Thermal Sciences and Mechanical Engineering Sections 1. Introduction, 2. The Concept of Temperature 3. Heat Transfer 4. Thermodynamics. 5. Thermal Deformation, 6. Heat Treatment 7. Energy and Environment, 8 Summary Objectives After learning this chapter you should be able to do the following Understand the concept of temperature and convert a temperature from one scale to another Discuss the different modes of heat transfer Understand that the design or analysis of a machine operating in a thermal cycle is governed by the laws of thermodynamics 1、 Introduction Thermal science is an area of scientific thought encompassing heat transfer and thermodynamics Heat transfer deals with the transfer of thermal energy Thermodynamics deals with converting heat to work and understanding the role of energy and other properties of matter in this conversion process Thermal Machinery Thermal Machinery wherein the working fluid or substance undergoes a thermal cycle includes: Power system (Heat engine)Refrigeration system Some systems produce work, such as internal combustion engines, fossil-fuel power plant (power system) The thermal efficiency n th of a power system @Thermal efficiency is a measure of how efficiently a heat engine converts the heat that it received to work Other systems require work input to produce other effects, such as refrigerators, air-conditioning systems (refrigeration system) Coefficient of performance(CoP) for a refrigeration system An objective of a mechanical engineer working in designing thermal machinery is to improve the efficiency or COP of these 2. The Concept of Temperature Temperature is a measurement of the energy of molecules due to their rapid movement. ( the degree of hotness or coldness of a substance. Thermometer measures the temperature by the expansion and contraction of a liquid (usually mercury) in a glass The equality of temperature is the only requirement for thermal equilibrium 2.1 The Oth Law of Thermodynamics f two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other Notes It may seem silly, but it cannot be concluded from the other laws of thermodynamics, and it serves as a basis for the validity of temperature measurement. Its value as a fundamental physical principle was recognized more than half a century after the formulation of the I st and the 2nd laws. It is so named because it logically precedes the Ist and the 2nd laws 2.2 Temperature Scales The Fahrenheit scale places the freezing point of water at 32 degrees and the boiling point of water at 212 degrees The Celsius scale places the freezing point at zero degrees and the boiling point at 100 degrees The relationship between the Celsius scale and the fahrenheit scaleThermal Sciences and Mechanical Engineering Sections 1. Introduction、2. The Concept of Temperature 、3. Heat Transfer 4. Thermodynamics 、5. Thermal Deformation、6. Heat Treatment 7. Energy and Environment、8. Summary Objectives After learning this chapter, you should be able to do the following : Understand the concept of temperature and convert a temperature from one scale to another. . Discuss the different modes of heat transfer. . Understand that the design or analysis of a machine operating in a thermal cycle is governed by the laws of thermodynamics. 1、Introduction Thermal science is an area of scientific thought encompassing heat transfer and thermodynamics. . __ Heat transfer deals with the transfer of thermal energy. __ Thermodynamics deals with converting heat to work and understanding the role of energy and other properties of matter in this conversion process. Thermal Machinery Thermal Machinery wherein the working fluid or substance undergoes a thermal cycle includes: Power system ( Heat engine ) Refrigeration system Some systems produce work, such as internal combustion engines, fossil-fuel power plants; . (power system) The thermal efficiency ηth of a power system : @Thermal efficiency is a measure of how efficiently a heat engine converts the heat that it received to work.. Other systems require work input to produce other effects , such as refrigerators, air-conditioning systems. (refrigeration system) Coefficient of performance (COP) for a refrigeration system : An objective of a mechanical engineer working in designing thermal machinery is to improve the efficiency or COP of these devices. 2、 The Concept of Temperature Temperature is a measurement of the energy of molecules due to their rapid movement. (the degree of hotness or coldness of a substance.) . Thermometer measures the temperature by the expansion and contraction of a liquid (usually mercury) in a glass tube. The equality of temperature is the only requirement for thermal equilibrium. 2.1 The 0th Law of Thermodynamics If two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. Notes It may seem silly, but it cannot be concluded from the other laws of thermodynamics, and it serves as a basis for the validity of temperature measurement. . . __ Its value as a fundamental physical principle was recognized more than half a century after the formulation of the 1st and the 2nd laws. It is so named because it logically precedes the 1st and the 2nd laws. 2.2 Temperature Scales The Fahrenheit scale places the freezing point of water at 32 degrees and the boiling point of water at 212 degrees. The Celsius scale places the freezing point at zero degrees and the boiling point at 100 degrees. The relationship between the Celsius scale and the Fahrenheit scale :