Thermodynamics problem Some equations to solve the problem will be enough A supe
ID: 1998734 • Letter: T
Question
Thermodynamics problem
Some equations to solve the problem will be enough
A superheat Rankine cycle power plant consists of a pump, a boiler/superheater, a turbine and a condenser. Saturated liquid water at 10 kPa enters the pump (eta = 0.90) and exits at 30 bar. The turbine (eta = 0.98) inlet temperature is 400 C. Use this data to determine the Pump specific work Boiler specific heat transfer Turbine exit quality Turbine specific work Condenser specific heat transfer. Sketch the four cycle processes on p-v, T-s and p-h diagrams. Which component has the largest specific entropy generation? Assume the surrounding temperature is 35 C. Propose a way to reduce it.Explanation / Answer
Answer --
Equations are:
Specific work is work per unit weight. Specific work in turbo machines as fans, pumps, compressors or turbines has the SI-units
Specific Work of a Pump or Fan
Specific work of a pump or fan working with an incompressible fluid can be expressed as:
w = (p2 - p1) / (1)
where
w = specific work (Nm/kg, J/kg, m2/s2)
p = pressure (N/m2)
= density (kg/m3)
Specific Work of a Turbine
Specific work of a turbine with an incompressible fluid can be expressed as:
w = (p1 - p2) / (2)
Specific Work of a Compressor
A compressor works with compressible fluids and the specific work for an isentropic compressor process can be expressed with the help of
p1 v1 = p2 v2 (3)
where
v = volume (m3)
= cp / cv - ratio of specific heats (J/kg K)
Specific work:
w = / ( -1) R T1 [( p2 / p1)((-1)/) - 1] (4)
where
R = individual gas constant (J/kg K)
T = absolute temperature (K)
Specific Work of a Gas Turbine
A gas turbine expands a compressible fluid and the specific work can be expressed as
w = / ( -1) R T1 [1 - ( p2 / p1)((-1)/)] (5)
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