G,2 • FLOW THROUGH POROUS METAL 



the coefficients a and /S and the percentage porosity of porous metals can 

 therefore be estabUshed only for a given metal. A more general correlation 

 of the measured permeability values obtained from different metals can- 

 not yet be obtained. 



The complexity of the permeability problem of porous metals so far 

 obtained lies in the fact that not all of the pores or channels are neces- 



106 



105 



10^ 



- 103 



o 



D 



cr 



(U 102 

 1/5 



10 



10-6 10-5 10-4 10-3 



Rate of flow, Ib/in^ sec 



10-2 



Fig. G,2a. Pressure-square difference vs. rate of flow of nitrogen for porous iron 

 specimens prepared with fine iron and fine ammonium bicarbonate powders. Air at 

 To = 540°R, MO = 0.017 centipoise. (From U].) 



sarily continuous throughout the metal specimen. Furthermore the vague 

 knowledge of the distribution of the pores and the complex passages inter- 

 connecting the pores in porous metals makes it very difficult to obtain 

 any quantitative correlation between the permeability coefficient and the 

 porosity of porous metals. 



The pattern of the flow of gases leaving a porous metal surface was 

 investigated experimentally at the Jet Propulsion Laboratory [5], The 



(433 > 



