THERMODYNAMICS A cylinder is filled with water. Water mass is constant (Closed c

Question

THERMODYNAMICS

A cylinder is filled with water.

Water mass is constant (Closed cylinder) = 2 kg

Cylinder diameter = 50 mm

Load mass = 20 kg

Atmospheric pressure = 1 bar

Opwarming af væsken = Heating the liquid

Fordampning = Evaporation

Overhedning af dampen = Heating of vapor

Heat is applied from state 1 to 4.

Determine the missing data using the following

State 1: Water with a temperature of 10 *C

State 2: Water at boiling point, start / initial

State 3: Water at boiling point, end

State 4: Water with a temperature of 200 *C

Hint 1: Pressure Ptotal should be calculated in order to use the tables

Hint 2: Reference specific entropy s(T=0*C)=0 and reference specific enthalpy h(T=0*C)=0.

Hint 3: Use Cp(water)= 4.20 kJ/(kg K) for states 1 and 2

Explanation / Answer

Given mass =2kg

For State 1;

when temperature is 10*C

volume =0.002 m3

volume in liters=2

specific volume =volume /mass=0.002/2=0.001

specific entropy =0.15104805629986 kJ / kg K defined as ratio of energy to mass and temperature

specific enthalpy=42.42947857467 kJ / kg

vapour content=0 since only liguid state is present

for state 2

the temperature =100*C

volume=2 liters

specific volume remains the same as well as the density

specific entropy=1.3067647849535kJ / kg K

specific enthalpy =419.33843832629 kJ / kg

vapour content =0

for state 3

temperature is greater than 100*C means start of vapours

volume of liquidts decreasing while vapour volume starts increasingowing phase star decreasing and since the pressure is decreased due to movement ofload mass

v=1/2 of intial volume =0.001 an 1 litre respectively density =2000

specific entropy =7.3540770509584 kJ / kg K for vapour

specific enthalpy=2675.5720292208 kJ / kg for vapour

vapour content =50%

for state 4

volume =0 and also specific volume =0

density=2000

specific entropy=6.4302967720321 kJ / kg K for vapour only

specific enthalpy=2792.0615640123 kJ / kg for vapour only

vapour content =100%

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