View by Category

The presentation will start after a short

(15 second) video ad from one of our sponsors.

Hot tip: Video ads won’t appear to registered users who are logged in. And it’s free to register and free to log in!

(15 second) video ad from one of our sponsors.

Hot tip: Video ads won’t appear to registered users who are logged in. And it’s free to register and free to log in!

Loading...

PPT – Entropy PowerPoint presentation | free to download - id: 109b12-NjM2N

The Adobe Flash plugin is needed to view this content

About This Presentation

Write a Comment

User Comments (0)

Transcript and Presenter's Notes

Entropy

- Second Law Characteristic

Entropy

- Clausius Inequality
- For internally reversible cycles

Entropy

- Entropy is defined as dS (dQ/T)int rev

(kJ/K) - S is entropy per unit mass (kJ/kgK)
- Entropy is a property of a state not a process
- Change of entropy

(No Transcript)

Entropy

- Increase of Entropy Principle
- The entropy of an isolated system during a

process always increases or, in the limiting case

of a reversible process, remains constant. - dS (dQ/T) where T is the thermodynamic

temperature at the boundary where dQ is

transferred to the surroundings

Entropy

- Process can occur in one direction only, not in

any direction. Must proceed in direction of

least increase in entropy. Sgen 0 - Entropy is a non-conserving property.
- Performance is degraded by irreversibilities,

entropy generation is a measure of the magnitude

of the irreversibilities during the process

Entropy

- Sgen gt 0 irreversible processes
- 0 reversible processes
- lt 0 impossible processes

Entropy

- Entropy of a fixed mass can be changed by
- Heat transfer
- Irreversibilities
- If no change, Isentropic
- Reversible, adiabatic process

Entropy Change of Pure Substance from tables

(No Transcript)

(No Transcript)

Isentropic Processes

- Isentropic process internally reversible,

adiabatic, entropy remains constant ?s 0 or

s2 s1

Entropy

- Essentially Isentropic Processes
- Pumps
- Turbines
- Nozzles
- Diffusers

(No Transcript)

(No Transcript)

Property Diagrams

- Temperature-entropy (T-s) diagrams
- Area under process curve on a T-s diagram equals

heat transfer during an internally reversible

process

Property Diagrams

- Isentropic processes are a vertical line on T-s

diagrams

Property Diagrams

- Enthalpy-entropy diagram, h-s diagram, Mollier

diagram - Change in h is a measure of work
- Change in s is a measure of irreversibilities

(No Transcript)

Entropy

- Entropy is measure of molecular disorder,

molecular randomness

Entropy

- Boltzmann equation
- S k ln(p)
- where k 1.380610-23 J/K
- p thermodynamic probability, number of

possible microscopic states of system

Third Law of Thermodynamics

- The entropy of a pure crystalline substance at

absolute zero temperature is zero, since there is

no uncertainty about the state of the molecules

at that instant - Provides an absolute reference point for

determining entropy

Entropy

- There is no entropy transfer associated with

energy transferred as work - Irreversibilities (friction) will case entropy

increase

Entropy

- Work changed to heat increases entropy

Entropy

- During heat transfer net entropy increases

Entropy

- To find the change in entropy, need to do the

cycle integral of dQ/T. - If isothermal, only need the function for Q
- If not isothermal, need functions for Q and T

Entropy

Entropy

Entropy

- Can find entropy by integration of either

equation - Need to know the relationship between du or dh

and temperature - For ideal gases
- du cv dT
- Or dh cp dT
- And PvRT

Entropy Changes of Liquids and Solids

- Liquids and solids are incompressible
- dv 0
- Also cv cpc and du c dT

Entropy Change of Ideal Gases

- In the basic equation, substituting du cv dT

and P RT/v - Substituting dh c dT and v RT/P

Entropy Change of Ideal Gases

- Need the relationship between the specific heats

and temperature - Assume constant specific heats, simpler

integration, approximate analysis - Work with variable specific heats, use tables,

exact analysis

Constant Specific Heats (Approximate Analysis)

Variable Specific Heats (Exact Analysis)

- If temperature change is large
- Specific heats are non-linear with temperature
- Need accurate relationships
- Calculate integrals with respect to reference

entropy (at absolute zero)

Variable Specific Heats (Exact Analysis)

- So we can find
- And substituting into
- Get

Variable Specific Heats (Exact Analysis)

(No Transcript)

(No Transcript)

(No Transcript)

