The First Law of Thermodynamics

Outline Forms of Energy Energy Transfer The Energy Balance Kinetic, Potential and Internal Energies The Work Term Injection Work

Outline (Continued) Restricted Forms of the Energy Equation Some Common Processes Unsteady-State Systems Less Restricted Systems

Objectives Introduce the forms of energy and energy transfer. Introduce the energy equation. Apply the energy equation to solve fluid flow problems.

Summary Forms of energy: kinetic, potential, internal, electrostatic, magnetic, surface and nuclear energies. In the absence of nuclear effects, the energy balance reduces to (Accumulation)=(Flow In)-(Flow Out) The rate form is (Rate of Accumulation)=(Flow Rate In)-(Flow Rate Out)

Summary (Continued) Using the energy equation becomes

Summary (Continued) Restrictions: 1. No electrostatic, magnetic, surface and nuclear energy effects. 2. Contents of the system are uniform. 3. Uniform inflow and outflow streams. 4. g = constant

Summary (Continued) Some common devices (see restrictions in class notes): 1. Adiabatic throttle: 2. Turbine, pump and compressor:

Summary (Continued) 3.Heater or cooler: 4.Steady-flow chemical reactor (see class notes) Filling bottle problem. Calculations are by trial-and error using:

Summary (Continued) Less restricted systems include: 1. Multiple flows 2. Nonhomogeneous systems 3. Variable gravity 4. Motion in a centrifugal force field