英文版工程热力学课件第一章.ppt

血压读数包括两个值：收缩压和舒张压。例如，120/80便是一个典型的读数。医生将臂带缠在您的手臂上并加压，目的是利用臂带向手臂施加压力，阻断血流。随着臂带压力的释放，血液又恢复流动，医生可以从听诊器中听到血流声。血液开始流动时的数值(120)就是心脏的最大输出压（收缩压读数）。医生一边继续释放臂带内的压力，一边倾听，直到声音消失。声音消失时的数值(80)表明心脏松弛时循环系统的压力（舒张压读数）。 简单可压缩系统是指与外界只有热量及准静态容积变化功（膨胀功或压缩功）交换的可压缩系统。 Pressure in Fluid P2=P1+ρgh ρ-density (kg/m3); h- depth (m) Same h, same P2. * Pressure Measurement Devices(测压计) Manometer(流压计), ?P=ρgh Bourdon Tube(波登管): consists of a hollow metal tube bent like a hook whose end is closed and connected to a dial indicator needle. pressure transducer (压力传感器): use electronics convert pressure to voltage, resistance, capacitance etc. * Chapter1 Introduction and Basic Concepts Overview of thermodynamics Unit system Basic/important concepts: system, boundary,surroundings, closed system, open system, properties, states, equilibrium, process, cycle. etc. Temperature and pressure Problem-solving technique * Problem Solving Technique * Step1: Problem Statement: state the problem in your own words (用自己的语言描述要解决的问题) Step 2:Schematic: Make a sketch of the physical system to be solved. W, E, Q, T, P (草绘出你所要解决的物理问题，以及所要求解的量) Step 3: Assumptions and Approximations: simplify (作假设或简化，将问题简单化) Step 4: Physical laws: apply relevant basic physical laws and principles. Determine the equations to be used. (确定问题所适用的定理，定律等，确定要使用的方程式) Step 5: Properties: known properties? unknown properties. (确定参数，由已知的，推出未知的) Step 6: Calculation: use the equations to calculate and solve the problem. (求解方程式，计算求得问题答案) Step 7: verification: to make sure your results is a good one. (验证以确保结果正确) * Remark on significant digits (有效数字) No special definition: usually 3 digits It is meaningless to have more significant digits than the known parameters ? A container: 3.75 L in volume; Filed with gasoline, whose density is 0.845kg/L : to have the mass of gasoline A: m= ρV=3.75 [L]*0.845[kg/L]=3.16875 [kg] =3.17[kg] * Chap. 1 Summary * Thermodynamics Energy Application areas A Science of Energy Thermodynamic System Zeroth