Aspen FRAN™

Performance simulation and rating of specialist feedwater heaters for power applications.

Aspen FRAN™ is a unique tool for performance modeling of shell and tube feedwater heaters where boiler feed is heated by steam or condensate extracted at intermediate turbine pressures. In simulation mode, it can be used to determine the optimum heat exchanger configuration or to revamp / retrofit old heaters to improve energy efficiency. In checking / rating mode, it can used for troubleshooting, in identifying cycle operating constraints or assessing the impact of fouling on plant efficiency.

Features

The following operating modes are available:

Checking / Rating - Condensing section operating pressure and required heat transfer rate for each zone, drains and feedwater outlet temperatures are specified by the user and the required surface area for each zone is calculated.

Simulation - Heater geometry, extraction steam inlet state, feedwater mass flowrate and inlet conditions specified by the user and FRAN calculates the heat transfer rate and outlet conditions.

Technical Summary

  • Heater geometry, including shell diameter, number of tubes and their dimensions, baffle arrangements and clearances. This includes:
    • One-, two- and three-zone heaters of the shell and tube type.
    • Horizontal or vertical orientation.
    • 1 or 2 tube passes.
    • Triangular, rotated triangular, square and rotated square tube layouts.
    • Plain tube type.
    • Rear head can be either U-tube or channel.
    • Single or double segmental plate type baffles.
    • Heat transfer and pressure drop correlation details can be supplied for special baffle types.
  • Details of integral desuperheating and drain-cooling zones, if fitted. This includes:
    • Counter-current or split flow desuperheating section.
    • Drain cooling section, either full-pass or split-pass type.
  • Process data such as extraction steam conditions, flash steam and inlet drains flowrate and condition, fouling resistances. This includes:
    • Accommodates flash steam and/or drains supplied separately to the heater shell, in addition to the extraction steam from the turbine.
    • The required drains and feedwater outlet temperatures must be specified in Checking mode.
  • Special Calculations
    • Flow induced vibration check.
    • Feedwater velocity can be specified and FRAN™ will evaluate the tube count and estimate shell diameter.
    • Default nozzle diameters calculated from HEI standards.
    • Condensate re-heat calculation: allowance can be made for heat transfer through the drain cooler shroud from the steam in the condensing zone to the condensate in the drain cooler.
    • Checks made for any wet-wall conditions in the desuperheating zone and flashing of condensate in the drain cooling zone
  • Output
    • Summary output and error log.
    • Summary tables of the zone geometrical details.
    • Vapor and liquid properties at the zone boundaries.
    • Vibration analysis on each zone with possible danger points flagged.
    • Calculated extraction steam flowrate and all other vapour and liquid flowrates.
    • Shellside and tubeside pressures, bulk and wall temperatures and specific enthalpies at the inlet and outlet of each zone.
    • Pressure drop, heat exchanged, mean shellside and tubeside heat transfer coefficients and mean temperature difference for each of the desuperheating, condensing and drain cooling zones.
    • For Checking mode, the ratio of actual to required surface area for each zone.
    • Terminal temperature difference and drain cooler approach.

Benefits

  • Improved design – FRAN is a comprehensive, easy-to-use tool for the design of feedwater heaters. Its use enables the more efficient design of new heaters and cost-effective revamp studies. It can also augment or replace in-house tools that are difficult to use and expensive to maintain and update.
  • Improved process operations – FRAN provides the benchmark to assess the effects of operational changes for load optimization and fouling.
  • Increased engineering efficiency – The complex interaction of the de-superheating, condensing and sub-cooling zones with the high-pressure feedwater on the tube-side is modeled with rigor in a user-friendly tool.


CURRENT VERSIONS

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