Forchheimer coefficient

Flow resistance descriptors of DPF walls, experimental protocols for their determination and useful correlations have been previously presented in Konstandopoulos (2003). At the filter wall scale flow resistance is determined by the Darcy permeability and the Forchheimer coefficient /i of the wall. 

The permeability of the foam monolith was calculated using the Darcy-Forchheimer law and the permeability and Forchheimer coefficient of the filter are determined by regression using equation (2). Table 4 summarizes the results for each filter sample tested. 

In Eq. (2), the factor p is generally called Forchheimer coefficient, is also called non-Darcy factor. 

Equation [1.43] for the case of high Reynolds numbers has a correction factor known as Forchheimer coefficient, F ... 

In other cases, researchers assume that the inertial resistance to flow in DLs adjacent to conventional flow fields is negligible and they tend to lump both viscous and inertial coefficients together. This may not be a correct assumption, especially when dealing with flow fields like the interdigitated design [129,212], in which higher velocities are experienced in the pores of the DL. The Forchheimer equation is an extension of Darcy s law and takes into account the inertial resistance at high velocities [211,213] ... 

Gurau ef al. [129] presented another apparatus used to measure the in-plane viscous and inertial permeability coefficients. In their method, an annular DL sample was placed between an upper and lower fixture. The gas entered the upper fixture and was then forced fhrough fhe DL info fhe ouflef porfs (open to the atmosphere). A strain sensor was located in the upper fixture in order to determine the thickness of fhe DL (i.e., deformation) because fhe whole assembly was compressed to a determined pressure. In fhis mefhod, the flow rate, temperatures in both fixtures, and pressures were monitored in each test. Once the data were collected, the in-plane permeability was determined from the Forchheimer equation by application of fhe leasf squares fit analysis method. 

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