Question

Air enters a diffuser witha velocity of 400 m/s, a pressure of 1 bar and temperature of 25 C. It exits with a temperature of 100 C. What is the exit velocity of the air? Assume there are no heat losses or change in potential energy Data:= 0.718 kJ/kg.°C. MW = 28.9 g/mol

Answer 1

Exit velocity of air is 96.43 m/s.

Step-by-step explanation:

Given that

`V_1=400\ m/s`

`T_1=25C`

`T_2=100C`

For air

`C_p=1.005\ KJ/kg.K`

Now from first law of thermodynamics for open system at steady state

`h_1+(V_1^2)/(2000)+Q=h_2+(V_2^2)/(2000)+w`

For diffuser

`h_1+(V_1^2)/(2000)=h_2+(V_2^2)/(2000)`

We know that

`h=C_pT`

`h_1+(V_1^2)/(2)=h_2+(V_2^2)/(2000)`

`1.005* 25+(400^2)/(2000)=1.005* 100+(V_2^2)/(2)`

`V_2=96.43\ m/s`

So the exit velocity of air is 96.43 m/s.