Question

What are the specific enthalpy and specific volume of steam at 400.0°C and 80.0 bar? Number Number kJ/kg Î= 0 m²/kg Is this steam superheated or saturated? O O saturated superheated If this steam is superheated, what is its degrees of superheat? If the steam is saturated, respond with "0". Number Estimate the temperature, specific enthalpy and specific volume of saturated steam at 5.25 bar. Number Number Number Tsar = 10 °C kJ/kg mº/kg

Answer 1

Answer:

Part 1:

Specific Enthalpy of steam at 400^oC and 80 bar is,

H = 3138.3 kJ/kg (Reference: Steam Table)

Specific volume of steam at 400^oC and 80 bar is,

V = 0.0343 m³/kg (Reference: Steam Table)

Part 2:

The temperature of saturated steam at 80 bar is 295.1 ^oC (Reference: Steam Table), but, the steam is at 400^oC, which is more than the saturated temperature.

Hence, the steam is superheated.

Part 3:

Degree of superheat = Actual steam temperature - saturated temperature = 400 - 295.1 = 104.9 ^oC

Part 4:

Saturated temperature of steam at 5.25 bar is,

T_sat = (151.85 + 155.47) / 2 = 153.66 ^oC (Reference: Steam Table)

Specific Enthalpy of saturated steam at 5.25 bar is,

H = (2747.54 + 2751.70) /2 = 2749.62 kJ/kg (Reference: Steam Table)

Specific volume of saturated steam at 5.25 bar is,

V = (0.375 + 0.342) / 2 = 0.3585 m³/kg (Reference: Steam Table)

Part 5:

Volumetric flow rate of steam at 400^oC and 80 bar = 18 m³/min (given)

Mass Flow of steam = Volumetric flow / Specific Volume (at 400^oC and 80 bar)

Mass Flow of steam = 18 (m³/min) / 0.0343 (m³/kg) = 524.78 kg/min

The mass flow of steam will remain constant by the law of conservation of mass.

The mass flow of steam at 5.25 bar is 524.78 kg/min.

The volumetric flow = Mass flow x Specific Volume (at 5.25 bar)

The volumetric flow of steam at 5.25 bar and 153.66 ^oC = 524.78 (kg/min) x 0.3585 (m³/kg) = 188.134 m³/min

Part 6:

Work done by a turbine = (Specific Enthalpy of steam at 80 bar - Specific Enthalpy at 5.25 bar) x Mass Flow of steam

Work done by a turbine = {[3138.3 - 2749.62] (kJ/kg) x 524.78 (kg/min)} / 60 (sec/min)

Work done by a turbine = 3399.52 kJ/s or kW