Thursday, June 12, 2008

Square-root-Square-root Formula Ease Saturated Steam-Codensate Temperature Prediction

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You are assigned to site to make a site visit. Your task is to investigate the serious water hammering issue in the condensate line. In the plant, you found a condensate return line with a pressure gauge indicating 10 barg, you would like to know the temperature of the condensate.


What is the quickest way to find this temperature with your pocket calculator ?


The simple Square-root-Square-root formula will help you. The formula is :





Earlier post "Conduct Steam-Water Balance MANUALLY using Water97_v13" has discussed the saturate steam - condensate temperature can be extracted using a special function, tSat(P) in Excel Add-on in (Water97_v13.xla or Alternative download). Of course, HYSYS has the capability of predicting the saturated steam-condensate temperature. The Saturation temperature at different pressure from 0 to 200 barg have been predicted using HYSYS, Water97_v13.xla and Square-root-Square-root formula. Results tabulated as follow :





Above simple studies showed that :
  • tSATW(P) function in Water97_v13.xla is virtually same as HYSYS prediction. Error is negligible.
  • Square-root-Square-root formula (compare to HYSYS) constantly over predict saturation temperature over the pressure range from 0-200 barg.
  • Square-root-Square-root formula (compare to HYSYS), over-predict is increased with pressure.
  • Square-root-Square-root formula (compare to HYSYS) prediction error in the range of 0.3 to less than 3%.
In view of above error, 0.3 to 3% error is rather small and Square-root-Square-root formula can be used to make a quick prediction of saturation temperature for steam-condensate.

Updated on June 15, 2008
- Unit P shall be in bar abs instead of barg. Thanks to
Manjushinee.

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