Efficiency

Entropy

**Entropy**

**If 1.00 mL of water at 0 C is frozen and cooled to -8.0 C by being in contact with a great deal of ice at -8.0 C, estimate the total change in entropy of the process.**

**37.8 J/K**

**A 2.8 kg piece of aluminum at 28.5 C is placed in 1.0 kg of water in a Styrofoam container at 20 C. Estimate the net change in entropy of the system.**

**.645 J/K**

**30.0 kg of water at 44.0 C is mixed with 15.0 kg of water at 20.0 C. Estimate the change in entropy.**

**128 J/K**

at position 1, P=400 KPa, T=300 K

at position 3, P=100 KPa, V=4000 cm^3, T=300 K

Find P,V,T everywhere.

Fill out the engine table

what is the efficiency of this engine?

V_1 = 1000 cm^3

V_2 = 1000 cm^3 , P_2 = 1007.9 kPa

T_3 = 755.95 C

0 911.9 911.9 J

911.9 0 -911.9 J

-554.5 -554.5 0 J

357.4 357.4 0 J

39.2 %

If these temps are the reservoir temperatures, what is the ideal efficiency?

What percent of the ideal efficiency is this engine running?

60.3 %

65 % of ideal

at position 1, P=100 KPa

at position 2, P=400 kPa, V=1000 cm^3 , T=400 K

at position 3, P=100 KPa, V=4000 cm^3 T=400 K

Find P,V,T everywhere.

Fill out the engine table

what is the efficiency of this engine?

V_1 = 2297 cm^3 T_1 =229.7 K

-255.4 0 255.4 J

554.5 554.5 0 J

-170.2 -425.6 -255.4 J

128.9 128.9 0 J

23.2 %

A diesel engine runs with two adiabatic and an isochoric and isobaric process. Starting at 25 C 1 atm and 1050 cm^3 compresses to about 70 cm^3. It also absorbs about 1000 J in the burning of the fuel. (it is usually diatomic, but we'll pretend monatomic)

Find n , P,V,T for this engine

Fill in the engine energy chart

What is the efficiency.

n=.0429

101300 Pa, .00105 m^3, 298 K

9242000 Pa, .00007 m^3, 1812.5 K

9242000 Pa, .0001132 m^3, 2931.4 K

226000 Pa, .00105 m^3, 664.8 K

1

2

3

4

-810 0 810 J

400 1000 600 J

1213 0 -1213 J

0 197 - 197 J

803 803 0 J

80.3 %

S =

Q

T

"Can we go over the difference between effeciency and COP?"

"I am still struggling with how a refrigerator works."

"My only question is about Adiabatic processes. I'm not understand them in relation to a PV diagram."

3

2

1

3

2

1

4

3

2

1