# Find the internal energy of 1 kg of steam at. solved problem

#### Find the internal energy of 1 kg of steam at 20 bar when (i) it is superheated, its temperature being 400°C ; (ii) it is wet, its dryness being 0.9. Assume superheated steam to behave as a perfect gas from the commencement of superheating and thus obeys Charle’s law: Specific heat for steam = 2.3 kJ/kg K.

Find the internal energy of 1 kg of steam at 20 bar when

(i) it is superheated, its temperature being 400°C ;

(ii) it is wet, its dryness being 0.9.

Assume superheated steam to behave as a perfect gas from the commencement of superheating and thus obeys Charle’s law: Specific heat for steam = 2.3 kJ/kg K.

1. Steam at 120 bar has a specific volume of 0.01721 m3/kg, find the temperature, enthalpy and the internal energy.

2. Calculate the internal energy per kg of superheated steam at a pressure of 10 bar and a temperature of 300 °C. Also find the change of internal energy if this steam is expanded to 1.4 bar and dryness fraction 0.8.

3. Find the internal energy of 1 kg of steam at 20 bar when

(i) it is superheated, its temperature being 400°C ;

(ii) it is wet, its dryness being 0.9.

Assume superheated steam to behave as a perfect gas from the commencement of superheating and thus obeys Charle’s law: Specific heat for steam = 2.3 kJ/kg K.

4. Two boilers one with superheater and other without superheater are delivering equal quantities of steam into a common main. The pressure in the boilers and main is 20 bar. The temperature of steam from a boiler with a superheater is 350°C and temperature of the steam in the main, is 250°C.

Determine the quality of steam supplied by the other boiler. Take cps = 2.25 kJ/kg.