Why isentropic mass is taken for calculation of area of nozzels

In summary, the conversation discussed an example of area calculation for a nozzle, where the given values were the mass flow rate and the coefficient of discharge. The speaker was initially confused about the given mass flow rate, thinking it was isentropic, and expected to calculate the actual mass flow rate from the coefficient of discharge. However, the example showed the opposite approach, where the given mass flow rate was actual and the isentropic mass was calculated from it to determine the nozzle area. The speaker questioned the use of isentropic mass in design problems, as they are typically based on actual conditions. They also asked for the definition of isentropic mass.
  • #1
engnr_arsalan
46
0
i was reading an example of area calculation of a nozzle,in which mass flow rate was and coeff. of discharge (ratio of actual mass flow rate to isentropic mass flowrate) was given.
i though the mass flow rate given in example is isentropic and we will first calculate actual mass flowrate from co.eff of discharge then area of nozzle..but totally opposite was done in example the mass flowrate given was actual and they calculated isentropic mass from it then area of nozzle..i didnt understand why they took isentropic mass..because design problems are based on actual condition..
kindly correct me if i am wrong..
 
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  • #2
What is the definition of isentropic mass?
 

1. What is isentropic mass?

Isentropic mass refers to the mass flow rate of a fluid in a system that undergoes a reversible and adiabatic process. This means that there is no heat transfer or work done on the fluid, and the process is considered to be ideal and efficient.

2. Why is isentropic mass used for calculating nozzle area?

Isentropic mass is used for calculating nozzle area because it takes into account the thermodynamic properties of the fluid, such as its temperature and pressure, which are important factors in determining the area of the nozzle. It also assumes that the fluid is flowing at a constant entropy, which is necessary for accurate calculations.

3. How is isentropic mass calculated?

Isentropic mass is calculated by using the formula: ṁ = A*ρ*V, where ṁ is the mass flow rate, A is the nozzle area, ρ is the fluid density, and V is the fluid velocity. This formula takes into account the conservation of mass and the properties of the fluid to determine the mass flow rate.

4. What are the benefits of using isentropic mass for nozzle calculations?

Using isentropic mass for nozzle calculations allows for more accurate and efficient designs. It takes into account the thermodynamic properties of the fluid, which can greatly affect the performance of the nozzle. By using isentropic mass, engineers can optimize the design for maximum efficiency.

5. Are there any limitations to using isentropic mass for nozzle calculations?

One limitation of using isentropic mass for nozzle calculations is that it assumes ideal and reversible conditions, which may not always be the case in real-world applications. Additionally, it does not take into account the effects of friction and other losses in the nozzle, which may affect the actual performance of the system.

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