# Thermo 1st Law open system question

1. Jun 10, 2014

### Abi_mecheng

1. The problem statement, all variables and given/known data
An insulated nozzle receives are at a negligible velocity at a pressure of 150kpa and temp of 25 degrees C. if the flow passing through the nozzle expands to 100kpa in an isentropic process, calculate the temperature and velocity of the air leaving the nozzle.

3. The attempt at a solution

Solution is attached but I don't understand how 1/2 becomes 1/2000 in the equation m(dot)[h2-h1)+1/2(v2^2 - v1^2)

Thanks

#### Attached Files:

• ###### 20140610_170828.jpg
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2. Jun 10, 2014

### SteamKing

Staff Emeritus
Be advised that the solution has P1 = 130 kPa, not 150 kPa.

3. Jun 10, 2014

### SteamKing

Staff Emeritus
Look at the units of the various parts of this equation. The additional factor of 1000 comes about to convert kg-m^2/s^2 to kJ (1 J = 1 kg-m^2/s^2).

4. Jun 10, 2014

### Abi_mecheng

Ohh ok totally missed that, thanks for pointing that out much appreciated.

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