Question

The following description applies to the next three problems.

Air enters steadily an electrical hair dryer at 100 kPa and 27 C. It leaves the hairdryer at a temperature of 80 C, an exit velocity of 10 m/s, and at the same pressure. The exit and inlet areas are 20 cm² and 40 cm² respectively.

(Assume properties of air cp= 1.007 kJ/kg.K, cv = 0.72 kJ/kg.K, and R= 0. 287 kJ/kg.K )

The mass flow rate of air entering the hairdryer, in kg/s, is closer to

The velocity of the air at the inlet of the hairdryer, in m/s, is closer to

The total power the hairdryer needs to operate at the stated conditions, in kW, is closer to:

Answer 1

Please comment below if any of the answers give you any trouble. I will try to respond asap.

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(a)

Mass flow rate is;

...(Answer)

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(b)

By conservation of mass flow rate;

...(Answer)

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(c)

Given,

c_p = 1.007 kJ/kg.K = 1007 J/kg.K

By steady state energy equation;

...(Answer)