Cork insulation; a complete illustrated textbook on cork insulation ...

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CORK INSULATION
ers and cross slats about three inches wide and about two inchesapart,
are essentials for the distribution of the refrigerated air. The
wire basket hanging free in the end of the car permits the warm air
entering at the top to flow without obstruction over the entire surface
of the ice and, as it cools, to fall to the floor. At the floor it is not
pocketed, but finds a ready exit under the rack, and so along the car
floor and up through the load, gathering heat as it goes and carrying
it to the upper bulkhead opening where again the ice has a chance to
absorb it.
If we place thermometers in the air of the car to determine its
temperature at the lower bunker opening, again at the middle between
the doors, then %t the ceiling midway of the car, then at the
ceiling quarter way, and finally about ten inches in front of the
upper bunker opening, we find a steady rise in temperature, the
upper bunker opening thermometer being the highest. Generally,
we find from two to four degrees difference between the air in the
upper, middle part of the car and that at the upper bunker opening.
If the thermometers are similarly placed in a car equipped with a
box bunker with open bulkhead and without the floor rack
the graduations of temperature in the upper part of the car are just
reversed. Here the temperature at the upper bunker opening is
ordinarily from two to four degrees lower than at the iniddle of car.
This observation has been made again and again and is further confirmed
by the performance of a box bunker combined with solid
bulkhead and a floor rack, with which there is good cooling in the
top of the load at the bunkers, but unsatisfactory results in the
upper, middle parts of the load. In other words, we have only a
partial air circulation. Even more striking are the results obtained
when salt is added to the ice in the basket bunker combined with the
insulated bulkhead, and floor rack, or the "standard type" bunker, as
it is now termed. So rapid is the removal of the very cold air from
the bottom of the bunker that fruit and eggs may be rapidly cooled
throughout the car without frosting the packages at the bulkhead.
Of course, the bulkhead, insulated with one or two inches of a
standard insulator, is an essential if the packages against it are to
be protected from the frigid air close to the ice and salt; but, that
this protection is not due entirely to the bulkhead, is proved by the
pocketing of the cold at the bottom of the bunker when the box
bunker with an insulated bulkhead is salted. Then the packages at
the bottom of the load, next to the bunker, are frosted. In other
words, there is no force to the air movement and it cannot be dis-
tributed with sufficient rapidity to prevent the intensive chilling of
itself. With the standard bunker and floor rack and a lading such as
cantaloupes or oranges, as much as 9 per cent of salt may be safely
used in the initial icing, and the same percentage, or a little less, may
be used on the two successive days, by which time the load is cooled
throughout. It is unnecessary to point out the great advantages
accruing to the transportation of such perishables as berries, peaches