Isentropic Processes of Ideal Gases

- Process that has
- No change in entropy, ?s 0
- Is internally reversible
- Is adiabatic

Isentropic Processes of Ideal Gases (Approximate

Analysis)

- Assume constant specific heats, so
- Where k cp /cv

Isentropic Processes of Ideal Gases (Approximate

Analysis)

- These equations can be stated as
- Since the specific heat ratio k, varies with

temperature, the average k should be used

Isentropic Processes of Ideal Gases (Exact

Analysis)

- Set up to use tables
- Working with
- Establish new dimensionless quantities from the

equations

Isentropic Processes of Ideal Gases (Exact

Analysis)

- The quantity exp(s/R) is defined as relative

pressure Pr - P is a function of T only, so can be tabulated

against T.

Isentropic Processes of Ideal Gases (Exact

Analysis)

- So using table A-17 for air

Isentropic Processes of Ideal Gases (Exact

Analysis)

- When specific volume ratios are given instead of

pressure - The quantity T/Pr is a function of T only,

defined as relative specific volume vr

(No Transcript)

(No Transcript)

(No Transcript)

Reversible Steady-Flow Work

- Work done during process depends on
- Properties at the end states
- Path between the end states
- Quasi-equilibrium work interactions
- Max work output
- Min work input

Reversible Steady-Flow Work

- Energy balance for steady-flow, internally

reversible process - Substituting

Reversible Steady-Flow Work

- For incompressible fluids, volume remains

constant - When the device has no work interactions (nozzle,

pipe sections), w 0 - The larger the specific volume, the larger the

reversible work produced or consumed

(No Transcript)

Minimizing Compressor Work

- Minimized when internally reversible
- Compressor work required
- Methods to minimize work
- Reduce irreversibilities
- Keep specific volume as small as possible
- Keep gas temperature as low as possible

Minimizing Compressor Work

- Look at three processes
- Isentropic process, no cooling
- Polytropic process, some cooling
- Isothermal process, maximum cooling

Minimizing Compressor Work

- Assume, same pressures, ideal gases, constant

specific heats, internally reversible

Minimizing Compressor Work

- Methods of removing heat
- Cooling jackets on compressor
- Multistage compressor with intercooling

Minimizing Compressor Work

- For multistage compression
- To minimize compressor work in 2-stage

compressor, the pressure ratio across each stage

must be the same

(No Transcript)

(No Transcript)

(No Transcript)

Isentropic Efficiencies of Steady-Flow Devices

- Ideal model for turbines, compressors, nozzles,

etc. - Adiabatic, no irreversibilities, isentropic

process - Measure actual devices against ideal model

Isentropic Efficiency of Turbines

- Turbine efficiency is the ratio of the actual

work output to the work output of an isentropic

process between the same states

Isentropic Efficiency of Turbines

- Actual efficiencies run from 90 for large

turbine to 70 for smaller turbines

Isentropic Efficiency of Compressors and Pumps

- Isentropic efficiency of a compressor is ratio of

the isentropic work required to raise the

pressure of a gas to the actual work input

Isentropic Efficiency of Compressors and Pumps

Compressor Efficiency

- Isothermal efficiency

Entropy Balance

- The entropy change during a process is equal to

the net entropy transfer through the system

boundary and the entropy generated in the system

Entropy Change of a System

- For a system
- Entropy is a property so entropy does not change

unless the state of the system changes

Mechanisms of Entropy Transfer

- Heat transfer

Mechanisms of Entropy Transfer

- Mass Flow

Mechanisms of Entropy Transfer

Entropy Generation

- Irreversibilities such as
- Friction
- Mixing
- Chemical reactions
- Heat transfer (finite temperature difference)
- Unrestrained expansion
- Non quasi-equilibrium compression or expansion
- Causes entropy increase or generation

Entropy Generation

Entropy Generation, Closed Systems

Entropy Generation, Open Systems

Entropy Generation, Open Systems

Entropy Generation Associated with Heat Transfer

About PowerShow.com

PowerShow.com is a leading presentation/slideshow sharing website. Whether your application is business, how-to, education, medicine, school, church, sales, marketing, online training or just for fun, PowerShow.com is a great resource. And, best of all, most of its cool features are free and easy to use.

