Question

You have water at 100Â°C and 1 bar that should be used to produce 1 kg/s of superheated steam at 5 bar and 300Â°C in a continuous process. The following two alternatives are considered. Alt. I: i) Evaporation at 1 bar ii) Adiabatic ideal compression from 1 bar to 5 bar iii) Heating of the steam until 300Â°C. Alt. II: i) Pumping from 1 bar to 5 bar ii) Heating of the liquid to the boiling point (152Â°C) and evaporation at 5 bar iii) Heating of the steam until 300Â°C. a) Sketch a flow sheet for the two alternatives. b) Find the supplied heat and work in each step for one of the alternatives. c) Explain, in a quantitative way, which option would be better in terms of supplied work. Data: You can assume ideal gas (even for the steam vapor). Liquid water Cp (specific heat capacity) = 4.18 kJ/kg K-1. AHap (enthalpy of vaporization) = 2140 kJ/kg @ 153Â°C & 5 bar. Vapor water Cp (specific heat capacity) = 1.87 kJ/kg K-1. AHvap (enthalpy of vaporization) = 2260 kJ/kg @ 100Â°C & 1 bar. For water vapor Cp/Cv (ratio of specific heat capacities) = 1.33. The density (p) of water = 1000 kg/m3.

          You have water at 100Â°C and 1 bar that should be used to produce 1 kg/s of superheated steam at 5 bar and 300Â°C in a continuous process. The following two alternatives are considered.

Alt. I: 
i) Evaporation at 1 bar 
ii) Adiabatic ideal compression from 1 bar to 5 bar 
iii) Heating of the steam until 300Â°C.

Alt. II: 
i) Pumping from 1 bar to 5 bar 
ii) Heating of the liquid to the boiling point (152Â°C) and evaporation at 5 bar 
iii) Heating of the steam until 300Â°C.

a) Sketch a flow sheet for the two alternatives.

b) Find the supplied heat and work in each step for one of the alternatives.

c) Explain, in a quantitative way, which option would be better in terms of supplied work.

Data: You can assume ideal gas (even for the steam vapor).
Liquid water Cp (specific heat capacity) = 4.18 kJ/kg K-1. 
AHap (enthalpy of vaporization) = 2140 kJ/kg @ 153Â°C & 5 bar.
Vapor water Cp (specific heat capacity) = 1.87 kJ/kg K-1. 
AHvap (enthalpy of vaporization) = 2260 kJ/kg @ 100Â°C & 1 bar.
For water vapor Cp/Cv (ratio of specific heat capacities) = 1.33.
The density (p) of water = 1000 kg/m3.

you have water at 100c and 1 bar that should be used to produce 1 kgs of superheated steam at 5 bar and 300c in a continuous process the following two alternatives are considered alti i evap 40068

Added by Stacy S.

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