Coefficient of discharge and flow coefficient

[ahbuckman]

Hi,

I'm looking into the calculation of volume flow rate through a louvre within Macroflo, as I will then be exporting this data to another software package.

In the macroflo theory there are two points which I would like some clarification on please.

The first is that the discharge coefficient through an opening is assumed to be 0.62 but is used in place of the flow coefficient. My understanding is that the flow coefficient (call it Cf) is related to the discharge coefficient (Cd) through:

Cf = Cd/((1-B^4)^(1/2))

where B is beta and represents the ratio of the orifice to the wall in the flow direction.

Would someone please tell me whether an assumption has been consciously made here, or possible I am mistaken somewhere?

The second question I have relates to a similar area:

Louvre manufacturers give out coefficients of discharge (=Cd) for their products, and I believe that IES then uses a "product coefficient of discharge (Cx)" within their calculations and equates this value to the flow coefficient.

How is the product coefficient of discharge different from a typical coefficient of discharge? And is there again an assumption made that this value equals the flow coefficient used in the calculation of flow through an orifice?

Thanks in advance,