind speed of 2-10 m/s) widely adopted for restraining measurement errors, although the wet bulb temperature approaches a theoretical value by destroying a saturated steam layer on the surface of the wet bulb and enhancing the evaporation rate, a new non-negligible error source is introduced, namely, firstly, forced air flow obviously increases the evaporatio