NCEES 2008 # 136 Pressure Enthalpy A/C Dia

[tmacier]

Hey guys-

I am working problem 136 on the 2008 NCEES and it asks to find 250 psia saturated of 134a on the Pressure/Enthalpy Diagram.

As you move horizontaly at 250 PSIA to saturated liquid the anwer the book gives for S inital is .118 - that appear to be in the middle of the dome but how does one know were to stop?

Anyone feel like explaining this to me a little?

Thanks in advance

Tim

 

[Relvinim]

Hey guys-
I am working problem 136 on the 2008 NCEES and it asks to find 250 psia saturated of 134a on the Pressure/Enthalpy Diagram.

As you move horizontaly at 250 PSIA to saturated liquid the anwer the book gives for S inital is .118 - that appear to be in the middle of the dome but how does one know were to stop?

Anyone feel like explaining this to me a little?

Thanks in advance

Tim

There is no horizontal movement from initial to final condition. The initial condition is 250 psi saturated liquid and then goes vertically down (since throttling is constant h) to 40 psi. The initial condition is on the liquid side of the curve.

 

[tmacier]

Hey guys-
I am working problem 136 on the 2008 NCEES and it asks to find 250 psia saturated of 134a on the Pressure/Enthalpy Diagram.

As you move horizontaly at 250 PSIA to saturated liquid the anwer the book gives for S inital is .118 - that appear to be in the middle of the dome but how does one know were to stop?

Anyone feel like explaining this to me a little?

Thanks in advance

Tim

There is no horizontal movement from initial to final condition. The initial condition is 250 psi saturated liquid and then goes vertically down (since throttling is constant h) to 40 psi. The initial condition is on the liquid side of the curve.

I understand that throttling is strait down - what I dont get is how they are getting the initial condition- the value .118 is not on the saturated line, but somewhere under the dome.

THanks

Tim

 

[Relvinim]

Hey guys-
I am working problem 136 on the 2008 NCEES and it asks to find 250 psia saturated of 134a on the Pressure/Enthalpy Diagram.

As you move horizontaly at 250 PSIA to saturated liquid the anwer the book gives for S inital is .118 - that appear to be in the middle of the dome but how does one know were to stop?

Anyone feel like explaining this to me a little?

Thanks in advance

Tim

There is no horizontal movement from initial to final condition. The initial condition is 250 psi saturated liquid and then goes vertically down (since throttling is constant h) to 40 psi. The initial condition is on the liquid side of the curve.

I was wondering the same thing. It's definitely an eye test. I was close enough to the answer with my approximations but I don't know how they read that entropy to within that accuracy.

I understand that throttling is strait down - what I dont get is how they are getting the initial condition- the value .118 is not on the saturated line, but somewhere under the dome.

THanks

Tim