Form HRSG

Pagina 1

Low temperature HRSG Definitions Approach point Pinch point Subcooling Data (mass and properties) mFG kg/s mw kg/s cpFG kJ/kgK cpw kJ/kgK (*) (*) Only valid for liquid water (economizer) Data (temperature) T1 °C Temperature of flue gases at gas turbine outlet T2 °C Temperature of flue gases at HRSG stack (outlet) TSH °C Temperature of superheated steam TEVA °C Evaporation temperature of water TIN °C HRSG inlet temperature of feedwater (economizer inlet) ΔTAP °C Approach point ΔTPP °C Pinch point ΔTSC °C Subcooling TA °C Temperature of flue gases at evaporator outlet TB °C Temperature of feedwater at the economizer outlet Data (pressure) pECO bar Economizer pressure pEVA bar Evaporator pressure (evaporation pressure of feedwater) pSH bar Superheater pressure Data (other) ξ*100 % Thermal losses of HRSG hSH kJ/kg Enthalpy of superheated steam h(pSH, TSH) hv,sat kJ/kg Enthalpy of saturated vapor h(pEVA) hl,sat kJ/kg Enthalpy of saturated liquid h(pEVA) Energy balance SH + EVA Energy balance ECO These two energy balances should be enough to compute all the unknown values of this page NB read carefully the text of the exercise to find out the pressure values for eco\eva\sh If no pressure drops are given assume all three sections are at the same pressure (at least one pressure value must be given) T [°C] Q [kW] T2 T1 TSH TEVA TIN SH EVA ECO TA TB ΔTAP = T1 − TSH ΔTPP = TA − TEVA ΔTSC = TEVA − TB 1 − ξ ∙ mFG ∙ cpFG ∙ T1 − ΔTPP − TEVA = mw ∙ hSH − hl,sat + cpw ∙ ΔTSC 1 − ξ ∙ mFG ∙ cpFG ∙ T1 − TA = mw ∙ hSH − hl,sat + cpw ∙ TEVA− TB 1 − ξ ∙ mFG ∙ cpFG ∙ TA − T2 = mw ∙ cpw ∙ TB − TIN Heat transfer area QECO kW QEVA kW QSH kW UECO kW/m2K UEVA kW/m2K USH kW/m2K ΔTMLECO K ΔTMLEVA K ΔTMLSH K TC °C AECO m2 AEVA m2 ASH m2 ATOT m2 NB pay attention to express both Q and U with the same…