6 BULLETIN 1398, U. S. DEPARTMENT OF AGRICULTURE 
degrees higher at the bottom layer during the first few days of the 
trip. | 
aie the difference in temperatures between the top and bottom 
layers at the bunkers is generally greater than between the top and 
bottom positions in other parts of refrigerator cars. This difference 
is more marked where the air circulation becomes choked through 
poor construction, faulty loading, or the shifting of the load. When 
the air is blocked at the bottom of the bunker the packages adjacent 
to it receive the full benefit of the cold air, while those at the top of 
the load remain comparatively warmer. ‘The type of construction at 
this point plays an important part in air circulation within the car. 
Figure 5 shows the record of the temperatures maintained at the 
middle layer, quarter length. The curves for cars A and B are 
———o——Car A, Divided WireBasket Bunker. 
——e—-Car B, WireBasket Bunker, 
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A.M. | P.M. 
Sept.21 
M. | A.M. P.M. | A.M. | PM. AM. PM. | A.M. | Pm. AM. P.M, | AM, UP.M. AM. P.M. | A.M. | P.M. 
Sept. 17 Sept. 18 Sept.!9 Sept.20 ept.22 Sept. 23 Sept.24 Sept.25 
Fig. 5.~Average fruit temperatures, first test, at top and bottom layers and 
fruit temperature at middle layers of the load at the quarter length 
practically the same, but if the initial fruit temperatures had been | 
the same, that for car A might have been slightly lower. Car A, 
however, records a more rapid fall in temperature than car B up to 
midnight of the first day and overcomes the disadvantage of the 
warmer fruit with which it was loaded. 
To understand fully the actual work done in cooling the load, con- 
sideration should be given not only to the temperatures maintained 
within the car at various positions but also to the average tempera- 
ture of the lading. Although this temperature is not so important 
as it might appear, it aids in determining the actual performance, 
particularly if the individual temperatures are given due weight., 
The average temperatures for the top and bottom layers are shown in 
Figure 5. The curves show a little difference, but the effect of the 
higher initial temperatures is readily seen. It is reasonable to make 
allowance for this factor by assuming that in so far as the average 
