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Thermodynamics 🔥👉🏻⚙️ > First Partial > Flashcards

First Partial Flashcards

1
Q

The word thermodynamics

A

From Greek: therme (heat)🔥dynamics (force)💪🏼.

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2
Q

Two definitions of Thermodynamics:

A

The science of energy, it studies the interconversions of heat into work.
~Cengel and Boles

Thermodynamics is a branch of the physics that studies the energy and work associated with a system. It began in XIX with the steam engines.
~NASA Glen Research Center

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3
Q

What does the thermodynamics do in general words?

A

Q (heat)👉🏻W (work)

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4
Q

Fundamental Laws:

A
  • Law zero: thermal equilibrium: The heat goes to the warmer object to the coldest one.
  • First law of thermodynamics: energy conservation: The energy is not created or destroyed but it can be transformed.
  • Second law of thermodynamics: entropy: the direction of the processes, whether the process is possible or not.

1850, Rankine, Clausius, Kelvin.

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5
Q

Molecules

A

A substance consists of a large number of particles called molecules.

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6
Q

Microscopic level

A

(statistical thermodynamics, kinetic theory)

The properties of the substance naturally depend on the behavior of these particles.

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7
Q

Macroscopic level

A

This approach does not study the behavior of individual particles, but considera the continuum model.

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8
Q

Theory of continuum.

A

The description of a substance should consider the behavior of each molecule. The equations that describe the behavior should be developed for each equation.

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9
Q

What does the continuum assume?

A

That it is possible to simplify the granular description of the substance by using averages, and considering adequate control volumes.

IMAGEN CON FORMULA

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10
Q

Adequate control volumes?

A

IMAGEN

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11
Q

Continuum

An example of the macroscopic approach

A

It is not possible to know the interactions between each of the different particles, to determine the pressure over a recipient.

Como en cálculo diferencial, para hacer una ecuación diferencial, tenemos que asegurar que el proceso sea continuo.

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12
Q

Examples of thermodynamics applications:

A 
Sumo wrestler.
A rock falling.
A house with solar panels.
Gas turbines.
Combined cycle plant.
Concentrated solar power plants.
Eolic turbines.
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13
Q

Measurement units

A
  • International system.

* English Systems.

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14
Q

Force

SI: F = …

A

SI: F = ma = kg m / s2 = Newton

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15
Q

Force

ES: 1 lbf = …

A

ES: 1 lbf = 32.174 lbm pies / s2

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16
Q

Force

1 kgf = …

A

1 kgf = 9.81 N

The weight of 1kg at sea level.

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17
Q

Work

SI: W = …

A

SI: W = F d = N m = 1 Joule

18
Q

Work

ES: 1 BTU = …

A

ES: 1 BTU = 1.0551 KJ

Energy necessary yo increase 1 F the temperature of 1 lbm at 68 F.

19
Q

Work

Calorie = …

A

Calorie = 4.1868 Joule

Energy required to increase in 1 C the temperature of 1 g of water at 14.5 C.

20
Q

Power

P = …

21
Q

What does power mean?

A

Capacity to do the job.

22
Q

Power

SI: 1 J / s = …

A

SI: 1 J / s = 1 watt

23
Q

Power

ES: 1 HP = …

A

ES: 1 HP = 746 w

24
Q

Basic concepts

25
Q

System and surroundings

System: …

A

A quantity of matter or a region in a space chosen for study.

Está definido por quien va a realizar el estudio, hay que definirlo bien. Depende del objeto de estudio.

26
Q

System and surroundings

Surroundings: …

A

Mass or region outside the system.

27
Q

System and surroundings

Boundary: …

A

The real or imaginary surface that separates the system from its surroundings. The boundary could be fixed or movable.

Ver dibujo.

28
Q

Different types of systems

A

Open: The matter and the energy go in and out. Ex, tobera and turbine.

Closed: Ex, gas with a piston and internal combustion engine.

Isolated: Everything occurs inside, neither the matter nor the energy go in or out.

Ver dibujos.

29
Q

Properties of a system

Property

A

Any characteristic of a system is called property.

30
Q

Familiar properties

A

Pressure (P), temperature (T), volume (V) and mass (M).

31
Q

Less familiar properties

A 
Viscosity
Thermal conductivity 
Modulus of elasticity
Thermal expansion coefficient
Electric resistivity
32
Q

Properties can be classified in

A

Intensive properties: temperature, pressure, density.

Extensive (depend of the size of the system): total volume, total mass.

Specific properties (extensive properties per unit mass): specific volume, specific energy.

33
Q

State and equilibrium

What characterize a system in a certain moment?

A

The properties characterize a system in a certain moment. When the properties maintain fixed values, this describes an specific equilibrium state.

34
Q

State and equilibrium

What does thermodynamics study?

A

Thermodynamics studies equilibrium states. There are no unbalanced potentials in the system (Thermal Eq, Mechanical Eq, Phase Eq, Chemical Eq).

35
Q

Process and cycle

Proces: …

A

Any change that a system undergoes from one state to another.

36
Q

Process and cycle

Trayectory: …

A

The serie of states that a system undergoes during a process.

37
Q

Process and cycle

A system is said to have…

A

A system is said to have undergone cycle if it returns to its initial state at the end of the process.

38
Q

See the property diagram to help to visualize the processes.

39
Q

Different types of processes

Quasi static.

A

When a process proceeds in such a manner that the system remains infinitesimally close to an equilibrium state at all times, it is called a quasi-static or quasi-equilibrium process.

40
Q

Different types of processes

See drawings a) and b)

41
Q

Different types of processes

See drawing of system properties and trajectory properties.

42
Q

Adicional types of processes

A

Isothermal Process: constant temperature.
Isobaric Process: constant pressure.
Adiabatic Process: there is no heat exchange.
Isochoric Process: constant volume.

Ver diagrama de esto.

Thermodynamics 🔥👉🏻⚙️ (1 decks)

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