Dear Wasif
First of all, you should have the scheme of the thermal circuit of the unit. After that, you need to know the enthalpies of the steam in the extraction points by drawing the line expansion in the Mollier's diagram and intersect it with the known isobars. The next step is to fix the enthalpies of the condensate in the heaters circuit. The last step is to create and to solve a nxn linear equation system, containing the mass and energy balance equation for each heater of the circuit.
Extraction flows are usually calculated on the basis of a mass and heat balance. See the attached document. Calculations can be done by the M&HB software Recon available at
http://www.chemplant.cz/download.asp.
With the software there is the Example E-10 solving this problém.
In the case that only the extraction pressure is known, a turbine stage isentropic efficiency is required to calculate the extraction temperature and thus the enthalpy.
The pressure alone will not allow any accuracy of calculation, as others noe yo need to do energy balances on the heated units. The pressure alone can allow you to calculate a maximum flow based on the nozzles sizes and pressures in the turbine: this should be part of the turbine data-sheets anyway. The other main issue is whether the pass-out is controlled (i.e. has a back-pressure valve) or a "free-bleed". In the former case the pressure is set at the pass-out point, in the latter it floats with turbine duty and the maximum flow varies with the load too.
- Badges
- Science topic
- Similar topics
- Linguistics
- Composition Studies
- Publication