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

428 CORK INSULATION
lading next to the bunker, and the floor rack provided a quick runway
for the very cold air, which soon lost its temperature of 20° F.,
or even less, by the absorption of the heat of the lading and of the
car.
Such results with the basket bunker, insulated bulkhead and floor
rack, combined, naturally raise the question of the relative value of
each of the three factors in producing and maintaining circulation,
and gaining the available refrigeration from the ice. Experimentation
shows that a rack on the floor of the car hastens the cooling of the
load, and affords very decided protection to the lower layer of goods
against both frost and heat. The floor rack, alone, however, is far
less efficient than the combination of the basket bunker and insulated
bulkhead with the floor rack. The addition of <strong>insulation</strong> to bulkhead
increases circulation and the lading is more rapidly and <strong>complete</strong>ly
cooled than when the bulkhead is either not insulated or is open.
For example. Chart II shows two cars of similar size and construc-
tion, one of which was provided with a floor rack and an insulated
bulkhead, the other as commonly used. Both were loaded with eggs.
The car with the insulated bulkhead and the floor rack reduced the
average temperature of the load 17° F. in sixty-four hours. The load
in the ordinary car showed a reduction of 7.5° F. during the same
period. The average temperature of the car with the insulated bulkhead
and the floor racks was 5.5° F. lower than the ordinary car.
That it is not advisable to cease improvements with the floor rack
and the insulated bulkhead is indicated by experiments which show
that quick cooling by ice and salt safely performed with basket insulated
bulkhead and floor rack is not possible without it. The
pocketed cold air at the box bunker, which is always observed with
bunkers of the box type, causes frosting of the goods against the
bulkhead even when that is insulated.
The failure of refrigerator cars to maintain even temperatures
throughout the load has been a serious menace to extremely perish-
able products. In order to produce temperatures at the top of the
load between the doors—commonly the warmest place in the car
low enough to carry dressed poultry safely, it has been necessary to
freeze the birds at the bunker. While freezing in transit does not
injure the food value of dressed poultry, it does lower its money
value at certain seasons or in some markets. Better air circulation
tends to equalize temperatures, as shown in Chart III. In the car
with the box bunkers and open bulkhead (car B), where the load
was placed on floor strips, the package at the bunker on the floor
froze solidly (23° F.) during a four-day haul, although the package
on the top of the four foot load was 35.4° F. A similar car (car A),
except that it had a basket bunker with insulated bulkliead and a
floor rack, maintained an average tcm])eraturc of 29.3° F. at the
bunker and 34.1° F. in the package on the top of the load between
the doors. In the one case, the average difference between the
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