Thermodynamic Losses in Prds

At 176bar,540 deg C, the enthalpy is h=3392.32 kJ/kg.

At 105bar,515 dec C, the enthalpy is h=3406.80 kJ/kg.

The change in enthalpy is -14.48 kJ/kg; 735 kW (14.48 kJ/kg * 180 tons/hr)

From steam tables:

• h(180barg, 500degC) = 3268kJ/kg
• h(180barg, 600degC) = 3555kJ/kg
• h(170barg, 500degC) = 3281kJ/kg
• h(170barg, 600degC) = 3564kJ/kg.

Interpolating, the start condition is: h(176bar, 540degC) ≈ 3387kJ/kg.

Steam at all the above temperatures and pressures is superheated.

From steam tables:

• h(110barg, 600degC) = 3616kJ/kg
• h(110barg, 500degC) = 3360kJ/kg
• h(100barg, 600degC) = 3624kJ/kg
• h(100barg, 500degC) = 3373kJ/kg

Interpolating, the end condition is: h(105bar, 515degC) ≈ 3404kJ/kg.

So energy needs to be added to get it to this condition: 3404-3387=17kJ/kg. It cannot get there by adiabatic expansion. At these end conditions, the steam is still superheated.

Er, around 800kW is needed.

Thanks. got the idea, shall continue from here.

From the calculation which is shown and according to what i did, its not evident that there is a loss of energy from inlet to outlet condition, as the specific enthalpy is increasing. Its obvious that the depressurising and detempering is a thermodynamic loss. Is there a method to show this loss.

Yes. Calculations based on the data in Steam Tables!

Dear Mr. Gautamkum,

As I nderstand from Your Question, IT is NOT CLEAR or defined correctly. You have referred " I need to evaluate the loss as a result of this depressurising and desuperheating,"

Which loss you want to evaluate.? What is the Temperature of De-Superheating water used.?

As already explained by other CR4 MEMBERS, the Difference in ENTHALPY/Kg. of Steam can be found out before de-superheating and after de-superheating and this quantity to be multiplied by 180x1000 Kgs. and this heat will be absorbed by the de-super heating water pumped/sprayed and the total quantity of de-superheated steam , will be obviously more.

Neglecting the RADIATION LOSSES (for discussions purpose) where is the question of "loss" that is to be estimated.?

Pl. clarify

RAJESWARI.