Installations for flasks and manifolds

These installations are relatively easy to handle, their disadvantage being the control of Tice. The heat transfer from the air is difficult to adjust, since it depends on the geometry of the containers and their location at the plant. If e. g. -30 °C has to be the ice temperature, the containers have to be cooled by a bath of approx. -10 °C. It is preferable to dry such products in a chamber with shelves, which can be cooled and heated. 

Rolfgaard [2.2] compared the types of trays and heating systems The ribbed trays are said to have an uneven temperature distribution, because the distances between shelf and tray vary between 0.1 and 1 mm. The ribs could compensate for this only partially. The variation in distances is correct, but Rolfgaard overlooked that the thermal conductivity in the bottom of the tray is so effective that practically no temperature differences are established in the bottom. Even with an evaporation of 3 kg ice/m2 h and the assumption that all heat is transmitted only in the center of the tray (8 cm from the border of the tray), the temperature difference between border and center is -5 °C. During the drying under actual conditions, no measurable temperature differences can exist. 

ribbed tray for cubes or granules of food, designed by Dr Otto Suwelack, D-48723 Billerbeck. All tests were carried out with the same granulate. Hatched columns heating 

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