Downloaded from https://www.everyspec.com MIL-STD-1311D FORCED COOLING 1. Purpose. The purpose of this test is to demonstrate: a. That air or liquid passages are not obstructed. b. That the temperature of the tube is held at an acceptable level when operated within its ratings, with the specified coolant and flow rate. This test is not to demonstrate satisfactory operation at the rated temperature extremes for the tube, but to determine that the design provides adequate cooling at normal ambient temperatures. 2. Test equipment. Temperature, pressure, and flow rate indicating devices are needed depending upon those characteristics to be controlled or measured, as specified on the TSS. 3.
Procedure. The TSS shall specify the coolant flow rate, and necessary dimensions of the external hardware (ducting, orifice size and position, or liquid coolant pipe sizes), including flexibility requirements where necessary to avoid stressing the tube unduly. The coolant used shall be as specified, and at the temperature specified. a. Pressure drop. When specified on the TSS, the pressure drop across the tube is to be measured when the coolant is flowing at the specified rate (purpose 1(a)). b. Rate of flow. When specified on the TSS, the rate of flow through the cooling system including the specified mating fixtures is to be measured at the specified pressure drop (purpose 1(a)). c.
Temperature. When specified on the TSS, the temperature at a point indicated on the outline drawing is to be measured. In the case of air cooling, this temperature shall not exceed the input air temperature by more than 50 ° C, or the value specified. In the case of liquid cooling, the TSS shall specify whether evidence of boiling is permissible or not (purpose 1(b)). 4. Precaution. In the case of liquid cooling, provision shall be made for removal of all coolant from the tube before storage or shipment, to avoid damage due to freezing. METHOD 1143A METHOD 1143A 1143-1 25 March 1970