高温压力蒸汽气-汽混合法相对湿度测量方法

Relative humidity measuring of high temperature and pressure steam by the air-steam mixing method

为实现含不凝气体组分高温压力蒸汽相对湿度精确测量,设计了带翅片的套管盘管空冷换热器和常压过热气体湿度精确监测装置。高温压力蒸汽所含水汽质量等于干空气与蒸汽混合形成的过热气体承载的水汽质量,通过干空气预热、气-汽充分混合、空冷-水浴二次控温后实时监测恒温、恒压、恒湿混合气流参数,采用实际气体状态方程修正计算出目标蒸汽所处温度、压力条件下的相对湿度值。气-汽混合法在露点温度128℃下测量不确定度0.93%,相对湿度测量偏差小于1%,具有测量精度高、测量速率快的特点。该方法实现了相对湿度国际单位制(SI)基本单位溯源,并能开展相对湿度瞬态测量。

For the accurate monitoring of the relative humidity of high temperature and pressure steam with non-condensable gas components,a coaxial fin coil air-cooled heat exchanger and an accurate monitoring device for superheated gas humidity are designed.The mass of water vapor contained in the high temperature steam is equal to the mass of water vapor carried by the superheated air formed by dry air and steam.The parameters of temperature,pressure and humidity of mixed gas are monitored in real time after the process of dry air preheating,non-condensing mixing of gas and steam,and secondary temperature control by air cooling apparatus and water bath equipment.The relative humidity value under the temperature and pressure conditions of the target steam is calculated by using the actual gas state equation model.The measurement uncertainty of the air-steam mixing method is 0.93%at the steam dew point temperature of 128℃,and the relative humidity measurement deviation is less than 1%.It has the characteristics of high measurement accuracy and fast measurement rate.This method can realize the traceability of the international system of units(SI)of relative humidity,and can realize the instantaneous measurement.