A piston-cylinder device containing carbon dioxide gas undergoes an isobaric process from 15 psia and 80°F to 170°F. Determine the work and the heat transfer associated with this process, in Btu/lbm. The properties of CO2 at room temperature are R = 0.04513 Btu/lbm·R and cv = 0.158 Btu/lbm·R.

See explanation

Explanation:

Given:

Initial pressure,

p

1

=

15

psia

Initial temperature,

T

1

=

80

∘

F

Final temperature,

T

2

=

200

∘

F

Find the gas constant and specific heat for carbon dioxide from the Properties Table of Ideal Gases.

R

=

0.04513

Btu/lbm. R

C

v

=

0.158

Btu/lbm. R

Find the work done during the isobaric process.

w

1

-

2

=

p

(

v

2

-

v

1

)

=

R

(

T

2

-

T

1

)

=

0.04513

(

200

-

80

)

w

1

-

2

=

5.4156

Btu/lbm

Find the change in internal energy during process.

Δ

u

1

-

2

=

C

v

(

T

2

-

T

1

)

=

0.158

(

200

-

80

)

=

18.96

Btu/lbm

Find the heat transfer during the process using the first law of thermodynamics.

q

1

-

2

=

w

1

-

2

+

Δ

u

1

-

2

=

5.4156

+

18.96

q

1

-

2

=

24.38

Btu/lbm