Carnot Cycle and Adiabatic process

[Bob19]

I have a question regarding Carnot Cycles and Adiabatic processs.

I have cylinder with n moles of a mono-atomic gas with a specific Volume, Pressure and Temperature. This Cylinder is closed by a piston.

This system undergoes the four step Carnot Cycle A-B, B-C, C-D and D-A.

A-B: Is the adiabatic process where no heat gets in or out Q=0. What I'm required to do is to calculate the change in Pressure, Volume and Temperature. Any hits or idears on how I do that?

Is it something about calculating the work done by the gas? Which during the adiabatic process expands the initial volume. But does this also change the pressure and temperature of the gas too ?

Sincerley and Best Regards,

Bob

 

[Bob19]

Thanks,

I will this out, and get back to You if the need more asistance.


/BOB

 

[Andrew Mason]

I have a question regarding Carnot Cycles and Adiabatic processs.

I have cylinder with n moles of a mono-atomic gas with a specific Volume, Pressure and Temperature. This Cylinder is closed by a piston.

This system undergoes the four step Carnot Cycle A-B, B-C, C-D and D-A.

A-B: Is the adiabatic process where no heat gets in or out Q=0. What I'm required to do is to calculate the change in Pressure, Volume and Temperature. Any hits or idears on how I do that?

Is it something about calculating the work done by the gas? Which during the adiabatic process expands the initial volume. But does this also change the pressure and temperature of the gas too ?

You will have to use the adiabatic condition: PV^\gamma = constant

AM

 

[Bob19]

Hello again,

The mono-atomic gas is not specified. Therefore which \gamma -value do I use ? 1.64 or 1.69 ??

/Bob

You will have to use the adiabatic condition: PV^\gamma = constant

AM

 

[Yegor]

Therefore which \gamma-value do I use ? 1.64 or 1.69 ??

i believed that for mono-atomic gas we assume \gamma=5/3=1.67

 

[Bob19]

i believed that for mono-atomic gas we assume \gamma=5/3=1.67

I have a second question.

As part of the carnot cycle I have the isothermical process D -> C, where

P_D = 711.3 \textrm{KPa} , V_D = 15.0 \textrm{L and} \ T_D = 584.43 \textrm{K}

Since D and C are on the same path in the carnot cycle then according to theory T_D = T_C.

I'm required to calculate V_C from the data availible to me. Which formula do I use to calculate V_C ?

Sincerely
Bob

 

[Yegor]

If A-B is adiabatic then C-D (or D-C) is also adiabatic.
Nevertheless, if both are isothermic, then you should use PV^\gamma = constant for adiabatic and PV = constant for isothermic.

P_D = 711.3 \textrm{KPa} , V_D = 15.0 \textrm{L and} \ T_D = 584.43 \textrm{K}

I think that any parameter in point B or A must be given. Isn't it?

 

[Bob19]

Since A and B are on the same path in the carnot cycle then

T_A = T_B

I have reached the following point (where I'm stuck in my calculation of V_C and P_{C}

P_{c} * V_{c} = T_{c} \frac{P_{D} * V_{D}}{T_c}

I get that P_{c} * V_{c} = 10671,5

Can I use this result to obtain V_{C} and P_{D} ??

/Bob

If A-B is adiabatic then C-D (or D-C) is also adiabatic.
Nevertheless, if both are isothermic, then you should use PV^\gamma = constant for adiabatic and PV = constant for isothermic.



I think that any parameter in point B or A must be given. Isn't it?

 

[Yegor]

A-B: Is the adiabatic process where no heat gets in or out Q=0. What I'm required to do is to calculate the change in Pressure, Volume and Temperature

Or it was another problem?

I have reached the following point (where I'm stuck in my calculation of and
P_{c} * V_{c} = T_{c} \frac{P_{D} * V_{D}}{T_c}
I get that P_{c} * V_{c} = 10671,5
Can I use this result to obtain V_{C} and P_{D}??

Yes, you can use, but it isn't enough.
Do you really have nothing more given?

P.S. How it's possible to quote? What is the right command?

 

[Bob19]

Hello again,

Yes its a different part of the problem this time:

First I made a typoo:

Here is the right formula

P_{c} * V_{c} = T_{c} \frac{P_{D} * V_{D}}{T_D}

I'm told that V_C = 24 \ Liters but how that's derrived from the above result I'm a bit unsure of ?

/Bob

Or it was another problem?

Yes, you can use, but it isn't enough.
Do you really have nothing more given?

P.S. How it's possible to quote? What is the right command?

 

[Yegor]

May be you should use any results from another parts of the problem!?

A-B: Is the adiabatic process where no heat gets in or out Q=0. What I'm required to do is to calculate the change in Pressure, Volume and Temperature. Any hits or idears on how I do that?

If you have worked this out you should have some information about other points of the cycle.

 

[Bob19]

I have data for D and A the volume in C but not other data.

So what do I do ?

BOB

May be you should use any results from another parts of the problem!?

If you have worked this out you should have some information about other points of the cycle.

 

[Yegor]

C-D and A-B are isothermic; and D-A and B-C - adiabatic.
Then V_C P_C= V_D P_D
V_A P_A= V_B P_B
P_D V_D^\gamma=P_A V_A^\gamma
P_B V_B^\gamma=P_C V_C^\gamma
Also use PV^\gamma = TV^{\gamma-1}=P^{1-\gamma}T^\gamma =constant for adiabatic. Now you can calculate all data

 

[Bob19]

C-D and A-B are isothermic; and D-A and B-C - adiabatic.
Then V_C P_C= V_D P_D
V_A P_A= V_B P_B
P_D V_D^\gamma=P_A V_A^\gamma
P_B V_B^\gamma=P_C V_C^\gamma
Also use PV^\gamma = TV^{\gamma-1}=P^{1-\gamma}T^\gamma =constant for adiabatic. Now you can calculate all data

Hi,

Which of these formulas do I then use to calcualte V_c ?

/Bob

 

[Yegor]

Hm. I think it's impossible. Imagine the P-V plot. You have two points D and A, as you told. There are no restrictions on where adiabata B-C intersects isothermas.

 

[Bob19]

Sorry scratch that:

I have discovered that V_C = 24 is avalible in the text.

Sorry I missed that cause I'm suffering from terrible hayfever today.

I'm Sorry :-)

/Bob