Discharge Position Explorer¶

Run the Discharge Position 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-codes.js, fan-drawings.js), or their published URLs, to the editor's index.html before pasting ch12-discharge-position-explorer.js.

About This MicroSim¶

A centrifugal fan's rotation and discharge are always named as seen from the drive side (Chapter 12). The discharge angle N counts from upblast (360) in the direction of rotation, in 45° steps, so the direction the air leaves, measured clockwise from straight up as seen from the drive side, is θ = N for a CW fan and θ = 360 − N for a CCW fan. A view from the inlet side is the mirror image: the drawing flips left to right and the rotation arrow appears reversed, but the name does not change.

The sim opens in Explore mode. Set the rotation (CW or CCW), step the discharge angle from 45 to 360, and switch the viewpoint between the drive side and the inlet side. The housing redraws with its rotation arrow and outlet, and the panel shows the abbreviation and full name, the designation ("CW 90"), the FanPedia "also known as" form ("Clockwise 90°") and the direction the air leaves as seen from the drive side. The small dial shows the angle counted from upblast.

The eight positions are UBD Upblast 360, TAU Top Angular Up 45, THD Top Horizontal 90, TAD Top Angular Down 135, DBD Downblast 180, BAD Bottom Angular Down 225, BHD Bottom Horizontal 270 and BAU Bottom Angular Up 315 (FanPedia pp. 46–47).

Press Start challenge for ten drawings in a fixed order. Each shows a housing from the drive side or, for drawings 8 and 9, from the inlet side. Choose a rotation and a discharge abbreviation as seen from the drive side and press Check. Both must match; there is no partial credit. You get two attempts. A wrong first attempt gets a hint: a wrong rotation on an inlet-side drawing says to mirror the view, a wrong rotation on a drive-side drawing says to read the arrow as drawn, and a wrong abbreviation says to count 45° steps from upblast in the direction of rotation. A second wrong attempt shows the answer and the reason, and the drawing counts as missed. Only first-attempt answers count; mastery is 8 of 10. Explore mode is never scored.

How to Use¶

In Explore mode, keep CW and press + 45° repeatedly from 360. Predict where the outlet goes before each step.
Switch to CCW at the same angle: the housing mirrors and the air direction changes side, while the name and angle stay the same.
Choose Inlet side: only the picture changes; the name and designation do not.
Press Start challenge. For each drawing choose CW or CCW and one of the eight abbreviations, then press Check (or Enter). A correct answer reads "✓ Correct: CW THD (CW 90)." in a solid green box; a wrong one reads "✗ Not quite." with a hint in a dashed red box.
Press Next drawing (or Enter). After drawing 10 the summary lists the score, the mastery line and any missed drawings with their reasons. Explore mode goes back to free exploration; Start over runs the ten drawings again.

Keyboard: Tab reaches every button and the angle slider (arrow keys move it). Space picks a rotation or an abbreviation; Enter checks the drawing, and Enter again goes to the next one.

Data label: "Source: FanPedia pp. 46–47 · Directions as seen from the drive side", 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/ch12-discharge-position-explorer/main.html"
        height="642px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan¶

Learning Objective¶

The learner will apply the drive-side viewing rule and the discharge-angle convention to name the rotation and discharge position of ten SWSI centrifugal housing drawings, with at least 8 of 10 correct on the first attempt (Bloom: Apply, verb: apply).

Audience¶

Adult professional development: new application engineers, sales staff, representatives and facilities staff who have read the "Viewed From the Drive Side", "Rotation", "Discharge Position" and "Discharge Angle" sections of Chapter 12.

Duration¶

10-15 minutes

Prerequisites¶

Drive side and viewed from the drive side
Rotation (CW and CCW)
Discharge position, discharge angle and the eight position names and abbreviations
Mirror image of an opposite-side view

Activities¶

Explore (4 min): Step the angle all the way around for CW, then for CCW. Find the two positions whose air direction is the same for both rotations, and say how their housings differ.
Challenge (6-8 min): Name the ten drawings. For drawings 8 and 9, mirror the view before naming the rotation.
Review (2 min): Read the missed drawings on the summary and recreate each one in Explore mode.

Common Misconceptions Addressed¶

The rotation seen from the inlet side is the fan's rotation: drawings 8 and 9 are inlet-side views, and a wrong rotation there gets "Check the viewpoint".
The discharge angle is a fixed compass bearing: switching CW to CCW at the same angle in Explore mode moves the air to the other side while the name stays.
Upblast and downblast housings are the same for both rotations: the explorer shows the CW upblast outlet on the left of the top and the CCW one on the right.
"Top Horizontal" alone tells which way the air goes: the "Air leaves toward" line changes with the rotation.

Assessment¶

"Correct on first attempt: n of 10" is the running score; mastery is 8 of 10 on the first attempt.
Follow-up: a submittal says CCW 135. Without the sim, say which way the air leaves and where the outlet sits.

References¶

Centrifugal fan - Wikipedia overview of centrifugal fan housings, rotation and discharge.
Mirror image - why a view from the opposite side reverses left and right and the apparent rotation.
FanPedia: The Fan & Blower Encyclopedia - Twin City Fan's reference; pp. 46–49 define the discharge positions viewed from the drive side.