11. ₁. A Carnot heat engine contains 8.00 moles of oxygen gas (assume CVm= 2.5R). The temperature of the heat source is 500.0 °C and the temperature of the cold reservoir is 25.0 °C. Calculate the thermodynamic efficiency, V₁, V2, V3, V4, P3, P4, w and q for each step of the cycle and the total heat and work of the cycle if P = 20.0 bar and P₂ = 5.00 bar.

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11,
.A Carnot heat engine contains 8.00 moles of oxygen gas (assume Cv.m= 2.5R). The
temperature of the heat source is 500.0 °C and the temperature of the cold reservoir is 25.0 °C.
Calculate the thermodynamic efficiency, V₁, V2, V3, V4, P3, P4, w and q for each step of the cycle
and the total heat and work of the cycle if P1 = 20.0 bar and P₂ = 5.00 bar.
Transcribed Image Text:11, .A Carnot heat engine contains 8.00 moles of oxygen gas (assume Cv.m= 2.5R). The temperature of the heat source is 500.0 °C and the temperature of the cold reservoir is 25.0 °C. Calculate the thermodynamic efficiency, V₁, V2, V3, V4, P3, P4, w and q for each step of the cycle and the total heat and work of the cycle if P1 = 20.0 bar and P₂ = 5.00 bar.
Expert Solution
Step 1

A carnot cycle consists of 4 steps. 

1) reversible isothermal expansion (P1,V1,TH to P2, V2,TH)

2) reversible adiabatic expansion   (P2, V2, TH to P3, V3, TC)

3) reversible isothermal compression  (P3, V3, TC to P4, V4, TC)

4) reversible adiabatic compression  (P4, V4, TC to P1, V1, TH)

P1 = 20 bar = 20x0.987 atm = 19.74 atm     {1 bar = 0.987 atm)

P2 = 5bar = 5x 0.987atm = 4.935 atm

TH = 500oc = 500+273 = 773 K

TC = 25oc = 25+273 = 298K 

Cv = 2.5R = (5/2) R

Cp = (7/2) R

γ = Cp/Cv = 7/5 

It follows ideal gas equation 

P1 V1 = nR TH

V1 = (nR TH)/ P1 = (8mole x 0.082 L atm mol-1 K-1 x 773 K) / 19.74 atm = 25.69 L

V2 = (nR TH) / P2 = (8mole x 0.082 L atm mol-1 K-1 x 773 K) / 4.935 atm = 102.75 L 

again TH V2γ-1 = Tc V3γ-1   (as adiabatic process) 

V3THTC1-γ x V2 = 773298-25× 102.75 = 70.18 L

So, P3nR TCV38×0.082×29870.18 = 2.785 atm

again,

TC×V4γ-1 = TH× V1γ-1 V4= THTC1-γ × V1 =773298-25× 25.69  = 17.54 L     (as adiabatic process) 

 

P4 = nR TCV4   = 8×0.082×29817.54 = 11.14 atm     

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