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Net Refrigeration Capacity Equations and Calculator

Heat Transfer Engineering Design

Net Refrigeration Capacity Test and Procedure, Equation and Calculator
Net Refrigeration Capacity System Design Equations and Calculator
Per. MIL-PRF-32017

To calculate the RU(Refrigeration Unit) capacity the heat leakage coefficient and setup from 4.3.1 shall be used. The capacity for the (Refrigeration Unit) RU unit shall be verified to be no less than 3,000 Btu/hr using the method described below. Recorded data shall be required and shall include all specified temperature readings, electrical heat input, suction and discharge pressures, and complete calculations. All panels and doors of the ADR system shall be in the normally closed position.

a. All accessories and appurtenances shall be in their proper place.

b. Thermocouples, shielded from radiant heat, shall be installed in the air streams entering the evaporator and leaving the evaporator section.

c. Shielded thermocouples shall be located at the approximate center of four equal areas of the condenser face. The condenser inlet temperature will be taken as an average of these four temperatures.

d. Recording pressure gages shall be used for the compressor suction and discharge pressures.

f. The RU shall then be operated with air surrounding and entering the condenser section at 110°F ± 2°F, and sufficient steady, non-varying heat shall be added to the interior of the IC to maintain 0°F 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 (FPM) any point 3 feet from the ADR system.

g. The test shall be considered concluded when eight consecutive half-hourly readings indicate that:

1. The average surrounding ambient temperature T , has been maintained at a steady state of 3 110°± 2°F.
2. Return air temperature entering the evaporator, T , has been maintained at 0°F ± 1F°. 4
3. The net refrigeration 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 The Heat Leakage Test and Calculations.

The net refrigeration capacity is given by:

Q = U (T3 - T4) + H2

Preview: Net Refrigeration Capacity System Design Calculator (Membership Required: Premium).

Q = Net refrigeration capacity (Btu/hr)
U = Overall heat leakage coefficient (Btu/hr/°F)
T3 = Average ambient temperature (°F) surrounding the RU
T4 = Return air temperature (°F) entering the evaporator
H2 = Sum of all heat energy added to the IC (Btu/hr)

Note: this is a military specification, commercial application requirements can be different.

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