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

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378 CORK INSULATION<br />

hours before starting test. Weigh ice at the start of test proper. Weigh<br />

ice left at terminati<strong>on</strong> of test proper. Obtain data:<br />

(a) Temperature of food chamber (t).<br />

(b) Temperature of room (T).<br />

(c) Square feet of surface exposure (S), calculated <strong>on</strong> exterior dimensi<strong>on</strong>s.<br />

To determine Ice Ec<strong>on</strong>omy, substitute in the following formula:<br />

IX 144<br />

R = Sx (T—t)<br />

where R is the rate of heat transmissi<strong>on</strong>, which may be defined as the<br />

number of B.t.u. that pass through <strong>on</strong>e square foot of surface daily when<br />

the difference between the surface is 1° F. ; I is the number of pounds<br />

of ice melted daily; 144 is the B.t.u. required to melt <strong>on</strong>e pound of ice;<br />

S is the surface exposure; T is the average atmospheric temperature;<br />

and t is the average temperature of food chamber. Score as follows<br />

SCORE FOR HEAT TRANSMISSION<br />

Value for R Rate<br />

1.13 20<br />

1.63 18<br />

2.0O 16<br />

2.33 14<br />

2.66 12<br />

3.00 10<br />

3.33 8<br />

3.66 6<br />

4.00 4<br />

4.33 2<br />

4.66 1<br />

5.00<br />

3. Humidity.—In making humidity tests, a wet and dry bulb thermometer<br />

should be used. Take twelve readings at intervals of <strong>on</strong>e hour.<br />

See U. S. Bureau of Standards' tables* for readings calculated up<strong>on</strong> dif-<br />

ferences in temperatures of wet and dry bulb thermometers. Score as<br />

follows<br />

SCORE FOR HUMIDITY<br />

Humidity<br />

55 to 65%<br />

Rate<br />

8.0<br />

65 to 76 7.5<br />

45 to 55 7.5<br />

40 to 45 7.7<br />

75 to 80 6.4<br />

30 to 40 6.0<br />

80 to 85 4.8<br />

20 to 30 4.8<br />

85 to 95<br />

90 and over<br />

2.4<br />

0.0<br />

20 and under 0.0<br />

4. Circulati<strong>on</strong> of Air.— ^Credit a maximum of 5 for probability that<br />

cold air will readily pass from the ice compartment to and through the<br />

food compartment and back again to the ice. If ice compartment is<br />

ample, credit 2. If doors do not fit snugly, subtract 1. If any wall is<br />

moist, subtract 3.<br />

5. Interior Finish.—Ease of cleaning refers to cleaning of food cham-<br />

ber, all shelves therein, and the drain pipes. If ease of cleaning is ideal,<br />

credit 5. If interior finish is hard and n<strong>on</strong>-absorbent, credit 2. If color<br />

is white, credit 5.<br />

*See Appendix for tables menti<strong>on</strong>ed.<br />

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