To utilize the wet-bulb temperature as a monitoring or controlling factor of a vacuum cooling process, the morphological improvements of a wet-bulb sensor have been carried out with an experimental vacuum cooler, and it's applicability has been investigated by setting it in vacuum chambers of some commercial plants. The procedures and results obtained are summarized as follows;
1) The changing characteristics of wet-bulb temperatures measured with some types of sensors, which were originally mounted in the vacuum chambers of commercial plants, indicated that the wet-bulb temperature was more useful than a chamber pressure to monitor the product temperature during after a flash point of cooling process, and also morphological improvements of the sensor were required to detect the flash point as the controlling factor of the plant.
2) The necessary conditions for the morphology of wet-bulb sensor, using a thermocouple as well as a water-bottle, to detect both flash point and product temperature during cooling processes were presented;
This is (a) The measuring point of thermocouple should be set at the point separated more than 2cm above the top of water-bottle while keeping the distance of 10-15cm between the measuring point and the free surface of water in the bottle.
(b) The initial temperature of water in the bottle should be lower than that of the product.
3) By installing an improved sensor in the vacuum chamber of practical plant, we verified that the wet-bulb temperature could be used stably as a controling factor of cooling process for commercial vacuum plants.
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