06ME 33: Basic Thermodynamics

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06ME 33 Basic Thermodynamics
VIJAYAVITHAL BONGALE
Assistant Professor Department of
Mechanical Engineering Malnad College of
Engineering Hassan 573201 Email
vvb_at_mcehassan.ac.in Fax
08172 -245683 Phone (O) 08172-245319 Mobile
9448821954
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06ME 33 Basic Thermodynamics
Second law of thermodynamics
SESSION V

• Numerical Problems and Solutions

Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Problem No.6
A Carnot refrigerator consumes 200 W of power in
summer when the ambient atmosphere is 40 0C. The
rate of energy leak into the refrigerator is
estimated at 20 W per degree Celsius temperature
difference between the ambient atmosphere and the
cold space of the refrigerator. If the
refrigerator is continuously operated, determine
the temperature at which the cold space is
maintained.
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Solution
Given TH 40273 313K,
We have
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Problem No.7
A direct heat engine operating between two
reservoirs at 3270C and 270C drives a
refrigerator operating between 270C and 130C. The
efficiency of the heat engine and the COP of the
refrigerator are each 70 of their maximum
values. The heat transferred to the direct heat
engine is 500 kJ. The net heat rejected by the
engine and the refrigerator to the reservoir at
270C is 400 kJ. Find the net work output of the
engine-refrigerator combination. Draw the
schematic representation.
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
SOLUTION
Given Q2Q4 400 kJ
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Problem No.8
A reversible heat engine operates between two
reservoirs at constant temperature of 1600C and
200C. The work output from the engine is 15 kJ /
sec. Determine (i) Efficiency of the cycle (ii)
Heat transfer from the reservoir at 1600C (iii)
heat rejected to the reservoir at 200C. If the
engine is reversed and operates as a heat pump
between the same two reservoirs, determine the
COP of the heat pump the power required when
the heat transfer from the reservoir at 200C is
300 kJ / min.
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
SOLUTION
Given TL 20273 293 K, TH
160273 433 K,
Heat rejected
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Case (ii)
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Problem No.9
A cyclic heat engine operates between a source
temperature of 800 0 C and a sink temperature of
30 0C. What is the least rate of heat rejection
per kW net output of the engine?
SOLUTION Given TH 8002731073 K

TL 30273303 K,
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Efficiency of the Carnot heat engine is given by,
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Problem No.10
A reversible heat engine operates with two
environments. In the first it draws 12000 kW from
a source at 400 0C and in the second it draws
25000 kW from a source at 100 0C. In both the
operations the engine rejects heat to a thermal
sink at 20 0C. Determine the operation in which
the heat engine delivers more power.
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
CASE I
CASE II
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Problem No.11
A Heat engine is used to drive a heat pump. The
heat transfers from the heat engine and from the
heat pump are used to heat the water circulating
through the radiators of a building. The
efficiency of the heat engine is 27 and the
coefficient performance of heat pump is 4.
Evaluate the ratio of heat transfer to the
circulating water to the heat transfer to the
heat engine.
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
We have Heat rejected from heat engine Heat
transfer from heat pump Heat
transfer to circulating water
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
? The ratio of heat transfer to the circulating
water to the heat transfer to the engine
We also have,
We have from (2),
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
From (3),
Substituting in equation (1), We obtain
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Problem No.12
A heat engine is supplied with 278 kJ / s of heat
at a constant fixed temperature of 283 0C and the
heat rejections take place at 5 0C. The following
results were reported. i) 208 kJ / s of heat
rejected. ii) 139 kJ / s of heat rejected. iii)
70 kJ / s of heat rejected. Classify which of the
results report a reversible cycle, irreversible
cycle or impossible cycle.
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Problem No.13
A household refrigerator is maintained at a
temperature of 2 0C. Every time the door is
opened, warm material is placed inside,
introducing an average of 420 kJ, but only a
small change in the temperature of the
refrigerator. The door is opened 20 times a day,
and the refrigerator operates at 15 of the
actual COP. The cost of work is 32 paise per
kWhr. What is the monthly bill for this
refrigerator. The atmosphere is at 30 0C.
Solution TH 30 273 303 K and TL 2273
275 K
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
Cooling effect to be produced per day QL20X
4208,400 kJ
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
For one month, W 30X57,026 1,71,079.5 kJ
The cost of work is 32 paise per kWhr

Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
REFERENCES

• Engineering Thermodynamics by D.B.Spalding and
  E.H.Cole, ELBS, Third Edition
• 2. Fundamentals of Classical thermodynamics by
  G.J.Van Wylen and R.E. Sonntag, John Wiley and
  Sons, Third Edition
• 3. Fundamentals of Engineering thermodynamics
  by
• E.Rathakrishnan, PHI, 2000

Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
4. Engineering thermodynamics Work and Heat
Transfer by Gordon Rogers and Yon Mayhew,
Pearson Education, Fourth edition. 5.
Engineering thermodynamics with applications by
M. David Burghardt, HIE, Third Edition 6.
Engineering thermodynamics by C.P.Gupta and
R.Prakash, Nemchand and Brothers
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
7. Applied Thermodynamics by T.D.Eastop and
A.McConkey, Pearson Education, Fifth
edition 8. Engineering Thermodynamics by P. K.
Nag, Tata McGraw- Hill Publishing Company
Limited, Eighth Reprint 1989 9.
http//hyperphysics.phy-astr.gsu.edu/hbase/thermo/
seclaw.html
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan
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06ME 33 Basic Thermodynamics
THANK YOU
Vijayavithal Bongale, Asst. Professor in
Mechanical Engg, MCE, Hassan