High-temperature air temperature and humidity measuring method

Abstract

A measuring method includes controlling mixed air temperature in measuring range of conventional hygeothermograph by adjusting the mixing ratio of high temperature and low temperature air, measuring out dry bulb temperature of high temperature air and dry-wet bulb temperature of low temperature air and mixing air, utilizing wet air thermodynamic relation to calculate out humidity of high temperature air so as to achieve to use conventional hygrothermograph for measuring humidity of high temperature air.

Description

technical field [0001] The invention relates to a method for measuring high-temperature air humidity, in particular to the measurement of state parameters of high-temperature and low-humidity ambient air, and belongs to the technical field of air state parameter measurement. Background technique [0002] Air humidity is a sign of the amount of water vapor in the air or the degree of dryness and humidity of the air. It is a very important physical quantity in the air state parameters that is difficult to measure accurately. The absolute moisture content of the air increases with the increase of the air temperature. At a high temperature above 100°C, even if the difference in the relative humidity of the air is small, the difference in the absolute moisture content may be large. Therefore, for high temperature For air, the accuracy of humidity measurement should be measured by the measurement accuracy index of absolute moisture content. At present, there are mainly the follow...

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Problems solved by technology

The measurement method is simple and low in cost; but the measurement range is narrow, the precision is low, and the maintenance and management process is complicated (Cheng Qifan, Air humidity and its measurement method, Liaoning Meteorology, 1996, (4): 36)

2. Dry and wet bulb hygrometer: This method has a high relative humidity measurement accuracy within the range, which can reach ±2%~±3%RH; but it is only suitable for gas humidity measurement within the temperature range of 0°C~85°C ( Humidity Measurement Technology. http: / / www.testo.de / US / lig / upload / mwmlus_1034594054750_1.pdf)

This method has high measurement accuracy under low temperature and low humidity conditions; but this measurement method is expensive and complicated, and at the same time in order to ensure the condensation temperature of the mirror, it needs to be precisely controlled, and it is rarely used in practice (Cheng Qifan, Air humidity and its measurement method , Liaoning Meteorology, 1996, (4): 36)

4. Impedance hygrometer: It is a humidity measurement method to obtain humidity according to the change of the impedance value of the humidity sensor. This method has the advantages of fast response, small hysteresis, and wide measurement range; but in high temperature and high humidity Insufficient measurement accuracy in the environment and unstable operation of the probe, easy to age

5. Microwave hygrometer: It measures the humidity of the air through the degree of microwave radiation absorbed by the air. Although this method has a wide measurement range, the instrument processing requirements are strict, the cost is high, and it is not suitable for measurement occasions where the humidity changes rapidly.

At present, the measurement accuracy of various existing air humidity measurement methods and instruments is generally based on the measurement accuracy of relative humidity, and there are not many that can be applied to the measurement of air humidity in high temperature environments. also unsatisfactory

Therefore, it is difficult to meet the high-precision measurement requirements of high-temperature air humidity with the current conventional measurement methods and instruments.

Although there are temperature and humidity measuring instruments in the high temperature range, such as the EE29 / EE31 multifunctional temperature and humidity transmitter of Pride Company, the relative humidity measurement accuracy can reach ±1%RH after special calibration, but for high temperature air, such as When the dry bulb temperature is 140°C and the relative humidity is 7%, the moisture content of the air is 206.99g / kg. The absolute error of measuring the moisture content with this instrument can reach ±35g / kg~±40g / kg, and the relative error 15% to 20%, such a large measurement error is unacceptable

Especially in the dry experimental measurement under the condition of high temperature and large air volume in the laboratory, the relative humidity measurement accuracy of ±1%RH may lead to completely wrong experimental results

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