In the process of heat-treating of materials during food processing by employing hot air or high temperature steam, the gas flow temperature, humidity, and pressure significantly affect the processed materials. In this study, we developed a humidity-measuring device that can continuously measure hot air flow above the boiling point. The measuring method is based on the principle of the psychrometer. Porous ceramics processed by injection molding are used as the wetted material for a wet-bulb

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... rmometer. Accuracy is evaluated by using a humidity generator that can generate arbitrary humidity over 100°C of humid air to superheated steam. The measurements were conducted under gas flow temperatures ranging from 160°C to 300°C, and at a gas flow velocity of 3 m/s.