At work we derive the steam flow entering the HP turbine stage of a
500MW steam turbine using the following equation:

Steam_flow = 735.7 x( 1st Stage steam pressure ) / Sqrt( 1st Stage steam
Temp )

where 1st Stage pressure is in MPa absolute and 1st stage temp is in Deg K.

The calculated value agrees well with the measured feedwater flow into the steam drum.

However, not being from a thermodynamics background nobody can tell me how the equation is derived, it just always seems to have been always like that!

Can anyone direct me to information that explains how the steam flow through a turbine is proportional to the inlet pressure divided by square root of inlet temp ?

Steam_flow = 735.7 x( 1st Stage steam pressure ) / Sqrt( 1st Stage steam

where 1st Stage pressure is in MPa absolute and 1st stage temp is in Deg K.

The calculated value agrees well with the measured feedwater flow into the steam drum.

However, not being from a thermodynamics background nobody can tell me how the equation is derived, it just always seems to have been always like that!

Can anyone direct me to information that explains how the steam flow through a turbine is proportional to the inlet pressure divided by square root of inlet temp ?