5. The First Law of Thermodynamics for a Control Volume
5.0 Chapter introduction and learning objectives
Many thermal devices, such as compressors, turbines, and heat exchangers can be modelled as open systems. A common feature of these devices is that they all have inlets and outlets, through which a working fluid transfers both mass and energy into and out of the devices. This chapter extends the concept of energy conservation to open systems with a focus on steady-state, steady flows (SSSF). Examples are given to illustrate the applications of the first law of thermodynamics in typical SSSF devices such as turbines, compressors, heat exchangers, expansion valves, and mixing chambers.
Learning Objectives
After completing the chapter, you should be able to
- Determine the enthalpy of real substances by using thermodynamic tables
- Calculate the enthalpy of ideal gases, solids, and liquids by using constant-pressure specific heat
- Calculate mass flow rate and volume flow rate
- Explain the differences between steady and transient flows
- Explain the physical meanings of mass and energy conservation
- Apply the conservation equations of mass and energy to steady-state, steady flow devices
