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Helium gas is throttled steadily from 400 kPa and 60°C.
Chapter 7, Problem 180P(choose chapter or problem)
Problem 180P
Helium gas is throttled steadily from 400 kPa and 60°C. Heat is lost from the helium in the amount of 1.75 kJ/kg to the surroundings at 25°C and 100 kPa. If the entropy of the helium increases by 0.34 kJ/kg·K in the valve, determine (a) the exit pressure and temperature and (b) the entropy generation during this process.
Questions & Answers
QUESTION:
Problem 180P
Helium gas is throttled steadily from 400 kPa and 60°C. Heat is lost from the helium in the amount of 1.75 kJ/kg to the surroundings at 25°C and 100 kPa. If the entropy of the helium increases by 0.34 kJ/kg·K in the valve, determine (a) the exit pressure and temperature and (b) the entropy generation during this process.
ANSWER:
Step by step solution Step1 of 3Express the rate of heat transfer out.Here, rate of heat transfer out is , specific heat at constant pressure is , initialtemperature is and exit temperature is .From ideal-gas specific heat of various common gasses table, select the specific heat atconstant pressure of helium asSubstitute for , for , for 3Hence, the rate temperature of helium is