Finding enthalpy at nozzle throat given total enthalpy and inlet conditions

[Naav_Gothalla]

Hi, This is my first post in this forum
I have a total enthalpy ht=3000 kj/kg with velocity at inlet v1=20 ms-1, Speed of sound a1=562.5 ms-1 and outlet pressure P2 = 1 bar
With the formula ht=h*+(a*2/2) how do i calculate actual value at throat h* ?

NOTE: (by trial and error)

• I can take any guesses for enthalpy at throat and i start by considering h*=2800 Kj/kg
• Total enthalpy and entropy remains constant at 3000 Kj/kg and Entropy with 6.5 Kj/K
• ht-htinlet != 0 i.e Δ=0

 

[boneh3ad]

Have you tried anything yourself yet?

 

[Naav_Gothalla]

Have you tried anything yourself yet?

Yes , Sir I found the result.
I guessed enthalpy at throat and i start by considering h*=2800 Kj/kg later on i find the speed of air(c^*) = velocity of sound at throat(v^*) for Mach 1. Furthermore, i calculate actual enthalpy at throat using the formula (h^*=h_t-c^*2/2). I use a solver in excel such that Δh=(h_t-h^*) should be equal to zero there by finding the actual enthalpy at the throat. Next I calculate pressure and temperature which are a function of enthalpy and entropy.

 

[boneh3ad]

Ah, good to hear that. Sorry no one answered your original post but it sounds like you didn't need it anyway. Carry on!