atoc 4720 class 11
Skip this Video
Download Presentation
ATOC 4720: class 11

Loading in 2 Seconds...

play fullscreen
1 / 13

ATOC 4720: class 11 - PowerPoint PPT Presentation

  • Uploaded on

ATOC 4720: class 11. 1. The first law of thermodynamics 2. Joule’s law 3. Specific heats 4. Enthalpy. 1. The first law of thermodynamics. A moving air mass: kinetic energy potential energy. Internal energy. Increase in internal kinetic energy: T.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about ' ATOC 4720: class 11' - viveca

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
atoc 4720 class 11
ATOC 4720: class 11
  • 1. The first law of thermodynamics
  • 2. Joule’s law
  • 3. Specific heats
  • 4. Enthalpy
1 the first law of thermodynamics
1. The first law of thermodynamics

A moving air mass: kinetic energy

potential energy

Internal energy

Increase in internal kinetic energy: T

Increase in internal potential energy: relative



Assume a body of unit mass:

Takes heat energy q (joules): thermal

conduction or radiation;

External work w:

Excess energy: q-w

If there is no change in macroscopic kinetic

and potential energy, energy conservation

requires that its internal energy must

Increase by q-w.




Before and




In differential form:

This equation states that increment of heat added

to a body is used to do external work by the

body and to increase the internal energy of

the body. This is the first law of



State 1, V1



State 2, V2


2 joule s law
2. Joule’s law

1848, lab experiments

When a gas expands without doing

External work, and without taking in

or giving out Heat, the temperature

of the gas does not change.

Ideal gas.

dq=0, dw=0, ===== > du=0

3 specific heat
3. Specific heat

dq is given to unit mass =>

T to T+dT

dq/dT is called specific heat

A specific heat at constant volume:



Joule’s law: du depends only on T, so


We may also define:

Physics: cp>cv


Cv=717 J/deg/kg;

Cp=1004 j/deg/kg,


First law of thermodynamics:

4 enthalpy
4. Enthalpy

If heat is added to a material at constant

pressure, so that the

specific volume of the material increases

from a1 to a2, the work done by a unit

mass of the material is p(a2-a1). Therefore, the heat dq added to a unit

mass of the material at constant pressure

is given by