Trays ribbed

Trays of type (a) are pushed through the plant between the heated shelves without contact (System Atlas Industries A/s, DK 2750 Ballerup, Danmark). The ribbed trays (b) are made... 

Fig. 2.15. Ribbed trays with seven compartments (type b in Fig. 2.14) (ALD Vacuum Technologies GmbH, D-63526 Erlensee).

Rolfgaard [2.2] compares 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 mm and 1 mm. The ribs could compensate this only partially. The variation in distances is correct, but Rolfgaard overlooks 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 approx. 5 °C. During the drying under actual conditions, no measurable temperature differences can exist. 

However there is a major difference between the two forms of trays and heating systems. As shown in Fig. 1.57, approx. 1.3 kg ice/h m2 can be sublimated by radiation heat, if the shelves have a temperature of + 100 °C and the product temperature is -20 °C. The main difference is the method of heat transfer With a flat tray and mostly radiation energy, the density of the heat flow is limited, and it can be substantially larger with ribbed trays standing on the heated shelf. Using the temperatures as above and an average value Klol = 100 kJ/h m2 °C from Tables 1.9 and 1.10, approx. 4.3 kg ice/h m2 can be sublimated. 

Ribbed tray for cubes or granules of food, designed by Dr. Otto Suwelack, D-48723 Billerbeck. All tests have been carried out with the same granulate. 

Fig. 2.19. Plots of a test to determine the specific water vapor flow or the water vapor speed in a production freeze drying plant with approx. 30 m2 shelf area. For the tests 300 kg of distilled water were filled into ribbed trays, which were placed on the shelves. Six RTD were placed in different trays and frozen with the water. The RTD temperatures and BTM measurements were practically identical, because the RTD were always immersed in the ice, and during the test only 25 % of the ice was sublimated.

Ribbed trays Steam- or brine heated In carriers on an overhead rail... 

Fig. 2.16.2. Ice sublimation rate (kg/m2 h) for five different types of tray. 1, Flat tray as in Figure 2.14(a), with 20 mm filling height 2, flat tray with one rib of 20 mm height 3, ribbed tray as in Fig. 2.15 4, ribbed tray as in Fig.

Pyle [4.18] described the freeze-drying of whole eggs which had been frozen in ribbed aluminum trays in a cold air flow and freeze-dried in two tunnels. The dry product had less than 1.5% RM and was packed under Nr The egg powder could be stored for 12 months at room temperature and after reconstitution with water had its original working qualities. 

Fig. 13.29 (a) The four-ribbed, end-fed rectangular tray mold used by Peters et al. (46) for... 

Trays are necessary for bulk products. Such trays should have ribs, if possible, and a machined bottom to achieve similar conditions as mentioned above. Details of ribbed trays are given in [7]. Trays should be avoided if vials are used ... 

Tray area, m2 Flat tray, kg/h Ribbed tray, kg/h kg/kg sublimated... 

Make a small cut between the ribs at the right between ribs eight and nine to allow blood to flow out of the thoracic cage into the tray. 

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