MIL-PRF-12574M
e. The procedures described in 4.3.2.3.1 (b), (c), (d), and
(e) shall be followed for this test.
f. The refrigeration unit shall then be operated with air
surrounding the condenser section and entering the condenser at a
minimum of 110 0F and sufficient, steady, non-varying heat shall be
0
added to the interior of the calorimeter to maintain 0
F
0
temperature of air entering the evaporator,
+ 1 F. A watt-hour
meter with scale increments of 0.1 kilowatt-hour or less shall be
used to indicate the quantity of electrical energy added. Air
velocity shall not exceed 100 feet per minute at any point 3 feet
from the refrigeration unit.
g. The test shall be considered concluded when eight
consecutive half-hourly readings indicate that:
1. The average calorimeter ambient temperature, T
3 has been
+ 2 F at a temperature of 100 0F to
0
maintained at steady state of
110 0F.
2. Return air temperature, T
, entering the evaporator has
4
been maintained at 0 0 F + 10F.
3. The net refrigerator capacity shall be considered as the
sum of the electrical energy, in Btu/hr, added during this test plus
the heat leakage gain in Btu/hr, as calculated from the calibration
specified in 4.3.2.3.1.
The net refrigeration capacity is given by:
Q = U (T 3 - T 4) + H 2
Q = Net refrigeration capacity in Btu/hr
0
U = Overall heat leakage coefficient Btu/hr/
F as
determined by paragraph (h)in 4.3.2.3.1
H2 = Sum of all heat energy added to the interior of
the calorimeter in Btu/hr, (f) above.
Capacity test (35 0F). The procedure specified in
4.3.2.3.3
4.3.2.3.2 shall be followed, with the following exceptions, to
verify that the capacity of the refrigeration unit is not less than
7,500 Btu/hr.
a. In 4.3.2.3.2 (b), the thermocouples shall be installed as
specified.
However, the temperature difference between the air
entering the evaporator and leaving the evaporator section shall not
be recorded.
b. In 4.3.2.3.2 (f), sufficient heat shall be added to maintain
35 F + 10F temperature of air entering the evaporator in place of 0
0
0
F
temperature specified.
13
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