Thermal-hydraulic modeling of the steady-state operating conditions of a fire-tube boiler

In this work, we are interested to simulate the thermal-hydraulic behavior of three-pass type fire-tube boiler. The plant is designed to produce 4.5 tons per hour of saturated steam at 8 bar destined principally for heating applications. A calculation program is developed in order to simulate the boiler operation under several steady-state operating conditions. This program is based upon heat transfer laws between hot gases and the fire-tube internal walls. In the boiler combustion chamber, the heat transfer has been simulated using the well-stirred furnace model. In the convection section, heat balance has been carried out to estimate the heat exchanges between the hot gases and the tube banks. The obtained results are compared to the steady-state operating data of the considered plant. A comparative analysis shows that the calculation results are in good agreement with the boiler operating data. Furthermore, a sensitivity study has been carried out to assess the effects of input parameters, namely the fuel flow rate, air excess, ambient temperature, and operating pressure, upon the boiler thermal performances. U ovom radu nastojimo da simuliramo termohidraulicno ponasanje parnog kotla sa grejnim cevima sa tri prolaza. Postrojenje je projektovano da proizvede 4,5 tone na cas zasicene pare pod pritiskom od 8 bar, uglavnom namenjene za grejnu primenu. Razvijen je racunarski program sa ciljem da oponasa rad kotla u nekoliko ravnoteznih radnih stanja. Program se zasniva na zakonima prenosa toplote izmedju vrelih gasova i unutrasnjih zidova grejnih cevi. U lozistu kotla, prenos toplote oponasan je koriscenjem modela peci sa dobrim mesanjem. U konvekcionoj deonici, sproveden je bilans toplote radi procene izmene toplote izmedju vrelih gasova i blokova cevi. Dobijeni rezultati uporedjeni su sa ravnoteznim radnim podacima razmatranog postrojenja. Komparativna analiza pokazuje da se rezultati proracuna dobro slazu sa radnim podacima kotla. Osim toga, izvedena je studija osetljivosti radi procene uticaja ulaznih parametara - brzine toka goriva, viska vazduha, temperature sredine i radnog pritiska - na termicke karakteristike kotla.