MIL-PRF-12571R
4.3.2 Operating requirements verification.
All operating
requirements shall be verified as follows.
4.3.2.1 Heat leakage test. A refrigeration unit or simulation
thereof shall be installed in the refrigerator for this test.
There shall be a minimum five-foot clearance from the test room
walls. The overall heat leakage shall be determined as follows:
a. An electrical fan, of sufficient capacity to ensure that
no uncirculated air pocket will exist, shall be installed inside
the refrigerator. The electrical energy of the fan motor shall be
measured by a watt-hour meter with a scale of 0.1 kilowatt-hour or
less and this heat equivalent shall be added to other sources of
heat added to the refrigerator.
b. Four thermocouples, shielded from the effects of radiant
heat, shall be installed inside the refrigerator and positioned
within 6 inches of the ceiling and floor at two opposite corners.
The interior temperature shall be taken as the average of the four
thermocouples.
c. Heating elements shall be installed approximately in the
center of the refrigerator. Electrical heat input shall be
measured by a watt-hour meter with a scale increment of 0.1
kilowatt-hour or less.
d. Eight thermometers or thermocouples, shielded from the
effects of radiant heat, shall be installed approximately 18
inches from each corner of the refrigerator in the room where it
is placed. The ambient temperature shall be taken as an average
of these eight thermocouple readings.
e. All openings in the refrigerator shall be sealed and the
refrigerator shall remain undisturbed throughout the test.
f. The ambient temperature shall then be maintained
constant within + 20F. Sufficient, steady, non-varying heat shall
be added to the interior of the refrigerator to maintain a minimum
of 60oF and a maximum of 100oF temperature difference between the
interior and exterior of the refrigerator.
g. The test shall be considered concluded when eight
consecutive half-hourly readings indicate that:
(1) The ambient temperature has been maintained constant
within + 2oF.
(2) The temperature inside the refrigerator has been
maintained constant within + 1oF.
h. The overall heat leakage coefficient U of the
refrigerator is given by:
H1
U=
(T1-T2)
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