Lesson: Energy Equation

Overview of this Lesson

In fluid mechanics, there are three conservation laws that are the foundation of the discipline. The first two conservation laws (mass, momentum) were introduced by the last two lessons. This lesson introduces the last of these conservation laws, which is conservation of energy.

Benefits of this Lesson

  • Gain a working knowledge of numerous practical concepts
    • power, energy, work ….
    • flow work, head loss, …
    • efficiency, pumps, turbines
    • Hydraulic grade line (HGL), Energy grade line (EGL) ….
  • Learn how to apply the energy equation. Examples:
    • Determining pump size requirements (how much power, how much flow)
    • Figuring out pressure drop in a run of pipe
    • Determining how much power can be produced by a turbine

Goals (Results we intend to create).

  • Learners know main concepts
    • Energy, Power, Work (subconcepts include flow work; shaft work)
    • Pump, Turbine
    • KE correction factor
    • Head (subconcepts include head loss, pump head, turbine head, velocity head, pressure head)
    • Efficiency
  • Energy Eqn. (7.29). Learners
    • (optional1) derive this equation with quality.
    • understand the knowledge found in EMTAD documentation.
  • Power Eqn. (eqs. 7.3 and 7.31) and the Efficiency eqn (7.32). Learners
    • Explain the meaning of the terms
    • Apply the equations to practical problems
  • Head Loss (sudden expansion). Learners can
    • Explain how to derive Eq. 7.37
    • Apply Eq. 7.37 to predict head loss
  • HGL & EGL. Learners
    • Explain the ideas of the HGL and EGL
    • Sketch EGLs & HGLs, explain how and why, and explain trends.

Resources (sources of knowledge for reaching goals)

  • Chapter 7

Plan (steps to reach the goals)

1. Goal Setting.
Recommend: Write down personal goals for this lesson. Ask yourself, what do I want? What are my motivations for studying engineering? Make your goals specific (i.e. measurable) and challenging. For more information, see "how to write goals."

2. Energy, Work, and Power
a. Do text problem 7.1
b. Read pp. 217 to 218. Work problem 7.4.
c. Construct "MREAC level" knowledge for energy, work, power.

3. Energy Equation
a. Read pp. 219 to 226.
b. Construct "MREAC level" knowledge for concepts: flow work, shaft work, pump, turbine, head loss, pump head, turbine head, velocity head, pressure head, kinetic energy correction factor).
c. Construct "EMTAD level" knowledge for the energy equation (7.29).
d. Problems 7.9, 7.10, 7.15 (recommend practice Wales/Woods; correct in red)
e. Problems 7.19, 7.20 (recommend practice Wales/Woods; correct in red)
f. Problems 7.26, 7.27, 7.30 (recommend practice Wales/Woods; correct in red)
g. Read section 7.5. Construct knowledge so you can explain how the energy equation differs from the Bernoulli equation.

4. Power and Efficiency.
a. Read pp. 227 to 228.
b. Construct "MREAC level" knowledge of efficiency.
c. Construct "EMTAD level" knowledge about the "power & efficiency eqns."
d. Problems 7.40, 7.43 (recommend practice Wales/Woods; correct in red)

5. Head Loss in Sudden Expansions.
a. Read pp. 230 to 232.
b. Construct "EMTAD level" knowledge of Eq. (7.37)
c. Problems 7.69, 7.72, 7.77 (recommend practice Wales/Woods; correct in red).

6. Energy Grade Line; Hydraulic Grade Line (EGL/HGL).
a. Read pp. 233 to 236.
b. Construct "MREAC level" knowledge of HGL and EGL.

7. Lesson Review (Reflective Thinking)
a. Please rate this lesson using the (anonymous) form; needs to be added.
b. Did you reach your goals? How do you know?
c. Complete an SII for yourself. Identify 3 strengths, 2 improvements, and 2 insights.

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