I have a question concerning enthalpy or energy contained in a fluid where dH = dU + d(PV).
In a non flow process with constant pressure dH = dU + Pdv = dU + d(PV) since P = constant. Therefore if dH was caused by the addition of heat (dQ) it is easy to see that:
dQ = dH = dU + Pdv = dU +...
Without going into detailed calculations, the basic issue here is that the relief valve has to be sized based on the maximum flowrate due to regulator failure in the wide open position. When this happens sonic gas flow will exist in the bore or port of the regulator. This will occur since...
If I remember correctly, the problem is that at very high velocities the foam picks up and absorbs the fuel so that the foam becomes in-effective. I think there is discussing in NFPA 11 or other related references.
When sizing vent piping for atmospheric tanks I use the Sptizglas equation for low pressure gas flow and determine the equivalent length of piping of the vent using standard values. For instance a goose neck vent would consist of a pipe inlet equivalent length, a small straight pipe length, two...
I meant to say in the response that the loss of energy due to internal fluid friction would reduce to flow to subsonic at the inlet of the pipe (not sonic).
My understanding is this. Sonic velocity can develop and will develop in the throat of the nozzle if the downstream pressure in the pipe is less than the critical sonic pressure of about 0.5 times the pressure upstream of the relief valve. A relief valve is not a converging-diverging nozzle...