Abstract
At first, the load test of the portable vacuum cooler reported on the part (1) was run using water in a plastic container in stead of agricultural products. Then, vacuum cooling tests were run on various agricultural products, and the characteristic cooling properties were obtained.
The results were as follows:
1) With the coil condenser, the refrigerator required a large cooling capacity especially during a short period after the flash point, and then the cooling load of the refrigerator decreased (Fig. 6). Little water vapor reached the pump, because 90-98% of vapor was frozen and caught by the coil condenser.
2) With the ice condenser, HAKUSAI (Chineese cabbage) was cooled safely and uniformly, although the vacuum pump could not reduce the operational pressure below 6mmHg and temperatures below 3°C were not readily obtained.
The ice condenser caught 80-90%, of water vapor. For a larger condensing capacity than the above the required quantity of crushed ice in the ice condenser box may be at least 3-4 times the total heat load of products.
3) Leafy products such as lettuce, HAKUSAI, spinach, celery, etc. were proved to be best suited for this type of precooling. Also vacuum cooling was efficient for strawberry, Holland pea (a field pea), sweet corn and mushroom.
