华中科技大学：《传热学》课程教学资源（课件讲义）英文版 Heat transfer

Heat transfer by J P Holman To Research on the heat Diffusing Transporting and Radiating in the Material Systems

Heat Transfer by J P Holman To Research on the Heat Diffusing , Transporting and Radiating in the Material Systems

Chapter One Introduction Heat Heat is a kind of energy Which occurs in the transfer process. the transferred energy contains the orderly work and disorderly heat) Energy: Concept of energy is used to specify the state of a system in thermodynamics a Heat Transfer a kind of application science, is concerned with analysis of the rate of heat transfer taking place in system, or with the research on the heat-transfer regularity

Chapter One Introduction „ Heat:Heat is a kind of energy, Which occurs in the transfer process. (the transferred energy contains the orderly work and disorderly heat) „ Energy: Concept of energy is used to specify the state of a system in thermodynamics „ Heat Transfer:A kind of application science, is concerned with analysis of the rate of heat transfer taking place in system, or with the research on the heat-transfer regularity

1 Some Basic Concepts and Definitions System research region or scope a physical space a Internal energy measure of motion of microscopic particles a Temperature measure molecular mean kinetic energy Enthalpy internal energy plus displacement work Work orderly energy force multiplies displacement in the force direction Heat flow transferred heat quantity per unit time

1 Some Basic Concepts and Definitions „ System research region or scope, a physical space „ Internal energy measure of motion of microscopic particles „ Temperature measure molecular mean kinetic energy „ Enthalpy internal energy plus displacement work „ Work orderly energy, force multiplies displacement in the force direction „ Heat flow transferred heat quantity per unit time

Some Basic Concepts and Definitions a Heat flux transferred heat quantity per unit time and per unit area perpendicular to the direction of the heat flow Heat source equipment or region to produce or provide heat flow for system a Heat transfer elements thermal resistance thermal capacity thermal inductance a Change in phase substance state is changed Continuity Supposition the macroscopic continuity but the microscopic discontinuity

1 Some Basic Concepts and Definitions „ Heat flux transferred heat quantity per unit time and per unit area perpendicular to the direction of the heat flow „ Heat source equipment or region to produce or provide heat flow for system „ Heat transfer elements thermal resistance, thermal capacity, thermal inductance „ Change in phase substance state is changed „ Continuity Supposition the macroscopic continuity but the microscopic discontinuity

2 Process of heat transfer a heat transfer process occurs when the internal energyfor enthalpy)in a system is not well distribution(has nt been even), or When the internal energy of system is different from that of its surrounding The energy transport by heat flow can't be measured directly. The concept has physical meaning because it is related to the measurable temperature

2 Process of heat transfer „ heat transfer process occurs when the internal energy(or enthalpy) in a system is not well￾distribution (has n ’t been even), or when the internal energy of system is different from that of its surrounding. „ The energy transport by heat flow can ’t be measured directly. The concept has physical meaning, because it is related to the measurable temperature

2 Process of heat transfer Substantially the heat flow amounts to disorderly variation of internal energy With time The temperature difference takes place the heat transfer

2 Process of heat transfer „ Substantially, the heat flow amounts to disorderly variation of internal energy with time „ The temperature difference takes place the heat transfer

3 Applications of heat transfer The problem of determining the temperature distribution and the heat flow is of interest in many branches of science and technology or engineering) In power engineering heat exchangers, boilers condensers, burners nuclear reactor cores radiators In aerospace technology temp. and heat flow, high velocity ,weight, safety In heating and air-conditioning building structure, estimate insulation, prevent excessive heat losses In electronic and electrical engineering heat distribution heat stress, dissipation

3 Applications of heat transfer „ The problem of determining the temperature distribution and the heat flow is of interest in many branches of science and technology (or engineering). „ In power engineering heat exchangers, boilers condensers, burners, nuclear reactor cores, radiators „ In aerospace technology temp. and heat flow,high velocity,weight, safety „ In heating and air-conditioning building structure, estimate insulation, prevent excessive heat losses „ In electronic and electrical engineering heat distribution, heat stress, dissipation

4 Study method a Classical macroscopic study method macroscopic phenomenology method Phenomenon→ Abstract→ Mathematical description(mould)= Solution (Analysis Numerical, Experimental) a Building mould Mass, momentum or energy conservation law plus the mass, fluid viscous or heat conductive basic law = differential equation

4 Study method „ Classical macroscopic study method (macroscopic phenomenology Method) „ Phenomenon ⇒ Abstract ⇒ Mathematical description(mould) ⇒ Solution (Analysis, Numerical, Experimental) „ Building mould Mass, momentum or energy conservation law plus the mass,fluid viscous or heat conductive basic law ⇒differential equation

5 Learning heat transfer a Have a profound grasp of the essential of heat transfer construction, research method, general regularity, mathematical and physical moulds a Know well the basic definitions, concepts, laws calculation methods Normal learning listen to teaching, write note discuss questions accomplish fixed exercises make experiments

5 Learning heat transfer „ Have a profound grasp of the essential of heat transfer construction, research method, general regularity, mathematical and physical moulds. „ Know well the basic definitions, concepts, laws, calculation methods. „ Normal learning listen to teaching, write note, discuss questions, accomplish fixed exercises, make experiments

1-1 Three Basic Modes of heat Transfer a three modes: conduction the aid of the motion of the microscopic particles convection the aid of the motion of the macroscopic fluids Radiation the aid of the propagation of electromagnetic waves The temperature field is controlled by combined effects, it is not possible to isolate entirely one mode. For simplicity, one mode can consider separately Give a brief qualitative description of the three modes

1-1 Three Basic Modes of heat Transfer „ Three modes: conduction the aid of the motion of the microscopic particles convection the aid of the motion of the macroscopic fluids Radiation the aid of the propagation of electromagnetic waves The temperature field is controlled by combined effects, it is not possible to isolate entirely one mode. For simplicity, one mode can consider separately. Give a brief qualitative description of the three modes