MIL-PRF-12574 Refrigeration Units, Mechanical, Panel Type, 5000 Btu For Refrigerator, Field, Portable \(150 Cubic Foot\)This document covers two types of panel type, mechanical, refrigeration units having a capacity of 5000 British thermal units \(Btu\) per hour and used with a 150-cubic foot, portable field refrigerator \(see 6.1\).

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MIL-PRF-12574M

maintenance shall be performed during this test and verification

shall be made that rated conditions are maintained during the 72-

hour period in an ambient temperature of 110

d. When the refrigeration unit being tested is a type I

unit, the fuel consumption shall be monitored and recorded.

Verification shall be made that the unit operates no less than 38

hours before refueling.

4.3.2.3

Refrigeration capacity tests

4.3.2.3.1 Calorimeter calibration . The calorimeter calibration

shall be run once prior to capacity tests to establish the

coefficient of heat leakage to be used for capacity calculation.

The coefficient of heat leakage for the calorimeter shall not

exceed 25 Btu/hr/ 0F and the volume shall not be less than 150 cubic

feet. A refrigeration unit shall be bolted to the evaporator

opening in the calorimeter with a minimum 5-foot clearance on the

front of the unit and the overall heat leakage coefficient shall be

determined as follows:

a. An electric fan(s), of sufficient capacity to insure that no

uncirculated air pocket will exist, shall be installed inside the

calorimeter. The electrical energy of the fan motor shall be

measured by the same meter used for the heating elements in

subparagraph (c) and this heat equivalent shall be added to other

sources of heat added to the calorimeter.

b. Four thermocouples, shielded from the effects of radiant

heat, shall be installed inside the calorimeter 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 calorimeter.

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 the radiant heat, shall be installed approximately 18

inches from each corner of the calorimeter in the room where it is

placed. The ambient temperature shall be taken as the average of

these eight temperatures.

e. All openings in the calorimeter shall be sealed, and the

calorimeter 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