Section: Thermodynamics | Type: NAT | Marks: 2
Air enters a hair dryer at 22 °C and 100 kPa with a velocity of 3.7 m/s, and leaves the dryer at 83 °C and 100 kPa with a velocity of 9.1 m/s. The exit area of the dryer is 18.7 cm2, and the ambient temperature is 22 °C. The air is an ideal gas with gas constant 𝑅 = 0.287 kJ/kg-K and isobaric specific heat 𝑐𝑝 = 1.005 kJ/kg-K. If the change in potential energy is neglected, the second law efficiency (in %) of the dryer is __________ (rounded off to one decimal place).
Answer: 8.9 to 9.4