# Class 4 - Equilibrium and Reversible Processes - PowerPoint PPT Presentation

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Class 4 - Equilibrium and Reversible Processes. Part 1 - Contact Before Work 5 min Part 2 - Review and Report Out 45 min Break 10 min Part 3 - Review (continued) 15 min Part 4 - Forces & Energy Transfer 10 min Part 5 - The Equations 10 min

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Class 4 - Equilibrium and Reversible Processes

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### Class 4 - Equilibrium and Reversible Processes

• Part 1 - Contact Before Work 5 min

• Part 2 - Review and Report Out 45 min

• Break10 min

• Part 3 - Review (continued)15 min

• Part 4 - Forces & Energy Transfer10 min

• Part 5 - The Equations10 min

• Part 4 - Solving the Equations10 min

• Part 5 - Clarification5 min

### Begin With the End in Mind :Class Learning Objectives

• Demonstrate Knowledge LoL for

• equilibrium(mechanical, thermal, electrical),

• an internally reversible process,

• a reversible process.

• what causes a process to be irreversible,

• the concept of ‘immediatesurroundings’,

• the concept of ‘steadystate’, and

• the ‘heattransfer’ heuristic.

• Demonstrate Knowledge LoL for constructing the entropyaccounting equation.

### Class 4 - Review (60 min)

Each sub-team of two persons, use a blank sheet of paper or a page from your Academic Journal to:

• State the two conditions required for a system to be in equilibrium.

• Name three'thermodynamicproperties of matter' that are included in the conservation and accounting equations (p. 484 and 517).

• What is the relationship between equilibrium and the 'thermodynamicproperties of matter’ ?

• Define an 'internally reversible', or 'quasi-equilibrium' path or process.

### Class 4 - Review (cont.)

• State the entropy accounting equation for the system and identify each term as 'flow in/out', 'thermal energy transfer', 'generation' or 'accumulation'. What is our heuristic for the entropygenerationterms for the system ?

• How is an internally reversible processdescribed or represented in the entropy accounting equation? (p. 518)

• What are the 5essentialfeatures of a reversible process or path? (p. 519)

• List the 9 major causes or sources of irreversibility in a process or path; include an example for each cause. (see p. 519)?

### Class 4 - Review (cont.)

• List 6processes or paths. (see p. 518)

10 What additional constraints are required to define a reversiblepath; i.e., both internally and externally reversible? (p. 519)

11Define the term 'immediatesurroundings'; what is included and what is excluded? (p. 520)

12Define the concept of 'steady state'.

13State the 'heat transfer heuristic' (p. 526)

### Break

Be back with your team, ready to work, in 10minutes : rememberourECE 340 Class

Code of Cooperation !

Body # B,

the crank

(partially hidden)

Body # C,

connecting rod

Outlet

C

IB

MC

A

Valve Closed

MOTION

Body # A, the flywheel

Valve Closed

System = ‘Control Volume’ which contains the gas being compressed.

Rotation

Inlet

Reciprocating Compressor

### Structure for ‘Doing the Work’

• Specify an appropriate coordinatesystem.

• Include the gravitationalfield in the surroundings; show all of the body and surface forces that the surroundings exerts on the system.

• Show all of the surface forces that the system exerts on the surroundings.

• Show how mass, totalenergy, and entropy are exchanged between the system and the surroundings.

• Construct the totalmass conservation equation; identify each term as ‘Accumulated’ or ‘Flow In/Out’

### Structure for ‘Doing the Work’

• Assume that the compressionprocess is internally reversible; what changes should be made to the labeled sketch?

• Construct the total energy conservation equation; identify each term as

• ‘Accumulated’ , ‘Flow In/Out’ ,

• ‘External Forces’ , ‘Pv’ Work , or ‘Heat’

• Construct the entropy accounting equation; identify each term as ‘Accumulated’ , ‘Flow In/Out’ , ‘Heat Transfer’, or ‘Generation’.

• Multiply both sides of these equations by dt and integrate the resulting terms.

### Model Analysis

1. Model Variables

From the Sketch …

From Equation 1...

From Equation 2, etc. ….

2. Analysis

Variables

- Equations

_______

Remaining Unknowns

- Data

- Specifications

- Parameters

- Initial Conditions

- Independent Variables

_______

Design Variables; Solvable ?

### Structure for ‘Doing the Work’

• Display the essentialfeatures of the problem in a(xx min)labeled sketch. Include an appropriate coordinatesystem.

• Identify an appropriate system ( or systems ).( x min)

• What extensiveproperties are to be accounted for ( x min)or conserved?

• What is an appropriate timeperiod for this problem?( x min)

• State the applicable balances for the extensive properties (xx min)in tabularform.

• Delineate the specifications, data, and definingrelationships.(xx min)

• Analyze the model ( i.e., count variables, equations, etc.(xx min)to determine if the problem can be solved )

• Make appropriate assumptions and quantify the behavior.( ? min)