You can use PowerShow.com to find and download example online PowerPoint ppt presentations on just about any topic you can imagine so you can learn how to improve your own slides and presentations for free. Or use it to find and download high-quality how-to PowerPoint ppt presentations with illustrated or animated slides that will teach you how to do something new, also for free. Or use it to upload your own PowerPoint slides so you can share them with your teachers, class, students, bosses, employees, customers, potential investors or the world. Or use it to create really cool photo slideshows - with 2D and 3D transitions, animation, and your choice of music - that you can share with your Facebook friends or Google+ circles. That's all free as well!

For a small fee you can get the industry's best online privacy or publicly promote your presentations and slide shows with top rankings. But aside from that it's free. We'll even convert your presentations and slide shows into the universal Flash format with all their original multimedia glory, including animation, 2D and 3D transition effects, embedded music or other audio, or even video embedded in slides. All for free. Most of the presentations and slideshows on PowerShow.com are free to view, many are even free to download. (You can choose whether to allow people to download your original PowerPoint presentations and photo slideshows for a fee or free or not at all.) Check out PowerShow.com today - for FREE. There is truly something for everyone!

You can use PowerShow.com to find and download example online PowerPoint ppt presentations on just about any topic you can imagine so you can learn how to improve your own slides and presentations for free. Or use it to find and download high-quality how-to PowerPoint ppt presentations with illustrated or animated slides that will teach you how to do something new, also for free. Or use it to upload your own PowerPoint slides so you can share them with your teachers, class, students, bosses, employees, customers, potential investors or the world. Or use it to create really cool photo slideshows - with 2D and 3D transitions, animation, and your choice of music - that you can share with your Facebook friends or Google+ circles. That's all free as well!

For a small fee you can get the industry's best online privacy or publicly promote your presentations and slide shows with top rankings. But aside from that it's free. We'll even convert your presentations and slide shows into the universal Flash format with all their original multimedia glory, including animation, 2D and 3D transition effects, embedded music or other audio, or even video embedded in slides. All for free. Most of the presentations and slideshows on PowerShow.com are free to view, many are even free to download. (You can choose whether to allow people to download your original PowerPoint presentations and photo slideshows for a fee or free or not at all.) Check out PowerShow.com today - for FREE. There is truly something for everyone!

presentations for free. Or use it to find and download high-quality how-to PowerPoint ppt presentations with illustrated or animated slides that will teach you how to do something new, also for free. Or use it to upload your own PowerPoint slides so you can share them with your teachers, class, students, bosses, employees, customers, potential investors or the world. Or use it to create really cool photo slideshows - with 2D and 3D transitions, animation, and your choice of music - that you can share with your Facebook friends or Google+ circles. That's all free as well!

For a small fee you can get the industry's best online privacy or publicly promote your presentations and slide shows with top rankings. But aside from that it's free. We'll even convert your presentations and slide shows into the universal Flash format with all their original multimedia glory, including animation, 2D and 3D transition effects, embedded music or other audio, or even video embedded in slides. All for free. Most of the presentations and slideshows on PowerShow.com are free to view, many are even free to download. (You can choose whether to allow people to download your original PowerPoint presentations and photo slideshows for a fee or free or not at all.) Check out PowerShow.com today - for FREE. There is truly something for everyone!

For a small fee you can get the industry's best online privacy or publicly promote your presentations and slide shows with top rankings. But aside from that it's free. We'll even convert your presentations and slide shows into the universal Flash format with all their original multimedia glory, including animation, 2D and 3D transition effects, embedded music or other audio, or even video embedded in slides. All for free. Most of the presentations and slideshows on PowerShow.com are free to view, many are even free to download. (You can choose whether to allow people to download your original PowerPoint presentations and photo slideshows for a fee or free or not at all.) Check out PowerShow.com today - for FREE. There is truly something for everyone!

Recommended

«

/ »

Page of

«

/ »

Promoted Presentations

Related Presentations

Page of

Page of

CrystalGraphics Sales Tel: (800) 394-0700 x 1 or Send an email

Home About Us Terms and Conditions Privacy Policy Contact Us Send Us Feedback

Copyright 2017 CrystalGraphics, Inc. — All rights Reserved. PowerShow.com is a trademark of CrystalGraphics, Inc.

Copyright 2017 CrystalGraphics, Inc. — All rights Reserved. PowerShow.com is a trademark of CrystalGraphics, Inc.

The PowerPoint PPT presentation: "Entropy" is the property of its rightful owner.

Do you have PowerPoint slides to share? If so, share your PPT presentation slides online with PowerShow.com. It's FREE!

Committed to assisting Clark University and other schools with their online training by sharing educational presentations for free