Mathematical models of leakage configurations and various flow theories are presented with the substantive experimental test data to provide background material for future design and failure analysis. Normal-rate leakage and emergency, high-rate leakage are considered

Jackson, J. K.

Thomas, E. C.

English

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NASA TECH BRIEF 
April 1970	 Brief 70-10201 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Prediction of Gas Leakage of Environmental Control Systems 
Theoretical determination of gas leakage rates of 
environmental control systems (ECS) depends largely 
upon assumed geometry conditions. Mathematical 
models of leakage configurations and various flow 
theories (including orifice, capillary and laminar pipe) 
are presented with the substantive experimental test 
data in order to provide background material for future 
design and failure analysis. 
Two types of leakage are considered: low, normal-
rate leakage and emergency high-rate leakage. It is 
assumed that the ECS pressure remains constant for 
the low rate; and on the other hand, the high-rate 
occurs whenpressure decay occurs in the ECS. Basic 
assumptions for the flow theories are: when the hole 
diameter is large compared to length, orifice flow 
occurs; leakage path in capillary flow is assumed to be 
a long, straight tube; continuum flow at constant tem-
perature is assumed for the laminar condition. 
The experimental instrumentation for determining 
steady-state leakage tests agrees quite well with the 
theoretical models from ECS pressures of 5 to 10 psia. 
Pressure decay tests were also run in a 157 cu. ft. 
ECS. The air lock was charged by metering-in the 
test gas to the partial pressures corresponding to the 
test atmospheres. Data were obtained using helium
and nitrogeli as diluents with the oxygen partial pres-
sure held at 3.5 psia. One pertinent finding in the 
helium-oxygen atmosphere was the premature failure 
of certain types of electronic instrumentation, notably 
seven vidicon television monitoring tubes. 
Note: 
The following documentation may be obtained from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65) 
Reference: NASA- CR-89l (N67-37320), 
Engineering Criteria for Spacecraft 
Cabin Atmosphere Selection 
Patent status: 
No patent action is contemplated by NASA. 
Source: Jack K. Jackson and Emory C. Thomas of 
Douglas Aircraft Co. 
under contract to 
NASA Headquarters 
(HQN- 10270) 
Category 05 
-.
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned .rights.
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Prediction of gas leakage of environmental control systems

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