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Airflow Path Explorer

Run the Airflow Path Explorer 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-drawings.js), or their published URLs, to the editor's index.html before pasting ch04-airflow-path-explorer.js.

About This MicroSim

This MicroSim shows seven fan configurations, one at a time, as side-view drawings with the shaft horizontal and the air coming in from the left. No airflow is drawn at first. For each fan you predict two directions, relative to the shaft:

  • Impeller exit: parallel to the shaft, at a right angle to the shaft, or diagonal (between parallel and right angle).
  • Fan exit: parallel to the shaft, at a right angle to the shaft through one outlet, or outward in all directions around the impeller.

When you commit both predictions, an animation shows the air entering along the shaft, passing through the impeller and leaving the fan, and each prediction is marked. On the tubeaxial and vaneaxial fans the particles also rotate around the shaft to show swirl; on the vaneaxial fan the swirl stops at the guide vanes.

# Configuration Impeller exit Fan exit
1 SWSI housed centrifugal fan in a scroll housing At a right angle At a right angle, through one outlet
2 DWDI housed centrifugal fan in a scroll housing At a right angle At a right angle, through one outlet
3 Plenum fan (unhoused centrifugal) in an air handler cabinet At a right angle Outward in all directions
4 Tubular inline centrifugal fan with straightening vanes At a right angle Parallel
5 Tubeaxial fan (no guide vanes) Parallel Parallel
6 Vaneaxial fan (guide vanes downstream) Parallel Parallel
7 Mixed flow fan in a tubular housing with straightening vanes Diagonal Parallel

The fans come in this fixed order. Each prediction gets one attempt, so the 14 predictions are all first attempts, and mastery is 12 of 14. Replaying the animation is exploration and is never scored. The paths follow FanPedia pp. 4–7 (fan types), p. 186 (axial versus centrifugal impellers) and the exploded views on pp. 15–17; the drawings are schematic, and the animation speed and particle counts are illustrative.

How to Use

  1. Read the fan's name and study the drawing: where are the inlet, the impeller, the housing or tube, any vanes and the outlet?
  2. Choose a direction in Impeller exit and in Fan exit, then press Commit predictions (or Enter). You cannot change a prediction once it is committed.
  3. Watch the animation. Each prediction is marked "✓ Correct." or "✗ Not quite. The answer is …", and the reason appears below. After the animation, arrows tagged "impeller exit" and "fan exit" stay on the drawing. Press Replay animation (or R) as often as you like.
  4. Press Next fan (or Enter). After fan 7, the summary shows your first-attempt score out of 14, whether you reached mastery, and every prediction you missed with your choice and the answer. Press Start over to reset the score and begin again at fan 1.

Keyboard: Tab reaches the two lists and the buttons; arrow keys change a list; Enter commits the predictions, then goes to the next fan; R replays the animation. Feedback is also announced to screen readers.

Data label: "Paths: FanPedia pp. 4–7, 15–17, 186 · Animation illustrative", shown 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/ch04-airflow-path-explorer/main.html"
        height="672px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan

Learning Objective

The learner will classify seven fan configurations by the direction air leaves the impeller and the direction air leaves the fan, relative to the fan shaft (Bloom: Understand, verb: classify).

Audience

Adult professional development: new application engineers, sales staff, representatives and facilities staff.

Duration

10-15 minutes

Prerequisites

  • Chapter 3: impeller, fan shaft, fan housing.
  • Chapter 4: fan family, centrifugal fan, axial fan, mixed flow fan, scroll housing, unhoused centrifugal fan, plenum fan, tubular housing, guide vanes, straightening vanes, inline centrifugal fan.

Activities

  1. Predict (8 min): Work through the seven fans in order, committing both predictions before each animation.
  2. Compare (3 min): In the summary, read the notice about fans 4, 6 and 7. Which part of each fan decides its family, and which part decides where the air leaves?
  3. Discuss (3 min): Why does the plenum fan's air go out in all directions, while the SWSI fan's air leaves through one outlet, when both impellers are centrifugal?

Common Misconceptions Addressed

  • A fan in a round, straight-through tube must be an axial fan: fans 4 and 7 have tubes and leave the fan parallel to the shaft, but their impellers send air out radially or diagonally.
  • Air leaves a centrifugal fan in the same direction it leaves the impeller in every case: fan 4's impeller exit is at a right angle, but its fan exit is parallel to the shaft.
  • Guide vanes add pressure by speeding the air up: on the vaneaxial fan the animation shows the vanes stopping the swirl without changing the main direction.
  • A mixed flow fan discharges at a diagonal out of the fan: only the impeller exit is diagonal; the tube and vanes return the air to the duct direction.

Assessment

  • Running count "Predictions correct: n of 14"; one attempt per prediction, so every prediction is a first attempt. Mastery is 12 of 14.
  • Watching and replaying the animation is exploration, not evidence.
  • Follow-up question: a customer calls a fan "axial" because it is a round tube in a duct. What would you look at to check, and what would you expect to see for a tubular inline centrifugal fan?

References

  1. FanPedia: The Fan & Blower Encyclopedia (PDF) - Twin City Fan & Blower; pp. 4–7 describe the fan types, p. 186 compares axial and centrifugal impellers, and the exploded views on pp. 15–17 show where the guide vanes and straightening vanes sit.
  2. FanPedia online - Twin City Fan & Blower's online version of the encyclopedia.
  3. Chapter 4: Centrifugal, Axial and Mixed Flow Fans - the fan families, housings, guide vanes and straightening vanes behind every configuration.
  4. Twin City Fan & Blower - current catalogs for the tubeaxial, vaneaxial, inline centrifugal and mixed flow lines.