Water is boiled at 300 kPa pressure in a pressure cooker. The cooker initially contains 3 kg of water. Once boiling started, it is observed that half of the water in the cooker evaporated in 30 minutes. If the heat loss from the cooker is negligible, the average rate of energy transfer to the cooker is

Question

Quizplus · Accepted Answer

Solved by EES Software. Solutions can be verified by copying-and-pasting the following lines on a blank EES screen. 
m_1=3 "kg"
P=300 "kPa"
time=30*60 "s"
m_evap=0.5*m_1
Power*time=m_evap*h_fg "kJ"
h_f=ENTHALPY(Steam_ IAPWS, x=0,P=P)
h_g=ENTHALPY(Steam_ IAPWS, x=1,P=P)
h_fg=h_g-h_f
"Some Wrong Solutions with Common Mistakes:"
W1_Power*time=m_evap*h_g "Using h_g" 
W2_Power*time/60=m_evap*h_g "Using minutes instead of seconds for time"
W3_Power=2*Power "Assuming all the water evaporates"

Water Is Boiled at 300 KPa Pressure in a Pressure