Transcript Introductory materials

Thermodynamics
Cengel-PPT a b c Apps
Prof. M. Kostic
Mechanical Engineering
NORTHERN ILLINOIS UNIVERSITY
What is Thermo…? Cengel-PPT a b c Apps
ENERGY Science
 Energy Conversion
What is Energy…? www.kostic.niu.edu/energy
 Cause Changes - Work, Heat, etc.
 Energy is property of matter!
 Therefore, ENERGY and
PROPERTY interrelations

Thermo Vocabulary
System, Surroundings, and Boundary
 Closed System - Control Mass
 Open System - Control Volume
 Control Surface
 Adiabatic System - NO Heat Transfer
 Isolated System - NO Energy Transfer

Forms of Energy

TOTAL Energy
–
thermal, kinetic, potential, electric, magnetic,
nuclear, ….
Macroscopic vs. Microscopic
 INTERNAL Energy (U)
- sum of ALL microscopic energies

System PROPERTIES

Extensive
–

m, V, U, E
Intensive
–
T, P, r, u, e
State, Equilibrium, Processes
State or Condition of a System
 Equilibrium - System in balance,
NO Changes

–
–
–
–
thermal/temperature balance - no HEAT
transfer/adiabatic
mechanical/pressure balance - no WORK
transfer
phase - no change of phases
chemical - no change of spices
Pressure Scales
Gauge
pressure
Local atm. pressure
Standard atm. pressure
101.325 kPa(abs)
14.696 psi(a)
760 mmHg(a)
29.92 inHg(a)
Vacuum
pressure
Local
atm.
pressure
Absolute
pressure
Ch.8: Temperature
Measurement

Temperature:
measure of hotness or coldness
indicating the direction in which heat
(energy) will spontaneously flow, i.e., from a
hotter body (one at a higher temperature) to a colder one
(one at a lower temperature).
Temperature is not the equivalent of the
system energy
 Historical background

Temperature Measurement
Devices
thermocouples,
 resistive temperature devices (RTDs and
thermistors),
 infrared radiators,
 bimetallic devices,
 liquid expansion devices, and
 change-of-state devices.

8.2: Temperature Standards
Temperature scale (ITS-90)
 Definition of the degree

Kelvin K, defined as the 1/273.16 fraction of the
thermodynamic temperature of the
triple point of water (TPW).
Fixed (reference) points
 Interpolation between the fixed points

Thermo Laws
Zeroth Law:
TA=TC and TB=TC then TA=TB
 First Law - Energy Conservation
 Second Law - Process Direction

In Conclusion
Be imaginative
 Try to differentiate
 Make sense of what you study
 Work and think hard and smart

Thermodynamics is a science of
ENERGY and MATTER and their relations