Respuesta :
Answer:
The heat needed to convert 1 kg of feed water at 20°C into dry saturated steam at a pressure of 9 bar is 2690.19 kJ/kg.
Explanation:
Step 1 : Obtain the enthalpy of staurated steam and enthalpy of evaporation at 9 bar pressure from the steam table:
From steam table, at 9 bar, the enthalpy of saturated water = 742.83 kJ /kg
enthalpy of evaporation = 2031.1 kJ /kg
Step 2: Calculate the enthalpy of dry saturated steam:
Enthalpy of dry saturated steam = enthalpy of saturated water + enthalpy of evaporation
= 742.83 + 2031.1 = 2773. 93 kJ/ kg
Step 3: Calculate the enthalpy of 1 kg of feed water at 20°C
Enthalpy of 1 kg of feed water = c * ( T2 -T1)
= 4.187 * (20-0)
= 83.74 kJ /kg
Step 4 : calculate the heat needed by 1 kg of feed water at 20°C to be converted to dry saturated steam at 9 bar:
Heat needed = Enthalpy of dry saturated steam - enthalpy of feed water
Heat needed = 2773.93 kJ/kg - 83.74 kJ/kg
Heat = 2690.19 kJ/kg
