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Fan Power and Efficiency Calculator

Run the Fan Power and Efficiency Calculator MicroSim Fullscreen

This sketch is built on the FanPedia MicroSim kit. To run it in the p5.js editor, add the ../shared-libs/ files it loads (fanpedia-sim.css, fanpedia-core.js, fanpedia-p5.js, fan-models.js), or their published URLs, to the editor's index.html before pasting ch10-fan-power-efficiency-calculator.js.

About This MicroSim

This calculator practices the power equations from the section "Brake Horsepower and Fan Efficiency" in Chapter 10:

  • Static air power (hp) = Q × FSP ÷ 6356
  • BHP = air power ÷ (static efficiency ÷ 100)
  • Static efficiency (%) = 100 × air power ÷ BHP

where Q is the airflow volume in CFM and FSP is the fan static pressure in in. wg. The sim starts with three challenge duties, in this fixed order. All three are illustrative values; challenge 1 is the chapter's worked example.

# Given Asked Model answer
1 10,000 CFM, 4.0 in. wg FSP, static efficiency 70% BHP 8.99 BHP
2 20,000 CFM, 6.0 in. wg FSP, static efficiency 75% BHP 25.17 BHP
3 5,000 CFM, 2.0 in. wg FSP, 2.5 BHP Static efficiency (%) 62.9%

An answer is correct when it is within 2% of the model value. You get two attempts per challenge. A wrong answer shows the worked calculation; an answer about 100 times too small also gets a reminder about decimals and percent. After the second wrong attempt the model value is shown and the challenge counts as missed. Once a challenge is resolved, the sim shows your answer next to the model value, the three-line calculation (air power, division, result) and two bars: air power, and BHP split into air power and losses.

Mastery is 3 of 3 challenges correct on the first attempt. After challenge 3, Explore mode unlocks three sliders: airflow volume (1,000 to 50,000 CFM), fan static pressure (0.5 to 15.0 in. wg) and static efficiency (40% to 90%). The air power and BHP readouts and the bars update at once. Explore mode is never scored.

How to Use

  1. Read challenge 1, type a number in Your answer (BHP for challenges 1 and 2, percent for challenge 3) and press Check (or Enter).
  2. A correct answer reads "✓ Correct: model value." in a solid green box. A wrong one reads "✗ Not quite." with the worked calculation in a dashed red box; use the second attempt.
  3. Press Next challenge (or Enter) and repeat for challenges 2 and 3. "Challenges correct: n of 3" keeps the running score.
  4. After challenge 3, press Start exploring. The panel shows the first-attempt score and the mastery line. Set 10,000 CFM and 4.0 in. wg, then lower the efficiency from 70% to 50%: BHP rises from 8.99 to 12.59 hp. Start over clears the score and returns to challenge 1.

Keyboard: Enter checks the answer, and Enter again goes to the next challenge. Tab reaches the answer box, every button and the three sliders; the arrow keys move a focused slider.

Data label: "Illustrative values · standard US fan units, constant 6,356", at the bottom left of the drawing.

Iframe Embed Code

You can add this MicroSim to any web page by adding this to your HTML:

<iframe src="https://moroshek.github.io/FanTASTIC-textbook/sims/ch10-fan-power-efficiency-calculator/main.html"
        height="642px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan

Learning Objective

The learner will calculate a fan's brake horsepower or static efficiency from its airflow volume, fan static pressure and one of the other two quantities, to within 2% of the model value (Bloom: Apply, verb: calculate).

Audience

Adult professional development: new application engineers, sales staff, representatives and facilities staff who have read the section "Brake Horsepower and Fan Efficiency" in Chapter 10.

Duration

10-15 minutes

Prerequisites

  • Airflow volume (CFM) and fan static pressure (in. wg)
  • Air power and the constant 6,356
  • Brake horsepower and static efficiency

Activities

  1. Challenges (5-8 min): Solve each challenge with a calculator before pressing Check. Write the air power first, then divide by the efficiency as a decimal.
  2. Review (2 min): Compare your answer with the three-line calculation. If you were 100 times off, find where the percent should have become a decimal.
  3. Explore (3-5 min): At 10,000 CFM and 4.0 in. wg, record BHP at 80%, 70%, 60% and 50% and compare with the chapter's table (7.87, 8.99, 10.49 and 12.59 BHP). Pick the motor size for each.

Common Misconceptions Addressed

  • BHP equals air power: the bars show BHP as air power plus losses, always larger.
  • Efficiency entered as a whole number (70 instead of 0.70): the sim spots an answer about 100 times too small and says so.
  • A less efficient fan needs less power because it "does less work": in Explore mode, lowering the efficiency at a fixed duty makes the BHP bar longer, not shorter.

Assessment

  • The running line "Challenges correct: n of 3" counts challenges solved on either attempt. At the end the sim shows "First-attempt score: n of 3" and the mastery line; mastery is 3 of 3 on the first attempt.
  • Moving the sliders in Explore mode is not evidence of mastery. Ask the learner why a fan selected far from its peak efficiency costs money twice (a larger motor and a larger electric bill).

References

  1. Fan (machine) - Wikipedia overview of fan types, performance and power.
  2. Brake horsepower - Wikipedia section on shaft power measured at the output shaft.
  3. FanPedia: The Fan & Blower Encyclopedia - Twin City Fan's reference on fan performance, horsepower and efficiency.