I notice that the other answers don't mention the use of Hungarian Notation. This is orthogonal to the length debate, but relevant to naming schemes in general.
double dR, dCV, dK, dDin, dDout, dRin, dRout
The "d" at the beginning of all these variables is meant to indicate that they're doubles; but the language is enforcing this anyway. Despite the terseness of these names, they're up to 50% redundant!
If we're going to use a naming convention to reduce errors, we're much better off encoding information which isn't being checked by the language. For example, no language will complain about
dK + dR in the above code, even though it's meaningless to adding a dimensionless number to a length.
A good way to prevent such errors is to use stronger types; however, if we're going to use doubles then a more appropriate naming scheme might be:
// Dimensions: // l = length // rl = reciprocal length double lR, rlCV, K, lDin, lDout, lRin, lRout
The language will still allow us to write
K + lR, but now the names give us a hint that this might be incorrect.
This is the difference between Systems Hungarian (generally bad) and Apps Hungarian (possibly good)