Humidity measurement method over boiling point temperature based on principle of psychrometer

(Development of humidity generator for accuracy verification)

Abstract

Superheated steam/high-humidity air over boiling point temperature is used as a heating media for food heating machineries, such as steamers and ovens. However, there is no suitable humidity measuring equipment under high temperature and humidity air. Therefore, we have developed a measuring device using porous ceramics based on the principle of the psychrometer. In this study, we have developed a humidity generator of calibrate the humidity measuring device. Standard humidity is generated by mixing of hot air and superheated steam. We have verified the accuracy by comparing values in steam mole fraction measured by the calibrated dew-point instrument and by the flow meters as well as by the psycrometer using porous ceramics. We have analyzed uncertainty of the generated humidity to evaluate the reliability.