Anh Văn Công Nghệ Nhiệt

Chapter 1: Introduction to thermodynamics Classification * Closed system control mass: - A fixed amount of mass, and no mass can cross its boundary.. - Energy, in the form of heat or wo

Anh văn Chuyên ngành Nhiệt English for thermal engineering

Tài liệu tham khảo

1 Fundamentals of thermal-fluid science, Y A Çengel.

2 Fundamentals of thermodynamics (sixth edition),

Sonntag, Borgnakke and van Wylen.

3 Fundamentals of engineering thermodynamics (Fifth

edition), Michael J Moran, Howard N Shapiro.

4 English for thermal engineering, Đặng Thành Trung, ĐHQG-HCM

Những trang Web tra từ chuẩn

Chapter 1: Introduction to thermodynamics

1.System

Definition:

A system is defined as a quantity of matter or a region in

space chosen for study

The mass or region outside the system the surroundings.

The real or imaginary surface that separates the system

from its surroundings is called the boundary.

Classification

* Closed system (control mass)

* Open system (control volume)

Chapter 1: Introduction to thermodynamics

Classification

* Closed system (control mass):

- A fixed amount of mass, and no mass can cross its boundary.

- Energy, in the form of heat or work, can cross the boundary;

And the volume of a closed system does not have to be fixed.

- An isolated system which is not allowed mass and energy to

cross the boundary.

1.System

Chapter 1: Introduction to thermodynamics

Classification

* Open system (control volume):

Both mass and energy can cross the boundary of a control volume

It usually encloses a device that involves mass flow such as a

compressor, turbine, or nozzle.

1.System

Chapter 1: Introduction to thermodynamics

The pressure due to the force

by the atmosphere’s mass

p a = 760 mmHg (at sea level,

15 0 C)

Gage pressure

The difference between the

absolute pressure and the

atmospheric pressure, and

the difference is positive

p g = p – p a > 0

Vacuum pressure

The difference between the absolute pressure and the atmospheric pressure, and the difference is negative

p v = p – p a < 0

2.Pressure

Chapter 1: Introduction to thermodynamics

Pressure’s units:

Chapter 1: Introduction to thermodynamics

The measurement of the degree of hotness or

coolness is temperature

3.Temperature

Temperature scales:

Celsius (0C), Fahrenheit (0F), Kelvin (K)

Conversion of temperature scales:

0C = 5/9(0F-32); K = 0C + 273.15; 0F = 9/50C + 32

Definition:

Chapter 1: Introduction to thermodynamics

Two bodies each in thermal equilibrium with a third body will be in thermal equilibrium with each other.

:

The Zeroth Law of thermodynamics:

Notice: The Zeroth Law of thermodynamics is a basis

for the validity of temperature measurement.

3.Temperature

Chapter 1: Introduction to thermodynamics

A device is used to measure temperature, by using materials that change in some way when they are

Chapter 1: Introduction to thermodynamics

4.Heat transfer

Definition

Heat is defined as the form of energy that is transferred between two

systems (or a system and its surroundings) by virtue of a temperature difference (  t  0).

Heat exists only as it crosses the boundary of a system and the

direction of heat transfer is from higher temperature to lower

Chapter 1: Introduction to thermodynamics

Sensible Heat is an interaction energy related to changes in

temperature of a gas or object with no change in phase.

Latent Heat is defined as the energy absorbed by or released from

a substance during a phase change from a gas to a liquid or a solid.

Heat transferred to a system

Heat transferred from a system

4.Heat transfer

Chapter 1: Introduction to thermodynamics

Specific heat: the measure of the amount of heat required

to raise the temperature of a unit mass of a substance one degree.

Cp is specific heat of the object at constant pressure.

Cv is specific heat of the object at constant volume.

4.Heat transfer

Chapter 1: Introduction to thermodynamics

Ideal-gas specific heats of various common gases:

4.Heat transfer

Chapter 1: Introduction to thermodynamics

Modes of heat transfer

The energy emitted by matter in the form of electromagnetic waves

as a result of the changes in the electronic configurations of the

atoms or molecules.

4.Heat transfer

Chapter 1: Introduction to thermodynamics

Modes of heat transfer

4.Heat transfer

Chapter 1: Introduction to thermodynamics

5 Work, W [J]:

Work, like heat, is an energy interaction between a system and its surroundings

In other word, work is the energy transfer associated with

a force acting through a distance

Definition:

W > 0: Work transferred out of a system

W < 0: Work transferred in a system

Chapter 1: Introduction to thermodynamics

Formula:

For a change in volume from V1 to V2, the work is obtained:

5 Work, W [J]:

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Thermodynamics (θɜ:məudai'næmiks): Nhiệt động họcSystem (ˈsɪs.təm): Hệ nhiệt động

Boundary (ˈbaʊn.dər.i): Biên hệ NĐ

Surrounding (səˈraʊnd): Môi trường xung quanh

Pressure ('preʃə): Áp suất

Absolute (ˈæb.sə.luːt):Tuyệt đối

Absolute pressure (n): Áp suất tuyệt đối

Vacuum ('vækjuːm) : Chân không

Vacuum pressure (n): Áp suất chân không

Atmosphere (ˈæt.mə.sfɪə): Khí quyển

Temperature (ˈtem.prə.tʃər): Nhiệt độ

Fluid (ˈfluː.ɪd): Chất lỏng

Conduction (kənˈdʌk.ʃən): Dẫn nhiệt

Convection (kənˈvek.ʃən): Đối lưu nhiệt

Radiation (ˌreɪ.diˈeɪ.ʃən): Bức xạ nhiệt

Sensible (ˈsen.sə.bəl) heat: Nhiệt hiện

Latent (ˈleɪ.tənt) heat: Nhiệt ẩn

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